Researchers may have found a new way to locate deposits of rare earth elements that are vital to the tech and energy industries.

Rare earth elements crystallize in Earth's mantle inside blobs of magma that are rich in alkali metals, such as sodium and potassium, and carbonate minerals, such as calcite and dolomite. In a new study, scientists found that these types of magma, known as alkaline and carbonatite magmas, form above ancient subduction zones, where one tectonic plate dives beneath another.

"This research shows that the ingredients for these critical mineral deposits were put in place many million[s] to even billions of years ago," study lead author Carl Spandler, a professor of mineralogy, petrology, geochemistry and economic geology at Adelaide University in Australia, said in a statement. "By identifying where these ancient processes occurred, we can significantly narrow down the search areas for future discoveries."

The study, published April 8 in the journal Science Advances, challenges previous theories that linked rare earth deposits primarily to mantle plumes — giant, mushroom-shaped columns of red-hot molten rock that originate near Earth's core. It's possible that mantle plumes are involved in making rare earth elements, the researchers wrote in the study. However, there is no clear overlap between the two, and plumes may be too hot to produce alkaline and carbonatite magmas.

In the study, the team used advanced modeling techniques to reconstruct Earth's plate tectonics and subduction processes over the past 2 billion years. (Scientists think plate subduction started at least 3.1 billion years ago, but the best models go back only 2 billion years.) Then, the researchers compared the positions of subduction zones with the locations of present-day rare earth deposits and regions of the mantle where alkaline and carbonatite magma blobs are known to exist.

Spandler and his colleagues found that, globally, known deposits of rare earth elements and the pockets of magma that host them frequently appear above ancient subduction zones.

When a tectonic plate plunges beneath another plate at a subduction zone, fluids (such as water) and halogen elements (fluorine, chlorine, bromine, iodine, astatine and tennessine) are released into the overlying mantle. The researchers proposed that these substances react with rocks such as peridotite, creating "fertilized" mantle regions that can remain stable for millions of years, before gradually melting to produce alkaline or carbonatite magma and, subsequently, rare earth deposits.

Various geological processes could theoretically melt the fertilized mantle material, including a mantle plume, the stretching and thinning of continents above, and a decrease in pressure resulting from deglaciation at Earth's surface, the researchers wrote in the study. Regardless of the specific process, the huge age gap between some subduction zones and overlying magma blobs and rare earth deposits in the study suggests that fertilized regions can endure for eons.

"This time lag is one of the most surprising aspects of our findings," Spandler said in the statement. "It shows that the Earth's mantle can store these enriched zones for incredibly long periods before the right conditions arise to form mineral deposits."

The results showed that 67% of known alkaline and carbonatite magma blobs and 72% of known rare earth deposits sit on top of fertilized mantle material. Because older rare earth deposits tend to be larger and of a higher grade than newer ones, the researchers redid the analysis for deposits older than 540 million years — and found that 92% of them are located above fertilized mantle regions.

The rare earth deposits that weren't connected to fertilized mantle regions in the study are probably linked to subduction zones older than 2 billion years, the researchers wrote. Notably, there were more alkaline and carbonatite magma blobs and rare earth deposits in regions of the world where multiple fertilized mantle areas overlap, they wrote.

There are 17 rare earth elements — yttrium, scandium and the 15 metallic elements found at the bottom of the periodic table. These elements are essential components in electric vehicle batteries, wind turbines and smartphones, but until now, locating deposits big enough to mine has been challenging.

The results could help countries and corporations find more rare earth element deposits, study co-author Andrew Merdith, a researcher in Adelaide University's School of Physics, Chemistry and Earth Sciences, said in the statement. "By focusing on these ancient tectonic zones, exploration companies and governments can take a more targeted and efficient approach to finding new deposits," Merdith said.

The best places to look may be areas that have ancient subduction zones, as well as magma that formed at low temperatures and highly stable crust and upper mantle regions, the researchers wrote in the study.

Refining the models and going further back in time could help scientists locate even more prospective regions, they added.

What's inside Earth quiz: Test your knowledge of our planet's hidden layers

Earth's core contains up to 45 times more hydrogen than the oceans do, making it the largest hydrogen reservoir on the planet, a new study suggests.

Researchers found that this vast amount of hydrogen entered the core during its formation around 4.5 billion years ago, and did not arrive via comets that pummeled Earth once the core was established. The finding could settle the debate about when and how hydrogen was delivered to our planet.

"That hydrogen on Earth, including hydrogen in the core, was delivered during planet formation is an established hypothesis," study lead author Dongyang Huang, an assistant professor in the School of Earth and Space Sciences at Peking University in China, told Live Science in an email. "What differentiates the community is when hydrogen was delivered along Earth's formation."

This debate has continued because hydrogen deep inside Earth is extremely difficult to quantify. Hydrogen is the smallest and lightest element in the universe, so most techniques do not have the resolution to properly detect it in high-pressure and high-temperature environments such as Earth's core.

But estimating how much hydrogen is locked inside the core is a key to understanding how the hydrogen got there in the first place, Huang said.

Previous research used a technique called X-ray diffraction to estimate the amount of hydrogen in Earth's core. This method quantifies the minerals and other substances in a material by analyzing how that material scatters X-rays. Because Earth's core is made almost entirely of iron, scientists added hydrogen to a sample of iron in the lab and measured the expansion of the iron's crystal structure to calculate how much hydrogen could be trapped inside the core.

The downside of X-ray diffraction in this case is that it makes a couple of crucial assumptions, Huang said. First, it assumes researchers have an accurate understanding of iron crystal structures and how they react under certain conditions. Second, it supposes that silicon and oxygen, both present in the core, do not deform the crystal structure when they dissolve into iron — which, it turns out, they do.

For the new study, Huang and his colleagues employed an alternative method known as atom probe tomography. This technique can "provide 3D nanoscale compositional mapping of all the elements in the periodic table" and is "ideal for high-pressure samples," Huang said.

The researchers simulated the conditions that likely existed when Earth's core was forming. To begin, they coated a tiny sample of iron metal with hydrous silicate glass to model the core covered in magma. Then, they placed this object inside a diamond anvil cell — a device in which two diamond crystals squeeze together to generate extreme pressure similar to that found in Earth's core. To create high-temperature conditions, the scientists used lasers that heated the object to about 8,730 degrees Fahrenheit (4,830 degrees Celsius).

The researchers used atom probe tomography in this context. They discovered that hydrogen, oxygen and silicon dissolve into iron crystal structures simultaneously under extreme conditions, thus altering the crystals in previously unknown ways.

Crucially, equal amounts of hydrogen and silicon entered the "core" from the "magma" in the experiment, which helped the researchers estimate that hydrogen makes up 0.07% to 0.36% of Earth's core by weight.

The results, published Tuesday (Feb. 10) in the journal Nature Communications, suggest Earth's core contains nine to 45 times as much hydrogen as the planet's oceans. If comets had delivered hydrogen to Earth after the core had finished forming, hydrogen would mostly occur in Earth's shallower layers. But the finding that the core is Earth's biggest hydrogen reservoir indicates that hydrogen was delivered before the core was fully formed, Huang said.

"This is the first time that the mechanism of how hydrogen enters the core was identified," he said.

What's inside Earth quiz: Test your knowledge of our planet's hidden layers

A weak spot in Earth's magnetic field over the South Atlantic Ocean has ballooned in size since 2014, satellite data reveals.

The region, known as the South Atlantic Anomaly, has grown by an area nearly half the size of continental Europe, sprouting a lobe in the direction of Africa where the field is weakening the fastest.

And the anomaly, linked to mysterious fluctuations near Earth's outer core, could pose a risk to satellites passing over the region, according to a study published in the November issue of the journal Physics of the Earth and Planetary Interiors.

"The South Atlantic Anomaly is not just a single block," study lead author Chris Finlay, a professor of geomagnetism at the Technical University of Denmark, said in a statement. "It's changing differently towards Africa than it is near South America. There's something special happening in this region that is causing the field to weaken in a more intense way."

Researchers first detected the South Atlantic Anomaly in the 19th century. Inside its boundaries, the magnetic field that radiates away from Earth's interior dips down to an altitude of about 120 miles (200 kilometers) above the planet's surface, which is much lower than the field's average altitude of about 400 miles (650 km).

This poses a threat to satellites and other spacecraft. Earth's magnetic field shields the planet and objects in low Earth orbit from charged solar particles and incoming X-ray and ultraviolet radiation, so spacecraft traveling over the South Atlantic Anomaly are exposed to more of these impacts. This could lead to malfunctions or damage in hardware, and even blackouts, according to the statement.

Finlay and his colleagues think the South Atlantic Anomaly is growing and spreading eastward due to strange fluxes at the limit between Earth's mantle and outer core, the layers of the planet sandwiched between Earth's crust and inner core.

Earth's magnetic field is largely generated by Earth's outer core — an ocean of swirling, molten iron located roughly 1,900 miles (3,000 km) beneath the planet's surface. The liquid iron dynamo generates electrical currents, and their flow induces a magnetic field that spreads up into the mantle and extends through Earth's atmosphere, forming two giant rings that join near the poles.

Scientists previously found that in some areas beneath the South Atlantic Anomaly, the magnetism generated by the outer core is looping back into the core instead of coming out. These patterns, known as reverse flux patches, can migrate and expand, explaining the growth of the South Atlantic Anomaly over the past 11 years, Finlay said.

“We can see one of these areas moving westward over Africa, which contributes to the weakening of the South Atlantic Anomaly [the magnetic field] in this region," he added.

The scientists spotted the unusual shifts in data from the European Space Agency’s (ESA's) ongoing Swarm mission, which uses three identical satellites to measure magnetic signals originating from Earth's interior and oceans. The data also revealed changes in magnetic field dynamics above Canada and Siberia, where magnetism has appeared more intense than average since Swarm began its observations in 2013.

Since 2014, the magnetic field above Canada has weakened slightly, and the magnetic field above Siberia has strengthened, the new study shows. The strong region over Canada has shrunk by an area nearly the size of India, while the strong region over Siberia has grown by an area the size of Greenland. The researchers attributed these changes to a shift in Earth's northern magnetic pole in Siberia's direction over recent years, but more monitoring is needed to see how the dynamics evolve.

"It's really wonderful to see the big picture of our dynamic Earth," Anja Strømme, ESA's Swarm mission manager, said in the statement. "The satellites are all healthy and providing excellent data, so we can hopefully extend that record beyond 2030."

Scientists may have just toppled a 100-year-old theory about what holds up the highest mountain range on Earth, new research shows.

The Himalayan mountains formed in the collision between the Asian and Indian continents around 50 million years ago, when tectonic forces squeezed Tibet so hard that the region crumpled and its area shrank by almost 620 miles (1,000 kilometers). The Indian tectonic plate eventually slipped under the Eurasian plate, doubling the thickness of Earth's crust beneath the Himalayas and Tibetan Plateau to the north, and contributing to their uplift.

For a century, the prevailing theory has been that this doubling of the crust alone carries the weight of the Himalayas and the Tibetan Plateau. Research published in 1924 by Swiss geologist Émile Argand shows the Indian and Asian crusts stacked on top of each other, together stretching 45 to 50 miles (70 to 80 km) deep beneath Earth's surface.

But this theory doesn't stand up to scrutiny, researchers now say, because the rocks in the crust turn molten around 25 miles (40 km) deep due to extreme temperatures.

"If you've got 70 km of crust, then the lowermost part becomes ductile… it becomes like yogurt — and you can't build a mountain on top of yogurt," Pietro Sternai, an associate professor of geophysics at the University of Milano-Bicocca in Italy and the lead author of a new study analyzing the geology beneath the Himalayas, told Live Science.

Evidence has long suggested that Arnand's theory is erroneous, but the idea of two neatly stacked crusts is so appealing that most geologists haven't questioned it, Sternai said. Historically, "any data that would come along would be interpreted in terms of a single, double-thickness crustal layer," he said.

Related: Will Mount Everest always be the world's tallest mountain?

However, the new study reveals there is a piece of mantle sandwiched between the Asian and Indian crusts. This explains why the Himalayas grew so tall, and how they still remain so high today, the authors wrote in the paper, published Aug. 26 in the journal Tectonics.

The mantle is the layer of Earth that sits directly beneath the crust. It is much denser than the crust and, therefore, doesn't liquefy at the same temperatures. Meanwhile, the crust is so light and buoyant that it behaves similarly to an iceberg, lifting up higher above Earth's surface the thicker it gets.

Sternai and his colleagues discovered the mantle insert by simulating the collision between the Asian and Indian continents on a computer. The model showed that as the Indian plate slipped beneath the Eurasian plate and started to liquify, blobs of it rose and attached themselves not to the bottom of the Asian crust, but to the base of the lithosphere, which is the rigid outer layer of the planet composed of the crust and upper mantle.

This is fundamental, Sternai said, because it means there is a rigid layer of mantle between the stacked crusts solidifying the whole structure beneath the Himalayas. The two crusts give enough buoyancy to keep the region lifted, while the mantle material provides resistance and mechanical strength. "You've got all the ingredients you need to uplift topography and sustain the weight of the Himalayas and Tibetan plateau," he said.

The researchers then compared their results with seismic data and information gathered directly from rocks. The mantle sandwich in the simulation matched previous evidence that Arnand's theory couldn't explain, study co-author Simone Pilia, an assistant professor of geoscience at King Fahd University of Petroleum and Minerals in Saudi Arabia, told Live Science.

"Things actually start to make sense now," Pilia said. "Observations that seemed to be enigmatic are actually now more easily explained by having a model where you have crust, mantle, crust."

The study presents strong evidence for this model, but contradicting Arnaud's 100-year-old theory is controversial because it has been so widely adopted, Pilia said.

"I think the authors are correct that this is controversial," Adam Smith, a postdoctoral research associate in numerical modeling at the University of Glasgow in Scotland who was not involved in the study, told Live Science in an email. "All prior work generally agreed that all the material beneath the Himalayas came from the crust."

But the results are still plausible, and they explain a number of geological oddities in the Himalayas, Smith said. "The authors run lots of simulations using different thicknesses for all of the layers, and they seem to always get this bit of mantle sandwiched between the crust of the two plates."

Douwe van Hinsbergen, a professor of global tectonics and paleogeography at Utrecht University in the Netherlands who wasn't involved in the study, disagreed that the results are controversial. "It's a nice new finding and an elegant interpretation," he told Live Science in an email. "If a continent shoves below another continent, you’d expect a sandwich that consists from top to bottom of crust and mantle lithosphere of the upper (Tibet) plate, and then the crust of the lower (Indian) plate."

What's inside Earth quiz: Test your knowledge of our planet's hidden layers

There's a lot more to Earth than meets the eye. Far from being just a roundish rock barreling through space, our planet is composed of several layers held together by intense forces of gravity.

Our planet's interior is much too deep and hot to explore with probes, so scientists rely on seismic waves to understand and model its structure. Seismic waves are shock waves that propagate through Earth's layers after an earthquake or explosive event, traveling at different speeds depending on the density and state of the material. The time it takes for these shock waves to bounce back up to Earth's surface reveals aspects of the composition and physical properties of the rocks beneath.

Geologists today have a good understanding of Earth's interior, based on pioneering work by Isaac Newton and Danish seismologist Inge Lehmann in the late 17th century and early-to-mid 20th century, respectively.

But how good is your knowledge of Earth's inner structure? Find out by taking this quiz. If you need a hint, hit the yellow button. Good luck!

More science quizzes

—Equator quiz: Can you name the 13 countries that sit on Earth's central line?

—Antarctica quiz: Test your knowledge on Earth's frozen continent

—Moon quiz: What do you know about our nearest celestial neighbor?

—Evolution quiz: Can you naturally select the correct answers?

—Conspiracy theory quiz: Test your knowledge of unfounded beliefs, from flat Earth to lizard people

The boundary zone between Earth's molten metal core and the mantle, its rocky middle layer, might be a diamond factory. 

A new laboratory experiment finds that, under extreme temperatures and pressures, the combination of iron, carbon and water — all potential ingredients found at the core-mantle boundary — can form diamond. If this process also happens deep inside Earth, it might explain some weird quirks of the mantle, including why it has more carbon in it than scientists expect. 

The findings also might help to explain strange structures deep in the core-mantle boundary where waves from earthquakes slow down dramatically. These regions, known as "ultra low velocity zones" are associated with strange mantle structures, including two giant blobs under Africa and the Pacific Ocean; they can be just a few miles across or many hundred. No one knows exactly what they are. Some scientists think they date back 4.5 billion years and are made of materials from the very ancient Earth. But the new research suggests that some of these zones may owe their existence to plate tectonics, which likely started well after Earth's formation, perhaps 3 billion years ago.

"We are adding a new idea that these are not entirely old structures," study lead author Sang-Heon Shim, a geoscientist at Arizona State University, told Live Science.

Simulating the deep Earth 

Where the core meets the mantle, liquid iron rubs up against solid rock. That's as dramatic a transition as the rock-to-air interface at Earth's surface, Shim told Live Science. At such a transition, especially at high pressures and temperatures, strange chemistry can happen. 

What's more, studies that use the reflections of earthquake waves to image the mantle have shown that materials from the crust may penetrate to the core-mantle boundary, some 1,900 miles (3,000 kilometers) below Earth's surface. At subduction zones, tectonic plates push under one another, driving oceanic crust into the subsurface. The rocks in this oceanic crust have water locked in their minerals. As a result, Shim said, it's possible that water exists in the core-mantle boundary and can drive chemical reactions down there. (One theory about the pair of mantle blobs under Africa and the Pacific is that they are made up of distorted oceanic crust that's been pushed deep into the mantle, potentially carrying water with it.)

To test the idea, the researchers pulled together the ingredients available in the core-mantle boundary and pressed them together with anvils made of diamond, generating pressures of up to 140 gigapascals. (That's about 1.4 million times the pressure at sea level.) The researchers also heated the samples to 6,830 degrees Fahrenheit (3,776 degrees Celsius). 

"We monitored what kind of reaction was happening when we heated the sample," Shim said. "Then we detected diamond, and we detected an unexpected element exchange between rock and the liquid metal." 

Churning out diamonds 

Under the pressure and temperature of the core-mantle boundary, Shim said, water behaves very differently than it does on Earth's surface. The hydrogen molecules split from the oxygen molecules. Because of the high pressure, hydrogen gravitates toward iron, which is the metal that makes up most of the core. Thus, the oxygen from water stays in the mantle, while the hydrogen melds with the core. 

When this happens, the hydrogen seems to push aside other light elements in the core, including, crucially, carbon. This carbon gets booted out of the core and into the mantle. At the high pressures present in the core-mantle boundary, carbon's most stable form is diamond. 

"That's how diamond forms," Shim said. 

These aren't the same diamonds that might sparkle in an engagement ring; most diamonds that make their way to the surface, and ultimately become someone's jewelry, form a few hundred kilometers deep, not a few thousand. But the core-mantle diamonds are likely buoyant and could get swept throughout the crust, distributing their carbon as they go. 

The mantle has three to five times more carbon than researchers would expect based on the proportion of elements in stars and other planets. The diamonds found in this layer of Earth might explain the discrepancy, Shim said. He and his team calculated that if even 10% to 20% of the water in oceanic crust makes it to the core-mantle boundary, it could churn out enough diamonds to explain the levels of carbon in the crust. 

If that's the case, many of the low-velocity zones in the mantle might be areas of water-driven melt, triggered by the churn of the oceanic plates deep into the planet. 

Proving this process happens thousands of kilometers below the surface is the next challenge. There are a couple of ways to look for evidence, Shim said. 

One is to search for structures within the core-mantle boundary that could be clusters of diamonds. Diamonds are dense and would transmit earthquake waves quickly, so researchers would need to find high-velocity zones alongside the already-discovered regions where waves travel slowly. Other researchers at Arizona State University are investigating this possibility, Shim said, but the work isn't yet published.

Another option is to study diamonds that may come from very deep in Earth's mantle. These diamonds can sometimes make it to the surface with tiny pockets, or inclusions, full of minerals that can form only under very high pressure. 

Even the famed Hope Diamond may have formed very deep in the planet's mantle. When scientists claim to have discovered very deep diamonds, those assertions are often controversial, Shim said, in part because the inclusions are so tiny that there is barely any material to measure. But it might be worth looking for core-mantle boundary inclusions, he said. 

"That would be some kind of a discovery, if someone could find evidence for that," he said.

The researchers reported their findings Aug. 11 in the journal Geophysical Research Letters.

Originally published on Live Science.

Scientists have detected a completely new type of magnetic wave that surges through Earth's outer core every seven years, warping the strength of our planet's magnetic field in the process.

The waves — dubbed "Magneto-Coriolis" waves because they move along the Earth’s axis of rotation, per the Coriolis effect — creep from East to West in tall columns that can travel up to 930 miles (1,500 kilometers) per year, the researchers wrote in a March 21 paper in the journal Proceedings of the National Academy of Sciences. Using a fleet of European Space Agency (ESA) satellites, the team pinpointed the mysterious waves to the outermost layer of Earth's liquid outer core, right where that layer meets the rocky mantle — roughly 1,800 miles (2,900 km) below the planet's surface.

According to the researchers, the existence of these waves could help explain mysterious fluctuations in the planet's magnetic field, which is generated by the movement of liquid iron in the planet's outer core. Satellite measurements of the magnetic field taken over the last 20 years show that the field's strength dips every seven years or so, coinciding with the oscillations of these newfound waves.

"Geophysicists have long theorized over the existence of such waves, but they were thought to take place over much longer time scales," lead study author Nicolas Gillet, a researcher at the Grenoble Alpes University in France, said in a statement. "Our research suggests that other such waves are likely to exist, probably with longer periods — but their discovery relies on more research."

Related: 50 interesting facts about Earth

The core of the matter

Earth's outer core is an orb of molten iron that churns and sloshes with constant motion. The flow of this rotating, electrically conducting fluid is thought to be the source of Earth's magnetic shield, which wraps around the planet and stretches for hundreds of thousands of miles into space, shielding Earth from harmful radiation.

The planet's magnetic field is always changing, both on short- and long-term time scales. Long-term, the magnetic field has been gradually weakening for hundreds of years. Recent measurements taken by ground- and satellite-based instruments also show regular variations in the magnetic field's strength and shape that occur every few years.

Scientists have long thought that these short-term variations in the field's strength are influenced by activity in the planet's outer core. This new study may provide the long-sought proof.

The study authors looked at more than 20 years of magnetic field data, collected by the ESA's Swarm satellite mission between 1999 and 2021. Swarm is a fleet of three identical satellites deployed to measure magnetic signals from the Earth's core, crust, oceans and atmosphere. The team combined this satellite data with earlier magnetic field measurements taken by ground-based sensors and then used a computer model to simulate the geodynamo, or the convective flow of fluid in the Earth's outer core.

Through these combined measurements, the team identified the presence of Magneto-Coriolis waves in the planet's core for the first time.

The source of these waves remains a mystery for now, but they likely stem from "disturbances deep within the Earth's [outer] core," Gillet said.

It's also likely that these waves aren't the only ones oscillating through the core-mantle boundary, Gillet added. While the Magneto-Coriolis waves explain some of the seven-year magnetic field fluctuations observed by Swarm and other sensors, other as-yet-undiscovered waves with even longer periodicities could account for magnetic field variations on longer timescales, Gillet said. To discover such waves, researchers will just have to keep their eyes on the core.

Originally published on Live Science.

An extremely rare type of helium that was created soon after the Big Bang is leaking out of Earth's metallic core, a new modeling study suggests. 

The vast majority of this gas in the universe, called helium-3, is primordial and was created just after the Big Bang occurred about 13.8 billion years ago. Some of this helium-3 would have joined other gas and dust particles in the solar nebula — the vast, spinning and collapsed cloud that is thought to have led to the creation of the solar system. 

The discovery that Earth's core likely contains a vast reservoir of helium-3 is further evidence to support the idea that Earth formed inside a thriving solar nebula, not on its periphery or during its waning phase, the researchers said.

Helium-3 is "a wonder of nature, and a clue for the history of the Earth, that there's still a significant amount of this isotope in the interior of the Earth," study lead author Peter Olson, a geophysicist at the University of New Mexico, said in a statement.

Related: Why do the planets in the solar system orbit on the same plane?

Helium-3 is an isotope, or variant, of helium that has one neutron instead of the usual two in its nucleus. It's a rare gas, making up just 0.0001% of helium on Earth. It comes from various processes, such as the radioactive decay of tritium, a rare radioactive isotope of hydrogen. But because helium is one of the earliest elements to exist in the universe, most helium-3 likely came from the Big Bang.

Scientists already knew that about 4.4 pounds (2 kilograms) of helium-3 escapes from Earth's interior annually, mostly along the mid-ocean ridge system where tectonic plates meet, the researchers wrote in the study, published online March 28 in the journal Geochemistry, Geophysics, Geosystems. 

This is "about enough to fill a balloon the size of your desk," Olson said.

But scientists weren't sure exactly how much of the  helium-3 came from the core versus the mantle, and how much helium-3 was in Earth's reservoirs.

To investigate, the research team modeled helium abundance during two important phases of Earth's history: the planet's early formation, when it was still accumulating helium, and after the formation of the moon, when our planet lost a lot of this gas. Scientists think that the moon formed when a colossal object about the size of Mars collided with Earth about 4 billion years ago. 

This event would have melted Earth's crust and enabled much of the helium inside our planet to escape.

However, Earth didn't lose all of its helium-3 at that time. It still retains some of the rare gas, which continues to seep out of Earth's innards. The core would be a good place for such a reservoir, "because it is less vulnerable to large impacts compared to other parts of the Earth system," the researchers wrote in the study, and it is not involved in tectonic plate cycling, which also releases helium gas.

The researchers coupled the modern helium-3 leak rate with models of helium isotope behavior. These calculations revealed that between 22 billion pounds (10 teragrams) to 2 trillion pounds (1 pentagram) of helium-3 are hanging out in Earth's core — an enormous amount, indicating that Earth formed in a solar nebula with high concentrations of the gas.

Their models of gas exchange "exchange during Earth's formation and evolution implicate the metallic core as a leaky reservoir that supplies the rest of the Earth with helium-3," the researchers wrote in the study.

However, because these results are based on modeling, the results aren't ironclad. The team had to make a number of assumptions — for example that Earth took on helium-3 as it formed in the solar nebula, that helium entered into core-forming metals and that some helium left the core for the mantle. These assumptions, in addition to other uncertainties, including how long the solar nebula lasted relative to the rate at which Earth formed, mean that there may be less helium-3 in the core than they calculated, the scientists said.

But the researchers hope to find more clues that support their findings. For instance, finding other nebula-created gases, such as hydrogen, that are leaking from Earth from similar spots and at similar rates as helium-3, could be a "smoking gun" showing that the core is the source, Olson said. "There are many more mysteries than certainties."

Originally published on Live Science.

Deep within Earth's mantle, there are two giant blobs. One sits under Africa, while the other is almost precisely opposite the first, under the Pacific Ocean. But these two blobs are not evenly matched. 

New research finds that the blob under Africa extends far closer to the surface — and is more unstable — than the blob under the Pacific. This difference could ultimately help to explain why the crust under Africa has been lifted upward and why the continent has seen so many large supervolcano eruptions over hundreds of millions of years. 

"This instability can have a lot of implications for the surface tectonics, and also earthquakes and supervolcanic eruptions," said Qian Yuan, a graduate associate in geology at Arizona State University (ASU) who led the research.  

A pair of blobs

The mantle blobs are properly known as "large low-shear-wave-velocity provinces," or LLSVPs. This means that when seismic waves generated by earthquakes travel through these deep-mantle zones, the waves slow down. This deceleration indicates that there's something different about the mantle at this spot, such as density or temperature — or both. 

Scientists aren't sure why the mantle blobs exist. There are two popular hypotheses, Yuan told Live Science. One is that they're made up of accumulations of crust that have subducted from Earth's surface to deep inside the mantle. Another is that they're the remnants of an ocean of magma that may have existed in the lower mantle during Earth's early history. As this magma ocean cooled and crystallized, it may have left behind areas that were denser than the rest of the mantle. 

Prior studies had hinted that these two blobs may not have been created equal, Yuan said, but none of this research had used global data sets that could easily compare the two. He and his adviser, ASU geodynamics assistant professor Mingming Li, examined 17 global seismic-wave data sets to determine the height of each blob. 

They found that the African blob extends about 620 miles (1,000 kilometers) higher than the Pacific blob. That's a difference of roughly 113 Mount Everests. In total, the Pacific blob extends 435 to 500 miles (700 to 800 km) upward from the boundary between the core and the mantle. The African blob extends upward about 990 to 1,100 miles (1,600 to 1,800 km).  

Blobular instability 

The researchers then used computer modeling to figure out which features of the blobs could explain these differences. The most important ones, they found, were the density of the blobs themselves and the viscosity of the surrounding mantle. Viscosity refers to the ease with which the mantle rocks can be deformed. 

For the African blob to be so much taller than the Pacific blob, it must be far less dense, according to Yuan. "Because it's less dense, it's unstable," he said. 

The African blob is still far from Earth's crust — the mantle is 1,800 miles (2,900 km) thick in total — but this deep structure's instability may have implications for the planet's surface. LLSVPs may be a source of hot plumes of mantle material that rise upward. These plumes, in turn, might cause supervolcano eruptions, tectonic upheaval and possibly even continental breakup, Yuan said. 

The African blob "is very close to the surface, so there is a possibility that a large mantle plume may rise from the African blob and may lead to more surface rising and earthquakes and supervolcano eruptions," Yuan said.

These processes occur over many millions of years and have been ongoing in Africa. There does seem to be a connection between the African blob and major eruptions, Yuan said. A 2010 paper published in the journal Nature found that in the past 320 million years, 80% of kimberlites, or huge eruptions of mantle rock that bring diamonds to the surface, have occurred right over the boundary of the African blob.  

Yuan and Li published their findings March 10 in the journal Nature Geoscience. They are now working on research into the origins of the blobs. Though those findings have not yet been published in a peer-reviewed journal, the researchers presented the results at the 52nd Lunar and Planetary Science Conference in March 2021; that research suggested that the blobs might be remnants of the planet-size object that slammed into Earth some 4.5 billion years ago, forming the moon. 

Originally published on Live Science. 

A group of mysterious, ultradense structures just outside Earth's core may be the remnants of an ancient interplanetary collision, new research suggests.

These strange structures are known as ultralow-velocity zones (ULVZs), because seismic waves generated by earthquakes travel about 50% more slowly through these zones than through the surrounding mantle. That means the ULVZs are also much denser than the rest of the mantle, and possibly made of heavier elements. 

It's hard to say anything for certain about these dense blobs of rock, because the ULVZs sit nearly 1,800 miles (2,900 kilometers) below Earth's surface — one group clustered deep below Africa, and another below the Pacific Ocean, where the rocky mantle and liquid-metal outer core meet. That's far too deep for human eyes to see; only seismic data can offer clues about the size, shape and structure of the ULVZs.

Now, using a new computer model and fresh seismic observations from deep below Australia and New Zealand, researchers may have added an important piece to the ULVZ puzzle. According to a study published Dec. 30, 2021,  in the journal Nature Geoscience, these zones aren't uniform structures but rather seem to be made of layers of different materials that accumulated over the eons.

"The most surprising finding is that the ultra-low velocity zones are not homogenous but contain strong structural and compositional variations within them," lead study author Surya Pachhai, a postdoctoral scholar at the Australian National University, said in a statement. "This type of ULVZ can be explained by chemical [variations] created at the very beginning of the Earth's history, which are still not well mixed after 4.5 billion years of mantle convection."

(Mantle convection is the process by which the solid rocks in the planet’s mantle slowly move in accordance with heat currents.)

After their computer simulations showed that a layered or mixed structure was likely within the ULVZs, the researchers suggested a possible origin story for the structures — a story that starts more than 4 billion years ago, around the time early Earth's rocky crust first formed. Beneath the surface, heavier elements, like iron, were sinking toward the planet's core, while lighter elements, like silicon, rose toward the mantle.

This organization all went haywire when a Mars-size planet known as Theia slammed directly into the early Earth — an ancient cataclysm that researchers call the giant impact hypothesis. The collision may have scattered enormous amounts of debris into Earth's orbit — possibly leading to the formation of the moon — while also raising the entire planet's temperature and creating a large "ocean" of magma on the planet's surface, Pachhai said.

Various rocks, gases and crystals forged during the collision would have been scattered through this magma ocean, the researchers said — but not forever. Over the following billions of years, heavier materials would have sunk toward the bottom of the mantle, followed by lighter ones — eventually creating a densely layered structure of iron and other elements at the core-mantle boundary. As the mantle churned over the ages, this dense layer would have separated into smaller clumps spread across the lower mantle — effectively giving us the ULVZs we know of today.

This scenario may not explain the source of all ULVZs, the researchers added, as there is also some evidence that other phenomena — such as melting ocean crust sinking into the mantle — could explain ULVZs. However, the team's models show that the giant impact hypothesis reliably explains how the dense, layered zones could have been created.

Originally published on Live Science.

A geological secret passage beneath Panama may explain why rocks from Earth's mantle are found more than 1,000 miles (1,609 kilometers) from where they originated. 

This opening, located some 62 miles (100 km) below Earth's surface, may allow a flow of mantle materials to travel all the way from beneath the Galápagos Islands to beneath Panama. 

This never-before-discovered form of transport may also help explain why Panama has very few active volcanoes. On the west coast of Central America, the Cocos tectonic plate is diving down and pushes oceanic crust under the continental crust of the North American, Caribbean and Panama tectonic plates, a process called subduction. This subduction zone creates a line of volcanoes called the Central American Volcanic Arc where lava pushes through the boundaries. But the volcanism stops in western Panama, which sits on the Panama plate , said David Bekaert, a postdoctoral scholar in marine chemistry and geochemistry at Woods Hole Oceanographic Institution in Massachusetts.

This relative peace has long been a mystery. Now, Bekaert and his colleagues report in a new study published Nov. 23 in the journal Proceedings of the National Academy of Sciences that the culprit may be a window-like opening in the Cocos tectonic plate that's being pushed down toward Earth's center.  

Tracking anomalies 

Bekaert and his colleagues are trying to understand more about how subduction works near Central America. The subduction of the Cocos plate under North America has the capacity to cause large earthquakes, including the 2017 Chiapas quake, a magnitude-8.1 temblor that killed dozens.

To learn more, the researchers delved into the geochemistry of the region, collecting volcanic rock samples as well as gas and fluid samples from hot springs. They were interested in looking at ratios of molecular isotopes, which are variations of the same atoms with different numbers of neutrons in their nuclei. In this case, the researchers were particularly focused on isotopes of helium and lead. 

"Different sources of geological material typically have different compositions, so we can track the contribution from different regions of the mantle," Bekaert told Live Science. 

The mantle is mostly made up of silicate rocks, which are rocks with a particular structure of silicon and oxygen atoms. But the precise composition can vary a lot over even small distances. The researchers found that there were some strange anomalies under Central America. 

"We found that in particular places of Central America, namely western Panama and behind the volcanic arc in Costa Rica, we have some exotic signatures [of geochemistry] that really resemble what you have in the Galápagos Islands," Bekaert said. 

Blowing in the (mantle) wind 

This was strange, because there was no clear way to explain how mantle elements from the Galápagos could get all the way to Panama, Bekaert said. The researchers then turned to seismic imaging of the mantle, which uses earthquake waves to map what's beneath the surface, and computer modeling to try to explain what might be going on.

They found that deep beneath Panama, the buried portions of the Cocos plate may hold the answer. When a tectonic plate slides under another tectonic plate during subduction, that subducting plate doesn't just disappear; it retains its structure as it grinds down into the mantle, only gradually heating and warping. 

"Just beneath Panama, there is a hole, a window through the slab, that allows for the influx of this mantle component," Bekaert said. 

This window may be the result of a natural, pre-existing fracture in the subducting Cocos crust, or it may be a place where the crust snapped during subduction. Either way, it lets materials pass through — from one side of the plate to the other — like a breeze through an open window.

That left the question of what might be driving the breeze. The researchers found two possibilities. The first is that the materials are moving through the Panama Fracture Zone, a zone of cracking in the crust and upper mantle that connects the Galápagos to Panama . But it's difficult to see what would drive long-distance transport through that zone, Bekaert said. It's not clear whether such transport is even possible. 

A more likely scenario, the researchers found, is that the typical, large-scale circulation of the mantle simply drives materials through the opening in the subducting slab.

"When we have done the modeling of the mantle circulation in this place, you expect this deep global mantle flow," Bekaert said. 

The existence of the mantle window can also explain the lack of active volcanoes in Panama, Bekaert said. Water locked into the crust of subducting slabs tends to promote the formation of volcanoes because water lowers the melting point of rocks, leading to the formation of magma. The opening in the slab under Panama means there is a gap in the water-rich crust in that spot, which in turn means it's harder to get melty magma flowing there. 

The mantle flow the team discovered is under-studied, Bekaert said, but there are unexplained anomalies in the chemistry of the mantle all over the world. The team hopes to conduct a similar analysis in Chile next, but ultimately wants to expand the method around the globe. 

"No one's been thinking about this process before," Bekaert said, "so I just want to consider all the data." 

Originally published on Live Science

Scientists have detected the deepest earthquake ever, a staggering 467 miles (751 kilometers) below the Earth's surface.

That depth puts the quake in the lower mantle, where seismologists expected earthquakes to be impossible. That's because under extreme pressures, rocks are more likely to bend and deform than they are to break with a sudden release of energy. But minerals don't always behave precisely as expected, said Pamela Burnley, a professor of geomaterials at the University of Nevada, Las Vegas, who was not involved in the research. Even at pressures where they should transform into different, less quake-prone states, they may linger in old configurations.

"Just because they ought to change doesn't mean they will," Burnley told Live Science. What the earthquake may reveal, then, is that the boundaries within Earth are fuzzier than they're often given credit for.

Crossing the boundary  

The quake, first reported in June in the journal Geophysical Research Letters, was a minor aftershock to a 7.9-magnitude quake that shook the Bonin Islands off mainland Japan in 2015. Researchers led by University of Arizona seismologist Eric Kiser detected the quake using Japan's Hi-net array of seismic stations. The array is the most powerful system for detecting earthquakes in current use, said John Vidale, a seismologist at the University of Southern California who was not involved in the study. The quake was small and couldn't be felt at the surface, so sensitive instruments were needed to find it. 

The depth of the earthquake still needs to be confirmed by other researchers, Vidale told Live Science, but the finding looks reliable. "They did a good job, so I tend to think it's probably right," Vidale said.

This makes the quake something of a head-scratcher. The vast majority of earthquakes are shallow, originating within the Earth's crust and upper mantle within the first 62 miles (100 km) under the surface. In the crust, which extends down only about 12 miles (20 km) on average, the rocks are cold and brittle. When these rocks undergo stress, Burnley said, they can only bend a little before breaking, releasing energy like a coiled spring. Deeper in the crust and lower mantle, the rocks are hotter and under higher pressures, which makes them less prone to break. But at this depth, earthquakes can happen when high pressures push on fluid-filled pores in the rocks, forcing the fluids out. Under these conditions, rocks are also prone to brittle breakage, Burnley said.

These kinds of dynamics can explain quakes as far down as 249 miles (400 km), which is still in the upper mantle. But even before the 2015 Bonin aftershock, quakes have been observed in the lower mantle, down to about 420 miles (670 km). Those quakes have long been mysterious, Burnley said. The pores in the rocks that hold water have been squeezed shut, so fluids are no longer a trigger.

"At that depth, we think all of the water should be driven off, and we're definitely far, far away from where we would see classic brittle behavior," she said. "This has always been a dilemma."

Changing minerals 

The problem with earthquakes deeper than around 249 miles has to do with the ways the minerals behave under pressure. Much of the planet's mantle is made up of a mineral called olivine, which is shiny and green. Around 249 miles down, the pressures caused olivine's atoms to rearrange into a different structure, a blue-ish mineral called wadsleyite. Another 62 miles (100 km) deeper, wadsleyite rearranges again into ringwoodite. Finally, around 423 miles (680 km) deep into the mantle, ringwoodite breaks down into two minerals, bridgmanite and periclase. Geoscientists can't probe that far into the Earth directly, of course, but they can use lab equipment to recreate extreme pressures and create these changes at the surface. And because seismic waves move differently through different mineral phases, geophysicists can see signs of these changes by looking at vibrations caused by large earthquakes. 

That last transition marks the end of the upper mantle and the beginning of the lower mantle. What's important about these mineral phases is not their names, but that each behaves differently. It's similar to graphite and diamonds, said Burnley. Both are made of carbon, but in different arrangements. Graphite is the form that's stable at Earth's surface, while diamonds are the form that's stable deep in the mantle. And both behave very differently: Graphite is soft, gray and slippery, while diamonds are extremely hard and clear. As olivine transforms into its higher-pressure phrases, it becomes more likely to bend and less likely to break in a way that triggers earthquakes. 

Geologists were puzzled by earthquakes in the upper mantle until the 1980s, and still don't all agree on why they occur there. Burnley and her doctoral advisor, mineralogist Harry Green, were the ones to come up with a potential explanation. In experiments in the 1980s, the pair found that olivine mineral phases were not so neat and clean. In some conditions, for example, olivine can skip the wadsleyite phase and head straight to ringwoodite. And right at the transition from olivine to ringwoodite, under enough pressure, the mineral could actually break instead of bending.

"If there was no transformation happening in my sample, it wouldn't break," Burnley said. "But the minute I had transformation happening and I was squishing it at the same time, it would break."

Burnley and Green reported their finding in 1989 in the journal Nature, suggesting that this pressure in the transition zone could explain earthquakes below 249 miles. 

Going deeper 

The new Bonin earthquake is deeper than this transition zone, however. At 467 miles down, it originated in a spot that should be squarely in the lower mantle.

One possibility is that the boundary between the upper and lower mantle is just not exactly where seismologists expect it to be in the Bonin region, said Heidi Houston, a geophysicist at the University of Southern California who was not involved in the work. The area off the Bonin island is a subduction zone where a slab of oceanic crust is diving beneath a slab of continental crust. This sort of thing tends to have a warping effect.

"It's a complicated place, we don't know exactly where this boundary between the upper and lower mantle is," Houston told Live Science.

The paper's authors argue that the subducting slab of crust may have essentially settled onto the lower mantle firmly enough to put the rocks there under a tremendous amount of stress, generating enough heat and pressure to cause a very unusual break. Burnley, however, suspects the most likely explanation has to do with minerals behaving badly — or at least oddly. The continental crust that plunges toward the center of the Earth is much cooler than the surrounding materials, she said, and that means that the minerals in the area might not be warm enough to complete the phase changes they are supposed to at a given pressure.

Again, diamonds and graphite are a good example, Burnley said. Diamonds aren't stable at Earth's surface, meaning they wouldn’t form spontaneously, but they don't degrade into graphite when you stick them into engagement rings. That's because there's a certain amount of energy the carbon atoms need to rearrange, and at Earth's surface temperatures, that energy isn't available. (Unless someone zaps the diamond with an X-ray laser.)  

Something similar may happen at depth with olivine, Burnley said. The mineral might be under enough pressure to transform into a non-brittle phase, but if it's too cold — say, because of a giant slab of chilly continental crust all around it — it might stay olivine. This could explain why an earthquake could originate in the lower crust: It's just not as hot down there as scientists expect it to be.

"My general thinking is that if the material is cold enough to build up enough stress to release it suddenly in an earthquake, it's also cold enough for the olivine to have been stuck in its olivine structure," Burnley said.

Whatever the cause of the quake, it's not likely to be repeated often, Houston said. Only about half of subduction zones around the world even experience deep earthquakes, and the kind of large quake that preceded this ultra-deep one only occurs every two to five years, on average.

"This is a pretty darn rare occurrence," she said. 

Originally published on Live Science.

There's a mystery brewing at the center of the Earth.

Scientists can only see it when they study the seismic waves (subterranean tremors generated by earthquakes) passing through the planet's solid iron inner core. For some reason, waves move through the core significantly faster when they're traveling between the north and south poles than when they're traveling across the equator.

Researchers have known about this discrepancy — known as seismic anisotropy — for decades, but have been unable to come up with an explanation that's consistent with the available data. Now, using computer simulations of the core's growth over the last billion years, a new study in the June 3 issue of Nature Geoscience offers a solution that finally seems to fit: Every year, little by little, Earth's inner core is growing in a "lopsided" pattern, with new iron crystals forming faster on the east side of the core than on the west side.

Related: 10 ways Earth revealed its weirdness

"The movement of liquid iron in the outer core carries heat away from the inner core, causing it to freeze," lead study author Daniel Frost, a seismologist at the University of California, Berkeley, told Live Science. "So this means the outer core has been taking more heat from the east side [under Indonesia] than the west [under Brazil]."

To visualize this lopsided growth in the core, imagine a tree trunk with growth rings radiating out from a central point, Frost said — but "the center of the rings is offset from the center of the tree," so that rings are spaced further apart on the east side of the tree and closer together on the west side.

A cross section of Earth's inner core might look similar to that. However, this asymmetric growth doesn't mean that the inner core itself is misshapen or at risk of becoming imbalanced, the researchers said.

On average, the inner core's radius grows evenly by about 0.04 inches (1 millimeter) every year. Gravity corrects for the lopsided growth in the east by pushing new crystals toward the west. There, the crystals clump into lattice structures that stretch along the core's north-south axis. These crystal structures, aligned parallel with Earth's poles, are seismic superhighways that enable earthquake waves to travel more quickly in that direction, according to the team's models.

Unpacking the snowball

What's causing this imbalance in the inner core, anyway? That's hard to say without looking at all the other layers of our planet, Frost said.

"Every layer in the Earth is controlled by what's above it, and influences what's below it," he said. "The inner core is slowly freezing out of the liquid outer core, like a snowball adding more layers. The outer core is then cooled by the mantle above it — so to ask the question of why the inner core is growing faster on one side than the other might be asking the question of why is one side of the mantle cooler than the other?"

Tectonic plates could be partially to blame, Frost said. As cold tectonic plates dive deep below the Earth's surface at subduction zones (places where one plate sinks below another), they cool the mantle below. However, whether mantle cooling could impact the inner core is still a subject of debate, Frost said.

Equally puzzling is whether or not the lopsided cooling in the core could be affecting Earth's magnetic field. The modern-day magnetic field is powered by the movement of liquid iron in the outer core; this liquid's movement is powered in turn by heat lost from the inner core. If the inner core is losing more heat in the east than the west, then the outer core will move more in the east too, Frost said.

"The question is, does this change the strength of the magnetic field?" he added.

Questions this big are beyond the scope of the team's new paper, but Frost said he has begun work on new research with a team of geomagnetists to investigate some possibilities.

Originally published on Live Science.

For the past 4.5 billion years, energized particles from the primordial sun have lurked in Earth's core, a new study suggests.

Researchers made the discovery by analyzing ancient particles within an iron meteorite, which came from a space rock that had an iron core, just like Earth does now, making the meteorite a good proxy for our planet's innards. The meteorite had "striking excesses of solar helium and neon," which are noble gases, or gases that are colorless, odorless, tasteless and nonflammable and occupy group 18 on the periodic table, the researchers wrote in the study.

Past research has tied the exposure of solar wind — the stream of plasma and charged particles that flows from the sun — to an elevation in helium and neon and the ratios in which they appear. So, it's likely that when the solar system's planets were still forming, the solar wind irradiated this meteorite with noble gas particles, which then became embedded in the meteorite's metals, the researchers said. Likewise, "Earth's core may have incorporated solar noble gases," the researchers wrote in the study. 

Over millions of years, these noble gases likely spread from the core and into Earth's mantle, the layer between the core and the upper crust, the team also discovered.

Related: Meteorites: Rocks that survived fiery plunge to Earth 

The meteorite, which was discovered in 1927 in Washington County, Colorado, falls into a rare class of "ungrouped" iron meteorites that make up just 5% of known meteorites discovered on Earth. Most of these meteorites are mere fragments of larger asteroids, which formed metallic cores during the solar system's first 1 million to 2 million years.

The Washington County iron meteorite, however, is larger than most meteorites in its class. Originally, it looked like a metal discus that was about 5.9 inches by 7.8 inches (15 by 20 centimeters) in diameter and 2.3 inches (6 cm) thick and weighed about 12.5 lbs. (5.7 kilograms), according to a 1928 report in the journal American Mineralogist. 

In the 1960s, research found that the Washington County meteorite contained "a remarkable excess" of unusual helium and neon isotopes, variations of elements that have a different number of neutrons in their nuclei. In 1984, another study showed that these isotopes had ratios similar to those seen in solar wind.

For the new study, the researchers studied just a few of the Washington County meteorite chunks, including one 1.1-inch-long (3 cm) slab. The team used a noble gas mass spectrometer to measure the ratio of noble gas isotopes. The helium and neon isotopic ratios were typical for those from the solar wind, the researchers confirmed.

Figuring out which of the noble gases in the meteorite came from the solar wind versus other sources, however, is a tricky business. For instance, noble gases can originate from other places in the cosmos.

"The measurements had to be extraordinarily accurate and precise to differentiate the solar signatures from the dominant cosmogenic noble gases," study first author Manfred Vogt, a postdoctoral researcher at the Institute of Earth Sciences at Heidelberg University in Germany, said in a statement.

It's likely that the solar-wind particles in the early solar system became trapped in the precursor materials that eventually became the asteroid, the team said. Then, these noble gases likely dissolved in the liquid metal, which later became the asteroid's solid metal core.

Earth's iron core probably went through a similar process when it was forming, the researchers said. To investigate this idea further, the team consulted their record of solar-wind helium and neon isotopes found in igneous rock from volcanic eruptions on oceanic islands, such as Hawaii in the Pacific and Réunion in the Indian Ocean.

Related: Hidden seafloor feature uncovered with satellites (photos)

The rocks they studied came from a special kind of volcano that is powered by plumes deep within Earth's mantle. These plumes have high solar gas ratios, which makes them different from shallow mantle volcanic activity seen at midocean mountain ridges, which have low solar gas ratios, the researchers said.

Now, the researchers have multiple threads of evidence indicating that Earth has solar noble gases in its core and mantle. In effect, the iron-cored Washington County meteorite has solar noble gases, so it's likely that Earth's iron core does too. And solar noble gases are found in volcanic rock that originated deep in the mantle, suggesting that some of the solar particles hanging out in Earth's core have since migrated to the mantle, the researchers found.

If Earth's core had "just 1% to 2% of a metal with a similar composition as the Washington Country meteorite," that could "explain the different gas signatures in the mantle," Vogt said. This finding suggests that the core influences the mantle's geochemistry in a previously unknown way, the researchers said. 

The study was published online May 14 in the journal Communications Earth & Environment.

Originally published on Live Science.

Deep within Earth, where the solid mantle meets the molten outer core, strange continent-size blobs of hot rock jut out for hundreds of miles in every direction. These underground mountains go by many names: "thermo-chemical piles," "large low-shear velocity provinces" (LLSVPs), or sometimes just "the blobs."

Geologists don't know much about where these blobs came from or what they are, but they do know that they're gargantuan. The two biggest blobs, which sit deep below the Pacific Ocean and Africa, account for nearly 10% of the entire mantle's mass, one 2016 study found — and, if they sat on Earth's surface, the duo would each extend about 100 times higher than Mount Everest. However, new research suggests, even those lofty analogies may be underestimating just how big the blobs really are.

In a study published June 12 in the journal Science, researchers analyzed the seismic waves generated by earthquakes over nearly 30 years. They found several massive, never before-detected features along the edges of the Pacific blob. 

"The structures we located are … thousands of kilometers across in scale," lead study author Doyeon Kim, a postdoctoral fellow at the University of Maryland, told Live Science in an email. According to Kim, that's an order of magnitude larger than typical features found along the blob's edge.

Related: The 9 best blobs of 2019

A map of trembling Earth

Because the blobs live deep, deep in Earth's interior, geologists can only begin to understand their shape and size by looking at the seismic waves (sound waves generated by earthquakes) that travel through them. These hot, dense regions can slow incoming waves by up to 30% relative to the surrounding mantle; the hottest, slowest regions are known as ultralow-velocity zones (ULVZs), and they typically occur near the edges of the blobs, Kim said.

In their study, Kim and his colleagues created a new map of ULVZs below the Pacific Ocean using an algorithm called "the Sequencer," which was originally developed to find patterns in stellar radiation. With this algorithm, the team analyzed 7,000 seismograms, or measures of seismic waves, collected between 1990 and 2018, created by hundreds of earthquakes of magnitude 6.5 or greater. The earthquakes occurred in Asia and Oceania, the researchers wrote; but as their seismic waves shuddered across the globe, they passed clearly through the Pacific Ocean mantle blob before reaching seismometers in the United States.

The algorithm revealed enormous sections of ULVZs never detected before, including a blobby region below the Marquesas Islands in the South Pacific Ocean, which measured more than 620 miles (1,000 kilometers) across. The Sequencer also showed that a segment of the blob deep below the Hawaiian Islands is considerably larger than previously thought.

"By looking at thousands of core-mantle boundary [seismograms] at once, instead of focusing on a few at a time, we have gotten a totally new perspective," Kim said in a statement.

The enormous size of these structures suggests that blobs along the core-mantle boundary — and particularly the hottest, densest ULVZs — are probably more widespread than previous research indicates. What's more, Kim added, the fact that these large zones lurk near known volcanic hotspots could also reveal some clues about their impact on Earth's geology. 

It's possible, for example, that ULVZs deep down in the mantle could feed into the large "plumes" of hot rock in the upper mantle that create volcanic hot spots on the surface, Kim said. Those mantle plumes might "suck on" the melty material collected in ULVZs and pull it upward, which could explain why the largest ULVZs are located deep under volcanic island chains like the Hawaiian and Marquesas islands. 

That's just one theory, Kim said; even with algorithms designed to pierce the void of space, the mysteries near the center of the Earth remain just as murky as ever. 

"In short, everything is unsure at the moment," Kim said, "but this is what makes our field of study so exciting."

• The 11 biggest volcanic eruptions in history
• The world's weirdest geological formations
• 7 ways Earth changes in the blink of an eye

Originally published on Live Science.

About 120 million years ago, a gargantuan blob of hot rock detached from the edge of Earth's core and oozed up toward the planet's surface. Today, a huge chunk of that blob — or "superplume," as geologists call it — may be lurking off the coast of New Zealand, new research suggests.

In a study published May 27 in the journal Science Advances, researchers measured the speed of seismic waves traveling through a layer of Earth called the mantle that sits between the planet's crust and outer core. They focused on Hikurangi Plateau — a vast, triangle-shaped chunk of volcanic rock located about 2,000 miles (3,200 kilometers) beneath the top of the South Pacific Ocean, just off the coast of New Zealand's North Island. The team found a match between the seismic waves traveling through that chunk and those traveling through two other nearby volcanic structures. 

According to the study authors, it's likely that all three of these underwater structures were once part of the same gargantuan mega-plateau, formed more than 100 million years ago during the largest outpouring of volcanic material in Earth's history.

"The associated volcanic activity may have played an important role in Earth history, influencing the planet's climate and also the evolution of life by triggering mass extinctions," study co-author Simon Lamb, an associate professor at Victoria University of Wellington in New Zealand, said in a statement. "It is an intriguing thought that New Zealand now sits on top of what was once such a powerful force in the Earth."

A lava blob legacy

According to Stern, mantle plumes form when huge "lava lamp blobs" of hot, buoyant rock break away from the boundary where Earth's mantle meets the outer core, then rise thousands of miles up toward the surface. While most of these blobs get caught in the mantle, smaller chunks continue to rise upward, gradually melting as pressure decreases and finally erupting at the surface through volcanoes. 

Geologists suspect that mantle plumes are responsible for some of the largest volcanic hotspots on Earth, including the Hawaiian-Emperor seamount chain, the long conga line of dead and active volcanoes stretching from the Hawaiian Islands to the Pacific coast of Russia. (The chain is also home to the single largest volcano on Earth.) 

But the mantle plume that welled up under the South Pacific 120 million years ago may be the world's largest, the researchers wrote, if the fragmented plateaus it left behind are any indication. The Hikurangi Plateau near New Zealand, for example, covers an area of approximately 150,000 square miles (400,000 square kilometers), making the submerged structure nearly twice as large as the New Zealand mainland. If it was once part of an even larger mega-plateau along with the Ontong-Java and Manihiki Plateaus, the researchers reasoned, the three structures must share similar rock properties, both above and below the seafloor.

To test that theory, the team measured the speed of seismic waves traveling under Hikurangi. Using data obtained from earthquakes and controlled undersea explosions, the team found that seismic waves traveled horizontally through the rocks at nearly 6 miles per second (9 km/s), roughly a mile per second faster than the average global speed at which seismic waves travel through the mantle.

Strangely, though, seismic waves moved much more slowly when traveling vertically upwards beneath the plateau. These speed characteristics are indicative of an ancient mantle superplume that has begun to collapse, the researchers wrote — and that strange relationship between vertical and horizontal wave speeds perfectly matched the wave speeds below the Ontong-Java and Manihiki Plateaus.

Related: In Photos: Ocean Hidden Beneath Earth's Surface

According to the researchers, these findings suggest that the three big, volcanic plateaus in the South Pacific are indeed broken pieces of one enormous whole, laid down by the single largest superplume ever detected on Earth. In its original form, that ancient mega-plateau — known as the Ontong-Java-Manihiki-Hikurangi Plateau — would have covered about 1% of the planet's surface, with an area about half as large as the continental United States, the study found.

"Subsequently, the motion of the tectonic plates broke up this plateau, and one fragment — today forming the Hikurangi Plateau — drifted away to the south," lead study author Tim Stern, a geophysicist at Victoria University of Wellington, said in the statement.

Hopefully, Stern added, the strange seismic wave speed signature linking these three plateaus could be used as a "fingerprint" to identify other scattered fragments of the once-giant superplume.

• The 9 best blobs of 2019
• In photos: Ocean hidden beneath Earth's surface
• Wow! Wild Volcanoes in Pictures

Originally published on Live Science.

A blob of magma entombed in a bubble smaller than the width of a human hair and found in South Africa may turn back the clock on Earth's first slow dance of the rocky slabs that make up its outer shell.

The chemicals inside that little blob suggest so-called plate tectonics revved up during the first billion years of Earth's existence.

Since the 1950s, scientists have known Earth's crust is made of giant slabs called tectonic plates that float above Earth's molten mantle. These colossal plates meet in subduction zones, where the lighter slab slides under the heavier one into the depths of the mantle. The sinking crust, infused with minerals collected from Earth's surface, melts into magma under the extreme pressures and temperatures of Earth's interior. [In Photos: Ocean Hidden Beneath Earth's Surface]

When exactly this planetary recycling began has been hotly debated. Estimates range from 1 billion to 4 billion years ago. Now, an international team of scientists has discovered that the subduction of Earth's crust likely began more than 3.5 billion years ago. Their results were published July 15 in the journal Nature.

"Plate tectonics may be the main process on Earth that makes it different from other planets in our solar system and that may be quite significant for the study of life on Earth," said Alexander Sobolev, lead author of the paper and a geochemist at Université Grenoble Alpes in France.

The microscopic bead of cooled magma at the root of their discovery laid dormant for more than 3.3 billion years, protected by its olivine crystal tomb and unaltered by its surrounding environment. It was a time capsule from one of the earliest eons in Earth's history.

The olivine crystal, no bigger than a grain of sand, was found in a komatiite rock, named after the Komati River in South Africa where such rocks were discovered. They formed when extraordinarily hot plumes of magma rose from the mantle to Earth's surface (once magma reaches Earth's surface, it's called lava) during the Archaean period (2.5 billion to 4 billion years ago). These rare rocks are exceptionally precious to geologists because they give a glimpse into the early conditions of Earth's mantle.

To study the tiny magma inclusion, Sobolev and his team remelted the ovaline crystals by heating them to more than 2,700 degrees Fahrenheit (1,500 degrees Celsius) and rapidly cooling them in ice water to form a glassy sample. They then used state-of-the-art instruments to measure the chemical makeup of the glassy magma and determine its origin.

The researchers discovered the magma contained a number of signatures of subducted oceanic crust, including high concentrations of water and chlorine, and low levels of deuterium (a heavy version of hydrogen). They concluded the magma originated in the melted remains of an ancient ocean seafloor.

"If that is the case, it means a lot," Sobolev said. "It means that seawater-altered crust from the surface went down into the mantle nearly 3.3 billion years ago. Because all these processes are slow, you can expect that from the point from when this source went down to the point where it reached the surface again, it took at least 100 to 200 million years. That means this process started within the first billion years of Earth's history."

• 50 Interesting Facts About Earth
• 7 Ways the Earth Changes in the Blink of an Eye
• 25 Strangest Sights on Google Earth

Originally published on Live Science.

Earth's magnetic shield defends our planet from the scourges of solar wind and cosmic radiation, making life on our planet possible. But every 10 years or so, it can be a real jerk.

"Geomagnetic jerks" are abrupt changes in the strength of Earth's magnetic field. While some variations in this field are expected to occur gradually, over hundreds to thousands of years, these sudden wobbles in intensity last only a few years at most, and may only alter the Earth's magnetism over specific parts of the world at a time. One of the first jerks documented, for example, briefly warped the field over Western Europe in 1969.

Since then, a new jerk has been detected somewhere in the world every 10 years or so, and scientists still don’t know what's causing them. While many geomagnetic phenomena, including the northern and southern lights, result from electrified solar wind bashing into Earth's magnetosphere, the jerks are thought to originate from deep inside our planet's core, where the magnetic field itself is generated by the constant churn of liquid-hot iron. The exact mechanism of action, however, remains a mystery. [The 8 Biggest Mysteries About Planet Earth]

Now, a new study published today (April 22) in the journal Nature Geoscience offers a potential explanation. According to a new computer model of the core's physical behavior, geomagnetic jerks may be generated by buoyant blobs of molten matter released from deep inside the core.

Who's the jerk?

In the new study, the researchers built a computer model that painstakingly recreates the physical conditions of Earth's outer core, and shows its evolution over several decades. After the equivalent of 4 million hours of calculations (sped up thanks to a French supercomputer), the core simulation was able to generate geomagnetic jerks that closely aligned with actual jerks observed over the last few decades.

These simulated jerks jiggled the magnetosphere every 6 to 12 years in the model — however, the events seemed to originate from buoyant anomalies that formed in the planet's core 25 years earlier. As those blobs of molten matter approached the outer surface of the core, they generated powerful waves that rushed along magnetic field lines near the core and created "sharp changes" in the flow of liquid that governs the planet's magnetosphere, the authors wrote. Eventually, these sudden changes translate into jerky disturbances in the magnetic field high above the planet.

"[Jerks] represent a major obstacle to the prediction of geomagnetic field behavior for years to decades ahead," the authors wrote in their new study. "The ability to numerically reproduce jerks offers a new way to probe the physical properties of Earth’s deep interior."

While it's impossible to confirm this simulation's results with actual observations of the core (it's too hot and high-pressured to get anywhere near our planet's center), having a model that can recreate historical jerks with high accuracy could be helpful in predicting the many jerks yet to come, the researchers wrote.

Knowing when the jerks are coming could also help monitor how they affect other geodynamic processes. For example, is it possible, as one 2013 study in Nature suggested, that the jerks are harbingers of longer days. According to that study, sudden changes in the fluid flow at Earth's core may also alter the planet's spin by the slightest bit, actually adding an extra millisecond to the day every 6 years or so. Periods where Earth's day lengthened seemed to correlate with several established instances of well-known jerks, the researchers reported.

If that's true, and geomagnetic jerks are responsible for a slightly longer workday every few years, at least we know we've given them the right name.

• Infographic: Earth's Atmosphere Top to Bottom
• Amazing Caves: Picture of Earth's Innards
• Images: Diving to Earth's Deepest Spot

Originally published on Live Science.

The Earth's mantle acts like a giant churn, circulating cool oceanic crust downward toward the core, where it heats up into a goopy solid and then rises again — a process that powers everything from plate tectonics to volcanism.

But there are some hitches in this system, and new research reveals why: A slippery layer about 416 miles (670 kilometers) deep stops chunks of crust in their tracks, creating "stagnant slabs" in the middle of the mantle, the layer between the Earth's crust and its core. [In Photos: Ocean Hidden Beneath Earth's Surface]

"This deflection of slabs was always puzzling to our understanding of [the mantle]," said Shijie Zhong, a physicist at the University of Colorado Boulder and the co-author of the new study published Oct. 1 in the journal Nature Geoscience.

Stalled out

There is no way to look directly at the mantle, but scientists study its dynamics using seismic waves from earthquakes. By detecting the waves as they propagate through the globe, researchers can construct a picture of the mantle, not unlike how radar can image objects using radio waves.

What happens in the mantle is related to what's going on in the crust. The crust is made up of tectonic plates that ride across the mantle like rafts on a very, very thick sea (the consistency of the crust is similar to that of hot asphalt). In some areas, called subduction zones, one tectonic plate dives under another, grinding chunks of oceanic crust down into the mantle. From seismology, Zhong said, researchers knew that some of these slabs of crust don't always travel the full 1,860 miles (3,000 km) to the core-mantle boundary. Essentially, they get stuck partway down.

Particularly in the western Pacific Ocean, near Japan and at the Mariana Trench, for example, the slabs of crust seem to stall out at around 416 miles (670 km) deep. In these areas, they seem to deflect and travel horizontally as much as 1,243 miles (2,000 km).

The layer of mantle at that particular depth is unusual, Zhong said, because the rock there goes through a sudden density increase, which is the result of the pressure of all the rock pushing down on top of it. In the new study, Zhong and University of Colorado graduate student Wei Mao built a computer model of the mantle's dynamics, including both this density increase and the past 130 million years of continental plate movements.

Model mantle

This more complete model of the mantle naturally produced the same sort of stagnating slabs seen in the real mantle, the researchers found. What seems to be going on, Zhong said, is that the accumulated pressure of the overlying rock at 670 km creates an area of reduced viscosity — in essence, the mantle is more slippery and less gooey.

"That reduced viscosity essentially provides what we call lubrication on the slabs," Zhong said. The chunks of crust are able to slip and slide sideways instead of continuing their downward plunge.

This hitch in the machine is only temporary. The slabs are probably only trapped for 20 million years or so, Zhong said — a blink of the eye in terms of Earth's history. But their dynamics might be important for some of the geological phenomena seen on the surface. For example, volcanic activity in northeastern China, far from the volcanic arc of Japan, could be due, in part, to some of these slab dynamics, Zhong said.

The model doesn't answer all the questions about the stagnating slabs. It's not clear, Zhong said, why the western Pacific seems to give rise to so many of these stagnant slabs, while subduction zones near North and South America currently don't. There are also other mystery spots around the globe, he said.

"In places like New Zealand, there is still some disagreement between our convection model and the observations," he said, "so we need to reconcile those places."

Original article on Live Science.

That special mineral that humans use to profess their love for one another? It might not be so special. A new study suggests that Earth's interior is filled with a quadrillion tons of diamonds.

A new study published in June in the journal Geochemistry, Geophysics, Geosystems suggests that there are 1,000 times more diamonds below the surface of the Earth than was previously thought.

But these diamonds are unreachable: They're located about 90 to 150 miles (145 to 240 kilometers) below the surface of the Earth in the "roots" of cratons, which are large sections of rock. Cratons lie beneath most continental tectonic plates and have barely moved since ancient times, according to a statement from MIT News. [Photos: The World's Weirdest Geological Formations]

A group of researchers from various universities around the world discovered the glitzy stash by looking at seismic waves beneath the Earth. Because these vibrations can change, based on the composition, temperature and density of various rocks that it hits, researchers can use these recordings to construct an image of the unreachable interior of the Earth.

They found that the underground vibrations, produced from natural processes such as earthquakes and tsunamis, tended to speed up when passing through cratonic roots; the speedup was greater than would be expected from the fact that cratons tend to be colder and less dense than surrounding structures (both of which are conditions that would speed up the waves).

Using records of seismic activity that were kept by government agencies such as the U.S. Geological Survey, the team created a three-dimensional model of the velocities of seismic waves that traveled through the planet's major cratons. Then, they created "virtual rocks" from various combinations of different minerals and calculated how fast seismic waves would travel through those rock compositions.

They found that the best explanation for the speeds actually observed underground versus those predicted in their virtual rock models was that 1 to 2 percent of the roots of the cratons was made up of diamonds, while the rest was made up of peridotite (the main type of rock in Earth's upper mantle) and a little bit of eclogite rocks (from the ocean's crust).

When "waves pass through the Earth, diamonds will transmit them faster than other rocks or minerals that are less stiff," said Joshua Garber, a postdoctoral student at UC Santa Barbara and lead author of the study.

Though "we found that much of the data were best explained by diamond … we cannot say for certain," Garber said. Since it's difficult to directly sample these regions (but not impossible, since sometimes parts of these cratonic roots are brought to the surface from erupting magma), this is the best explanation right now, Garber said.

But other researchers have suggested some alternative explanations: Perhaps, these cratonic rocks are cooler than what the literature suggests, which means the rock will be stiffer — and thus, seismic waves will travel more quickly through them — even without the diamond or eclogite rocks, Garber added. However, based on their data, he thinks this latter scenario is less likely.

"Our understanding of the deep Earth continues to improve as we make more measurements, do more experiments and occasionally get samples," Garber said. "I suspect we will continue to be surprised by what we find."

Originally published on Live Science.

One day, about a billion years ago, Earth's inner core had a growth spurt. The molten ball of liquid metal at the center of our planet rapidly crystallized due to lowering temperatures, growing steadily outward until it reached the roughly 760-mile (1,220 kilometers) diameter to which it's thought to extend today.

That's the conventional story of the inner core's creation, anyway. But according to a new paper published online this week in the journal Earth and Planetary Science Letters, that story is impossible.

In the paper, the researchers argued that the standard model of how the Earth's core formed is missing a crucial detail about how metals crystallize: a mandatory, massive drop in temperature that would be extremely difficult to achieve at core pressures. [6 Visions of Earth's Core]

Weirder still, the researchers said, once you account for this missing detail, the science seems to suggest that Earth's inner core shouldn't exist at all.

The paradox at the center of our planet

"Everyone, ourselves included, seemed to be missing this big problem," study author Steven Hauck, a professor of Earth, Environmental and Planetary Sciences at Case Western Reserve University in Ohio, said in a statement. Namely, they were missing "that metals don't start crystallizing instantly unless something is there that lowers the energy barrier a lot." 

In chemistry, this extra energy is known as the nucleation barrier: the point at which a compound visibly changes its thermodynamic phase. Liquid water, for example, freezes into a solid at the familiar 32 degrees Fahrenheit (0 degrees Celsius). If you've ever made ice cubes at home though, you know that even water stored at its freezing point can take several hours to fully crystallize. To speed up the process, you need to either expose the water to significantly colder temperatures (this is called "supercooling") or expose it to an already-solid piece of ice to lower the nucleation barrier, reducing the amount of cooling required.

Supercooling is easily achieved for a single ice cube, but for Earth's gigantic inner core, things get a little trickier, the researchers said.

"At the pressures of the core, it would have to cool 1,000 degrees Kelvin [1,000 degrees C or 1,800 degrees F] or more below the melting temperature in order to crystallize spontaneously from pure liquid," Hauck told Live Science. "And that's a lot of cooling, especially since at the moment, the scientific community thinks the Earth cools maybe about 100 degrees K per billion years."

According to this model, "the inner core shouldn't exist at all, because it could not have been supercooled to that extent," study author Jim Van Orman, also a professor of Earth, Environmental and Planetary Sciences at Case Western, told Live Science. The molten inner core's nucleation barrier, he said, must have lowered some other way — but how?

The core of the problem

In their paper, the researchers proposed one possibility: Perhaps a massive nugget of solid metal alloy dropped from the mantle and plunged into the liquid core. Like an ice cube dropped into a glass of slowly freezing water, this solid chunk of metal could have lowered the core's nucleation barrier enough to kick-start a rapid crystallization.

There's a big caveat, though: It would have to be a truly massive chunk of metal to work.

"In order to be released into the core and then make it all the way down to the center of the Earth without dissolving … this droplet would have to be on the order of about 10 km [6.2 miles] in radius," Van Orman said. That means a diameter about the length of the island of Manhattan.

The Case Western researchers said that while they favor this new explanation over the conventional model, they're eager for members of the scientific community to weigh in with theories of their own.

"We've talked about what ideas are implausible, and we've suggested an idea that's potentially plausible," Hauck said. "If it happened that way, it's possible that some signature of that event might be detectable through seismic studies. Studying the centermost part of the planet is about the hardest to access with these waves, so it'll take time."

Hopefully, we can look forward to an answer within the next billion years.

Originally published on Live Science.

Rocks from the eastern shore of the Hudson Bay in Canada contain elements of some of Earth's earliest crust, new research finds.

The rocks themselves are granites that are 2.7 billion years old, but they still hold the chemical signals of the precursor rocks that were melted and recycled to form the rocks that exist today. The new study, published online today (March 17) in the journal Science, finds that these precursors formed around 4.3 billion years ago.

The Earth is 4.6 billion years old, and the astronomical impact that formed the moon took place about 4.5 billion years ago. That makes the precursor rocks to the Canadian granites among the earliest crust after the moon-forming impact, said study leader Jonathan O'Neil, a geoscientist at the University of Ottawa in Canada. [Photo Timeline: How the Earth Formed]

Hadean history

The new research is an attempt to peek back into the Hadean eon, a mysterious and rather molten phase of Earth history. The Hadean begins with Earth's formation and ends about 4 billion years ago, and very few geological remnants of this era remain. Most rocks from the Hadean were long ago recycled back into the planet's mantle.

"Rocks that are 3.6 [billion] to 3.8 billion years old or older, we can count them on the fingers of our hand, basically," O'Neil told Live Science. "We have a very limited amount of rock sample to understand the first billion years of Earth history."

The granites found north of Canada's Hudson Bay don't date to the Hadean, but they do butt up against the Nuvvuagittuq greenstone belt, a formation thought to contain the oldest known rocks on Earth, between 3.8 billion and 2.48 billion years old. (The only older geological material are small mineral grains called zircons from Australia's Jack Hills, but the original rocks that held those grains have long since weathered away.)

Some scientists think that both the Jack Hills zircons and the Nuvvuaguittuq greenstone belt contain traces of the earliest life on the planet, though those findings are controversial.

A geological family tree

O'Neil and his co-author, Richard Carlson of the Carnegie Institution for Science, were interested in the 2.7-billion-year-old granites because they knew that rocks of that sort had to be formed by a "parent" rock that had been buried and partially melted before reforming. The question was, how old was that parent rock?

To find out, the researchers turned to samarium-neodymium dating, a method that uses ratios of different variations of those two rare-earth elements to determine age. One  molecular variation, or isotope, of samarium, samarium-146, no longer exists on Earth: It all underwent radioactive decay within the first 500 million years of the planet's history, O'Neil said.

Samarium-146 decays into neodymium-142, so any rock that formed after the first 500 million years of Earth's history holds the same ratio of neodymium-142 to other neodymium isotopes. Any rock that shows variation in this neodymium ratio must have formed in the first 500 million years of Earth history, the researchers said.

It was just that sort of variation that scientists found in the Hudson Bay rocks — a deficit in the neodymium-142 to neodymium-144 ratio compared with modern rocks.

"It means their parent rock had to be very old," O'Neil said. The researchers also found that the parent rock was likely basaltic oceanic crust rather than dry land.

The researchers estimate that the parent rock was 1.5 billion years older than the modern granites that survive today. That's interesting not just because the parent rock was some of the earliest crust on Earth, O'Neil said, but because the parent rock stuck around for so long before it was recycled. Today's oceanic crust persists at the surface for only about 200 million years before being pushed back into the mantle and partially melted, O'Neil said. The parent rock of the Hudson Bay granites stayed at the surface for more than a billion years before being recycled, five times as long as today's oceanic crust survives.

Original article on Live Science. 

Lava from Earth's hottest spots may be flecked with primordial rock that existed 4.5 billion years ago, before the moon had formed, new research suggests.

The traces of ancient Earth likely come from dense primordial reservoirs buried deep below the Earth's surface, at the boundary between the mantle and the core. As plumes of molten rock in the Earth's mantle rise toward the surface, they pull in some of this primeval rock. These plumes then warm Earth's surface at volcanic hotspots, oozing lava that contains signatures of the young planet, according to the study, which was published on Monday (Feb. 6) in the journal Nature.

"We're finding the hottest plumes are sampling the oldest domains on the Earth," said study co-author Matthew Jackson, a geochemist at the University of California, Santa Barbara. "These lavas are sampling a domain in the Earth that had to have formed in the first 100 million years of Earth's history." [Photo Time Line: How the Earth Formed]

Smashing beginning

Around 4.54 billion years ago, Earth formed during several massive collisions, the last of which occurred about 100 million years after the solar system's coalescence, when Earth crashed into the planetoid Theia. The vaporized remains of this planetoid then condensed to form the moon.

Though the violent churning of the Earth has erased almost all traces of this early history, in the past few decades, scientists have found evidence that bits of this young Earth may still exist in places like Hawaii and Iceland. These locations are among the 50 volcanic hotspots on the planet, where heat from the Earth's mantle rises in a plume, melting rock at the base of the tectonic plates that form Earth's surface.  The molten rock, or magma, then oozes through fissures in the Earth to erupt and form volcanoes.

In the 1980s, scientists sampling lava in Hawaii noticed that in some spots, the ratio of helium-3 (helium with just one neutron per atom) to the version with two neutrons per atom, called helium-4, was higher than expected based on the surrounding rock's composition.

"This ratio is associated with the building blocks of the planet, primitive meteorites, the atmosphere of Jupiter, the solar wind," Jackson said. (Jupiter's atmosphere likely formed early in the solar system's history.)

In other words, the high ratio of helium-3 to helium-4 suggested a very ancient source, he said. Follow-up studies produced ratios of other isotopes, such as tungsten and xenon, that suggested these lavas may come from the first 50 million years of Earth's history.

"It records the earliest history of the planet," Jackson told Live Science.

Hottest spots, oldest rock

However, only some hotspots held lava with high helium-3/helium-4 ratios. Why then were some hotspots sampling this primordial soup when others weren't?

To answer that question, Jackson and his colleagues took helium-isotope data from 38 volcanic hotspots around the world and combined that information with data on how fast seismic waves travel through the upper mantle. Seismic waves travel more slowly through hotter mantle. They found that the areas with the slowest seismic waves (and therefore the hottest mantle) also had a helium signature associated with primordial reservoirs.

The new research suggests that the hottest of hotspots may be the only ones pulling from this primordial pool of ancient rock, the study said. The hottest spots are likely fed by the most buoyant plumes in the mantle, meaning the plumes are better able to rise up in relation the surrounding mantle rock, the researchers said. These ultrahot plumes are also able to cause more melt, the scientists added.

Under this hypothesis, these dense blobs of primordial rock lie about 1,860 miles (3,000 kilometers) below the Earth's surface, at the boundary with the core. Because these blobs are so dense, only the hottest mantle plumes can melt bits of this material and transport it, Jackson said.

The high density "also explains how something so ancient could survive in the chaotically convecting mantle for 4.5 billion years," he said in a statement. "The density contrast makes it more likely that the ancient helium reservoir is preserved rather than mixed away."

While the findings suggest an explanation for why only some lava contains traces of ancient Earth, the results don't answer larger questions about these primeval reservoirs, Jackson said. For instance, scientists have little idea what these primordial reservoirs are made of or how they formed, he said.

Originally published on Live Science.

After analyzing the crater from the cosmic impact that ended the age of dinosaurs, scientists now say the object that smacked into the planet may have punched nearly all the way through Earth's crust, according to a new study.

The finding could shed light on how impacts can reshape the faces of planets and how such collisions can generate new habitats for life, the researchers said.

Asteroids and comets occasionally pelt Earth's surface. Still, for the most part, changes to the planet's surface result largely from erosion due to rain and wind, "as well as plate tectonics, which generates mountains and ocean trenches," said study co-author Sean Gulick, a marine geophysicist at the University of Texas at Austin. [Crash! 10 Biggest Impact Craters on Earth]

In contrast, on the solar system's other rocky planets, erosion and plate tectonics typically have little, if any, influence on the planetary surfaces. "The key driver of surface changes on those planets is constantly getting hit by stuff from space," Gulick told Live Science.

The researchers in the new study looked at Earth features to learn more about impact effects found on other solar system objects. Major craters sometimes possess rings of rocky hills in their centers. Most of these "peak rings" exist on extraterrestrial rocky bodies such as the moon or Venus, making it difficult to analyze these structures in detail and pin down their origins.

So to learn more about peak rings, scientists investigated a gargantuan crater on Earth that measures more than 110 miles (180 kilometers) across, located near the town of Chicxulub (CHEEK-sheh-loob) in Mexico's Yucatán Peninsula. This crater likely resulted from the epic crash of an object about 6 miles (10 km) wide, and the resulting impact is thought to have ended the age of dinosaurs about 65 million years ago.

The researchers focused on the Chicxulub crater because it has the only intact peak ring on Earth. In contrast, larger craters on Earth, such as Sudbury in Canada or Vredefort in South Africa, "have [been] heavily eroded — neither one has peak rings anymore," Gulick said. "On the other hand, Chicxulub's peak ring is completely preserved."

The structures that the researchers wanted to examine were under about 60 feet (18 meters) of water in the Gulf of Mexico. To collect samples from these structures, the scientists traveled to the site in the spring of 2016 in a "liftboat" that could lower three pillars into the seafloor and lift the boat off the water by about 50 feet (15 m). The liftboat then lowered drills into the seafloor and "drilled into the crater for two months, to as low as 1,335 meters [4,380 feet] below the seafloor," Gulick said. (Lifting the boat from the water helps it avoid waves that can rock the vessel and snap the drill pipe.)

In the peak ring samples, the scientists discovered granite that likely once was deeply buried for about 500 million years, Gulick said. "These deeply buried rocks rose up to the surface of the Earth within the first few minutes of the impact," Gulick said. "They showed evidence they experienced a high degree of shock from the impact."

After the impact, "the earth there would have temporarily behaved like a slow-moving fluid," Gulick said. "The stony asteroid would have opened up a hole probably almost the thickness of Earth's crust, almost 30 km [18 miles] deep, and on the order of 80 to 100 km [50 to 62 miles] wide."

And similar to how fluids behave, the earth would immediately flow to fill in the hole, meaning the sides of the crater would collapse inward, he added. [When Space Attacks: The 6 Craziest Impact Craters]

"At the same time, the center of this hole starts reaching upwards, like when you throw a rock in a pond and you get a water droplet rising in the middle," Gulick said. "The center would have risen up from the surface of the Earth as much as 15 km [9 miles], and then become gravitationally unstable, collapsing downwards and outwards."

The end result of this dynamic process is a ring of mountains, or the peak ring, the researchers said.

The study's findings support one of the two main hypotheses that describe peak ring formation, the researchers said. One explanation suggested that peak rings originate closer to the surface: As an impact causes a peak to form in the middle of the crater, the uppermost part of this peak melts, causing the material to disperse into a ring of peaks. The other hypothesis suggested that peak rings formed because impacts dug deep into their targets.

"It turns out the models based on the deeper origins seemed to have gotten it right," Gulick said. "The model these findings support is based on what are known as hydrocode models, which are used for simulating nuclear bomb blasts. Those models simulate an asteroid impacting a target at close to about 20 km per second [44,740 mph], which can get the crust to flow."

Unexpectedly, the researchers noted that rocks from peak rings "got fundamentally altered by their journey upward during the impact," Gulick said. "They end up lower in density by a lot, with their porosity increasing from 1 to 2 percent to 10 percent."

These changes may have proven critical for the evolution of life on Earth, and perhaps on other planets, Gulick said. "When you get rocks with 10 percent more pore space, microbial life living below the surface may find new habitats on the surface," he said. "Our next area of research involves looking at whether ecosystems can get started by craters."

The scientists detailed their findings online today (Nov. 17) in the journal Science.

Original article on Live Science.

Earth's inner core is a metallic mix of iron and light elements such as sulfur, hydrogen and silicon, a new study finds.

This isn't the first time scientists have proposed that Earth's fiery depths are filled with brimstone, another name for sulfur. That's because the inner core is less dense than it would be if the solid metal ball were pure iron. However, the new research further confirms the idea with tests of pure iron at the extreme temperatures and pressures found in the inner core. 

Researchers at Tohoku University in Sendai, Japan, mimicked the inner core in a laboratory equipped with a laser-heated diamond anvil cell. A small crumb of pure iron was squeezed between two diamond-tipped anvils to create high pressure and blasted with laser beams to boost the temperature. The experiment reached 163 gigapascals (about 1.6 million times the pressure at sea level) and about 5,000 degrees Fahrenheit (3,000 kelvins, or about 2,700 degrees Celsius). [Religion and Science: 6 Visions of Earth's Core]

During the experiment, the team measured how fast sound waves traveled through iron at these conditions. If the Earth's inner core was pure iron, then the speed of sound waves traveling through the core should be similar to the experimental results.

But instead, the researchers discovered the velocity of sound waves through Earth's actual core is lower than if it were made only of iron. The data and observations match more closely if 5 to 10 percent of the core's weight is a mix of sulfur, hydrogen and silicon, the researchers report today (Feb. 26) in the journal Science Advances.

"This result helps us constrain the candidate elements in the core," said lead study author Tatsuya Sakamaki, of Tohoku University. "We already know that the Earth's core contains some amount of light elements because the density of the core is smaller than that of iron. In this study, we newly show that the velocity of the core is also smaller than that of iron," Sakamaki told Live Science in an email interview.

Although scientists cannot directly measure the Earth's core, they can estimate its size and composition with models based on how fast earthquake waves zip around inside the planet.

Measuring the amount of light elements in the inner core can help add detail to models of Earth's violent formation, the researchers said. Scientists think Earth was bombarded by giant impacts late in its birth cycle. The chemistry of the core relates to the size of the cataclysmic collisions and the temperature of the magma ocean that emerged afterward.

The core formed as metals sunk out of the magma ocean, trickling down toward the center of the planet — a process that is sensitive to temperature. "In other words, the core composition may reflect the temperature condition of the magma ocean," Sakamaki said. Knowing the temperature of the roiling sea of molten rock can help pin down the size of early impacts, according to Sakamaki.

Follow us @livescience, Facebook& Google+. Original article on Live Science.

SAN FRANCISCO — Scientists have jury-rigged a microwave oven and a liquid made of food and cosmetics thickener to recreate the Earth's mantle, the mysterious middle layer of the planet.

The mock-up mantle could help scientists determine whether a hidden pool of radioactive elements is producing heat deep in Earth's interior, Angela Limare, a physicist at the Institut de Physique du Globe de Paris in France, said Tuesday (Dec. 15) here at the annual meeting of the American Geophysical Union.

"It looks like the upper mantle is really depleted of radioactive elements," Limare said. "If they are not in the upper mantle, they must be somewhere below." [In Photos: Ocean Hidden Beneath Earth's Surface]

Mystery mantle

The Earth's mantle is a molten mass of unanswered questions. The rocky shell between the core and the crust makes up four-fifths of the planet but is the least understood portion. Because it begins anywhere from 5 miles (8 kilometers) to 20 miles (32 km) below the planet's surface and extends about 1,800 miles (2,900 km) below the Earth's surface, scientists can't drill deep enough to determine what it's made of, how the elements in the mantle are distributed or exactly how it moves. Instead, they often use a process called seismic tomography to send seismic waves through the Earth and then analyze their return paths to infer its composition. Volcanologists may also sample the elements in magma from volcanoes that oozes up from mantle plumes deep in the Earth, Limare said.

One question in particular has long puzzled scientists. The Earth generates about 46 terawatts of heat. Scientists have calculated that about 8 terawatts come from the continental crust floating atop the mantle, while heat generation from the core, which sustains Earth's magnetic field, contributes another 10 to 16 terawatts. This means that about half of Earth's heat is generated by the radioactive decay of elements in the mantle.

The trouble is, seismic tomography suggests that, except for the top and bottom of the mantle, radioactive elements are sprinkled evenly throughout the mantle, and the concentration of those radioactive elements seems to be too low to generate the remaining heat, Limare said. And at the bottom of the mantle, seismic tomography detects two large regions of slow-moving material that must be chemically distinct from the rest of the mantle.  Meanwhile, magma from volcanoes fed by mantle plumes that reach deep into the lowest depths of the mantle can show different chemical compositions, even if the volcanoes are separated by just a handful of miles, she said. Altogether, that suggests there could be material at the innermost layer of the mantle that is very different in composition from the rest of the mantle.

As a result, some scientists have proposed that a hidden reservoir of radioactive elements lurks deep in the mantle and produces the missing heat. If this hidden reservoir exists, it must be very stable and must not be mixing with the rest of the ever-churning mantle, because otherwise, seismic tomography would have detected it, Limare said.

With no way to experimentally test this notion, however, geophysicists have been left to hash out their debates in a flurry of models, equations, numerical theories and simulations. [Photo Timeline: How the Earth Formed]

Nuke the mantle

So, Limare and her colleagues decided take a more hands-on approach. They simulated the mantle using a sheet of cellulose-derived Natrosol that was 11.8 by 11.8 by 2 inches (30 by 30 by 5 cm) thick. At first glance, a small, viscous liquid may seem to have very little in common with 1,800 miles of sandy rock that make up the mantle.

But by carefully calibrating some of the properties of the gel — such as its depth, length, viscosity and temperature — the researchers can create a scaled-down model with heat and fluid transport properties very similar to those of the mantle. Limare's team used the Natrosol because it is very easy to vary its viscosity by adding more or less water, while the material can be made denser by sprinkling in salt or.less dense by thinning with alcohol. The material also makes it easy to create two adjacent layers of the "mantle" with different properties, she said.

Next, the scientists mimicked the extremely uniform internal heat generation of radioactive elements inside the mantle. For that, they looked to a ubiquitous household appliance — the microwave oven. Microwaves enter and are absorbed by the food, and generate internal heat in the process.

"That's how we heat up food; it's exactly the same process," Limare told Live Science.

Of course — do we even need to say it? — don't try this at home! The researchers' microwave may have started out as a commercial oven, but it's been eviscerated and tricked out with sophisticated and high-tech modifications, from liquid crystal thermometers to laser sheets to fancy cameras that operate in two different wavelength ranges.

"The only thing left from the commercial stuff is the external box and the door, because the door is very well done," Limare said.

In the experiment, the boundaries between the Earth's layers are not exactly true to life; the mantle rubs against the molten core and the bottom of the continental crust, but the Natrosol mixture had to be put in a plexiglass container so it wouldn't lie in a puddle at the bottom of the microwave, Limare said.

Narrowing in on the hidden reservoir

Still, the model has already provided a few early insights. For instance, when the researchers modeled a mantle with a dense, low-viscosity "hidden reservoir," rivers of heat flowed from the top of the mantle to the bottom. If these rivers of heat reach far enough into the mantle, they would destabilize a hidden reservoir of radioactive elements lurking at the bottom of the mantle. So if a hidden reservoir does exist, it probably wouldn't density, thickness and other characteristics that create a destabilized regime in the mockup mantle, the researchers said.

The microwavable mantle is important because it could help scientists narrow the range of conditions that could exist in a hidden reservoir of radioactive elements, said Gaël Choblet, a planetary interior researcher at the CNRS (Centre national de la recherche scientifique) and the University of Nantes in France, who was not involved in the current study.

The new technique is novel because it's the first time scientists have produced extremely uniform internal heating in a viscous material that can mimic the mantle, Choblet told Live Science.

Though the new results on their own are unlikely to solve the mystery of the hidden reservoir, "it's always very good to compare laboratory experiments and numerical models," Choblet said. "The comparison is usually quite fruitful."

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Enormous rivers of hot rock spanning hundreds of miles across and reaching all the way down into the planet's metal-rich core have been seen for the first time.

The searing-hot plumes, which feed volcanoes on the surface, are likely themselves fed by two "superblobs" beneath Africa and the Pacific Ocean, the researchers said.

The new finding comes from supercomputer visualizations of the Earth's interior derived from seismic data on hundreds of earthquakes over the last several decades.

The new results may settle a long-standing debate about whether these molten jets of magma, called mantle plumes, trigger volcanic eruptions. [Video: See How Hot Mantle Plumes Form Volcanic Islands]

Mystery plumes

For decades, scientists have debated the existence of mantle plumes, or hot columns of magma that rise in the Earth's mantle, the layer between the crust and the molten iron and nickel outer core.

Earth's crust floats on a layer of molten rock known as magma. The dominant theory is that volcanoes form where one tectonic plate dives beneath another, squeezing magma up through fissures in the Earth's crust.

But volcanoes, such as those that form the Hawaiian Islands and Iceland, often erupt far from any plate boundary. In 1971, geologist W. Jason Morgan proposed a completely different mechanism for the formation of these off-plate volcanoes: deep jets of magma coming straight from the mantle-core boundary.

In this hypothesis, the fat head of the mantle plume creates a hot pocket in the Earth's crust, creating a volcanic core. As the plates move and the position of the hotspot changes relative to the surface, this process would create a string of volcanic islands — such as those found in Hawaii and the Galapagos Islands. [Infographic: Tallest Mountain to Deepest Ocean Trench]

But no one had definitively shown that such deep-dwelling rivers of molten rock existed.

Detailed visualization

In the new study, researchers created the equivalent of a computed tomography (CT) scan for the planet based on seismic data from 273 strong earthquakes that occurred over the last two decades. As the earthquakes shook the planet, seismic waves ricocheted inside the planet's interior. By recreating the zigzagging paths of those waves using a supercomputer simulation, the team revealed the temperature and extent of plumes in the interior.

The researchers found molten jets that were about 700 degrees Fahrenheit (400 degrees Celsius) hotter than the nearby rock. These plumes stretched from the Earth's crust all the way to the boundary between the mantle and the core, more than 1,800 miles (2,900 kilometers) below the surface. And these rivers of molten rock seem to consist of a different type of rock than the rest of the mantle.

One surprise: Deeper in the mantle, these plumes become incredibly wide — up to 600 miles (1,000 km) across. The mantle plumes also have a different shape than previously predicted. Historically, geologists thought mantle plumes had narrow bases and fat heads, which sat right beneath volcanic island chains. Instead, as the tops of the plumes bump against the less viscous upper mantle rock, the plumes fan out like branches of a tree, the researchers reported today (Sept. 2) in the journal Nature.

"These columns are clearly separated in the lower mantle, and they go all the way up to about 1,000 km below the surface, but then they start to thin out in the upper part of the mantle, and they meander and deflect," study co-author Barbara Romanowicz, an earth and planetary scientist at the University of California, Berkeley, said in a statement. "So while the tops of the plumes are associated with hotspot volcanoes, they are not always vertically under" the volcanoes.

The plumes seem to emanate from two gigantic masses of hot rock, each about 3,000 miles (5,000 km) in diameter, which are fixed at the boundary with the Earth's core. The researchers speculate that these two superblobs, which lie beneath Africa and the Pacific Ocean, have been stationary for 250 million years.

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

The fiery demise of ancient huts in southern Africa 1,000 years ago left clues to understanding a bizarre weak spot in the Earth's magnetic field — and the role it plays in the magnetic poles' periodic reversals.

Patches of ground where huts were burned down in southern Africa contain a key mineral that recorded the magnetic field at the time of each ritual burning. Those mineral records teach researchers more about a weird, weak patch of Earth's magnetic field called the South Atlantic Anomaly and point the way toward a possible mechanism for sudden reversals of the field.

"It has long been thought reversals start at random locations, but our study suggests this may not be the case," John Tarduno, a geophysicist from the University of Rochester in New York and lead author of the paper, said in a statement. [How Earth's Magnetic Field Shielded Us from 2014 Solar Storm]

Tarduno told Space.com in an interview that data from the huts suggest that the strange weak patch "forms, and it decays away, and it forms, and it decays away; eventually, one might form and get really large, and then we might actually have a geomagnetic reversal."

Something strange in the South Atlantic

The South Atlantic Anomaly is a dent in Earth's shield against cosmic radiation, 124 miles above the ground (200 kilometers). It may be the most dangerous place in the Earth's sphere for satellites and spacecraft to traverse, because anything electronic traveling through it is vulnerable to strong radiation from space and tends to malfunction.

Even the Hubble Space Telescope takes no measurements when passing over  the anomaly. It's an area where, instead of pointing outward, part of the Earth's magnetic field actually ushers energetic particles down instead of repelling them, weakening the overall field in the area. And it has been growing.

"Some have postulated that the Earth's magnetic field is leaking out the wrong way at that particular spot," Rory Cottrell, a geologist also at the University of Rochester and co-author of the new paper, told Space.com. "One theory is that changes in the South Atlantic Anomaly could be responsible for the decrease in the overall magnetic field that we're seeing, because these patches are growing or changing over time."

Many researchers have speculated that this kind of anomaly is temporary, caused by changes of flow within the Earth's outer, iron core, which generates the planet's magnetic field. Such anomalies, in weakening the magnetic field, may bring the Earth closer to a magnetic reversal — when the magnetic north and south poles on Earth switch places, rearranging the magnetic field over the course of 1,000 to 10,000 years (although it can happen faster). The process generally happens every 200,000 to 300,000 years, after the magnetic field weakens enough, but the last magnetic-field reversal occurred 780,000 years ago.

The new data from the African burnings suggests that the South Atlantic Anomaly was up to its same field-weakening tricks over 1,000 years ago; if it's caused by something permanent near the Earth's core, it might play an important role in the Earth's magnetic-pole reversals.

Burn it all down

Modern magnetic records only stretch back for the past 150 years or so, and within that time frame, researchers have seen the Earth's magnetic field rapidly decrease in intensity. But the researchers used the Iron Age remnants of African villages to extend their view even further back, from A.D. 1,000 to A.D. 1,850 — and the record reveals that the South Atlantic Anomaly was going strong at that time, too. [Earth Quiz: Do You Really Know Your Planet?]

Throughout that time, the inhabitants of ancient African villages would burn down the huts and grain bins in their villages on a regular basis, giving scientists key, consistent data throughout that time period.

"They had this ritualistic burning of villages," Tarduno told Space.com. "Particularly in times of drought, the conclusion would be that there might have been some offence in the village, so the solution was to have a burning down of the village." The process was intended to cleanse the village, their collaborator archaeologist Thomas Huffman, from Witwatersrand University in South Africa, said in the statement.

At the very least, it cleansed the ground: The burning villages would reach temperatures of over 1,800 degrees Fahrenheit (1,000 degrees Celsius), which would melt the magnetic compounds like magnetite in the clay floors. The magnetite would become remagnetized by the Earth's magnetic field at the precise instant it cooled, ready to be analyzed centuries later.

"The hut floors are actually very good magnetic recorders," Tarduno said. "Sort of like minimagnetic observatories back in time."

Researchers had obtained very little historical data in the southern hemisphere, and none in southern Africa before these findings. The new baked-clay records revealed an eerily familiar picture of the Earth's magnetic field: Just like today, the Earth's magnetic field at the time was steadily weakening, with a focus on that same South Atlantic Anomaly. The effect did not appear to be continuous, but rather seemed to be a recurring event in that part of the globe, whose weakening power comes and goes over time.

Digging deeper

To Tarduno's group, that consistently recurring spot of weakening suggests that a permanent feature deep below the Earth's surface may be generating the South Atlantic Anomaly and might therefore play a role in the reversal of the Earth's magnetic field.

That feature is a section of particularly hot and dense mantle rock just above the Earth's outer core. The section is 1,860 miles (3,000 km) below southern Africa and the Atlantic, and it's about as wide as the distance between New York and Paris. Scientists call it the Large Low Shear Velocity Province, and Tarduno's group suspects that its sharp boundaries might disrupt the flow of iron within the Earth's core, creating a strange, field-weakening eddy that could lead to reversals time and time again.

The researchers' model is only one of many theories about magnetic pole reversal, and they're focusing on refining the mathematics and gathering more, even earlier data from southern Africa to further track the weak spot.

"No one knows what causes reversals, and there is no agreement on whether we can ever even find convincing evidence to forecast a reversal," Ron Merrill, a geophysicist from the University of Washington, who was not involved in the study, told Space.com in an email.

While the new magnetic field records in Africa are useful in their own right, he wrote, it will take much more testing and theory to make a solid connection between the feature near the Earth's core and the magnetic field's weakening and reversal (and the long-lasting nature of the South Atlantic Anomaly).

The new research can't predict the next magnetic field reversal, but finding a connection between the ancient irregularity near the Earth's core and a weakening magnetic field would be one more step toward deciphering the incredibly complex magnetic system that protects humanity from the harsh radiation of space.

This research is detailed in the July 28 edition of the journal Nature Communications.

Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com

This story was updated at 11:16 a.m. ET.

Biblical views of the center of the Earth as a hellish pit raging with fire and brimstone have some support from new research. Scientists have found that the vast majority of brimstone — reverently referred to in biblical times as "burning stone," but now known more commonly as sulfur — dwells deep in the Earth's core.  

"In a way, we can also say that we have life imitating art," study lead author Paul Savage, a research scientist in the Department of Earth Sciences at Durham University in the United Kingdom, said in a statement."For millennia, tales have been told of the underworld being awash with fire and brimstone. Now at least, we can be sure of the brimstone."

The researchers estimate that the Earth's core contains 10 times the amount of sulfur than in the rest of the world, or comparable to about 10 percent of the mass of the moon. [Religion and Science: 6 Visions of Earth's Core]

Inside Earth

Scientists have generally understood that at the time of Earth's formation, heavy metals such as iron and nickel sunk to the planet's core, and light elements, like oxygen, silicon, aluminum, potassium, sodium, and calcium, mostly concentrated in the outer layers of the Earth, in the mantle and crust.

However, the mass of the Earth's solid inner core, which is too light to be composed solely of metal, has been an enduring inconsistency in our understanding of the planet's distribution of elements. To explain the core's lighter-than-expected weight, scientists assumed that the core had to contain some lighter elements, such as oxygen, carbon, silicon and sulfur.

"Scientists have suspected that there is sulphur in the core for some time, but this is the first time we have solid geochemical evidence to support the idea," Savage said.

Confirming the presence of lighter elements, like sulfur, in the core, provides information about the temperatures, pressures and oxygen content in the Earth's mantle, which surrounds the core and separates it from the crust on which we walk. "It'd be nice to know what the Earth is formed of, as a fundamental aspect of understanding the Earth," Savage told Live Science.

Peeling back the layers

Without the technology to dig 1,800 miles (2,900 kilometers, or the equivalent of around 3,000 Eiffel Towers stacked on top of one another), scientists looked for clues created by a 4.47 billion-year-old impact— the moon-forming collision between Earth and a large, planet-size body called Theia.

"The giant impact wouldn't have just formed the moon; it wouldn't have just sort of sliced a bit of material off and end up becoming the moon," Savage said. "The amount of energy involved in this sort of impact would have, if not completely, it would have partially melted the Earth's mantle to a certain depth." When the mantle melted, some of its sulfur-rich liquid seeped into the core, and some of it evaporated into space, he added.

"You could lose a lot of it during evaporation," Savage said. "Just by looking at the sulfur, we can't really tell much about how much is in the core versus how much has been lost to space," making sulfur virtually impossible to directly measure. [Photo Timeline: How the Earth Formed]

To track and quantify the elusive sulfur, the researchers looked to copper isotopes (atoms of the same element with different numbers of neutrons). "We chose copper, because it is a chalcophile element, which means it prefers to be in sulphide-rich material — so it is a good element to trace the fate of sulphur on Earth," Frédéric Moynier, the study's senior author and a professor at the Institut de Physique du Globe in Paris, said in a statement. "Generally, where there is copper, there is sulphur; copper gives us a proxy measurement for sulphur."

Searching for sulfur

The researchers measured the copper isotope values from both the mantle and core to discover where they would find sulfur. Meteorites were used to represent the "bulk Earth," which includes the core, mantle and crust. Meteorites are jumbles of extraterrestrial matter that have been orbiting the sun since even before planets formed. "They're like cosmic sediments," Savage said. "If we got a planet and milled it down, if we sort of crushed it up and mixed it around, that's what we assume would be in meteorites."

Samples formed from lava eruptions, as well as from tectonic events, which pushed the mantle onto the surface of the Earth, were used to represent so-called "bulk silicate Earth" values, which include the copper content in the mantle and crust. Researchers can then figure out the copper content in the Earth's core by subtracting the "bulk silicate Earth" value from the "bulk Earth" value.

The scientists measured a heavy "bulk silicate Earth" copper isotope value compared with the "bulk Earth" value, which could indicate that the mantle has a lot of heavy copper and the core does not. However, through experiments, they found that the "copper in the core should be slightly heavy compared to the mantle — so the core cannot balance out the heavy mantle compared to meteorites, because it is also heavy," Savage said. If there are a lot of heavy copper isotopes in one part of the Earth, another part will have a lot of light copper isotopes.

To explain copper's "heaviness" in both the mantle and core, the researchers predicted that a sulfur-rich liquid with "light" copper formed after the impact that created the moon. "So the [melted mantle] is light, the mantle is heavy, and the two, when mixed together, would equal bulk Earth (meteorites)," Savage said.

After the Earth formed from meteorites and other extraterrestrial matter like dust and rock, it started to melt, forming its core. During core formation, some "heavy" copper left the melting mantle and entered the core, leaving the mantle with "lighter" copper, Savage said. Then, following the giant moon-forming impact, the Earth's mantle re-melted, forming a sulfur-rich liquid. "Light" copper attached itself to the liquid, leaving the mantle with the "heavier" copper, reflected in the compositions measured in present-day lava and rocks, the researchers said.

"This study is the first to show clear geochemical evidence that a sulphide liquid must have separated from the mantle early on in Earth's history — which most likely entered the core," Savage said.

The researchers detailed their findings yesterday (June 16) in the journal Geochemical Perspectives Letters.

Editor's Note: This story was updated to reflect the accurate number of Eiffel Towers it would take to get to the Earth's core. 

Elizabeth Goldbaum is on Twitter. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science

A messy paradox that has plagued geoscientists who study Earth's core and the magnetic field it produces may now be solved.

The puzzle is only a few years old. It was raised in a 2012 paper in which geophysicists in the United Kingdom published a widely accepted supercomputer model that found Earth's iron core was incredibly efficient at conducting heat. In conduction, heat moves, but the material transferring the heat stays still — think of a kitchen pan warming up. The transfer of the heat from the stovetop to the pan is conduction. 

In that study, the researchers examined how heat may move through the Earth's core, at the level of atoms and electrons. Put simply, the paradox is that in this model, so much heat escaped from the core via conduction that there wasn't enough energy left over to fuel convection (when heat creates motion) in the liquid outer core. The implication: Earth's magnetic field shouldn't exist. (If kitchen pans were as effective at conducting heat as the core, then meat would never cook because all the heat would escape into the air.)

"The study attracted a lot of attention because of the serious consequences," said Bruce Buffett, a geophysicist at the University of California, Berkeley, who was not involved in the research.

But now, new research finds that inside the deep Earth, where temperatures can match those on the surface of the sun, iron's electrons move heat by more means than just the usual way, through rapid vibrations, according to a study published today (Jan. 28) in the journal Nature. Electrons also bash into one another, transferring energy through collisions known as electron-electron scattering. [What Is Earth Made Of?]

The results resolve the paradox, the researchers concluded in the new paper. "There was a big problem in how you generate a magnetic field, and now, because of our results, that problem has basically gone away," said study co-author Ron Cohen, a staff scientist at the Carnegie Institution for Science in Washington, D.C., and a professor at University College London in the United Kingdom.

Shiver and shake

Lead study author Peng Zhang, also of the Carnegie Institution, used a National Science Foundation supercomputer to calculate how iron's electrons zip and zwing within the core. The modeling work is akin to predicting to position of every water droplet in a rain cloud, Cohen said. "We're worrying about where every single electron is, and how they interact and scatter and bounce off each other," Cohen told Live Science.

The Earth's inner core is solid, and about the size of the moon. The outer core is liquid; about 1,400 miles (2,250 kilometers) thick; and topped by 1,800 miles (2,900 km) of crystalline mantle that flows like warm plastic. This is all encased in a cold, hard shell of rock called the crust. The core is not pure iron metal — elements such as oxygen, carbon and nickel are also present.

Zhang's team discovered that in the core, collisions between electrons are as important as collisions between electrons and vibrating atoms (known as electron-phonon scattering) when it comes to heat energy. The earlier modeling work, also published in Nature, had concluded that the Earth's core is losing two to three times as much heat to conduction than previously thought. Zhang's new findings put the amount of lost heat back in line with conventional models (because accounting for the electron-electron collisions gives iron a lower conductivity).

Laboratory experiments can determine whether the team's model is correct, Cohen said.

"These calculations are difficult, as are the experiments, but confirmation of these results will be important," said Dave Stevenson, a geophysicist at the California Institute of Technology who was not involved in either study. However, he said, it is not yet clear that the new results overturn the earlier findings from 2012.

"Science is never that simple," Stevenson said. And the new study won't solve all the questions that remain, such as how the Earth actually cooled throughout its history, Stevenson said.

Protecting the planet

Since the 2012 model was published, geoscientists have come up with alternate explanations for how Earth's magnetic field may work,under the premise that most heat was escaping through conduction. The planet's magnetic field has existed for at least 3.4 billion years, according to magnetic minerals in ancient rocks.

Convection is when heat creates motion. Heat from below causes material to rise, and as the material cools, it falls back down again — just like you see in a pot of boiling water or when all the hot air in a room collects near the ceiling. Scientists think that convection currents in the core's liquid metal may flow in spirals due to Earth's constant rotation. The spiraling metal generates the planet's magnetic field. Without a magnetic field, Earth would have no protection from the the solar wind, and life as we know it wouldn't exist. [Photo Timeline: How the Earth Formed]

One alternate way to explain the magnetic field, that doesn't require heat-driven convection, holds that the convection is driven by changes in composition inside of the Earth. The inner core started forming about 1 billion years ago, when temperatures finally dropped low enough for iron metal to freeze solid, scientists think. As iron continues to solidify, lighter elements in the metal mixture, such as oxygen and carbon, may escape and rise toward the mantle, fueling convection currents.

It's also possible that a heat-driven magnetic field, or geodynamo, existed before the inner core formed, said Monica Pozzo, a geophysicist at University College London and leader of the 2012 modeling work.

"A sure impact of this [new] work will be to intensify the current debate on the thermal history of the Earth and the workings of the geodynamo," Pozzo said.

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science .

Plate tectonics is the movement of the crust that builds mountains and opens ocean basins. How this gargantuan process got started on early Earth has been quite a mystery. Now, a new computer model suggests the motion started because of gravity: Whole continents flattened out under their own weight.

That's not how the Earth's crust gets jostled today. Currently the continents and ocean basins all float on the mantle, the layer beneath the crust, which flows like putty. Deep parts of the mantle heat up, and rise, and as they do they cool down, sinking again, creating huge circular currents. The currents push and pull the tectonic plates across Earth's surface.

When plates smash into each other, they make mountains like the Himalayas, and where they spread apart, molten rock bubbles up and makes new crust, as in the Mid-Atlantic Ridge. Crust is recycled at subduction zones, like the one that marks the "Ring of Fire" in the Pacific Ocean, where it sinks back down into the mantle. [In Images: How North America Grew as a Continent]

But early in Earth's history, the mantle was hotter, and perhaps too hot to latch onto the continents — it wasn't viscous enough to "stick" and impart much force. In addition, the continental and oceanic crust was thicker and would have been of similar buoyancy because of the additional heat from below. Plates would have just been immobile — they wouldn't subduct or move much. Only when the mantle cooled could it generate enough force to get the motion going — think of the difference between sliding over water and sticking to honey. That's why most geologists think current plate tectonics started after the mantle's temperature dropped, said Patrice Rey, an associate professor at the University of Sydney and lead author of the new study.

Gravity moves Earth

However, there are bits of rock called xenoliths that are found in ancient continental plates (cratons), which are some of the oldest rocks on Earth. They show evidence of repeated melting and cooling, in a layered structure. The new computer model explains how such layered rocks can appear on a young, hot Earth, even without modern plate tectonics, and end up in the cratons.

Instead of subduction driven by the moving mantle, the early rocky plates that made up the crust of our planet began spreading out like melting cheese and bumping up against other plates along their edges. The result was some plates sliding over the others, causing the plate on the bottom to dive into the mantle, or subduct. [Infographic: Tallest Mountain to Deepest Ocean Trench]

As the plates spread out under their own weight, they would partially melt on the bottom, since they'd be thinner and easier to heat from below. Rey and his team estimate continents' bases could go from being about 140 miles (225 kilometers) down to about 46 miles (74 km). That thinning of the crust brought up more mantle material. The mantle material cooled and hardened, becoming crustlike, accreting on the ancient plate.

For up to 150 million years, gravitational spreading could have driven early plate tectonics – it was getting the ball rolling for later plate tectonic activity.

The spreading in the new model occurs because the ancient continents and the mantle just underneath were warmer, by about 360 degrees Fahrenheit (200 degrees Celsius) in the lower layers, down to about 100 miles (160 km) below the surface.  That makes it more ductile – by comparison to today's crust it would have been rather soft.

"The gravitational force in a geological context has the same origin as the force responsible for the spreading of a piece of Camembert under its own weight," Rey told Live Science. A piece of the creamy cheese will, on a warm day, spread out and flatten, even though it won't melt.

Gravitational spreading is still a force in geology today, Rey said, though it isn't as prominent. "On the present-day Earth, the gravitational force … explains the occurrence of extensional deformation in the Tibetan plateau, which tends to spread laterally."

There is still work to be done – it's a computer model – but Rey thinks it goes some way to help explain the composition and structure of the current crust.

The researchers, including Rey, Nicolas Colticeat the University of Lyon and Nicolas Flamentat the Institut Universitaire de France, detail the work today (Sept. 17) in the journal Nature.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Antarctica is rising unusually quickly, revealing that hot rock in the Earth's mantle hundreds of miles below the icy continent is flowing much faster than expected, researchers say.

Antarctic ice is more than 2.6 miles (4.2 kilometers) thick on some parts of the continent, a reminder that glaciers that were miles thick once covered many parts of Earth's surface. When these ice sheets shrink, as is happening now in the world's polar regions due to climate change, the underlying Earth rebounds upward, like how mattresses typically decompress after people get off them.

Past research suggested this rebound involved very slow uplift of the Earth's surface over thousands of years. However, an international research team now reveals that at GPS stations on the Northern Antarctic Peninsula, the land is actually surging upward at the rate of up to 0.59 inches (15 millimeters) a year. [Vanishing Glaciers: Stunning Images of Earth's Melting Ice]

Furthermore, "closer to the site of the ice loss — that is, right next to the thinning glaciers where we do not have any GPS sites — the Earth is likely to be rebounding significantly more than 15 millimeters [0.59 inches] per year," lead study author Grace Nield, a geophysicist at Newcastle University in England, told Live Science."As much as 47 millimeters [1.85 inches] per year has been predicted from our models."

How much uplift?

The usual models of the Earth cannot account for this much uplift.

"You would expect this rebound to happen over thousands of years, and instead we have been able to measure it in just over a decade," Nield said in a statement. "You can almost see it happening, which is just incredible."

Since 1995, several ice shelves in the Northern Antarctic Peninsula have collapsed, causing the solid Earth to bounce back.

"Think of it a bit like a stretched piece of elastic," Nield said. "The ice is pressing down on the Earth, and as this weight reduces, the crust bounces back."

The scientists analyzed data from seven GPS stations situated across the Northern Antarctic Peninsula to see how the Earth's surface was moving.

"What we found when we compared the ice loss to the uplift was that they didn't tally," Nield said. "Something else had to be happening to be pushing the solid Earth up at such a phenomenal rate."

Flow in the mantle

The researchers suggest that characteristics of the Earth's mantle layer — the region of the planet directly below the Earth's crust — can explain why this rebound is happening so quickly. Specifically, 250 miles (400 km) below the Northern Antarctic Peninsula, the upper part of the mantle is at least 10 times less resistant to flow than previously thought, and much less resistant to flow than the rest of Antarctica.

"Because the mantle is 'runnier' below the Northern Antarctic Peninsula, it responds much more quickly to what's happening on the surface," Nield said. "So as the glaciers thin and the load in that localized area reduces, the mantle pushes up the crust."

The mantle under the Northern Antarctic Peninsula may be comparatively runny due to subtle differences in temperature or chemical composition, the researchers say. This means the region is less viscous, so it flows more easily.

"The mantle is flowing so fast that we can observe it in just a few years," Nield said.

A question scientists might ask "is whether the uplift recorded by the GPS stations could be caused by something other than ice loss," Nield said. "This is unlikely, as prior to ice-shelf collapse and ice unloading, the GPS records show almost no uplift at all."

The next step is to look at the horizontal motions caused by the shrinking of the ice sheet to get more of a 3D picture of how the Earth is deforming, Nield said.

"In theory, the Earth should not only be moving up, but also away from the location of the ice loss. Examining horizontal deformation can therefore verify the results we have," Nield said. "Additional GPS stations can also help to refine the results, and several such stations have recently been installed in this region of Antarctica."

The scientists detailed their findings online May 12 in the journal Earth and Planetary Science Letters.

Follow Live Science @livescience, Facebook& Google+. Original article on Live Science.

The carbon dioxide that makes soft drinks fizz could help solve the mystery of why rocks melt the way they do beneath the seafloor, researchers say.

These findings could help explain the motion of the giant tectonic plates that surf over Earth's mantle (the rocky inner layer above the core). By understanding these movements, scientists can get a better picture of how the continents have drifted over time, as well as gain more insight into disasters such as earthquakes and volcanic eruptions.

Scientists think a layer of relatively soft, weak rock in Earth's upper mantle layer sits right underneath the planet's crust, or outer layer. This layer would help lubricate the motion of tectonic plates and explain how they can move as freely as researchers have observed. [In Images: How North America Grew as a Continent]

A popular candidate for the source of this lubrication is a very small degree of melting of the upper mantle. Such melting would also explain the high electrical conductivity seen in the rock below the plates, as well as the low speed or velocities of seismic waves rippling through them.

However, this idea has run into trouble, because computer models had suggested a relatively large amount of molten rock was needed to explain the electrical properties and seismic velocities seen under the oceanic tectonic plates. Such large amounts of molten rock could escape from the surrounding rock, which is not what investigators have seen.

To help solve this mystery, researchers analyzed in the lab what happened if the kind of silicate rock found in the mantle was rich in both water and carbon dioxide, the basic ingredients of soda water. Surface rock that is rich in water and carbon dioxide gets driven into the mantle at the borders of tectonic plates.In lab experiments, the investigators subjected this "juice, a molten mixture of carbon dioxide, water and silicate," to the kinds of high pressures and high temperatures found in the mantle, said study author Fabrice Gaillard, a geoscientist at the University of Orleans in France.

The scientists found this melted rock was highly electrically conductive. Their computer models suggest that very small amounts of such molten rock — making up less than 0.5 percent of the mantle's volume — could explain both the electrical properties and seismic velocities seen under oceanic plates.

"Such a small amount of melt could have a major impact on large-scale processes — a bit like David winning against Goliath," Gaillard told Live Science.

The scientists detail their findings in the May 1 issue of the journal Nature.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Updated Tues., April 22 at 1:34 p.m. ET.

Mysteriously, most of the gas xenon that scientists expected to find in Earth's atmosphere is missing. Now, researchers say they might have the answer to this puzzle: This noble gas, which usually does not bond with other atoms, may chemically react with iron and nickel in Earth's core, where it's held.

Xenon is a noble gas, so, like other noble gases, such as helium and neon, it is mostly chemically inert. Scientists have long analyzed xenon to study the evolution of Earth and its atmosphere.

Strangely, atmospheric levels of xenon are more than 90 percent less than scientists would have predicted based on levels of other noble gases such as argon and krypton. [8 Chemical Elements You've Never Heard Of]

"The missing xenon paradox is a long-standing question," said study author Yanming Ma, a computational physicist and chemist at Jilin University in Changchun, China.

Although some researchers have suggested this xenon may have escaped from the atmosphere into space, the majority of scientists think it is hidden in the Earth's interior. However, investigators have long failed to find a way in which Earth might incorporate this gas into chemically stable compounds — For instance, there is no known way for ice or sediments to realistically capture xenon on Earth, meaning it should just escape into the atmosphere.

Past research had suggested Earth's core might hold xenon. However, "all the previous attempts to implicate the capture of xenon in the Earth's core have failed," Ma said.

Earth's core, which contains about one-third of the planet's mass, is made of iron and nickel. In 1997, scientists reported experiments that suggested xenon would not react with iron.

"Through a careful analysis of their work, however, we found that the experiment was carried out only up to 150 gigapascals, a pressure far from the Earth's inner-core pressure of 360 gigapascals," Ma said. (In comparison, 1 gigapascal is more than nine times greater than the pressure at the bottom of the Mariana Trench, the deepest part of the ocean.)

This past research also theoretically extrapolated what might happen if xenon were trapped at the high pressures found in Earth's inner core, and concluded that xenon would not bond with iron. However, those prior studies assumed xenon would form a so-called "hexagonal close-packed lattice" — essentially, a lattice of atoms resembling a solid whose bottom and top faces are hexagons and whose side faces are rectangles. This assumption was made because iron atoms normally form this kind of structure with other iron atoms.

However, Ma and his colleagues reasoned that, if the structures of iron-xenon compounds are different, they could form a compound. Their calculations now suggest that at the extreme temperatures and pressures found in Earth's core, xenon can bond with both iron and nickel. The most stable of these molecules are ones with one xenon atom and three iron atoms — XeFe3 — or one xenon atom and three nickel atoms — XeNi3. XeFe3 forms cubic lattices, while XeNi3 forms lattices whose top and bottom faces are hexagons and whose side faces are triangles.

These findings suggest Earth's core may hold all of the missing xenon. "We do hope future high-pressure experiments can be carried out to confirm our predictions," Ma said. Such high pressures could be achieved by squeezing objects between diamonds.

However, for those high-pressure experiments, "a high temperature of more than 6,000 Kelvin (10,340 degrees Fahrenheit or 5,727 degrees Celsius) must be applied. Such a high temperature, if not properly controlled, can easily lead to the breaking of the diamonds used for pressure generation. This might be the major obstacle for the experiment."

It remains uncertain what effects, if any, these xenon compounds might have had on the evolution of Earth's core. "This needs to be more deeply analyzed," Ma said.

The scientists detailed their findings online April 20 in the journal Nature Chemistry.

Editor's Note: This article was updated to fix some odd wording that occurred during the editing process.

Follow us @livescience, Facebook& Google+. Original article on Live Science.

A battered diamond that survived a trip from "hell" confirms a long-held theory: Earth's mantle holds an ocean's worth of water.

"It's actually the confirmation that there is a very, very large amount of water that's trapped in a really distinct layer in the deep Earth," said Graham Pearson, lead study author and a geochemist at the University of Alberta in Canada. The findings were published today (March 12) in the journal Nature.

The worthless-looking diamond encloses a tiny piece of an olivine mineral called ringwoodite, and it's the first time the mineral has been found on Earth's surface in anything other than meteorites or laboratories. Ringwoodite only forms under extreme pressure, such as the crushing load about 320 miles (515 kilometers) deep in the mantle.

What's in the mantle?

Most of Earth's volume is mantle, the hot rock layer between the crust and the core. Too deep to drill, the mantle's composition is a mystery leavened by two clues: meteorites, and hunks of rock heaved up by volcanoes. First, scientists think the composition of the Earth's mantle is similar to that of meteorites called chondrites, which are chiefly made of olivine. Second, lava belched by volcanoes sometimes taps the mantle, bringing up chunks of odd minerals that hint at the intense heat and pressure olivine endures in the bowels of the Earth.

In recent decades, researchers have also recreated mantle settings in laboratories, zapping olivine with lasers, shooting minerals with massive guns and squeezing rocks between diamond anvils to mimic the Earth's interior.

These laboratory studies suggest that olivine morphs into a variety of forms corresponding to the depth at which it is found. The new forms of crystal accommodate the increasing pressures. Changes in the speed of earthquake waves also support this model. Seismic waves suddenly speed up or slow down at certain depths in the mantle. Researcher think these speed zones arise from olivine's changing configurations. For example, 323 to 410 miles (520 to 660 km) deep, between two sharp speed breaks, olivine is thought to become ringwoodite. But until now, no one had direct evidence that olivine was actually ringwoodite at this depth. [Infographic: What is Earth Made Of?]

"Most people (including me) never expected to see such a sample. Samples from the transition zone and lower mantle are exceedingly rare and are only found in a few, unusual diamonds," Hans Keppler, a geochemist at the University of Bayreuth in Germany, wrote in a commentary also published in Nature today.

Earth's deepest ocean

The diamond from Brazil confirms that the models are correct: Olivine is ringwoodite at this depth, a layer called the mantle transition zone. And it resolves a long-running debate about water in the mantle transition zone. The ringwoodite is 1.5 percent water, present not as a liquid but as hydroxide ions (oxygen and hydrogen atoms bound together). The results suggest there could be a vast store of water in the mantle transition zone, which stretches from 254 to 410 miles (410 to 660 km) deep.

"It translates into a very, very large mass of water, approaching the sort of mass of water that's present in all the world's ocean," Pearson told Live Science's Our Amazing Planet.

Plate tectonics recycles Earth's crust by pushing and pulling slabs of oceanic crust into subduction zones, where it sinks into the mantle. This crust, soaked by the ocean, ferries water into the mantle. Many of these slabs end up stuck in the mantle transition zone. "We think that a significant portion of the water in the mantle transition zone is from the emplacement of these slabs," Pearson said. "The transition zone seems to be a graveyard of subducted slabs."

Keppler noted that it's possible the volcanic eruption that brought the deep diamond to Earth's surface may have sampled an unusually water-rich part of the mantle, and that not all of the transition-zone layer may be as wet as indicated by the ringwoodite.

"If the source of the magma is an unusual mantle reservoir, there is the possibility that, at other places in the transition zone, ringwoodite contains less water than the sample found by Pearson and colleagues," Keppler wrote. "However, in light of this sample, models with anhydrous, or water-poor, transition zones seem rather unlikely."

Ride on a rocket

A violent volcanic eruption called a kimberlite quickly carried this particular diamond from deep in the mantle. "The eruption of a kimberlite is analogous to dropping a Mentos mint into a bottle of soda," Pearson said. "It's a very energetic, gas-charged reaction that blasts its way to Earth's surface."

The tiny, green crystal, scarred from its 325-mile (525 km) trip to the surface, was bought from diamond miners in Juína, Brazil. The mine's ultradeep diamonds are misshapen and beaten up by their long journey. "They literally look like they've been to hell and back," Pearson said. The diamonds are usually discarded because they carry no commercial value, he said, but for geoscientists, the gems provide a rare peek into Earth's innards. [Shine On: Photos of Dazzling Mineral Specimens]

The ringwoodite discovery was accidental, as Pearson and his co-authors were actually searching for a means of dating the diamonds. The researchers think careful sample preparation is the key to finding more ringwoodite, because heating ultradeep diamonds, as happens when scientists polish crystals for analysis, causes the olivine to change shape.

"We think it's possible ringwoodite may have been found by other researchers before, but the way they prepared their samples caused it to change back to a lower-pressure form," Pearson said.

Editor's note: This story was updated March 17 to correct that hydroxide forms from oxygen and hydrogen atoms, not molecules.

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook and Google+. Original article at Live Science's Our Amazing Planet.

Inside most of the Earth, olivine is a hot mineral whose creepy behavior drives plate tectonics.

In the upper mantle — the top of the planetary layer between the crust and core — olivine's unusual behavior presents a paradox. These solid crystals must change shape for plate tectonics to work, oozing like toothpaste over long time scales. (The mantle's flow helps push and pull Earth's crustal plates.)

By mimicking the extreme pressures and temperatures of the mantle in a laboratory, scientists have found that olivine crystals move by contorting along internal defects. The defects allow one part of a crystal to slip and slide (or shear) over another part. That's how a single crystal morphs without breaking. The paradox? There's a missing defect. According to models, Earth's mantle flows in such a way that there should be three independent directions of movement for olivine crystals. But until now, researchers had found only two, said Patrick Cordier, a geophysicist at the University of Lille in France.

"Olivine shows only defects along two directions, not three," Cordier said. "This is not enough for achieving a general deformation. However, olivine-rich natural rocks show pervasive evidence suggesting that olivine deforms very easily in the mantle."

Cordier and his colleagues recently discovered a new kind of olivine crystal defect, one that could explain the paradox. The findings were published Feb. 26 in the journal Nature.

With an advanced electron microscopy technique, the researchers saw linear defects, called dislocations, at the boundaries between olivine crystals. The dislocations let individual crystals slide past one another. Malleable metals also have similar dislocations, which is why jewelry makers can bend and twist gold and silver into beautiful shapes. [50 Amazing Facts About Earth]

"Dislocations allow crystals to be sheared along some specific directions and on some specific planes," Cordier said. "If a crystalline solid has enough different kinds of those defects, it can exhibit an ability to deform which seems to ignore its crystalline structure. This is the case for metals. This is also the case for minerals and rocks," he told Live Science's Our Amazing Planet.

More work is needed before geoscientists will know whether the new discovery resolves the olivine paradox, said Greg Hirth, a geophysicist at Brown University who was not involved in the study. However, the study marks the first time dislocations have been discovered in geological materials, and will further understanding of the processes that control the mantle, Hirth said in a commentary on the findings that was also published in Nature.

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook and Google+. Original article at Live Science's Our Amazing Planet.

Dense chunks of Earth's crust may have dripped into the mantle layer underneath it early in the planet's history, a new study suggests.

The study, detailed online Dec. 1 the journal Nature Geoscience, reveals the crust once behaved very differently than it does now, and helps shed light on how the cores of modern continents were born, scientists said.

During the Archean eon that began about 4 billion years ago, some 600 million years after Earth was born, the planet retained more of the heat of its creation and had more radioactive matter than it does now, making the world's innards much hotter than they are currently. This led more of the mantle layer to melt, and this molten rock would have risen upward and cooled to become part of an ancient, primitive crust that was much thicker than it is today.

"At mid-ocean ridges on the modern Earth, temperatures are such that around 5 to 10 percent of the mantle melts to produce crust of around 5 to 10 kilometers [3 to 6 miles] thickness," said study lead author Tim Johnson, a petrologist at the University of Mainz in Germany. In contrast, under the much higher mantle temperatures during the Archean, "40 percent or more of the mantle may have melted, and would have produced a crust perhaps 40 kilometers [24 miles] or more in thickness," he said.

However, the amount of this ancient crust remaining today is low. This suggests that much of it was recycled back into the mantle, but scientists were uncertain how that happened.

Dripping crust

New computer models from Johnson and his colleagues suggest the rock at the base of this ancient thick crust was denser than the hot mantle underneath it. This would cause large portions of the crust to sink, dripping straight downward.

In contrast, the tectonic plates that make up Earth's crust nowadays mostly drift horizontally. Also, modern crust mostly gets recycled into the mantle at the border of tectonic plates, where one plate dives under another, not directly from the undersides of plates, Johnson said.

These findings could also help explain a conundrum over the nature of Archean crust uncovered after past studies of some of the oldest features of Earth's crust — the so-called tonalite–trondhjemite–granodiorite complexes found in areas such as Scotland and Greenland. These conglomerations of rocks are most commonly present in cratons, the oldest and most stable cores of modern continents.

These ancient complexes most likely originated from a source low in the element magnesium, but prior calculations suggested the ancient crust should have been high in magnesium. These new findings suggest that after the dense crust sunk into the mantle, it would generate a return flow of mantle rock that would melt to potentially generate the kind of magnesium-poor crust required for these ancient rocks.

"We have shown how the early Earth might have operated," Johnson told LiveScience.

Follow us @livescience, Facebook & Google+. Original article on LiveScience.

SAN FRANCISCO — The vast two-thirds of the planet that is covered by water is largely invisible to us. But now, researchers are trying to map the areas of the deep ocean and beyond using seismic equipment.

The idea, described here Monday (Dec. 9) at the annual meeting of the American Geophysical Union, is to place hundreds of floating seismic devices into the seas to measure the vibrations of earthquakes coming from the seafloor. The insights from the new devices could be used to understand processes that occur deep within the Earth's mantle. And the floating seismic stations have now passed their first tests on two real excursions, showing they can distinguish the sounds of relatively small-magnitude earthquakes from the din of whale calls, ships passing and other ocean noise.

Though seismologists track earthquakes from thousands of devices on land, just a few permanent island stations record earthquakes at sea. As a result, when waves from a deep earthquake travel through the Earth's mantle and core, most of a wave's path goes unrecorded, hidden in the depths of the ocean. [The 10 Biggest Earthquakes in History]

That makes it difficult for scientists to understand many fundamental processes that occur deep within the Earth's interior, Guust Nolet, a geophysicist at Géoazur, who helped develop the project, said in a news conference.

Floating seismic stations

To understand these mantle processes better, scientists need a way to track seismic waves that are only detectable in the two-thirds of the planet covered by the oceans. So Nolet and his colleagues have developed floating seismic stations.

The devices, called MERMAIDs (or Mobile Earthquake Recorder in Marine Areas by Independent Divers), combine a float with a microprocessor and a tiny underwater sound recorder called a hydrophone. The MERMAIDs can float down to a depth between 2,300 and 6,600 feet (700 and 2,000 meters) below the ocean surface and stay at those depths for up to 10 days, passively listening for the signature vibrations of earthquakes. The simple systems run on the same batteries that power a flashlight, and unlike existing sea-based hydrophones, which are often fixed to the seafloor, the MERMAIDs float with the current to investigate many locations. When they pick up a sound, a sophisticated algorithm filters the sound to distinguish earthquake vibrations from the sounds of fin whales, passing ships and other ocean noise.

The "MERMAID is essentially a floating computer that never stops listening," said Yann Hello, director of research and development with Géoazur.

So far, the team has deployed two of the floating seismic stations in the Mediterranean Sea and two more in the Indian Ocean. Already, one of the devices detected a magnitude-5.0 vibration that triggered a swarm of 200 temblors.

"This was recorded nowhere else on Earth," Nolet said.

Now the team hopes to develop a next-generation of the device that can last for several years, plumb deeper reaches of the sea and harness the energy of ocean waves to run. Ultimately, they hope to deploy 300 to 400 of them across the world's oceans.

Follow Tia Ghose on Twitter  and Google+. Follow us @livescience, Facebook & Google+. Original article on LiveScience.

Earth may have possessed a magnetic field shortly after its birth, suggesting that magnetic shielding could have played a larger role in the development of life on Earth than currently thought, researchers say in a new study.

Nowadays, churning that occurs in Earth's liquid outer core creates the dynamo that generates Earth's magnetic field. This churning, known as convection, happens because of heat flow — electrically conductive molten iron alloy in the core's outer layer gets hot and rises, then dissipates this heat and sinks.

Investigations of ancient rocks suggest Earth has possessed a magnetic field for at least the past 3.5 billion years of its 4.6-billion-year history. Earth's magnetic field leaves an imprint on magnetically sensitive minerals in cooling lava, literally setting in stone the direction the planet's magnetic poles were aimed when the rocks formed.

However, recent experiments hint Earth's core might not have been able to generate a magnetic field until about 2.1 billion years ago. These studies suggested the amount of heat flowing out of the core needs to be nearly three times greater than once thought to create enough convection to generate a dynamo. The core could not sustain this huge amount of heat flow for the entire 3.5-billion-year history of Earth's magnetic field.

In the new study, researchers suggest Earth's first magnetic field may not have originated from the planet's core as it does today, but from a giant ocean of magma sitting on top of the core.

Moreover, this magma ocean may have given Earth a magnetic field beginning 4.5 billion years ago, some 1 billion years earlier than Earth is currently suspected to have possessed a magnetic field.

"If the model is correct, it shatters nearly every assumption about the early Earth," study author Dave Stegman, a geophysicist at the University of California, San Diego, told LiveScience's OurAmazingPlanet.

'Far-reaching consequences'

Past research suggested a magma ocean might have existed in the lowermost part of Earth's mantle layer between the core and crust from very early in Earth's history. This ocean would have existed from about 4.5 billion years ago to at least about 2.5 billion years ago. Oregon State University geophysicist and study co-author Leah Ziegler read about how a magma ocean within Jupiter's moon Io might influence Jupiter's magnetic field and wondered if Earth's ancient magma ocean could have generated a magnetic field.

Ziegler and Stegman modeled a range of electrical and magnetic properties that molten silicate rock in this magma ocean might have possessed. The researchers found that the molten rock's electrical conductivity might have been high enough to drive a dynamo early in Earth's history.

"The most important implication is that the Earth's early magnetic field was not generated in the core as has always been previously thought, but rather from inside the mantle," Stegman said.

If Earth had a magnetic field shortly after its birth, "this could have far-reaching implications," Stegman added. For example, if Earth had magnetic shielding from the sun that early on, this may have had consequences for the development of life on Earth.

"The first living cells on Earth may have first appeared 3.5 billion years ago, so perhaps the origin of life was related to the stable surface environment allowed by [the] protection of a magnetic field around Earth," Stegman said. "Magnetic shielding would also protect the atmosphere from being eroded away by the solar wind."

It remains uncertain if silicate liquids at the extreme pressures and temperatures found in this magma ocean would have been electrically conductive enough to drive a dynamo. The researchers plan to test their idea with a more sophisticated model of magnetic field generation.

"If our next results are also favorable, that should provide enough impetus for other disciplines to more seriously consider investigating this model," Stegman said.

Ziegler and Stegman detailed their findings online Nov. 26 in the journal Geochemistry, Geophysics, Geosystems.

Follow OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article at LiveScience's OurAmazingPlanet.

A series of deadly earthquakes that shook New Zealand in 2010 and 2011 may have weakened a portion of Earth's crust, researchers say.

New Zealand lies along the dangerous Ring of Fire — a narrow zone around the Pacific Ocean where about 90 percent of all the world's earthquakes, and 80 percent of the largest ones, strike.

A devastating magnitude- 6.3 quake struck New Zealand's South Island in 2011. Centered very close to Christchurch, the country's second-largest city, it killed 185 people and damaged or destroyed 100,000 buildings. The earthquake was the costliest disaster to ever strike New Zealand, consuming about one-sixth of the country's gross domestic product.

This lethal earthquake was the aftershock of a magnitude-7.1 temblor that struck 172 days earlier (in 2010) in the area, causing millions of dollars in damage to bridges and buildings, and seriously injuring two people. Although the 2010 temblor was stronger than its aftershock, it caused less damage because it occurred farther away from any city. The 2011 earthquake was, in turn, followed by a number of large aftershocks of its own. [Image Gallery: This Millennium's Destructive Earthquakes]

Scientists found that most of the earthquakes that struck New Zealand during these two years released abnormally high levels of energy, consistent with those seen from ruptures of very strong faults in the Earth's crust. To learn more about this long series of energetic quakes, researchers analyzed the rocks beneath the area hit, known as the Canterbury Plains.

Widespread weakening

Approximately 6 miles (10 kilometers) below the Canterbury Plains lies a large, extremely strong block of volcanic rock called the Hikurangi Plateau, which was pulled underground about 100 million years ago, when the portion of the Earth's surface it rested on dove under the edge of the ancient supercontinent Gondwana. It remains attached to Earth's crust, welded to chunks of a dark, gray sandstone known as greywacke.

The scientists analyzed seismic waves detected before and after the quakes by GeoNet, a network of seismographs across New Zealand. Based on this data, including seismic waves from more than 11,500 aftershocks of the 2010 quake, they mapped the 3D structure of the rock under the Canterbury Plains, similar to the way ultrasound data can provide an image of a fetus in a womb.

Beneath the surface broken by the quakes, the researchers identified a broad region that appeared to be dramatically weaker after the quakes. This suggests there was widespread cracking of greywacke 3 miles (5 km) around the fault. In contrast, earthquakes of similar magnitude in the crust elsewhere typically only "produce zones of cracked rock around the fault which are a few hundred meters wide," said study lead author Martin Reyners, a seismologist at research institute GNS Science in Lower Hutt, New Zealand.

Until now, scientists had assumed that the strength of Earth's crust remains constant during aftershocks. But these new findings, detailed online Nov. 24 in the journal Nature Geoscience, suggest energetic quakes can lead to widespread weakening of the crust.

"Such widespread weakening is not common, and has not been reported previously," Reyners told LiveScience's OurAmazingPlanet.

Why there?

To explain why weakening was seen in that particular region and not elsewhere after strong quakes, Reyners noted the increasing pressure and temperature seen with increasing depth in the crust that usually means that at depths of more than about 6.8 miles (10.9 km), rocks are no longer brittle. As a result, the rocks often flow, not crack, when force is applied to them.

"This is known as the brittle-plastic transition," Reyners said.

However, "because of the very strong rock unit underlying Canterbury, the brittle-plastic transition is very deep — it lies at about 35 kilometers [22 miles] depth," Reyners said. As such, widespread cracking and weakening of the rock occurred.

The researchers will now focus on figuring out how widespread this strong block of rock is at shallow depths throughout the eastern portion of the South Island of New Zealand. "This is important for defining the seismic hazard for communities in this region," Reyners said.

Follow OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article at LiveScience's OurAmazingPlanet.

Something is not quite right inside the Earth's core. When seismic waves from earthquakes ripple through its solid center, they hit a speed bump.

The seismic vibrations should zip along about 30 percent faster than their actual speed, according to experiments and computer models recreating the conditions inside the inner core. Scientists have tried to explain this odd observation by playing around with the core's properties — adding metal such as nickel, or suggesting that iron acts strangely deep inside the planet.

Now, a new computer model of Earth's inner core explains the seismic wave slowdown via changes in iron's strength just before the metal melts. The findings were published Oct. 10 in the journal Science.

Scientists think the Earth's outer core is liquid, but the heart is solid iron and nickel, plus traces of elements such as sulfur and gold. Seismic waves passing through the core provide a snapshot view, similar to a CT scan, of its structure. The planet's magnetic field and the rotation of the Earth also offer clues to the core's composition and structure.

The new model indicates that inside the inner core, just before iron melts, the metal's strength weakens dramatically, according to researchers at University College London in the United Kingdom. Weaker iron is less stiff, so one kind of seismic wave that passes through the core, called a shear wave, can travel more quickly. In the team's computer model of the inner core, when iron is at about 99 percent of its melting temperature, the seismic velocities match the speeds picked up by instruments that monitor earthquakes.

"The proposed mineral models for the inner core have always shown a faster wave speed than that observed in seismic data," Lidunka Vočadlo, a co-author of the study, said in a statement. "This mismatch has given rise to several complex theories about the state and evolution of the Earth's core."

"The strong premelting effects in iron shown in our paper are an exciting new development in understanding the Earth's inner core," said Vočadlo, a geophysicist at University College London. "We are currently working on how this result is affected by the presence of other elements, and we may soon be in a position to produce a simple model for the inner core that is consistent with seismic and other geophysical measurements."

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on LiveScience.

Billions of years ago, the newborn Earth morphed from a messy ball of mixed-up rock to a perfectly layered planet with an iron core.

A new model explaining this mysterious process suggests the core was created as dribs and drabs of iron percolated inward from Earth's lower mantle, according to a study published Oct. 6 in the journal Nature Geoscience. The mantle is the viscous, rocky layer between the crust and Earth's iron core.

To confirm the model, researchers recreated the conditions of the early Earth. By squeezing a tiny speck of iron and rock between two diamond-tipped anvils, and then zapping the whole shebang with a laser, scientists mimicked the hot temperatures and high pressures inside the young planet.

The experiment revealed that the right conditions were present in the lower mantle for iron blobs to connect and form continuous channels, and then tunnel into the core. [What Is Earth Made Of?]

Earlier studies had found that in the upper mantle, iron stayed in isolated pockets, leading researchers to pooh-pooh the idea that iron percolated into the core.

"In order for percolation to be efficient, the molten iron needs to be able to form continuous channels through the solid," lead study author Wendy Mao, a geoscientist at Stanford University in Palo Alto, Calif., said in a statement. "Scientists had said this theory wasn't possible, but now we're saying, under certain conditions that we know exist in the planet, it could happen. So this brings back another possibility for how the core might have formed."

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook & Google+. Original article on LiveScience's OurAmazingPlanet.

The Earth's magnetic field controls the direction and speed at which Earth's inner and outer cores spin, even though they move in opposite directions, new research suggests.

Scientists have long suspected that Earth's magnetic field — which protects life from harmful space radiation — drifts in a slightly westerly direction. That theory was established in the 1690s, when geophysicist Edmund Halley (the same Halley who spotted the eponymous comet) sailed aboard a research vessel through the South Atlantic Ocean and collected enough compass readings to identify this shift.

By the mid-20th century, geologists had gathered further evidence for this drift and had determined that the westerly rotation of the magnetic field exerts a force on the liquid outer core— composed of a molten mix of iron and nickel — that causes it to rotate in a westerly direction. Decades later, geophysicists used deep seismic data to determine that the inner core — a solid iron-nickel alloy that is about the size of the moon — rotates in an easterly direction, at a greater speed than the rotation of the Earth itself.

But, until now, scientists have regarded these rotations within the two layers of the core as separate, with no relation to each other.   

Now, researchers at the University of Leeds in England have found a common link between the two rotations by creating a computer model that shows how the rotation of the Earth's magnetic field can both pull the liquid outer core in a westerly direction while also exerting an opposite force on the inner core that causes an easterly rotation.

"Previously, there have been these two independent observations, and there has not been a link between them," study co-author Philip Livermore, of the University of Leeds, told LiveScience's OurAmazingPlanet. "We argue that the magnetic field itself is pushing on the outer core, and there is an equal and opposite push on the inner core."

The Earth's magnetic field — created by the convection of hot liquid metal within the outer core — undergoes slight fluctuations roughly every decade. The inner core's rotation rate has also been shown to fluctuate on a similar timescale. These new results help explain why these two phenomena occur on the same timescale, since one has now been shown to affect the other, the researchers say.

The findings were detailed in the Sept. 16 issue of the journal Proceedings of the National Academy of Sciences.

Follow Laura Poppick on Twitter. Follow LiveScience on Twitter, Facebook and Google+. Original article on LiveScience's OurAmazingPlanet.

The way heat flows near the Earth's core, which is key to understanding the planet's evolution, has now been revealed to move more sluggishly than previously thought, researchers said.

The manner in which heat flows inside the Earth helps control how the world's innards move. That in turn drives major events on the planet's surface — for instance, the drifting of the continents, or the rise of giant pillars of hot molten rock from near Earth's core. However, due to its depth, much remains uncertain about the way heat flows near the deep lower mantle region some 400 to 1,800 miles (660 to 2,900 kilometers) below the surface. (Earth is made up of a solid inner core, surrounded by a liquid-metal outer core, above which is the solid but flowing mantle, covered by the planet's crust.)

To deduce the way Earth's lower mantle behaves, researchers have sought to subject rock to the kind of heat and pressure found there, which is no easy task. In this experiment, researchers used a new technique to for the first time measure the way heat flows in rock while under the extreme pressure found in the region. [Religion and Science: 6 Visions of Earth's Core]

"The lower mantle sits on top of the core where pressures range from 230,000 to 1.3 million times the pressure at sea level," researcher Douglas Dalton at the Carnegie Institution of Washington, said in a statement. "Temperatures are like an inferno — from about 2,800 to 6,700 degrees F (1,500 to 3,700 degrees C)."

The researchers experimented with magnesium oxide, which is found in major components of the mantle. They squeezed the samples between two diamonds with an anvil. "We went up to 600,000 times atmospheric pressure at room temperature," researcher Alexander Goncharov, a physicist at the Carnegie Institution, said in the statement.

In the past, scientists could measure only the thermal conductivity of minerals, or how easily they transfer heat, under relatively low pressures — it can be difficult placing probes for testing thermal conductivity in the limited confines used to generate high pressures. To overcome this obstacle, Goncharov and his colleagues used lasers that could scan the surface of a sample and measure its reflectiveness. The researchers could then use that number to deduce the sample's temperature, avoiding the need to fit into tight spaces to keep in touch with sampled materials.

"The laser technique, which our team was using, is truly unique," Goncharov said. "It was indeed a very exciting moment when our group managed to perform reliable measurements under pressure."

Their findings revealed thermal conductivity was less dependent on pressure than predicted. As such, heat should flow more slowly in the lower mantle than researchers had predicted. At the boundary of the core and mantle, the team estimated total heat flow was about 10.4 terawatts, or 60 percent of the power used today by civilization.

In the future, the scientists will test other mineral components of the mantle.

"The results suggest that this technique could really advance other high pressure and temperature studies of the deep Earth and provide a better understanding of how Earth is evolving and how materials act under intense conditions," Goncharov said in the statement.

The scientists detailed their findings online Aug. 9 in the journal Scientific Reports.

Follow LiveScience on Twitter, Facebookand Google+. Original article on LiveScience.

Giant fountains of hot rock under central Africa and the central Pacific that have apparently remained stationary for at least 250 million years are helping drive the movements of the massive tectonic plates making up Earth's surface, researchers say.

Below the rocky layer that makes up Earth's outermost skin, known as the lithosphere, is the searing hot rock of the mantle layer. The way this viscous rock flows drives movements in Earth's surface, resulting in the birth and death of supercontinents and the building of mountains when tectonic plates smash together.

Pinpointing what patterns might exist in mantle flow has proved difficult because of uncertainty in how to interpret scans of the inner Earth. Now researchers find they can deduce mantle flow patterns through another route — by looking at the way tectonic plates have drifted over the eons, as this drift is based on how the viscous innards of the planet have flowed.

"This knowledge will help us understand how mantle dynamics affect processes such as mountain-building and volcanism that have shaped our planet over geologic time," researcher Clinton Conrad, a geophysicist at the University of Hawaii at Manoa in Honolulu, told LiveScience's OurAmazingPlanet.

'Fascinating' flow

Conrad and his team analyzed past models of the motions of tectonic plates for the past 250 million years, when Earth's landmasses were combined into the supercontinent Pangaea. They next inferred how the mantle should have churned underneath those plates to produce those movements.

The investigators discovered tectonic plates are diverging away from points beneath central Africa and the central Pacific. These points have apparently remained stationary for the past quarter-billion years despite continuing formation and destruction of seafloor and supercontinents at the surface.

"I found it fascinating that the basic flow patterns in such a complicated and obscure place such as the mantle could be so simple and stable over geologic time," Conrad said.

The researchers suggest these points are essentially giant stable upwellings of hot rock that rise up from the lowermost mantle and drive mantle flow and plate tectonics.

"The dynamics of these giant upwellings are not well understood — their stability is thus an interesting feature that helps to define them," Conrad said. "Typically, upwellings in the mantle form very thin 'plumes' that are only a few hundred kilometers across, such as the plume that is thought to be rising beneath Hawaii. Giant plumes, on the other hand, which are thousands of kilometers across, tend not to be as stable as smaller plumes."

Giant upwellings apparently result from the interactions of two different materials in the mantle — "a dense one below and a lighter one above," Conrad said. "Models do not typically show these upwellings to remain stably positioned, so that is something new."

'Uncertain mechanism'

One factor that might help keep these upwellings stable over long times "is that they may be chemically different than the surrounding mantle — they may be chemically a little bit denser, which keeps them from fully rising to the top of the mantle," Conrad said. However, this requires some as-yet-uncertain mechanism to keep such material separate from the rest of the mantle over millions of years, he said.

Some have speculated the location of these upwellings might have something to do with the rotation of the Earth, which is adjusting itself to position these relatively dense spots on its equator, much like how tightrope walkers might hold their arms out to keep more stable.

"However, the details of this have not been well worked out yet," Conrad said.

Incidentally, the so-called plate tectonic dipole, "the one point on the Earth toward which all the plates are on average converging, happens to be in North Korea!" Conrad wrote in an email.

In the future, Conrad and his colleagues would like to peer even further back in time, "to 500 million years or so," he said, to see if the upwellings were in place then as well.

The scientists detailed their findings in the June 27 issue of the journal Nature.

Follow OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article at LiveScience's OurAmazingPlanet.

Arrays of sensors stretching across more than 1,500 miles in Africa are now probing the giant crack in the Earth located there — a fissure linked with human evolution — to discover why and how continents get ripped apart.

Over the course of millions of years, Earth's continents break up as they are slowly torn apart by the planet's tectonic forces. All the ocean basins on the Earth started as continental rifts, such as the Rio Grande rift in North America and Asia's Baikal rift in Siberia.

The giant rift in Eastern Africa was born when Arabia and Africa began pulling away from each other about 26 million to 29 million years ago. Although this rift has grown less than 1 inch (2.54 centimeters) per year, the dramatic results include the formation and ongoing spread of the Red Sea, as well as the East African Rift Valley, the landscape that might have been home to the first humans.

"Yet, in spite of numerous geophysical and geological studies, we still do not know much about the processes that tear open continents and form continental rifts," said researcher Stephen Gao, a seismologist at the Missouri University of Science and Technology in Rolla, Mo. This is partly because such research has mostly focused on mature segments of these chasms, as opposed to ones that are still in development, he explained. [Earth Quiz: Mysteries of the Blue Marble]

Seismic SAFARI

Geodynamic models suggest that below mature rifts, a region called the asthenosphere is upwelling. The asthenosphere is the hotter, weaker, upper part of the mantle that lies below the lithosphere, the planet's outer, rigid shell. So far, there are two contenders for what might cause this upwelling: anomalies deeper in the mantle or thinning of the lithosphere due to distant stresses.

To help find out which of the two different rifting models is correct, the Seismic Arrays for African Rift Initiation (SAFARI) project installed 50 seismic stations across Africa in the summer of 2012, each spaced about 17 to 50 miles (28 to 80 kilometers) apart.

"One of the techniques that we will use to image the Earth beneath the SAFARI stations is called seismic tomography, which is in principle similar to the X-ray CAT-scan technique used in hospitals," Gao told LiveScience's OurAmazingPlanet. "The only differences are that our sources of the 'rays' are earthquakes and man-made explosions, and the receivers are the seismic stations such as the 50 SAFARI stations."

Altogether, these arrays encompass a length of about 1,550 miles (2,500 km) and are located in four countries — Botswana, Malawi, Mozambique and Zambia.

"I think the project has a positive impact on local communities," Gao said. "Some of our 50 SAFARI seismic stations are on local schools, and the teachers and students were excited and were proud about the fact that their school was selected for a high-tech scientific instrument. We believe that this project showed some kids that the outside world is different and even fascinating."

The arrays will image the areas under the Okavango, Luangwa and Malawi rifts, the southwest and southernmost segments of the East African Rift system. These so-called incipient rifts are not yet mature and could thus shed light on why and how rifting occurs.

"This is the first large-scale project to image the structure and deformation beneath an incipient rift," Gao said. "The Okavango rift in Botswana is as young as a few tens-of-thousand years, while most other rifts such as the Rio Grande and Baikal rifts are as old as 35 million years."

Upwelling or thinning?

If thermal or dynamic anomalies deep in the mantle are responsible for rifting, then upwelling from the asthenosphere should already be occurring beneath these incipient rifts. In contrast, if thinning of the lithosphere is the cause of rifting, then any levels of upwelling should be insignificant because the lithosphere should not have thinned adequately for major upwelling to occur yet.

A magnitude-5.6 earthquake in November near the northern end of the Indian Ocean's mid-ocean ridge sent out seismic waves that were more than 1 second slower than predicted. This supports the idea that the mantle layer beneath Southern Africa is hotter than normal, perhaps due to a jet of magma known as a mantle plume that geologists have proposed exists beneath this area.

To image the structures beneath these rifts and pin down what the rifting mechanism in Eastern Africa is, researchers need data from more than just one event. The seismic arrays will be deployed for 24 months, and each station will sample the Earth for seismic waves 50 times per second.

"We are anxious to see if there are melted rocks in the mantle beneath the rifts, if there is convective mantle flow that is driving the rifting process, and how much the crust has been thinned in different portions of the rifts," Gao said. "But this cannot be done until next summer, when all the data recorded by SAFARI are processed."

The scientists detailed their findings to date in the June 11 issue of Eos, the online newspaper of the American Geophysical Union.

Follow OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article at LiveScience's OurAmazingPlanet.

The mystery of whether or not giant plumes of hot rock from near Earth's core force volcanic island chains to form could soon be solved with the largest campaign ever to map such jets of magma beneath the Earth's surface.

Volcanoes are typically found near the borders of tectonic plates, born as these plates either violently push or pull at each other. Strangely, volcanoes sometimes erupt far away from these boundaries in the middle of these plates. The sources of these outbursts might be mantle plumes, streamsof molten rock rising up from deep in the Earth to penetrate overlying material like a blowtorch. As the Earth's surface drifts over such plumes, geologists think chains of volcanic isles, such as the Hawaiian Islands, emerge.

However, more than 40 years after mantle plumes were first proposed, scientists are debating whether they actually exist. For example, it remains hotly debated whether and how mantle plumes can remain active and stationary for more than 100 million years.

To help resolve the controversy, a French-German project now aims to image a plume that may have played a role in the extinction of the dinosaurs.

The scientists have deployed nearly 60 seismometers in the Indian Ocean over a vast area of seafloor of more than 1.1 million square miles (3 million square kilometers) around Réunion Island, one of the most active volcanoes in the world. The seabed the devices rest on can vary from 7,500 feet (2,300 meters) to 18,000 feet (5,500 m) below the ocean's surface.

The seafloor devices join about 60 other seismometers on islands in the Indian Ocean, such as Réunion, Mauritius, Madagascar and the Seychelles. These land-based stations reduce the need for expensive sensors on the ocean bottom, researchers explained. [Infographic: Tallest Mountain to Deepest Ocean Trench]

"We are starting from a stage where almost nothing is known of the deep mantle structure beneath La Réunion and beneath the whole Indian Ocean region," researcher Guilhem Barruol, a seismologist at the University of La Réunion, told OurAmazingPlanet. "It's indeed exciting to take part of this deep Earth exploration."

Lurking beneath the surface

The plume that may lurk under Réunion is suspected to have seared a track of volcanic activity that stretches about 3,400 miles (5,500 km) northward from Réunion to the Deccan Plateau region of what is now India. At the end of the Age of Dinosaurs about 65 million years ago, massive volcanism in the Deccan area spewed lava across 580,000 square miles (1.5 million square km), radically altering Earth's climate and perhaps hastening the giant reptiles'demise.

The Réunion Hotspot and Upper Mantle-Réunions Unterer Mantel (RHUM-RUM) project aims to image the crust and mantle under Réunion at all depths for the biggest plume hunt so far. The network of ocean floor sensors will illuminate structures under the island down to about 600 miles (1,000 km) below the Earth's surface, while the land-based seismometers will image the area below that all the way to the boundary of the core and mantle. Coincidentally, two other seismological experiments are deploying 50 more seismic stations in Madagascar, data that, along with recent seismic-scanning initiatives such as AfricaArray, should help boost imaging of the mantle layer under Réunion.

The stems of mantle plumes are challenging to image because they may be 60 to 300 miles (100 to 500 km) or so wide, similar to the wavelengths of the seismic waves used to scan them. Using state-of-the-art techniques, such as methods that account for how seismic waves scatter around narrow conduits of magma, the researchers hope to pin down the existence and location of any plume that might exist, as well as how it might erode or spread under overlying rock.

Plume to ridge

Scientists think heat rising from oceanic mantle plumes may channel heat to nearby midocean ridges. Such flow channels might explain a series of anomalies near Réunion, such as volcanism on Rodrigues Island. RHUM-RUM will analyze Rodrigues Ridge to help confirm or refute this idea — the most recent volcanism on Rodrigues Island dates back 1.5 million years, so any flow channel should still be operating and will hopefully become the first to be clearly imaged, researchers said.

The researchers hope to provide insights "on the presence, or absence, of a deep mantle plume beneath a long-lived hotspot such as La Réunion and therefore bringing answers to important questions," Barruol said. "Is a rising plume present beneath the volcano? Is it continuous? Does it originate from the upper mantle? From the transition zone? From the lower mantle? From the core-mantle boundary as proposed [in] the plume models?"

The seafloor seismometers will analyze the Earth for about 13 months before the buoyant part of each machine detaches and rises, with all its data, back to the surface. Early results from RHUM-RUM are expected in 2015. Barruol and his colleague Karin Sigloch at Ludwig Maximilian University of Munich detailed their work to date in the June 4 issue of Eos, a trade publication of the American Geophysical Union.

Follow OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article at LiveScience's OurAmazingPlanet.

A pocket of water some 2.6 billion years old — the most ancient pocket of water known by far, older even than the dawn of multicellular life — has now been discovered in a mine 2 miles below the Earth's surface.

The finding, announced in the May 16 issue of the journal Nature, raises the tantalizing possibility that ancient life might be found deep underground not only within Earth, but in similar oases that may exist on Mars, the scientists who studied the water said.

Geoscientist Barbara Sherwood Lollar at the University of Toronto and her colleagues have investigated deep mines across the world since the 1980s. Water can flow into fractures in rocks and become isolated deep in the crust for many years, serving as a time capsule of what their environments were like at the time they were sealed off.

In gold mines in South Africa 1.7 miles (2.8 kilometers) deep, the scientists previously discovered microbes could survive in pockets of water isolated for tens of millions of years. These reservoirs were many times saltier than seawater, "and had chemistry in many ways similar to hydrothermal vents on the bottom of the ocean, full of dissolved hydrogen and other chemicals capable of supporting life," Sherwood Lollar said. [Strangest Places Where Life Is Found on Earth]

To see what other ancient pockets of water might exist, Sherwood Lollar and her colleagues investigated copper and zinc mines near the city of Timmins in Ontario, Canada. "As the prices of copper, zinc and gold have gone up, mines now go deeper, which has helped our search for long-isolated reservoirs of water hidden underground," Sherwood Lollar said.

'Mind-blowing' find

"Sometimes we went down in cages — they're not called elevators underground — that dropped us to the levels we wanted to go," Sherwood Lollar told OurAmazingPlanet. "Other times, we went down ramp mines, which have curling spiral roadways, so we could actually drive all the way down."

The scientists analyzed water they found 2 miles (2.4 km) deep. They focused on noble gases such as helium, neon, argon and xenon. Past studies analyzing bubbles of air trapped within ancient rocks found that these rare gases could occur in distinct ratios linked with certain eras of Earth's history. As such, by analyzing the ratios of noble gases seen in this water, the researchers could deduce the age of the water.

The scientists discovered the fluids were trapped in the rocks between 1.5 billion and 2.64 billion years ago.

"It was absolutely mind-blowing," Sherwood Lollar said. "These weren't tens of millions of years old like we might have expected, or even hundreds of millions of years old. They were billions of years old."

The site was formed by geological activity similar to that seen in hydrothermal vents. "We walked along what used to be ocean floor 2.7 billion years ago," Sherwood Lollar said. "You could still see some of the same pillow lava structures now seen on the bottom of the ocean."

Signs of life?

This ancient water poured out of the boreholes the team drilled in the mine at the rate of nearly a half-gallon (2 liters) per minute. It remains uncertain precisely how large this reservoir of water is.

"This is an extremely important question and one that we want to pursue in our future work," Sherwood Lollar said. "We also want to see if there are habitable reservoirs of similar age around the world."

Sherwood Lollar emphasized they have not yet found any signs of life in the water from Timmins. "We're working on that right now," she said. "It'd be fascinating to us if we did, since it'd push back the frontiers of how long life could survive in isolation."

And the implications of such a finding would extend beyond the extremes of life on Earth.

"Finding life in this energy-rich water is especially exciting if one thinks of Mars, where there might be water of similar age and mineralogy under the surface," Sherwood Lollar said.

If any life once arose on Mars billions of years ago as it did on Earth, "then it is likely in the subsurface," Sherwood Lollar said. "If we find the water in Timmins can support life, maybe the same might hold true for Mars as well."

Follow OurAmazingPlanet @OAPlanet, Facebook and Google+.Original article at LiveScience's OurAmazingPlanet.

Earth's solid-metal inner core is a key component of the planet, helping to give rise to the magnetic field that protects us from harmful space radiation, but its remoteness from the planet's surface means that there is much we don't know about what goes on down there. But some secrets of the inner core are being revealed by acoustic waves passing through the planet's heart and iron squeezed to enormous pressures in the lab.

Two new studies, both detailed online May 12 in the journal Nature Geoscience, reveal that Earth’s inner core may actually be softer than previously thought, and that the speed at which it spins can fluctuate over time.

Under the liquid-metal outer layer of the Earth's core is a solid ball of superhot iron and nickel alloy about 760 miles (1,220 kilometers) in diameter. Scientists recently discovered the inner core is, at 10,800 degrees Fahrenheit (6,000 degrees Celsius), as hot as the surface of the sun.

Churning in the liquid outer core results in the dynamo that generates Earth's magnetic field. Geoscientists think interactions between the inner and outer cores may help explain the nature of the planet's dynamo, the details of which remain largely unknown.

"The Earth's inner core is the most remote part of our planet, and so there is a lot we don't know about it because we can't go down and collect samples," said Arianna Gleason, a geoscientist at Stanford University in California. [Infographic: Tallest Mountain to Deepest Ocean Trench]

Shifting speeds

One way scientists can learn more about the inner core is by analyzing acoustic waves from earthquakes that ripple through the inner core as they pass through the planet. Hrvoje Tkalcic, a geophysicist at the Australian National University in Canberra, and his colleagues relied on earthquake doublets — earthquakes that occur in pairs and generate extraordinarily similar acoustic waves — to investigate the inner core. Because these waves are so alike, the data they return are readily comparable, and because they are separated relatively briefly in time, they can help the researchers image subtle changes that might occur in that time frame.

Seismic observations and computer models of the Earth's innards suggested the inner core spins at a different rate than the mantle does, but there were conflicting estimates for how fast the inner core actually rotated. By analyzing 24 earthquake doublets, Tkalcic and his collaborators found the speed at which the inner core spun apparently fluctuated over the course of approximately decades between 1961 and 2007.

"It is the first observational evidence that the inner core rotates at a variety of speeds with respect to the mantle...It also reconciles old discrepancies," Tkalcic told OurAmazingPlanet. (Past analyses of how fast the inner core rotated came up with different speeds.)

The inner core, on average, rotates eastward. At the speeds it travels, it might, on average, complete a revolution every 750 to 1,440 years. However, these speeds appear unstable, which makes it uncertain just how long it actually takes to finish a turn on its axis, Tkalcic said.

It remains unknown exactly why these fluctuations in speed happen. Gravitational and magnetic forces likely both play a part, Tkalcic said.

Weak iron

In another study, Gleason and her colleagues sought to learn more about the inner core by mimicking its conditions in the lab. They measured the strength of iron by squeezing it within a diamond anvil at room temperature while scanning it with X-rays.

"We know the Earth's inner core is composed mostly of iron, but we don't really know too much about the behavior of iron under the pressure and temperature at conditions in the core," Gleason said.

The metal was subjected to more than 200 billion pascals of pressure, or about 180,000 times the pressure of the average human bite.

"We found the inherent mechanical strength of iron under those conditions is quite low, surprisingly weak," Gleason said.

These findings may help explain why material within Earth's inner core is apparently distributed in a lopsided way, Gleason said. The weakness of iron might lead crystallites in the inner core to flow and line up a certain way, she explained.

Gleason noted that the researchers did not mimic the extreme temperatures found in the inner core, nor did the metal they experimented with match the composition of the inner core. In future experiments, they hope to use lasers to heat the metal to the proper temperatures, and test various iron-nickel alloys.

Follow OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article at LiveScience's OurAmazingPlanet.

Most of Earth's carbon clusters deep beneath the surface, in hot mantle rocks that churn below the planet's thin crust.

"Most people probably don't recognize that the vast majority of carbon — the backbone of all life — is located in the deep Earth, below the surface — maybe even 90 percent of it," Elizabeth Cottrell, a geologist at the Smithsonian's Museum of Natural History, said in a statement. Cottrell is lead author of a new study examining how the mantle's carbon cycle changes the chemistry of lava that forms new ocean crust.

At mid-ocean ridges, the gaping fractures that criss-cross Earth's ocean floors, lava oozes out directly from the mantle. Studying this lava gives geoscientists clues to what's going on thousands of miles below the surface.

Cottrell and co-author Katherine Kelley of the University of Rhode Island snared seafloor rocks from around the world, then analyzed their chemistry. Ratios of certain isotopes (atoms of an element with different numbers of neutrons), as well as oxidized iron, suggest carbon reservoirs stored for billions of years strongly influence mantle chemistry, the authors report in the May 2 issue of the journal Science Express.

When the mantle melts and erupts at mid-ocean ridges, it produces a handful of distinct rock chemistries. The reason for the different chemistries could be different sources. For example, the melt could come from ancient, subducted oceanic crust, driven deep into the mantle by plate tectonics, or a deep plume rising from near the core-mantle boundary.

The researchers discovered that one of these handful of rock chemistries, called enriched mantle, tends to carry reduced iron, while another, deemed depleted mantle, matches up with oxidized iron. The pairings make sense, if carbon is playing a role in controlling iron chemistry in the mantle, the researchers said.

"Carbon provides both a mechanism to reduce the iron and also a reasonable explanation for why these reduced lavas are enriched in ways we might expect from melting a carbon-bearing rock," Cottrell said.

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook & Google+. Original article on LiveScience's OurAmazingPlanet.