A tsunami that struck an Alaskan fjord in 2025 sloshed higher than the height of the top floor of One World Trade Center in New York, new research shows.

The study, published May 6 in the journal Science, found that the tsunami reached 1,578 feet (481 meters) up the slopes of the fjord, making it one of the tallest tsunamis ever recorded. It would have easily washed over the roof of New York's One World Trade Center, which stands 1,368 feet (417 m), not including its spire.

The study also found that the tsunami formed a standing wave, or "seiche," that sloshed back and forth in the narrow fjord for over a day. It's only the second time such a seiche has been recorded.

The tsunami hit Tracy Arm fjord, south of Juneau, on Aug. 10, 2025, when a massive landslide dropped 2.1 billion cubic feet (60 million cubic meters) of rock into the fjord's waters. The fjord is the outlet for the South Sawyer Glacier, which had been on a rapid retreat. It's not clear whether that retreat destabilized the slope or whether recent rains were more to blame, but the resulting tsunami was one of the largest on record. The only one known to be higher is a 1958 earthquake-triggered wave in Lituya Bay, Alaska, which scoured one slope to the height of 1,720 feet (524 m).

Although the fjord is often visited by cruise ships, it was empty on Aug. 10. Kayakers at the fjord's mouth, miles away, reported that their equipment was washed away by strong waves, but no one was hurt or killed by the tsunami.

Because no one saw the wave, discovering exactly what happened took some detective work. Thomas Monahan, a senior research associate in engineering at the University of Oxford, and his colleagues used satellite imagery and seismic data to build computer models of the tsunami. They observed long-lasting reverberations indicating that the wave splashed back and forth as a seiche. This phenomenon was previously observed in Greenland in 2023. The signal was more complex in Alaska than in Greenland, however, the researchers reported.

"This study shows that enclosed basins like fjords can effectively act as giant tuning forks, with the resonance determined by their shape and geometry," Monahan said in a statement. "This gives each fjord a unique 'signature' when they are affected by energetic events such as megatsunamis."

The satellite observations, gleaned from the Surface Water Ocean Topography satellite operated by NASA and France's space agency, also showed that the wave was more energetic than computer models would have predicted, Monahan said.

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Credit: The OLI (Operational Land Imager) on Landsat 8 and Landsat 9.

Cruise lines have canceled their incursions into the fjord this year due to the possible risk of another slide. Study co-author Stephen Hicks, an Earth scientist at University College London, said the research might point to a way to predict such slides.

"With hindsight, there were some warning signs," he said in the statement. "Tiny earthquakes occurred at an increasing rate in the days to hours before the landslide, signaling that this mass of rock was starting to crack. Many seismic monitoring stations provide data in real-time, so this gives us some optimism that we can turn what we have learned into a warning system."

The 2011 Tohoku earthquake that triggered a devastating tsunami in eastern Japan was worsened by a thick layer of slippery clay, new research finds.

The clay layer, which was up to 98 feet (30 meters) thick on the ocean floor, created a weak spot that enabled the magnitude 9.1 quake's movement to travel all the way to the seafloor. That motion thrust the seafloor upward by 164 to 230 feet (50 to 70 m) over about 310 miles (500 kilometers). And the motion of the seafloor thrusting into the overlying ocean is what created the tsunami wave that inundated 217 square miles (561 square kilometers) of Japan.

"It's low-friction, so that clay is weak," said Ron Hackney, a geophysicist at the Australia National University and the director of the Australian and New Zealand International Scientific Drilling Consortium. "It can slip very easily."

The side-to-side breakage of the fault was about half of what researchers would have expected, Hackney told Live Science, which concentrated the upward motion into a smaller area, probably intensifying the resulting tsunami. The findings explain why the tsunami was larger and more concentrated than expected, he said, and these kinds of detailed studies can help provide better warnings for future quakes.

"We can be a bit more prepared in terms of informing people of what to expect and how to respond when an earthquake does happen," he said.

The 2011 quake happened along a subduction zone, where the Pacific Plate slides under Japan. In 2024, Hackney and other researchers aboard the research vessel Chikyu drilled directly into the fault that caused the quake. After drilling 23,000 feet (7,000 m) below the ocean surface and another 3,300 feet (1,000 m) below the seafloor, they pulled up cores of sediments from within the fault and from the Pacific Plate.

They found that the Pacific Plate is covered with a thick, goopy layer of clay that has been accumulating slowly for around 130 million years. This layer compresses as the Pacific Plate pushes under Japan, also squeezing the continental rocks above. The result is a mechanical weak point, almost like a perforation on a piece of notebook paper, where the rock is prone to breaking.

The researchers published their findings December 2025 in the journal Science.

Similar clay layers may or may not exist at other subduction zones, Hackney said. There is some evidence that they might be present near Sumatra, Indonesia, the site of the magnitude 9.1 earthquake that caused a devastating tsunami on Dec. 26, 2004. But less is known about the materials coming into the fault zone at places like the Kamchatka Peninsula, where large quakes also occur, he said.

Hackney and his colleagues are working to find links between topography and rock density and ultimate earthquake movement. Earth scientists are getting increasingly good at predicting how large a quake will be and where the shaking will be felt once a quake happens, enabling early warning systems that can alert people to incoming shaking seconds to minutes in advance. Tsunami warnings have an even longer lead time, so perfecting the understanding of how the seafloor moves to better predict where a tsunami will go could save even more lives.

A landslide into a river in Canada's Yukon territory last December sent a tsunami of ice slabs flying over two football fields away, severing trees in the process.

Now, new research suggests that the damage from this "ice tsunami" was worsened by the destructive force of the river ice. However, it was also restricted to a smaller area than if the landslide had hit in summer and created an ice-free wave.

"This effect is an important consideration for future landslide and tsunami hazard assessments in cold regions," study author Derek Cronmiller, a permafrost geologist with the Yukon Geological Survey, wrote in a new paper. Cronmiller visited the remote disaster site 24 days after the landslide and published his findings Sept. 25 in the journal Landslides.

The ice tsunami hit on Dec. 17, 2024, when a steep slope above the Takhini River failed without warning. About 4.1 million cubic feet (118,000 cubic meters) of dirt and rock tumbled into the river, which was covered in ice at the time. The impact created an ice-studded tsunami that washed over 17.8 acres (7.2 hectares) of the river and its banks. River ice cracked up to 820 feet (250 m) away, and chunks of ice over 43 square feet (4 square m) were found 656 feet (200 m) from the landslide.

The icy wave scoured vegetation from the river's banks, stripping all but the four largest trees from the bank opposite the landslide. On that slope, only trees with trunks of diameters over 11.8 inches (30 centimeters) survived.

Some slabs of river ice were flipped over, with about 4 inches to a foot (10 to 30 cm) of sand stuck to them. These slabs had been frozen solid to the bottom of the river, Cronmiller wrote, and the force of the tsunami ripped the riverbed up with them.

Landslides are typically triggered by snowmelt, rainfall or human activity, but Cronmiller found no evidence of an external trigger for the Dec. 17 event. Instead, the slope underwent a "brittle failure," meaning it cracked without any signs of warping or deformation.

Fortunately, no one was hurt in the incident, which happened 15.5 miles (25 km) northwest of Whitehorse, Yukon, in a rural area. The river is a destination for outdoor activities, however. Dogsledders and snowmobilers use it as a thoroughfare in winter, while river rafters traverse the Takhini in the summer.

The landslide narrowed the river by 50% and clogged it with debris, which could be hazardous to paddlers for years to come, Cronmiller wrote. The new study found that it will likely take the Takhini River more than a decade to carve its way back through the landslide debris.

Scientists have made the first direct observations of a strange seismic event that shook the world for nine consecutive days in 2023 and confirmed its cause: two "mega-tsunamis" that sloshed around an East Greenland fjord.

The gigantic waves — one of which measured 650 feet (200 meters) high, or about half the height of the Empire State Building — entered East Greenland's Dickson Fjord and rocked back and forth for nine days in September 2023, sending seismic waves reverberating through the planet's crust.

The signal was initially a mystery to scientists, but ground and satellite imagery traced the likely culprit to landslides in the fjord. These landslides unleashed the waves, known as seiches, following the climate-change-induced melting of a glacier behind the fjord. However, no direct evidence of these seiches was found.

Now, the theory has been confirmed by a new satellite that tracks water on the surface of the ocean. The findings were published Tuesday (June 3) in the journal Nature Communications.

"Climate change is giving rise to new, unseen extremes," study lead author Thomas Monahan, a graduate student in engineering science at the University of Oxford, said in a statement. "These extremes are changing the fastest in remote areas, such as the Arctic, where our ability to measure them using physical sensors is limited. This study shows how we can leverage the next generation of satellite Earth observation technologies to study these processes."

Related: 'This is a very big earthquake': The science behind Myanmar's magnitude 7.7 earthquake

Typically, scientists study the movements of tsunami waves using a method called satellite altimetry, in which radar pulses are sent to the ocean's surface from orbit to measure a wave's height based on the time it takes for the pulses to return.

But because satellites have long gaps in coverage and their instruments can only measure what's beneath them, they are unable to measure the differences in water height in confined areas like those within the fjord.

To confirm the existence of the seiches, the scientists turned to data captured by the new Surface Water and Ocean Topography (SWOT) satellite, a joint project of NASA and CNES, France's space agency. Launched in December 2022, the satellite uses an instrument called the Ka-band Radar Interferometer (KaRIn) to map 90% of the water across the ocean's surface.

KaRIn works by using two antennae mounted across a boom on each side of the satellite to triangulate the return signals of radar pulses with unprecedented accuracy — measuring water levels with a resolution of up to 8.2 feet (2.5 m) along a 30-mile (50 kilometers) arc.

SWOT data taken above the fjord during the two mega-tsunamis revealed two cross-channel slopes moving in opposite directions between it, confirming their presence. Seismic observations made thousands of miles away, alongside weather and tidal readings, further enabled the researchers to reconstruct the waves and conclusively link them to the mysterious seismic signals.

"This study is an example of how the next generation of satellite data can resolve phenomena that has remained a mystery in the past," co-author Thomas Adcock, a professor of engineering science at the University of Oxford, said in the statement.

"We will be able to get new insights into ocean extremes such as tsunamis, storm surges, and freak waves," he added. "However, to get the most out of these data we will need to innovate and use both machine learning and our knowledge of ocean physics to interpret our new results."

Scientists have discovered evidence of an ancient tsunami in Japan — which is hidden in tree amber that dates to the age of the dinosaurs. The amber samples are deformed in a particular way that suggests trees and plant debris were rapidly swept out to the ocean and sank to the seafloor around 115 million years ago, the researchers said, which the team interpreted as evidence of one or more tsunamis. The scientists published their findings today (May 15) in the journal Scientific Reports.

Scientists typically estimate when tsunamis happened in the past using geological evidence such as giant fossilized boulders that were swept away and deposited onto coasts, or by looking at abrupt changes in sediment deposits near coastlines. However, it can be difficult to differentiate tsunami traces in the fossil record from severe storms, which leave similar deposits.

Amber, which is fossilized tree resin — a fluid produced by trees — can also be transported to the ocean when a tsunami sweeps trees and plant debris out to sea, leaving behind a record of the tsunami event.

In the new study, the researchers analyzed amber-rich silica deposits from the Shimonakagawa Quarry in northern Hokkaido, Japan, which were deposited sometime between 116 million and 114 million years ago, during the Early Cretaceous period (145 million to 100 million years ago), when this region was deep seafloor.

The team used fluorescence imaging — a technique that photographs the amber samples while shining ultraviolet light onto them — to observe the amber's structure.

The amber samples showed a pattern similar to what geologists call "flame structures," a deformation that happens when soft sediment is deposited somewhere and changes shape before fully hardening — resulting in upward-pointing, flame-shaped tongues between the sediment layers. Amber deposits more commonly form other shapes, as tree resin dries when exposed to air.

The research team interpreted the flame structures to mean the amber was suddenly swept out from the land to the ocean by one or more tsunamis, without being exposed to the air (which would have hardened it), then sank to the seafloor. The amber would have then been covered by a layer of silt and preserved for millions of years.

"Identifying tsunamis is generally challenging," and it was not immediately apparent that tsunamis were behind the unusual amber samples, study co-author Aya Kubota, a paleontologist at Chuo University in Tokyo, told Live Science in an email. "By combining detailed field observations with the internal structures of amber, we were able to conclude that the most plausible cause was tsunamis."

Other evidence from the area backed up this hypothesis, including signs of a nearby landslide around the same time that may have been caused by an earthquake; large chunks of mud seemingly ripped up by the destruction of the seafloor; and large tree trunks on what was at the time the seafloor. Severe storm waves would not have affected the seafloor in this way, and if the tree trunks were stacked slowly over time they would have shown evidence of erosion, which these trunks did not — meaning all the evidence points to a huge amount of plant debris being transported quickly and suddenly to the seafloor.

The researchers suggested that looking at ocean floor geological and fossil evidence — that is, beyond just coastal evidence — paints a more complete picture of previous tsunamis, and that examining amber deposits can provide information that helps differentiate tsunamis in the prehistoric record from severe storms.

"Resin offers a rare, time-sensitive snapshot of depositional processes," Kubota said. Although the study of amber has typically focused on organisms like insects trapped inside samples, "the emerging concept of 'amber sedimentology' holds exciting potential to provide unique insights into sedimentological processes," Kubota added.

A magnitude 7 earthquake hit off the coast of northern California on Thursday (Dec. 5).

However, a tsunami warning that had initially been prompted by the earthquake has now been canceled, according to the U.S. Tsunami Warning System.

The earthquake hit at 10:44 a.m. PST (18:44 UTC) at a depth of about 0.4 mile (0.6 kilometers), according to the U.S. Geological Survey (USGS). The earthquake occurred off the coast, about 39 miles (63 km) northwest of the city of Petrolia in Humboldt County. It's likely that these numbers will be updated as the USGS gathers more information.

Related: The 20 largest recorded earthquakes in history

Currently, the USGS is reporting that the "landslides triggered by this earthquake are estimated to be limited in number." According to the USGS Shake Map, people reported feeling extreme shaking on the California coast by the earthquake.

Other small earthquakes, including a magnitude 4.2 and a magnitude 3.3, have also hit the area today. There are no immediate reports of damage, according to the Los Angeles Times.

Editor's note: This story was updated at 3:38 p.m. EST to note that the tsunami warning has been canceled.

Tidal waves and tsunamis — the two most powerful types of wave on Earth— are often confused in popular discourse. While the terms are sometimes used synonymously, tidal waves and tsunamis actually have distinct causes.

"The English term tidal wave dominated until the 2004 Indian Ocean tsunami, partly because most tsunami observations until then described water phenomena that resembled fast advancing or fast-receding tides," Costas Synolakis, director of the Tsunami Research Center at the University of Southern California, told Live Science. "In 2004, we got access to several videos from the tsunami in Indonesia and Thailand, and realized that giant tsunamis do not resemble tides."

Tidal waves are caused by the gravitational interaction between Earth and the moon — and to a lesser extent, the sun. These waves are products of the tidal patterns that result in daily low and high tides in coastal areas, meaning they are generally predictable, correlating to the phases of the moon.

Tides are highest during the new moon — when the moon is between Earth and the sun; and the full moon, when Earth sits between the moon and the sun.

Related: Tsunamis up to 90 feet high smash into New Zealand every 580 years, study finds

The moon's gravity exerts a greater force on the regions of Earth closest to the moon, which pulls on water there, causing the ocean to rise in a bulge. Meanwhile, oceans on the side of Earth opposite the moon also experience a bulge due to inertia — the natural tendency of a moving object to keep moving or a motionless object to remain motionless. The water moving away from the moon resists the gravitational forces that attempt to pull it in the opposite direction.

These two bulges move around Earth as our planet rotates and the moon orbits us, meaning most regions experience high tide twice every 24 hours and 50 minutes. Low tides, meanwhile, occur in the areas that are not either closest or farthest from the moon.

A tidal wave may stretch for thousands of miles. In many cases, tidal waves are small. But certain geographic features, such as narrow inlets and river mouths, can concentrate the energy of tides, creating enormous waves in some areas.

Tidal waves, however, are no match for the destructive force of tsunamis — a term meaning "harbor wave" in Japanese. Unlike tidal waves, tsunamis are largely unpredictable. They result from underwater earthquakes, landslides, volcanoes and even meteorites.

Underwater earthquakes at subduction zones, where one continental plate slides beneath another, frequently cause large tsunamis. Earthquakes with a magnitude of 6.5 or greater that occur at relatively shallow depths and lift Earth's crust are likely to cause tsunamis. In addition, volcanoes and landslides — either underwater or on land adjacent to the ocean — result in the movement of large amounts of magma and rocks that can trigger tsunamis. These events may be missed by early detection systems, Synolakis said.

The force from events like these displaces water, and the energy from that displacement propagates as a wave. Tsunamis can be local, regional or distant, depending on the magnitude. Tsunamis may result from events that occur close to where the wave hits the shoreline but can also occur thousands of miles away.

Tsunamis may be barely visible, raising the ocean's surface by mere inches. But they can travel at speeds of 500 mph (800 km/h). Periods range from a few minutes to two hours. While the shallower depths near coastlines slow the waves down, they increase the height because the waves following the initial wavefront catch up, adding force behind it. This phenomenon accounts for the massive walls of water that can occur as tsunamis make landfall.

Because tsunamis are largely unpredictable, people in vulnerable coastal areas may have only a few minutes of warning to get to higher ground. Some of the largest tsunamis have created waves that inundated areas several miles inland. In the wake of the devastating 2004 Indian Ocean tsunami, which resulted in nearly 230,000 deaths, sensors were installed in at-risk regions to create an early warning system.

"Tsunamis are monitored with the Deep-ocean Assessment and Reporting of Tsunamis (DART) system. This is a network of offshore buoys which relay a signal from ocean floor pressure recorders to the ocean surface then to satellites, which in turn relate the signal to the warning centers," Synolakis said. But the system is far from perfect.

"The problem is that now about 50 DARTs cover the Pacific and Indian Oceans. About half work at any given time. We need at least 150 distributed around the world's oceans for an effective system with targeted warnings," he said.

Scientists have finally identified the cause of a mysterious seismic signal that shook Earth for nine consecutive days last year. It turns out that our planet was rocked by a mega tsunami trapped inside a fjord after a mountaintop collapse.

The gigantic wave, measuring 650 feet (200 meters) high, sloshed back and forth inside East Greenland's Dickson Fjord for nine days in September 2023, its movement sending seismic waves reverberating through the planet's crust.

Scientists were initially baffled by the signal. But an investigation using satellite and ground imagery eventually tracked the cause of the seismic activity to the mountain, which was destabilized by climate change melting the glacier at its base. The researchers published their findings today (Sept. 12) in the journal Science.

"When we set out on this scientific adventure, everybody was puzzled and no one had the faintest idea what caused this signal," study lead author Kristian Svennevig, a geologist at the Geological Survey of Denmark and Greenland (GEUS), said in a statement. "All we knew was that it was somehow associated with the landslide. We only managed to solve this enigma through a huge interdisciplinary and international effort."

After being picked up by seismic monitoring stations in September, two aspects of the signal puzzled scientists. Firstly, unlike higher-frequency earthquakes, it was oscillating with a 92-second interval between peaks. And secondly, it was doing this for days on end.

Scientists soon tied the possible cause to a landslide in the fjord, but to understand how it produced the signal, the scientists combined field measurements, satellite imagery and supercomputer models to reconstruct what happened.

Related: When was the last time Antarctica was ice-free?

Their investigation revealed that a massive landslide most likely caused a tsunami wave to rock back and forth across the narrow fjord — a phenomenon known as a seiche.

"It was a big challenge to do an accurate computer simulation of such a long-lasting, sloshing tsunami," study co-author Alice Gabriel, a seismologist at the University of California, San Diego, said in the statement.

The landslide that caused the giant tsunami was the result of climate change, the researchers said. Climate change is melting the ice around the poles at an accelerating rate, and in the fjord's case it dislodged 33 million cubic yards (25 million cubic meters) of rock and ice — roughly the equivalent of 10,000 Olympic-size swimming pools — and sent it crashing into the sea.

No one was harmed by the collapse, but the wave did destroy $200,000 of infrastructure at an unoccupied research station on nearby Ella Island. The researchers say that the worsening effects of climate change could cause more destructive landslides around polar regions.

"Climate change is shifting what is typical on Earth, and it can set unusual events into motion," Gabriel said.

The researchers hope that their discovery of the seismic signal's origins will inspire others to look through the seismic record for similar events, which could help them identify the exact conditions that lead to potentially devastating polar landslides.

"This shows there is stuff out there that we still don't understand and haven't seen before," study co-author Carl Ebeling, a geophysicist at the University of California, San Diego, said in the statement. "The essence of science is trying to answer a question we don't know the answer to — that's why this was so exciting to work on."

At least nine people have been killed and more than 900 injured after an earthquake hit the east coast of Taiwan on Wednesday morning.

The powerful quake, Taiwan's strongest in 25 years, collapsed buildings, knocked out power and triggered landslides, while also prompting tsunami warnings in southern Japan and the Philippines. Taiwanese officials reported the quake as having a magnitude of 7.2, while the U.S. Geological Survey (USGS) seismometers logged a magnitude of 7.4.

The quake struck southwest of Hualien City at 7:58 a.m. local time and was followed by a swarm of powerful aftershocks that sent tremors across the island. The earthquake occurred 21 miles (35 kilometers) below the surface, according to the USGS, and has left 77 people trapped in tunnels and beneath collapsed buildings, according to Taiwanese officials. 

"Disaster response is underway," Tsai Ing-wen, Taiwan's president, wrote on X, formerly known as Twitter, this morning.

Despite the strength of the quake, its toll on Taiwan was relatively modest. This is because the island's buildings are constructed to withstand strong earthquakes and its population is well-drilled for when they hit.

Related: Nearly 75% of the US is at risk from damaging earthquakes, new map reveals

Taiwan's frequent temblors are a consequence of its location along the Pacific Ocean's "Ring of Fire," a 25,000-mile (40,000 kilometers) arc where the Pacific plate meets with others such as the Eurasian, North American, Cocos, Philippine Sea and Nazca plates. 

The friction between these plates as they slide past and dive beneath each other can store energy, which is suddenly released in the form of quake-spawning ruptures.

In Taiwan, the interaction between the Philippine Sea plate and the Eurasian plate generates ruptures called reverse faults that lift one plate above the other.

Around 2,000 earthquakes of magnitude 4.0 or greater have rocked the island since 1980. The deadliest, the magnitude 7.7 Chi-Chi earthquake that struck on Sept. 21, 1999, killed 2,415 people, injured 11,305 and caused $300 billion in damages.

Satellite images captured striking changes in the coastline of Japan's Noto Peninsula following a massive earthquake on New Year's Day.

A 7.6 magnitude earthquake struck Japan on Jan. 1 around 2:10 a.m. EST (0710 GMT, or 4:10 p.m. local time in Japan), prompting orders for residents to evacuate affected coastal areas that experienced significant uplift. Satellite imagery of the area before and after the quake shows that the intense uplift extended the coastline by up to 820 feet (250 meters), which is greater than the length of two American football fields.

Images of Japan's Noto Peninsula shared on X (formerly Twitter) by Nahel Belgherze show coastal areas where the seafloor has risen above the water, creating newly exposed beaches. The photos capture the coastline changes after the earthquake and tsunami had already subsided, leaving some ports completely dry and inaccessible to boats.

"During a field investigation along the northwest coast of the Noto Peninsula, we found evidence at 10 locations, from Kaiso to Akasaki sites, of coseismic coastal uplift related to the Noto Peninsula Earthquake (M7.6)," researchers with the Earthquake Research Institute at the University of Tokyo said in a statement on Jan. 4. 

Related: Deadly swarm of earthquakes in Japan caused by magma moving through extinct volcano

"The pattern of estimated coseismic coastal uplift appears to be decreasing southward from Kaiso to Akasaki," they added.

The area near Akasaki port also experienced nearly 14-foot-high (4.2 meters) tsunamis, according to the university's field investigations that revealed water stains on building walls.

The Japan Aerospace Exploration Agency's (JAXA) Advanced Land Observing Satellite-2 (ALOS-2) also captured the coastal uplift caused by the earthquake. Satellite images compare the coastline from June 2023 to Jan. 2, showing how the shoreline shifted seaward in multiple areas, including Nafune port, Wajima city and Minazuki bay, according to a statement from the Geospatial Information Authority of Japan.

While the satellite images capture significant changes following the Jan. 1 earthquake, investigations along the coast are still ongoing, according to the statement.

Originally posted on Space.com.

Tsunami waves 92 feet (28 meters) high could hit parts of New Zealand in a worst-case earthquake scenario, research finds. 

In the study, researchers used a new method of examining simulated earthquakes to understand possible tsunami risks to New Zealand's North and South Islands. They found that the largest waves are likely to strike along the northeast coast of North Island. That's because the Hikurangi subduction zone, where the Pacific tectonic plate dives under the Australian tectonic plate, sits just offshore. 

"There’s a really short timespan [between] when these earthquakes happened and when the tsunami waves hit," study first author Laura Hughes, a doctoral student at Victoria University of Wellington, told Live Science. 

Because of New Zealand's proximity to subduction zones, which can create large, tsunami-generating earthquakes, it's important to understand the risk of these devastating waves. 

Previous efforts have used historical quakes to try to understand future risk, study senior author Martha Savage, a geophysicist at Victoria University of Wellington, told Live Science. But historical records only go back about 150 years. Geological studies can turn up evidence of older quakes, but those records are incomplete. 

Related: 1st mega-tsunami on record since antiquity was triggered by Tonga volcanic eruption

Instead, the researchers turned to a different method: synthetic earthquakes. This method used computer models, into which researchers added everything they know about the geometry and physics of fault systems, including things like the locations of faults and the amount of friction on them. They then simulated tens of thousands of years of quakes to try to determine how often major ones occur. 

The method isn't perfect because the fault systems aren't fully known, Savage said, but it complements the historical and geological record. 

"We’re able to put in a variety of properties we think may exist and get that range of potential earthquakes and range of potential tsunamis that may happen," Hughes said.

In the new study, published Nov. 29 in the journal JGR Solid Earth, the researchers created a catalog of 30,000 years of simulated time focused on the fault systems around New Zealand. The results revealed 2,585 earthquakes with magnitudes between 7.0 and 9.25. 

The model suggests that the Hikurangi subduction zone is the most dangerous source of tsunami quakes near New Zealand, though the Tonga-Kermadec subduction zone north of North Island can also generate large, tsunami-causing quakes, just a bit further from shore. The researchers were surprised to find that the tsunami hazard was caused by smaller, shallower faults called crustal faults, rather than the subduction faults themselves, Hughes said. 

"Yes, the subduction zones are doing what we expect them to do," she said, "but our crustal faults also have a significant component of the hazard that we also need to account for." 

The team found the maximum height of a tsunami was 92 feet, which would result from a 9.13 magnitude earthquake about 394 miles (634 kilometers) northeast of Auckland in the South Pacific. The 2011 Tohoku tsunami in Japan was a 130-foot (40 meter) wave, for comparison. 

The results suggest that New Zealand can expect a tsunami of 16.4 feet (5 m) approximately every 77 years, with a wave of at least 49.2 feet (15 m) approximately every 580 years. 

Tsunamis over 3.3 feet (1 meter) high trigger land evacuations, Hughes said, while smaller waves can damage ports and harbors. 

Though this is the first time the synthetic earthquake method has been used to study tsunamis, the same thing could be done for other at-risk places around the globe, Hughes said. There is also more work needed to map out the risk to New Zealand, she added. The current study didn't take into account far-flung earthquakes around the Pacific, which can cause tsunami waves that resonate around the entire ocean. 

"It is this huge step forward in risk assessment that we can now create a chain from what is creating the earthquakes, to what the earthquake looks like, and then what that looks like for the tsunami," Hughes said. 

Archaeologists excavating a 2,800-year-old temple at a sanctuary in Greece have uncovered several artifacts, including figurines of a dog, a woman and a snake, according to the Greek Ministry of Culture.

Some of these figurines may have been used as votive offerings, or gifts to the gods, intended for Poseidon, a Greek god of the sea.

The sanctuary, dedicated to Poseidon, is located in the ancient city of Elikis (also known as Helike) on the northern coast of the Peloponnese in Greece. In addition to the artifacts, the archaeologists analyzed sediments at the site, finding that the sanctuary flooded several times around 2,800 years ago, they said in a translated statement. Eventually, the sanctuary fell into disrepair when Elikis was destroyed in an earthquake and tsunami that occurred more than 2,300 years ago.

Related: Roman-era statues of Aphrodite and Dionysus unearthed in Turkey

The discovered artifacts include a bronze figurine that appears to be a dog and a clay figurine of a woman. They also found a snake head crafted out of bronze, a clay wing that may have been part of a sphinx or mermaid, and part of a gold necklace.

Related: 31 ancient temples from around the world, from Göbekli Tepe to the Parthenon

These artifacts may have been used as offerings to Poseidon and any other gods that may have been worshipped in the temple, Anastasia Gadolou, director general of the Archaeological Museum of Thessaloniki, who is overseeing the excavation of the site, told Live Science in an email.

While the artifacts may have been used as offerings, any deeper understanding of their religious purpose — for instance, why a dog-shaped figurine was used — is uncertain. "A thorough study taking into consideration all evidence [derived] from the archaeological strati is more than essential," Gadolou said.

The archaeologists have been excavating the sanctuary for nearly 20 years. Its discovery and association with Poseidon were noted in a series of papers published between 2011 and 2022. Ancient texts say that there was a sanctuary dedicated to Poseidon at this site and the discoveries at the site support this identification, archaeologists noted in the papers.

About 2,500 years ago, a volcanic eruption in Fiji triggered a massive tsunami. How do scientists know this? We examined the oral traditions of Fiji's Indigenous people, whose storytelling describes a volcanic eruption — an event that left behind geologic clues — and a tsunami, which didn't leave behind any physical traces that survive today, our new study finds.

Our research in the journal Oral Tradition shows memories of a volcanic eruption in Fiji some 2,500 years ago were encoded in oral traditions through riddles, tales of fantastic beings flying through the sky, fighting each other and noisily drinking the ocean dry.

These oral traditions were never intended as fanciful stories, but rather as the pragmatic foundations of a system of local risk management.

Life-changing events

Around 2,500 years ago, at the western end of the island of Kadavu in the southern part of Fiji, the ground shook, the ocean became agitated, and clouds of billowing smoke and ash poured into the sky.

When the clouds cleared, the people saw a new mountain had formed, its shape resembling a mound of earth in which yams are grown. This gave the mountain its name — Nabukelevu, the giant yam mound. (It was renamed Mount Washington during Fiji's colonial history.)

Related: Antarctica was likely discovered 1,100 years before Westerners 'found' it

So dramatic, so life-changing were the events associated with this eruption, the people who witnessed it told stories about it. These stories have endured more than two millennia, faithfully passed on across roughly 100 generations to reach us today.

Scientists used to dismiss such stories as fictions, devalue them with labels like "myth" or "legend". But the situation is changing.

Today, we are starting to recognize that many such "stories" are authentic memories of human pasts, encoded in oral traditions in ways that represent the worldviews of people from long ago.

In other words, these stories served the same purpose as scientific accounts, and the people who told them were trying to understand the natural world, much like scientists do today.

Battle of the vu

The most common story about the 2,500-year-old eruption of Nabukelevu is one involving a "god" (vu in Fijian) named Tanovo from the island of Ono, about 35 miles (56 kilometers) from the volcano.

Tanovo's view of the sunset became blocked one day by this huge mountain. Our research identifies this as a volcanic dome that was created during the eruption, raising the height of the mountain several hundred feet.

Enraged, Tanovo flew to Nabukelevu and started to tear down the mountain, a process described by local residents as driva qele (stealing earth). This explains why even today the summit of Nabukelevu has a crater.

But Tanovo was interrupted by the "god" of Nabukelevu, named Tautaumolau. The pair started fighting. A chase ensued through the sky and, as the two twisted and turned, the earth being carried by Tanovo started falling to the ground, where it is said to have "created" islands.

We conclude that the sequence in which these islands are said to have been created is likely to represent the movement of the ash plume from the eruption, as shown on the map below.

'Myths' based in fact

Geologists would today find it exceedingly difficult to deduce such details of an ancient eruption. But here, in the oral traditions of Kadavu people, this information is readily available.

Another detail we would never know if we did not have the oral traditions is about the tsunami the eruption caused.

In some versions of the story, one of the "gods" is so frightened, he hides beneath the sea. But his rival comes along and drinks up all the water at that place, a detail our research interprets as a memory of the ocean withdrawing prior to tsunami impact.

Other details in the oral traditions recall how one god threw a massive spear at his rival but missed, leaving behind a huge hole in a rock. This is a good example of how landforms likely predating the eruption can be retrofitted to a narrative.

Our study adds to the growing body of scientific research into "myths" and "legends", showing that many have a basis in fact, and the details they contain add depth and breadth to our understanding of human pasts.

The Kadavu volcano stories discussed here also show ancient societies were no less risk aware and risk averse than ours are today. The imperative was to survive, greatly aided by keeping alive memories of all the hazards that existed in a particular place.

Australian First Peoples' cultures are replete with similar stories.

Literate people, those who read and write, tend to be impressed by the extraordinary time depth of oral traditions, like those about the 2,500-year old eruption of Nabukelevu. But not everyone is.

In early 2019, I was sitting and chatting to Ratu Petero Uluinaceva in Waisomo Village, after he had finished relating the Ono people's story of the eruption. I told him this particular story recalled events which occurred more than two millennia ago — and thought he might be impressed. But he wasn't.

"We know our stories are that old, that they recall our ancient history," he told me with a grin. "But we are glad you have now learned this too!"

Acknowledgements: The original research was conducted in collaboration with Loredana Lancini and Rita Compatangelo-Soussignan (University of Le Mans), Meli Nanuku and Kaliopate Tavola (Fiji Museum), Taniela Bolea (University of the Sunshine Coast) and Paul Geraghty (University of the South Pacific).

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate change could unleash gigantic tsunamis in the Southern Ocean by triggering underwater landslides in Antarctica, a new study warns. 

By drilling into sediment cores hundreds of feet beneath the seafloor in Antarctica, scientists discovered that during previous periods of global warming — 3 million and 15 million years ago — loose sediment layers formed and slipped to send massive tsunami waves racing to the shores of South America, New Zealand and Southeast Asia. 

And as climate change heats the oceans, the researchers think there's a possibility these tsunamis could be unleashed once more. Their findings were published May 18 in the journal Nature Communications.

Related: Widening chasm births Antarctic iceberg larger than Los Angeles

"Submarine landslides are a major geohazard with the potential to trigger tsunamis that can lead to huge loss of life," Jenny Gales, a lecturer in hydrography and ocean exploration at the University of Plymouth in the U.K., said in a statement. "Our findings highlight how we urgently need to enhance our understanding of how global climate change might influence the stability of these regions and potential for future tsunamis."

Researchers first found evidence of ancient landslides off Antarctica in 2017 in the eastern Ross Sea. Trapped underneath these landslides are layers of weak sediment crammed with fossilized sea creatures known as phytoplankton. 

Scientists returned to the area in 2018 and  drilled deep into the seafloor to extract sediment cores — long, thin cylinders of the Earth’s crust that show, layer by layer, the geological history of the region. 

By analyzing the sediment cores, the scientists learned that the layers of weak sediment formed during two periods, one around 3 million years ago in the mid-Pliocene warm period, and the other roughly 15 million years ago during the Miocene climate optimum. During these epochs, the waters around Antarctica were 5.4 degrees Fahrenheit (3 degrees Celsius) warmer than today, leading to bursts of algal blooms that, after they had died, filled the seafloor below with a rich and slippery sediment — making the region prone to landslides. 

"During subsequent cold climates and ice ages these slippery layers were overlain by thick layers of coarse gravel delivered by glaciers and icebergs," Robert McKay, director of the Antarctic Research Centre at Victoria University of Wellington and co-chief scientist of International Ocean Discovery Program Expedition 374 — which extracted the sediment cores in 2018 — told Live Science in an email. 

The exact trigger for the region's past underwater landslides isn’t known for sure, but the researchers have found a most-likely culprit: the melting of glacier ice by a warming climate. The ending of Earth’s periodic glacial periods caused ice sheets to shrink and recede, lightening the load on Earth’s tectonic plates and making them rebound upwards in a process known as isostatic rebound. 

After the layers of weak sediment had built up in sufficient quantities, Antarctica’s continental upspringing triggered earthquakes that caused the coarse gravel atop the slippery layers to slide off the continental shelf edge — causing landslides that unleashed tsunamis.

The scale and size of the ancient ocean waves is not known, but the scientists note two relatively recent submarine landslides that generated huge tsunamis and caused significant loss of life: The 1929 Grand Banks tsunami that generated 42-foot-high (13 meters) waves and killed around 28 people off Canada’s Newfoundland coast; and the 1998 Papua New Guinea tsunami that unleashed 49-foot-high (15 m) waves that claimed 2,200 lives.

With many layers of the sediment buried beneath the Antarctic seabed, and the glaciers on top of the landmass slowly melting away, the researchers warn that — if they’re right that glacial melting caused them in the past — future landslides, and tsunamis, could happen again.

"The same layers are still present on the outer continental shelf — so it is 'primed' for more of these slides to occur, but the big question is whether the trigger for the events is still in play." McKay said. "We proposed isostatic rebound as a logical potential trigger, but it could be random failure, or climate regulated shifts in ocean currents acting to erode sediment at key locations on the continental shelf that could trigger slope failure. This is something we could use computer models to assess for in future studies."

The Tonga underwater volcanic eruption rivaled the strength of the largest U.S. nuclear bomb and produced a "mega-tsunami" nearly the height of a 30-story skyscraper, a recent study finds.

On Jan. 15, 2022, the Hunga Tonga-Hunga Ha'apai submarine volcano — a large, cone-shaped mountain located near the islands of the Kingdom of Tonga in the South Pacific — erupted with a violent explosion. The eruption generated the highest-ever recorded volcanic plume, which reached 35 miles (57 kilometers) tall. The outburst triggered tsunamis as far away as the Caribbean, as well as atmospheric waves that traveled around the globe several times.

To determine the strength of the eruption, scientists collected before-and-after satellite optical and radar images, drone maps and field observations to generate a computer simulation of the catastrophe.

They discovered that the explosion may have been as strong as 15 megatons (millions of tons) of TNT, making it about as strong as the United States' largest nuclear detonation, Castle Bravo, in 1954, according to the Atomic Heritage Foundation. It would also make the eruption "the largest natural explosion in more than a century," study lead author Sam Purkis, professor and chair of the Department of Marine Geosciences the University of Miami Rosenstiel School of Marine and Atmospheric Science, told Live Science in an email.

Related: Is the Yellowstone supervolcano really 'due' for an eruption?

The eruption released at least five blasts, generating a tsunami up to 279 feet (85 m) high one minute after the largest explosion. This led to waves as high as 147 feet (45 m) on the Tongan island Tofua and 55 feet (17 m) on Tongatapu, they found. 

"Our data prove that the waves generated by the explosion comfortably place Hunga Tonga-Hunga Ha'apai in the 'mega-tsunami' league," said Purkis, who is also chief scientist at the Khaled bin Sultan Living Oceans Foundation in Annapolis, Maryland. "We have observed an event in real time using modern instrumentation that had previously only been recognized in antiquity. This is all incredibly exciting."

Until now, the extent of the eruption and its aftermath had proved elusive due to the scarcity of scientific instruments near the site of the eruption. "Obscured from casual view, submarine volcanoes are much harder to monitor than volcanoes on land," Purkis said.

The scientists found that the complex, shallow nature of the region's underwater terrain helped to trap low-velocity waves from the eruption. This, in turn, helped generate a mega-tsunami that lasted more than an hour. "We show how submarine volcanic eruptions can generate massive tsunami," Purkis said. "A series of small blasts hailed the arrival of the big one, which generated the largest tsunami."

The scientists said the strength of the 2022 eruption rivaled that of the 1883 eruption of Krakatau that killed more than 36,000 people. In contrast, the 2022 eruption killed an estimated six people.

The low death toll is a testament to the effectiveness of safety drills and awareness efforts carried out in Tonga in the years before the eruption, Purkis said. The eruption's relatively distant location from urban centers also may have saved Tonga from a worse fate, the scientists noted.

The computer simulations also revealed that the coral reefs that fringe the Tongan islands helped suppress the waves that ultimately made their way to shore. This finding suggests these reefs may have experienced substantial damage, Purkis said.

Still, "clearly the reefs can recover from such damage," Purkis noted. "Archaeological evidence pins a major tsunami in the mid-15th century with runup heights up to 30 meters [98 feet] — that is, similar in size to the 2022 event." However, "when I surveyed the coral reefs of the Tongan archipelago with the Living Oceans Foundation in 2013, we found the reefs to be healthy and vibrant. The damage from the event 500 years ago had been erased."

Future research should focus on the best way to place sensors to record data from submarine volcanoes and the coastlines of vulnerable islands as "an effective means of keeping tabs on submarine volcanoes," Purkis said.

The scientists published their findings online April 14 in the journal Science Advances.

The dinosaur-killing asteroid that slammed into Earth 66 million years ago also triggered a jumbo-size tsunami with mile-high waves in the Gulf of Mexico whose waters traveled halfway around the world, a new study finds.

Researchers discovered evidence of this monumental tsunami after analyzing cores from more than 100 sites worldwide and creating digital models of the monstrous waves after the asteroid's impact in Mexico's Yucatán Peninsula. 

"This tsunami was strong enough to disturb and erode sediments in ocean basins halfway around the globe," study lead author Molly Range, who conducted the modeling study for a master's thesis in the Department of Earth and Environmental Sciences at the University of Michigan, said in a statement.

The research on the mile-high tsunami, which was previously presented at the 2019 American Geophysical Union's annual meeting, was published online Tuesday (Oct. 4) in the journal AGU Advances. 

Related: Could an asteroid destroy Earth?

Range dove into the tsunami's journey immediately following the asteroid's collision. Based on earlier findings, her team modeled an asteroid that measured 8.7 miles (14 kilometers) across and was zooming 27,000 mph (43,500 km/h), or 35 times the speed of sound when it struck Earth. After the asteroid hit, many lifeforms died; the nonavian dinosaurs went extinct (only birds, which are living dinosaurs, survive today) and about three-quarters of all plants and animal species were wiped out.

Researchers are aware of many of the asteroid's pernicious effects, such as sparking raging fires that cooked animals alive and pulverizing sulfur-rich rocks that led to lethal acid rain and extended global cooling. To learn more about the resulting tsunami, Range and her colleagues analyzed the Earth's geology, successfully analyzing 120 "boundary sections," or marine sediments laid down just before or after the mass extinction event, which marked the end of the Cretaceous period. 

These boundary sections matched the predictions of their model of wave height and travel, Range said. 

The initial energy from the impact tsunami was up to 30,000 times larger than the energy released by the December 2004 Indian Ocean earthquake tsunami that killed more than 230,000 people, the researchers found.

Once the asteroid struck Earth, it created a 62-mile-wide (100 km) crater and kicked up a dense cloud of dust and soot into the atmosphere. Just 2.5 minutes after the strike, a curtain of ejected material pushed a wall of water outward, briefly making a 2.8-mile-tall (4.5 km) wave that crashed down as the ejecta plummeted back to Earth, according to the simulation.

At the 10 minute mark, a 0.93-mile-high (1.5 km) tsunami wave about 137 miles (220 km) away from the impact site swept through the gulf in all directions. An hour after the impact, the tsunami had left the Gulf of Mexico and rushed into the North Atlantic. Four hours following the impact, the tsunami passed through the Central American Seaway — a passage that separated North from South America at the time — and into the Pacific.

A full day after the asteroid's collision, the waves had traveled through most of the Pacific and the Atlantic, entering the Indian Ocean from both sides, and touching most of the globe's coastlines 48 hours after the strike.

Related: 52-foot-tall 'megaripples' from dinosaur-killing asteroid are hiding under Louisiana

Tsunami's power 

After the impact, the tsunami radiated mostly to the east and northeast, gushing into the North Atlantic Ocean, as well as to the southwest via the Central American Seaway flowing into the South Pacific Ocean. Water traveled so quickly in these areas that it likely exceeded 0.4 mph (0.6 km/h), a velocity that can erode the seafloor's fine-grained sediments.

Other regions largely escaped the tsunami's power, including the South Atlantic, the North Pacific, the Indian Ocean and what is now the Mediterranean sea, according to the team's models. Their simulations showed that the water speeds in these areas were less than the 0.4 mph threshold.

The team even found outcrops — or exposed rocky deposits — from the impact event on eastern New Zealand's north and south islands, a distance of more than 7,500 miles (12,000 km) from the Chicxulub crater in Mexico. Originally, scientists thought that these outcrops were from local tectonic activity. But due to their age and location in the tsunami's modeled route, the study's researchers pinned it to the asteroid's massive waves.

"We feel these deposits are recording the effects of the impact tsunami, and this is perhaps the most telling confirmation of the global significance of this event," Range said.

While the models didn't assess coastal flooding, they did reveal that open-ocean waves in the Gulf of Mexico would have exceeded 328 feet (100 m), and waves would have reached heights of more than 32.8 feet (10 m) as the tsunami approached the North Atlantic's coastal regions and parts of the South America's Pacific coast, according to the statement.

As the water became shallow near the coast, wave heights would have risen dramatically.

"Depending on the geometries of the coast and the advancing waves, most coastal regions would be inundated and eroded to some extent," the authors wrote in the study. "Any historically documented tsunamis pale in comparison with such global impact."

Archaeologists have found evidence of the largest known earthquake in human history — a terrifying magnitude-9.5 megaquake that caused a 5,000-mile-long (8,000 kilometers) tsunami and prompted human populations to abandon nearby coastlines for 1,000 years, a new study finds.

The earthquake struck about 3,800 years ago in what is now northern Chile when a tectonic plate rupture lifted the region's coastline. The subsequent tsunami was so powerful, it created waves as high as 66 feet (20 meters) and traveled all the way to New Zealand, where it hurled car-size boulders hundreds of meters inland, the researchers found. 

Until now, the largest earthquake ever recorded was the 1960 Valdivia earthquake, which hit southern Chile with a magnitude between 9.4 and 9.6, killing up to 6,000 people and sending tsunamis barreling across the Pacific Ocean. The rupture that caused the Valdivia earthquake was enormous, extending as far as 500 miles (800 km) in length. But, as scientists detail in research published April 6 in the journal Science Advances, the newly discovered ancient megaquake was even bigger, coming from a rupture roughly 620 miles (1,000 km) long.

Related: Strange earthquakes in South Carolina traced to man-made lake

"It had been thought that there could not be an event of that size in the north of the country simply because you could not get a long enough rupture," study co-author James Goff, a geologist at the University of Southampton in England, said in a statement. 

Like the Valdivia earthquake, the ancient quake was a megathrust earthquake, the most powerful type of earthquake in the world. These earthquakes occur when one of Earth's tectonic plates gets forced, or subducted, underneath another. The two plates eventually get locked into place by friction, but the forces that caused the plates to collide continue to build. Eventually, so much strain gathers that the point of contact between the plates rips apart, creating a gigantic rupture and releasing energy in the form of devastating seismic waves. 

Evidence for the giant quake was found in marine and coastal items — such as littoral deposits (boulders, pebbles and sand native to coastal regions) and marine rocks, shells and sea life — that the researchers discovered displaced far inland in Chile's Atacama Desert. 

"We found evidence of marine sediments and a lot of beasties that would have been living quietly in the sea before being thrown inland," Goff said in the statement. "And we found all these very high up and a long way inland, so it could not have been a storm that put them there."

To get a better sense of what brought these deposits so far from the sea, the researchers used radiocarbon dating. This method involves measuring the quantities of carbon 14, a radioactive carbon isotope, found inside a material to determine its age. As carbon 14 is everywhere on Earth, deposits easily absorb it while they form. The half-life of carbon 14, or the time it takes for half of it to radioactively decay, is 5,730 years, making it ideal for scientists who want to peer back into the last 50,000 years of history by checking how much undecayed carbon 14 a material has.

After dating 17 deposits across seven separate dig sites over 370 miles (600 km) of Chile's northern coast, the researchers found that the ages of the out-of-place coastal material suggested that it had been washed inland some 3,800 years ago. 

Further evidence also came in the form of ancient stone structures that the archaeologists excavated. These stone walls, built by humans, were found lying beneath the tsunami's deposits, and some were lying backward, pointing toward the sea, suggesting that they had been toppled by the strong currents of the tsunami's backwash.

"The local population there were left with nothing," Goff said. "Our archaeological work found that a huge social upheaval followed as communities moved inland beyond the reach of tsunamis. It was over 1,000 years before people returned to live at the coast again, which is an amazing length of time given that they relied on the sea for food."

As this is the oldest known discovery in the Southern Hemisphere of an earthquake and tsunami devastating human lives, the researchers are excited to probe the region further. They think their research could better inform us of the potential dangers of future megathrust quakes.

"While this had a major impact on people in Chile, the South Pacific islands were uninhabited when they took a pummeling from the tsunami 3,800 years ago," Goff said. "But they are all well-populated now, and many are popular tourist destinations. So when such an event occurs next time, the consequences could be catastrophic unless we learn from these findings."

Originally published on Live Science.

Editor's Note: This story was updated at 9:00 a.m. ET on Sept. 26, 2022 to correct the distance boulders were thrown by the tsunami. 

The mysterious source of a globe-spanning tsunami that spread as far as 6,000 miles (10,000 kilometers) from its epicenter was an "invisible" earthquake, a new study has found.

In August 2021, an enormous tsunami rippled out into the North Atlantic, Pacific and Indian oceans. It was the first time a tsunami had been recorded in three different oceans since the catastrophic 2004 Indian Ocean earthquake; at the time, scientists thought it was caused by a 7.5-magnitude earthquake detected near the South Sandwich Islands (a British Overseas Territory in the southern Atlantic Ocean).

But not everything was as it seemed. Scientists were baffled to find that the supposed epicenter of the earthquake was 30 miles (47 km) below the ocean floor, which is far too deep to cause a tsunami, and that the tectonic plate rupture that  spawned it was nearly 250 miles (400 km) long — that kind of rupture should have caused a much larger earthquake.

Related: Photos: Hawaii's new underwater volcano

Now, a new study published Feb. 8 in the journal Geophysical Research Letters, has revealed that the earthquake was actually a sequence of five sub-quakes, separated in time by mere minutes. And the third of these mini-quakes — a shallower, "invisible" earthquake hidden in the data and missed by monitoring systems at the time — was an 8.2-magnitude quake responsible for the tsunami. 

"The third event is special because it was huge, and it was silent," Zhe Jia, a seismologist at the California Institute of Technology, said in a statement. "In the data we normally look at [for earthquake monitoring], it was almost invisible."

The researchers were able to retrieve the third quake's signal from the tangle of seismic waves by chopping up the data into longer, 500-second chunks and using an algorithm to tease out its constituent parts. Only then did the 200-second quake, which Jia said made up 70% of the energy released during the entire event, appear. The hidden quake, which ruptured a 125-mile-long (200 km) interface between two plates, took place just 9.3 miles (15 km) beneath Earth's surface — an ideal depth to spawn a tsunami.

The researchers say that the earthquake stayed hidden because it was a hybrid between two types of ocean earthquakes, the "deep rupture" type that results from a sudden slipping of plates, and a "slow tsunamigenic slip" created by a much slower, sometimes weeks-long grinding of one plate against another. Slow slip earthquakes can release just as much tectonic energy as a high-magnitude earthquake, but their slow pace, alongside the fact that they don't cause any pronounced seismic shaking, can often make them hard to detect.

In fact, most earthquake and tsunami warning systems tend to focus on tracking the short to medium periods of seismological waves, leaving waves with longer periods, which are still capable of generating life-threatening tsunamis, buried inside the data, Jia said. The researchers want to change this, and have set out a long-term goal to design a system that can automatically detect and warn coastal regions about more complex tsunami-causing quakes in much the same way that current systems do for simpler ones.

"With these complex earthquakes, the earthquake happens and we think, 'Oh, that wasn't so big, we don't have to worry.' And then the tsunami hits and causes a lot of damage," Judith Hubbard, a geologist at the Earth Observatory of Singapore who was not involved in the study, said in the statement. "This study is a great example of how we can understand how these events work, and how we can detect them faster so we can have more warning in the future."

Originally published on Live Science.

A powerful underwater volcano eruption in Tonga on Saturday (Jan. 15) was captured as it happened in stunning images from an Earth-watching satellite, showing the sheer power for the explosive event in the South Pacific. 

The volcano eruption on the island of Hunga Tonga-Hunga Ha'apai is visible as a spectacular explosion in views from the GOES West Earth-observing satellite operated by the U.S. National Oceanic and Atmospheric Administration (NOAA). A video of the eruption shows a vast plume from the volcano rising high into the atmosphere like a giant mushroom during the eruption as a shockwave extends outward from Hunga Tonga-Hunga Ha'apai, one of the 170 islands that make up the South Pacific kingdom of Tonga. 

Related: 10 incredible volcanoes in our solar system

The eruption spawned a 4-foot tsunami that hit Tonga's capital of Nuku’alofa, which is about 40 miles (65 kilometers) south of the volcano. A sonic boom from the eruption was heard across the Pacific Ocean, reaching as far away as Alaska, according to the Associated Press. 

Nuku’alofa was reportedly covered in a thick film of volcanic dust, according the AP. There have been no official reports of injuries or damage from Tonga's capital, but its internet access was interrupted by the event,  the AP added.

The volcano on Hunga Tonga-Hunga Ha'apai first erupted on Dec. 20 and then exploded with a massive eruption on Jan. 13, which was also spotted by GOES West, NOAA officials said in a statement. That eruption was seven times more powerful than the December event and sent a huge plume of ash and gas over 12 miles (20 kilometers) into Earth's atmosphere.

Saturday's eruption also sent an ash plume to an altitude of nearly 12 miles, New Zealand Prime Minister Jacinda Ardern told the AP. New Zealand officials hope to send military surveillance flights over the volcano on Monday to assess its status, followed by aid and supplies for Tonga, where water supplies may be contaminated, Ardern added. 

Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik. Follow us @Spacedotcom, Facebook and Instagram. 

Ancient "megaripples" as tall as five-story buildings are hiding deep under Louisiana, and their unique geology indicates that they formed in the immediate aftermath of the asteroid strike that killed the nonavian dinosaurs, a new study finds.

The 52-foot-tall (16 meters) megaripples are about 5,000 feet (1,500 m) under the Iatt Lake area, in north central Louisiana, and date to the end of the Cretaceous period 66 million years ago, when that part of the state was underwater, the researchers said. The megaripples' size and orientation suggest that they formed after the giant space rock, known as the Chicxulub asteroid, slammed into the Yucatán Peninsula, leading to the Chicxulub impact tsunami, whose waves then rushed into shallower waters and created the megaripple marks on the seafloor, the researchers said. 

The occurrence of "ripples of that size means something very big had to disturb the water column," study lead researcher Gary Kinsland, a professor in the School of Geosciences at the University of Louisiana at Lafayette, told Live Science. "This is just further evidence that the Chicxulub impact ended the Cretaceous period."

Related: In images: How North America grew as a continent 

The project began when the energy corporation Devon Energy took a 3D seismic survey of Iatt Lake. A seismic survey entails creating loud sound waves (often made with "explosives or big thumps," Kinsland said) and placing surface detectors around the area that can capture the returning sound waves, which are reflected when they hit various underground rock layers. Data from these sound waves allow researchers to make maps of the underground geology. 

Study co-researcher Kaare Egedahl, then a master's student of petroleum geology at the University of Louisiana at Lafayette, took the Devon Energy data and created a seismic image of the subterranean area. "Kaare brought it to me, and he said, 'What's this?' because it's so different than anything you would expect to see in deposits laid down by the sea or by rivers," Kinsland said. "I looked at it, and I went 'OMG.'"

Kinsland had previously studied the Chicxulub impact crater. When he looked at the seismic image, "I immediately saw the ripples, and I immediately knew the direction the water would have had to have been traveling [to create them]," he said. "And I knew that if you go backwards from that, you run right in Chicxulub."

Kinsland was able to determine the tsunami's direction because the megaripples are asymmetrical, which shows the direction the water was flowing when they were made. In this case, the long, asymmetrical side of the megaripples have a south-southeast-facing slope, which points back to the Chicxulub impact crater, he said. 

The megaripples have an average wavelength (from one crest to the next) of 1,968 feet (600 m). That, combined with their 52-foot-high amplitude, makes them "the largest ripples documented on Earth," the researchers wrote in the study.

Moreover, these megaripples are at the top of the Cretaceous/Paleogene geological boundary dating to 66 million years ago, and lie beneath a layer of debris that were kicked up in the aftermath of the Chicxulub impact, the researchers wrote in the study.

Related: Waves of destruction: History's biggest tsunamis

How did the megaripples persist?

The megaripples indicate that after the space rock hit Earth 66 million years ago, a tsunami rushed across the Gulf of Mexico and then shoaled and broke offshore as it "reached the abrupt shallowing of the Gulf of Mexico within what is now central Louisiana," the researchers wrote in the study. "The resulting pulses of water flowing north-northeast over the shelf area produced the asymmetric megaripples which are imaged within the seismic data."

But tiny ripples left by waves on a sandy beach are short-lived. So how did the megaripples persist for 66 million years?

After the tsunami created the megaripples, they remained underwater. They were deep enough underwater that when storms swept through the Gulf of Mexico, the megaripples remained undisturbed, Kinsland said. Then, the megaripples were buried by shale — in essence, a sedimentary rock made of mud mixed with clay and mineral fragments — over a period of about 5 million years, during the Paleocene epoch (66 million to 56 million years ago), he said. Later, that shale was covered by even younger sediments, he added.

The study was published online July 2 in the journal Earth and Planetary Science Letters.

Originally published on Live Science.

Could gas escaping the gravitational grasp of supermassive black holes be forming "tsunamis" in space? 

In a new, NASA-funded study, astrophysicists used computer simulations to model the environment around supermassive black holes in deep space. They found that there could be massive, tsunami-like structures forming near these black holes that are essentially massive, swirling walls of gas that have narrowly escaped the intense gravitational pull of the black hole. They even think that supermassive black holes could host the largest tsunami-like structures in the universe. 

"What governs phenomena here on Earth are the laws of physics that can explain things in outer space and even very far outside the black hole," Daniel Proga, an astrophysicist at the University of Las Vegas, Nevada (UNLV), said in a NASA statement. 

Gallery: Black Holes of the Universe

In this study, researchers took a close look at the strange environment around supermassive black holes and how gases and radiation interact there.

Supermassive black holes sometimes have large disks of gas and matter that swirl around them, feeding them over time in a combined system known as an active galactic nucleus. These systems, which often shoot out jets of material, emit bright, shining X-rays above the disk, just out of gravitational reach of the black hole. This X-ray radiation pushes winds that stream out of the center of the system. This is called an "outflow." 

This X-ray radiation could also help to explain denser, gaseous regions in the environment around supermassive black holes called "clouds," the researchers think.

"These clouds are 10 times hotter than the surface of the sun and moving at the speed of the solar wind, so they are rather exotic objects that you would not want an airplane to fly through," lead author Tim Waters, a postdoctoral researcher at UNLV who is also a guest scientist at Los Alamos National Laboratory in New Mexico, said in the same statement. 

The team showed with computer simulations how, far enough away from the black hole to be outside of its reach, the atmosphere of the disk spinning around the black hole can start to form waves of gas and matter. With the addition of the outflow winds that are pushed out by X-ray radiation, these waves can grow into massive tsunamis. These swirling waves of gas can stretch up to 10 light-years above the disk, the researchers found. Once these tsunami-like structures form, they are no longer under the influence of the black hole's gravity, according to the statement. 

In these simulations, the researchers showed how bright X-ray radiation close to a black hole seeps into pockets of hot gas in the outer atmosphere of the disk. These bubbles of hot plasma expand into nearby, cooler gas at the edges of the disk, helping to spur the tsunami-like structures. The bubbles also block the outflow wind and spiral off into separate structures up to a light-year in size. These side structures are known as Kármán vortex streets, which are weather patterns that also occur on Earth (though on Earth, this pattern of swirling vortexes looks quite different.) 

Kármán vortex streets are named for the Hungarian-American physicist Theodore von Kármán, whose name also marks the boundary between Earth's atmosphere and space.

This research goes against previous theories that have suggested that clouds of hot gas near an active galactic nucleus form spontaneously because of fluid instability, according to the statement. This study also contradicts the previous notion that magnetic fields are necessary to move cooler gas from a disk around a supermassive black hole. 

While no satellites currently operational can confirm their work, the team hopes to bolster their findings with future research and hopefully telescopic observations. Additionally, observations of plasma near active galactic nuclei from NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton space telescope are consistent with this team's findings, according to the statement from NASA.

This work was published June 15 in the Astrophysical Journal.

Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.

A tsunami warning has been issued for parts of New Zealand, with some residents being told to evacuate, after a strong earthquake struck off the country's coast on Friday (March 5), according to news reports.

The powerful 8.1-magnitude earthquake occurred at 8:28 a.m. local time near New Zealand's Kermadec Islands, which are part of New Zealand and lie about 500 miles (800 kilometers) northeast of the country's main North Island, according to CNN. It was the third strong earthquake — higher than a magnitude 7.0 — to strike the region in a span of less than eight hours, according to The Washington Post.

Residents in New Zealand's coastal areas were being urged to check for updates on the tsunami threat, and residents of some areas being told to evacuate due to a risk of flooding, according to the warning issued by the New Zealand National Emergency Management Agency.

"Evacuation advice overrides the current COVID-19 Alert Level requirements," the agency wrote on Twitter. "Listen to local Civil Defence authorities and follow any instructions. If you are told to evacuate do not stay at home."

"Tsunami activity will continue for several hours and the threat must be regarded as real until this warning is cancelled," the agency said.

The quake also prompted a tsunami warning in American Samoa, due to a risk of sea-level fluctuations along beaches, according to The Weather Channel. A tsunami watch was also issued for Hawaii, but was later discontinued, according to the Post.

The earthquake was the strongest one to strike anywhere in the world since May 2019, when an 8.0-magntidue earthquake struck Peru, the Post reported.

New Zealand is situated on the edge of the boundary between the Pacific tectonic plate and the Australian tectonic plate. That 1,864-mile-long (3,000 kilometers) boundary extends from south of Macquarie Island to the southern Kermadec Island chain, the U.S. Geological Survey reported. Where this particular earthquake occurred, the Pacific plate is diving beneath or subducting the Australian plate, the Post reported. That movement releases energy in the form of seismic shaking, or an earthquake.

Jeanna Bryner contributed reporting.

Originally published on Live Science.  

At the center of almost every galaxy in the universe is a supermassive black hole gobbling up incredible amounts of matter, and belching out incredible amounts of radiation. The biggest and hungriest of these gobblers — called quasars (or quasi-stellar objects, because they look deceptively like stars when seen through most telescopes) — are some of the most energetic objects in the universe. 

As infalling matter swirls around the quasar's maw at near-light-speed, that matter heats up and flies outward, propelled by the incredible force of its own radiation. All that intergalactic indigestion makes a quasar an awesome sight, capable of shining a thousand times brighter than a galaxy of 100 billion stars. However, a series of new papers suggests, the very same radiation that puts quasars on our maps of the universe may be devastating the galaxies that host the insatiable objects.

In six studies published March 16 in a special edition of The Astrophysical Journal supplemental series, astronomers used NASA's Hubble Space Telescope to spy on 13 quasar outflows — that is, gusts of high-speed radiation pouring out of distant quasars. By observing the outflows over several years and in many wavelengths across the electromagnetic spectrum, the team found that the wind and gas gushing out of a quasar can travel at more than 40 million mph (64 million km/h) and reach billions of degrees in temperature. 

Related: The 15 Weirdest Galaxies in Our Universe

One outflow the team studied accelerated from nearly 43 million mph (69 million km/h) to roughly 46 million mph (74 million km/h) over a three-year period — the fastest-accelerating wind ever detected in space.

This hot, fast gas is capable of causing incredible damage to a quasar's host galaxy, the researchers found, rampaging through the galaxy's disk like a tsunami and blasting potential star-forming material deep into space. In a single year, one quasar outflow can push hundreds of suns-worth of matter into intergalactic space, the researchers found, creating a stunning fireworks display while preventing new stars from forming.

These findings could help answer a long-standing conundrum about our universe: Why do large galaxies seem to stop growing after reaching a certain mass? When the team plugged their new quasar outflow data into models of galaxy formation, they found that the gales of radiation were capable of stunting the birth of new stars in large galaxies. 

"Theoreticians and observers have known for decades that there is some physical process that shuts off star formation in massive galaxies, but the nature of that process has been a mystery," Jeremiah P. Ostriker, an astrophysicist at Columbia University in New York and Princeton University in New Jersey not involved in the study, said in a statement. "Putting the observed outflows into our simulations solves these outstanding problems in galactic evolution." 

Further study of these mighty outflows, which the researchers believe will only accelerate as their quasars suck in more material, could fill in more details about how the universe's most energetic objects make (and break) entire galaxies.

• 9 epic space discoveries you probably missed in 2019
• The 12 strangest objects in the universe
• 9 Ideas about black holes that will blow your mind

Originally published on Live Science.

In case you've forgotten, Earth's sun is totally epic: It's home to towering fountains of plasma, "lava lamp blobs" of mystery matter 500 times larger than Earth, and a writhing magnetic field that twists, turns, snaps and lashes out into space every 11 years or so, seriously screwing with Earth's power grid.

While trying to better understand that 11-year stellar-tantrum cycle, characterized by a sudden increase in sunspot activity near the sun's equator, scientists discovered a new form of solar epicness you should probably be aware of. When one solar cycle ends and the next begins, the researchers wrote, the sun may experience cataclysmic magnetic field collisions — known as "terminator events" — resulting in gargantuan tsunamis of plasma that can charge across the sun's surface for weeks at a time.

According to the authors of two new studies (published February 4 in the journal Scientific Reports and July 9 in the journal Solar Physics), these solar tsunamis could be a missing link in the solar cycle, kick-starting the production of sunspots — gigantic spots on the sun that tend to form near strong magnetic field lines and are cooler than other parts of the sun’s surface — near the sun's middle latitudes — just a few weeks after they start to disappear near its equator.

"We have observed the sunspot cycle for hundreds of years, but it's been a mystery what mechanism could transport a signal from the equator, where the cycle ends, to the sun's mid-latitudes, where the next cycle begins, in such a relatively short amount of time," Mausumi Dikpati, a senior scientist at the High Altitude Observatory in Boulder, Colorado, and a co-author of both new studies, said in a statement.

Solar tsunamis, Dikpati and colleagues argue, may be the answer.

For the first study, researchers looked at 140 years' worth of solar observations taken from Earth and satellites. The scientists focused on the movement of coronal bright points — small loops of plasma that form over magnetic hotspots in the sun's atmosphere; these points shine with extreme ultraviolet light before disappearing, usually within a single day. Unlike sunspots, which appear only during periods of high solar activity (known as solar maximums), bright points can occur during less-active periods (called solar minimums), providing a more comprehensive view of solar activity across cycles, the researchers wrote.

Tracking these bright points revealed an interesting pattern: They first appeared around 55 degrees latitude (about 20 degrees higher than sunspots tend to appear), then migrated toward the equator by a few degrees latitude every year. Once the points reached about 35 degrees latitude, they began overlapping with sunspots. The points and spots continued moving toward the equator in tandem for several years; when they got there, they all vanished in a "terminator" event. A few weeks after a termination, bright points always started popping up like clockwork in the sun's mid-latitudes again.

Some physical feature of these terminator events seemed to be triggering the start of the next cycle in higher latitudes — but, what? Here's where the tsunamis come in.

In the second paper (co-authored by two of the researchers who worked on the first), researchers explained how terminator events could end in the collision of two huge magnetic field lines near the sun's equator, resulting in dual tsunamis of plasma.

According to the study, magnetic field lines like these — called "toroidal magnetic field lines," because they stretch around the diameter of the sun in a donut (or toroid) shape — may be responsible for the emergence of bright points and sunspots as they move across the sun's surface. It's possible the field lines also serve as magnetic "dams," the researchers wrote, trapping plasma behind them as they advance toward the sun's equator.

When two opposing field lines (one generated by the sun's north pole and the other by the south pole) meet at the equator, their opposing charges cancel each other out, resulting in what the researchers call "mutual annihilation." The field lines snap, releasing the plasma trapped behind them in two massive tidal waves that rush forward, bounce off each other, and surge backward toward the poles in twin tsunamis, traveling 1,000 feet (300 meters) per second.

Within a week or two, these waves reach the mid-latitudes of either hemisphere, where they reach another set of magnetic field lines that are already drumming up bright points for the next solar cycle. When the tidal wave hits this new set of lines, it buoys those magnetic field lines up toward the surface, causing a surge in sunspot creation to accompany the bright points.

This, the researchers wrote, could explain the strangely consistent gap between the termination of one cycle and the start of the next. Computer simulations showed that solar tsunamis like this are theoretically possible — however, for now, they remain just a really cool idea. Luckily, astronomers may soon have a chance to find real evidence of these solar tsunamis; judging from current bright point activity near the equator, the researchers wrote, the sun is due for its next tsunami by 2020.

• The 12 Strangest Objects in the Universe

• 15 Amazing Images of Stars

• 9 Strange Excuses for Why We Haven't Met Aliens Yet

Originally published on Live Science.

When the dinosaur-killing asteroid collided with Earth more than 65 million years ago, it did not go gently into that good night. Rather, it blasted a nearly mile-high tsunami through the Gulf of Mexico that caused chaos throughout the world's oceans, new research finds.

The 9-mile-across (14 kilometers) space rock, known as the Chicxulub asteroid, caused so much destruction, it's no wonder the asteroid ended the dinosaur age, leading to the so-called Cretaceous-Paleogene (K-Pg) extinction.

"The Chicxulub asteroid resulted in a huge global tsunami, the likes of which have not been seen in modern history," said lead researcher Molly Range, who did the research while getting her master's degree in the Department of Earth and Environmental Sciences at the University of Michigan. [Image Gallery: Ancient Monsters of the Sea]

Range and her colleagues presented the research, which has yet to be published in a peer-reviewed journal, at the American Geophysical Union's annual meeting on Dec. 14 in Washington, D.C. And the research, first reported by EOS, is novel. "As far as we know, we are the first to globally model the tsunami from impact to the end of wave propagation," Range told Live Science.

The idea for the project got started when Range's two advisors — Ted Moore and Brian Arbic, both in the Department of Earth and Environmental Sciences at the University of Michigan — realized there was a glaring gap in the Chicxulub research field. Mainly, no one had published a global simulation of the tsunami the asteroid created.

"It wasn’t until starting this project that I realized the actual scale of this tsunami, and it’s been a fun research story to share," Range said.

Getting to work

The researchers knew that the asteroid hit shallow water in the Gulf of Mexico. But to correctly model its huge impact, they needed a model that could compute "the large scale deformation of the [Earth’s] crust that formed the crater, as well as the chaotic waves from the initial blast of water away from the impact site, and waves from ejecta falling back into the water," Range said. So, the group turned to Brandon Johnson, an assistant professor who studies impact cratering at Brown University in Rhode Island.

Johnson ran a model detailing what happened in the 10 minutes following the impact, when the crater was nearly a mile deep (1.5 kilometers) and the blast was so powerful, there wasn't any water in the crater yet. "At this point, some water was moving back toward the crater," Range said. According to the model, "this water will then rush into the crater and then back out, forming the 'collapse wave.'"

In a second model, the team studied how the tsunami propagated through oceans around the world. They did this by taking the results from the first model (particularly the crater shape) and the impact's waves with respect to resting sea level and water speeds, Range said. They then used data sets on the ancient terrain of the ocean, and used that to determine how the tsunami would have played out.

The results show the effects of the tsunami were felt all around the world. [In Pictures: Japan Earthquake & Tsunami]

"We found that this tsunami moved throughout the entire ocean, in every ocean basin," Range said. In the Gulf of Mexico, water moved as fast as 89 mph (143 km/h), she found. Within the first 24 hours, the effects of the tsunami's impact spread out of the Gulf of Mexico and into the Atlantic, as well as through the Central American seaway (which doesn't exist anymore, but used to connect the Gulf to the Pacific).

After the initial nearly mile-high (1.5 km) wave, other huge waves rocked the world's oceans. In the South Pacific and North Atlantic, waves reached a whopping maximum height of 46 feet (14 m). In the North Pacific, they reached 13 feet (4 m). Meanwhile, the Gulf of Mexico saw waves as high as 65 feet (20 meters) in some spots and 328 feet (100 m) in others.

To put that in perspective, the largest modern wave ever recorded in the Southern Hemisphere was a "measly" 78 feet (23.8 m) tall, which struck near New Zealand in May 2018, Live Science previously reported.

Hard evidence

There's evidence that supports the models, Range said. According to the second model, fast-moving water from the impact likely caused erosion and sediment disruption in South Pacific, North Atlantic and Mediterranean ocean basins.

In a separate study (which also has yet to be published), Moore examined sediment records across the ocean. His findings agree with the tsunami model, Range said.

It can be hard to imagine such a cataclysmic tsunami, so the researchers compared it to the 2004 Indian Ocean tsunami that killed at least 225,000 people. The two tsunamis were as different as night and day, they found. "Over the first 7 hours of both tsunamis, the [Chicxulub] impact tsunami was 2,500 to 29,000 times greater in energy than the 2004 Indian Ocean tsunami," Range said.

Of course, the giant tsunami wasn't the only event that did in the non-avian dinosaurs. The asteroid also triggered shock waves and sent a vast amount of hot rock and dust into the atmosphere, which rubbed together with so much friction that they started forest fires and cooked animals alive. These particles also hovered in the atmosphere and blocked the sun's rays for years, killing plants and the animals that ate them.

• Crash! 10 Biggest Impact Craters on Earth
• Photos: The World's Weirdest Geological Formations
• In Photos: The UK's Geologic Wonders

Originally published on Live Science.

Gravity is pulling Mount Etna toward the sea, raising the possibility that the flank of the active volcano may someday suffer a catastrophic collapse.

There is no indication that such a collapse is imminent, but new research finds that the Italian volcano's southeastern flank is moving both above ground and under the sea. These movements mean that the risk of a slope collapse is higher than previously believed, researchers reported today (Oct. 10) in the journal Science Advances.

"We need to understand better how this transition works and what sort of triggers does it take for a collapse," study co-author Morelia Urlaub, a researcher in marine geodynamics at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, told Live Science. [History's Most Destructive Volcanoes]

Eruptive Etna

Mount Etna is Europe's most restless volcano. This mountain has experienced active periods since at least around 6000 B.C. and is currently in an eruptive cycle that has been ongoing since September 2013, according to the Smithsonian Institution's Global Volcanism Program.

Researchers using satellite data and GPS measurements have also observed that Mount Etna's southeastern flank has been creeping seaward for at least 30 years. In March, scientists from The Open University in the United Kingdom reported that the slope moved an average of about a half-inch (14 millimeters) each year between 2001 and 2012 alone.

The debate, Urlaub said, has been whether this creep results from magma moving beneath and within the volcano or whether it results mostly from gravity. Mount Etna is constantly spewing material onto its slopes, she said, and gravity pulls that new material downward.

"That's common with these big volcanoes," Urlaub said. "They spread at the base."

Mount Etna also has its "feet in the water," Urlaub said. Its slopes continue below the Sicilian coast and into the Mediterranean. Until now, though, no one had measured how the flank was moving below sea level.

Submarine slipping

Using a network of seafloor sensors, Urlaub and her team measured how sound traveled from transponder to transponder every 90 minutes between April 2016 and July 2017. The time it took sound to travel reveals the distance between transponders, so the researchers could detect any changes in the seafloor over the study period.

They found that during an eight-day period in May 2017, a fault on the mountain's submarine flank shifted as much as 1.6 inches (4 centimeters). This was not an earthquake; the movement happened without a fault rupture or seismic waves, but rather as a gradual slip.

The area where the researchers measured the slip is far from the magma chambers at the center of Etna, Urlaub said. That means that the movement did not result from magma rising within the volcano's subterranean chambers; instead, it's the inexorable work of gravity, which pulls on the entire slope above and below the water.

That's bad news for Etna's risk to human life, Urlaub said.

"We know from other volcanoes in the geological record that these have collapsed catastrophically and caused really, really big, fast landslides," she said, "and if these landslides enter the sea, they can cause a tsunami."

The chance of that happening at Etna can't yet be quantified, Urlaub said. Scientific observations of the mountain date back only a few decades, she said, and the whole history of Etna spans 500,000 years. More monitoring is needed to detect whether there are any changes in how the slope is moving and to estimate its risk of collapse, she said.

"There is a hazard," Urlaub said. "We just have to keep an eye on Etna's flank and how it is moving."

Originally published on Live Science.

Damaged buildings

On Friday (Sept. 28), a 7.5-magnitude earthquake hit near Sulawesi, Indonesia. A tsunami with waves as tall as 18 feet (5.5 meters) followed shortly after. Disaster response officials announced Oct. 2 that the death toll was over 1,200. The earthquake and tsunami crushed and damaged many houses and vehicles like these ones photographed on Oct. 1 in the city of Palu. This coastal city in Central Sulawesi was hit the worst.

Quiet aftermath

Earthquake survivors ride by a boat in Palu, Indonesia, on Oct. 1.

Search for food

An earthquake victim searches for usable items next to a collapsed mosque in Palu. Following the disaster, many desperate survivors also looted shops for food and water.

Damaged roads

A few days after the disaster, a motorcyclist photographs a damaged road in the Petobo village in Palu.

Collapsed bridges

The tsunami and earthquake damaged homes, hospitals, hotels, shopping centers and bridges — like this one in Palu.

Collapsed bridges

Following the disaster, a bridge lies collapsed in Palu. Damage to bridges and and roads have made it difficult to bring aid to survivors.

Damaged roads

People walk near a damaged road in the Balaroa village in Palu.

Debris

A survivor in Palu looks at the debris that resulted from the disaster.

Collapsed hotel

This aerial photo taken on Sept. 30, shows a collapsed 10-story hotel in Palu.

Hindered Transportation

The Mutiara Sis Al Jufri airport in Palu was damaged by the tsunami and earthquake and remains partially closed.

Coastal debris

Debris in Palu can be seen spread out across the coast.

Editor’s Note: This story was updated at 11:33 a.m. E.T. on Tuesday, Oct. 2

On Friday (Sept. 28), a 7.5-magnitude earthquake hit near Sulawesi, Indonesia. Shortly after, a tsunami with waves of up to 18 feet (5.5 meters) hit the coast, leaving at least 1,200 people dead and dozens missing.

Rescue efforts continue, as people work to dig out the dozens of others thought to be stuck under piles of rubble. The death toll is expected to rise as rescuers reach areas that lost power and communication following the earthquake. [Photos: The Devastating Damage from Indonesia Earthquake and Tsunami]

The city of Palu, which sits at the center of a bay in the northwestern side of Central Sulawesi, was hit the worst and had the greatest number of deaths. From there, a bystander captured a video of the incoming tsunami.

The devastation raised criticism of the country's alert system. Though a tsunami warning was sent out, it was lifted just 34 minutes later, according to Reuters. Some, who had lost power, didn't receive the alerts. Further, the warning underestimated the size of the waves, according to the BBC.

Sutopo Purwo Nugroho, a spokesman for Indonesia's National Disaster Mitigation Agency, told the BBC that the tsunami detector buoys — 21 floating devices connected to deep-sea sensors — weren't working. The detection systems had either been damaged or stolen.

In the hills above Palu, volunteers are working to dig a mass grave, big enough for thousands of bodies, according to the BBC. Among the dead are 34 children who were attending a Bible camp at a church near Palu.

This area of Indonesia has seen about 15 earthquakes with magnitudes larger than 6.5 over the last century, according to the U.S. Geological Survey. The largest, a magnitude 7.9, hit in 1996, about 60 miles (100 kilometers) north of this new earthquake, and resulted in 10 deaths.

Editor’s Note: This story was updated to include the most recent death toll estimates.

Originally published on Live Science.

A massive landslide and tsunami that denuded the slopes of an Alaskan fjord could reveal warning signs that could help predict future disasters.

In a new paper, researchers described the geological fingerprints of the tsunami, which tore through Taan Fjord on Oct.17, 2015, at an estimated 100 mph (162 km/h). Using satellite imagery and field-based measurements, the team discovered that the slope was displaying signs of instability for at least two decades before it failed.

The "geologic evidence can help [us] understand past occurrences of similar events and might provide forewarning," the researchers wrote Thursday (Sept. 6) in the journal Scientific Reports. [The 11 Deadliest Natural Disasters in History]

The fall

Taan Fjord sits in Wrangell-St. Elias National Park and Preserve in southeastern Alaska. The rugged landscape is dotted with glaciers, including the Tyndall Glacier, which used to fill the entirety of Taan Fjord. Between 1961 and 1991, however, the glacier retreated 10.5 miles (17 kilometers) to the end of the fjord.

As glaciers retreat and permafrost melts, the rocky hillsides once supported by all that ice become unstable, wrote the team of researchers led by the University of Washington Tacoma's Dan Shugar and environmental nonprofit Ground Truth Trekking's Bretwood Higman. The situation is made worse by Alaska's restive nature; minor earthquakes regularly jolt the fjord walls.

Those factors may explain what happened in 2015, when an enormous chunk of hillside in front of the Tyndall Glacier suddenly failed. Fortunately, no human eye was around to witness the catastrophe, which spawned seismic waves equivalent to a magnitude-4.9 earthquake. Roughly 180 million tons of rock and dirt crashed toward the fjord, about one-third of the material landing on the glacier itself and the other two-thirds hitting the water. The resulting tsunami traveled 633 feet (193 meters) up the opposite side of the fjord; down-fjord, it reached 328 feet (100 m) in many places. After the wave of debris and water hit, hillsides that had once been covered with 32-foot (10 m) trees were stripped entirely bare.

Warning signs

It's unknown what triggered the final slope failure, the researchers wrote. About 2 minutes before the tsunami, the seismic waves from a magnitude-4.1 earthquake that hit more than 300 miles (500 km) away reached the fjord. The shaking wouldn't have been much, nor would it have been unusual for the region, the authors wrote, but it might have been enough. The previous months had also been unusually wet, which could have further destabilized the slope.

Whatever the reason that the slope failed at that moment, the landslide was inevitable, the researchers wrote. Satellite imagery revealed that the slope had been slumping since 1996, and depressed areas called grabens — created as the surface of the hillside stretched downward — had been visible from above since 1995. For two decades, the researchers found, the signs of a failing slope were apparent from satellite data.

The deposits that the tsunami left behind were unique, unlike those left by other modern tsunamis, the researchers found. These deposits occurred in three distinct layers, one consisting of fine sands, one made up of cobble-size rocks between about two and ten inches (5 to 25 cm) in diameter and boulders, and a final layer made of a mixture of everything from sand to boulders 16 feet (5 m) in diameter.

Seeing those patterns in a modern, well-documented landslide tsunami provides new clues about what to look for in the geological record when searching for ancient tsunamis, the researchers wrote. The findings also hint at ways to monitor unstable hillsides as climate change continues to force the retreat of the glaciers. Taan Fjord is remote, but the Tidal Fjord in tourist-heavy Glacier Bay, Alaska, saw a landslide in June 2016. Fortunately, the debris from that event didn't reach the water, avoiding a tsunami. In Rink Fjord in Greenland in 2017, a landslide tsunami had a far more tragic outcome: Four people died.

"More such landslides are likely to occur as mountain glaciers continue to shrink and alpine permafrost thaws," the researchers wrote.

Original article on Live Science.

Editor's note: This article has been updated to correct the amount of rock and dirt that moved during the landslide. It was 180 million tons, not 180 billion.

Update: This story was updated to indicate the cancellation of the tsunami watches and warnings.

A strong earthquake struck off the southern coast of Alaska early Tuesday (Jan. 23), prompting a tsunami warning, which was later canceled.

The earthquake, which had a magnitude of 7.9, hit 175 miles (280 kilometers) southeast of the island of Kodiak at 12:31 a.m. local time (4:31 a.m. EST), according to the U.S. Geological Survey (USGS). The quake struck at a depth of about 16 miles (25 km).

The Kodiak Police Department urged residents to get to higher ground, and tsunami sirens sounded the alarm in the middle of the night, according to the Anchorage Daily News.

According to the National Tsunami Warning Center (NTWC), a tsunami warning was in effect along a large stretch of coastline, from Canada's British Columbia province to Alaska's Aleutian Islands.

In areas where a tsunami warning is in effect, damaging waves, powerful currents and coastal flooding are possible, the alert from the NTWC said.

A tsunami watch, meanwhile, was in effect for the coastal areas of the United States from Washington state south through California, and residents were urged to stay alert and prepare to take action if needed.

In a message posted to Twitter, Alaska's Gov. Bill Walker said his office is "closely monitoring" the tsunami warnings and urged residents to heed local warnings to move inland or to higher ground. 

The tsunami advisories were canceled about 3 hours after the earthquake.

"A tsunami was generated by this event, but no longer poses a threat," an update from the NTWC said. "Some areas may continue to see small sea level changes."

The highest tsunami waves recorded in southern Alaska reached 0.7 feet (21 centimeters).

Original article on Live Science.

The Year's Biggest Natural Disasters

This year was one for the record books, from political election results that took the world by storm to actual storms that shook spots across the globe. The year began with winter storm Jonas, also known as "The Storm of the Century," which brought a record amount of snowfall to the Northeast. But 2016 may well be known as the year of the earthquake, as areas around the world trembled from seismic activity. Here are some of the headline-grabbing natural disasters that occurred this year.

Winter Storm Jonas

The massive winter storm left the northeast U.S. covered in such extensive snowfall that the white precipitation was clearly visible from space. Over the course of one weekend (Jan. 23-24), Jonas broke records for snowfall in places along the East Coast. Airports near Baltimore recorded about 29 inches (74 centimeters) of snow; approximately 28 inches (71 cm) of snow fell in Newark, New Jersey, and Philadelphia recorded 22 inches (55 cm) of snow, according to the Weather Channel. The town of Glengary, West Virginia, received the highest snow total: a whopping 42 inches (107 cm). At least 49 people died as a result of the mammoth snowstorm, due to car accidents, hypothermia, carbon monoxide poisoning or overexertion from shoveling snow. [Read the full story on winter storm Jonas' epic snowfall"]

Taiwan Earthquake

On Feb. 6, a 6.4-magnitude earthquake hit 17 miles (28 kilometers) northeast of Pingtung City in southern Taiwan. It's relatively shallow depth (14 miles, or 23 km, below the surface) caused widespread damage, toppling buildings in the city of Tainan. The quake caused an estimated 117 deaths and left hundreds more injured, according to the Tainan City government. Most of the fatalities and injuries came from the collapse of the Wei-Guan Golden Dragon high-rise tower (shown here), a residential building in Tainan, according to authorities.

California Wildfires

A series of wildfires blazed across California this year, burning more than half a million acres. According to the California Department of Forestry and Fire Protection, 6,938 fires had burned 565,070 acres (229,000 hectares) as of Dec. 11. The Blue Cut wildfire (shown here), for instance, burned through more than 37,000 acres (more than 12,000 hectares) in Southern California this summer and through the fall, according to the Los Angeles Times. The state's lingering drought has killed more than 100 million trees, according to the U.S. Forest Service's latest aerial survey, leaving a "fuel buildup" that led to this season's longer, hotter fire season. The fires this year killed seven people, including one firefighter, and damages are still being tallied.

Louisiana Flooding

Tremendous downpours inundated Louisiana in August, when some regions received more than 20 inches (50.8 cm) of rain over a 72-hour span (from Aug. 12‑14). At least six rivers hit record levels during the rainfall, the most extreme of which was along the Amite River, which exceeded its previous height record by more than 6 feet (1.8 meters). The National Weather Service described the heavy rain event as an "inland sheared tropical depression," where a deadly combination of tropical moisture and low pressure fueled immense rainfall. Thirteen people lost their lives, and an estimated 30,000 people were forced from their homes. [Read more about Louisiana's historic flooding]

Italy Earthquakes

Central Italy was rattled this year by three strong earthquakes in just three months. A 6.2-magnitude earthquake struck Aug. 24 about 6.5 miles (10.5 kilometers) southeast of Norcia, Italy. The initial quake was followed by several aftershocks, including a 5.5-magnitude earthquake that struck 2.5 miles (4 km) northeast of Norcia the same day. The temblors rocked Central Italy, killing hundreds of people as medieval-era stone buildings collapsed. [Read more about the Norcia quake in August] The "tectonically and geologically complex" region sits atop the Tyrrhenian basin, which is beneath the Mediterranean Sea where the earth is spreading apart. It was struck again in October when two strong earthquakes just 2 hours apart rattled the center of the country. A 5.5-magnitude quake struck about 6 miles (9 km) southeast of Norcia, followed two hours later by a larger, magnitude-6.1 quake about 11 miles (18 km) from the town and just 1.6 miles (2 km) from the smaller town of Visso. [Read the full story about the two earthquakes that struck central Italy in October]

Hurricane Matthew

Hurricane Matthew was a powerhouse of a storm that circulated through the Atlantic Ocean in October. The strongest storm seen in the Atlantic since Hurricane Felix in 2007, Matthew briefly reached Category 5 hurricane status — with winds exceeding 157 mph (252 km/h). The storm dropped to Category 4 strength, though winds were still incredibly strong at 140 mph (225 km/h). The high-speed winds, storm surges and "life-threatening rain" made Matthew a destructive and deadly disaster. Over 1,600 estimated deaths were attributed to the hurricane, and damages are estimated in excess of $10.5 billion. [Read the full story on Hurricane Matthew]

New Zealand Earthquake and Tsunami

A powerful 7.8-magnitude earthquake struck New Zealand on Nov. 14. Though the quake's epicenter was northeast of Christchurch, the massive temblor was felt as far away as New Zealand's capital of Wellington, located 120 miles (200 km) away, on the North Island. About 2 hours after the initial quake, tsunami waves over 7 feet (2 meters) tall hit the coast. The island nation also continued to shake from hundreds of aftershocks well after the main temblor, including a 6.3-magnitude quake. Two deaths were reported, and much of the rural landscape was devastated from the powerful quake. New Zealand Prime Minister John Key estimated that reconstruction would take months and cost billions of dollars. The magnitude-7.8 quake also transformed the underlying faults in the region, rupturing six major faults, according to new maps by the geoscience consultancy group GNS Science in New Zealand. [Read the full story on New Zealand's devastating quake]

Fukushima Earthquake

A powerful earthquake shook northern Japan on Nov. 21, generating a small tsunami that hit the same Why Do So Many Big Earthquakes Strike Japan?] 

Tennessee Wildfires

Areas around Gatlinburg, Tennessee, were consumed by wildfires on Nov. 28, closing the Great Smoky Mountain National Park and forcing thousands to flee their homes. The inferno spread rapidly through the area's drought-stricken forest, pushed by gusty winds. According to meteorologists, the gusty winds blowing dry leaves spread the blaze, also knocking over power lines and sparking new fires. The deadly combination allowed the fires to move quickly, wreaking havoc on the area. The historic Gatlinburg fires left 14 dead, 134 injured and scorched more than 1,600 structures. [a href="http://www.livescience.com/57015-how-tennessee-wildfire-spread-so-fast.html>Read more about Gatlinburg's wildfires]

Indonesia Earthquakes

During the first week of March, a 7.8-magnitude temblor struck about 500 miles (800 km) southwest of Sumatra, an island in western Indonesia. Though the quake was strong, it occurred far enough away from the islands to cause significant damage. [Read more about the Sumatra earthquake] On Dec. 7, another earthquake shook the island nation. The shallow 6.5-magnitude quake's epicenter was 12 miles (19 km) southeast of Indonesia's Aceh province, according to the United States Geological Survey (USGS). It damaged hundreds of structures in the district of Pidie Jaya in Aceh, CNN reported. At least 100 people were killed and 136 seriously injured, according to Indonesia's Disaster Management and Mitigation Agency. Indonesia was again hit by an earthquake on Dec. 21, when a 6.7-magnitude temblor struck the Banda Sea off Indonesia and East Timor, the USGS reported. The quake was felt as far away as Darwin, the capital of the Northern Territory of Australia. According to news reports, residents said the quake lasted several minutes. The USGS alert listed the quake as having moderate shaking and a low likelihood of casualties and damage. Original article on Live Science.

Fifteen years ago, Galen Gisler had a gut feeling that something wasn't right about the Hollywood portrayal of asteroid impacts in the world's oceans.

"Movies like 'Deep Impact' and 'Armageddon' suggested that an ocean impact would produce a devastating tsunami that would affect everything along the shorelines surrounding an ocean basin ... but I was skeptical," Gisler, a scientist at Los Alamos National Laboratory in New Mexico, told Seeker.

Generally speaking, getting hit by an asteroid is a bad day for life on Earth, even if it is a part of the natural cycle of living in the dynamic and evolving solar system. Marauding space rocks fly around interplanetary space with no regard for Earth's precious biosphere. If they have our planet in their sights, they're going to hit us. And depending on their mass and speed, they could hit us hard.

But depending on where an asteroid hits, the fallout will vary greatly. If an asteroid was predicted to hit land near a major city, we might be able to evacuate in time (and disaster response agencies have carried out drills that focus on this possibility), but the damage to society, infrastructure and economy would be terrible, obviously. But if an asteroid hits one of our oceans — water makes up for 70 percent of our planet's surface and is therefore a more likely scenario — the scope of the impact is poorly understood.

RELATED: What Happens If an Asteroid Takes Aim at Los Angeles?

Gisler is determined to better understand the realities of a massive impact in the ocean and presented his team's findings at the American Geophysical Union's Fall Meeting in San Francisco last week, showcasing the dramatic 3-D modeling results of an ocean-impacting asteroid. Never before has an impact scenario like this been studied in such detail and the simulation revealed that Gisler's original instincts had merit: devastating post-impact tsunamis we see in the movies are as fictional as the science fiction plot lines they are a part of.

"An asteroid impact is a point source and it only affects the immediate region around the impact point and moreover, to create a tsunami, you need something that disturbs the entire water column," said Gisler.

He likens an asteroid ocean impact to throwing a rock into a pond. Sure, the energy of the rock hitting the water will produce waves, but the ripples are very dispersive. In other words, they lose their energy very quickly. These dispersive waves in an ocean will be very localized and won't have the energy that a tsunami does. "It's very different physics," he added.

RELATED: Large-ish Meteor Hits Earth... But No One Notices

Tsunamis occur when there's large scale shifts of mass in the seabed, such during a submarine earthquake or landslide. These shifts cause a huge movement in a massive column of water, from the seabed to the surface, that can create wavelengths of a hundred kilometers or more, said Gisler, which is many times longer than the depth of the ocean (of a few kilometers). Tsunamis aren't very dispersive and therefore don't lose energy as they travel through the ocean basin, hitting coastlines hundreds or maybe thousands of kilometers away, often with devastating results.

But that's not to say an asteroid impact in the middle of an ocean wouldn't be dramatic.

"They're spectacular to be sure; they would produce splashes that go up tens of kilometers," he added. According to the model, a jet of water would also protrude from the ocean's surface by a few kilometers, producing rim waves surrounding the transient water crater reaching 400 meters in height. "That's awfully high! But unless it's very close to a shore, it's not going to be very dangerous."

In addition, a significant fraction of the kinetic energy of the impacting asteroid will go into vaporizing huge quantities of water, according to the team's award-winning video explaining the research findings. Water vapor is a potent greenhouse gas, so the injection of vapor into the stratosphere could linger for months or years, altering global climates.

Intense shock waves and violent winds will also wreak havoc on the surface, so the further the impact is from any populated coastal regions, the better.

RELATED: Huge Tsunamis May Have Ravaged Ancient Mars

Gisler's research adds another layer of understanding of how an asteroid impact would affect Earth and, for asteroids of 300 meters wide or less, we could use an ocean impact as a strategy to limit global damage.

"I think it gives us more options. If you find an asteroid in this size range is on a collision course with Earth, and you can't deflect it from hitting the Earth's surface, you might be able to deflect it into the middle of the ocean," he said.

Although NASA and other agencies are working to identify and track asteroids that pose a significant threat to Earth, we could be blind-sided and have little time to prepare a mission to knock the asteroid off course. But now we have more of an understanding about how an ocean impact may go down, we might be able to slightly nudge it toward a new target that will produce less collateral damage, like the middle of the ocean.

Originally published on Seeker.

A magnitude-6.9 earthquake struck off the coast of Fukushima, Japan, today (Nov. 21), triggering a tsunami warning.

The earthquake, which was originally reported as a magnitude-7.3, struck around 6 a.m. local time on Nov. 22, about 23 miles (37 kilometers) southeast of Namie, Japan, the U.S. Geological Survey reported. A tsunami warning issued by the Japan Meteorological Agency has predicted wave heights of up to 10 feet (3 meters).

According to the Japan Meteorological Agency, a tsunami warning typically means damage due to tsunami waves is expected and residents should immediately evacuate coastal regions and riverside areas. These warnings also mean that tsunami waves are expected to hit repeatedly, and people should not leave safe ground until the warning is lifted. [Image Gallery: This Millennium's Destructive Earthquakes]

The area is no stranger to catastrophic quakes; on March 11, 2011, a magnitude-9.0 earthquake struck Japan. The so-called Tohoku quake, which released hundreds of years of pent-up stress at the subduction region where the Pacific Plate is diving beneath the Eurasian Plate, set off a massive tsunami with run-up heights of 128 feet (39 m) and inundation reaching 6 miles (9.7 km) inland.

The multistory waves inundated the coastal Fukushima Daiichi Nuclear Power Plant and triggered a level 7 nuclear meltdown. Four years after the quake, 230,000 people who lost their homes were still in temporary housing, according to Japan's Reconstruction Agency. Since the disaster, radioactive waste, such as cesium-134 and cesium-137, has floated across the Pacific Ocean and washed ashore on the West Coast of the U.S.

The epicenter of today's earthquake was about 80 miles (130 km) southwest of the 2011 Tohoku quake's epicenter, but that number can give a misleading impression of how far apart the two quakes occurred, said Don Blakeman, a geophysicist with the USGS in Golden, Colorado. With quakes as large as the 2011 earthquake, "the fault rips for many man tens of kilometers," Blakeman told Live Science. 

While the Japan Meteorological Agency issued a tsunami warning for the region around Fukushima and an advisory for the entire coastline of the country, the current quake is unlikely to trigger a Pacific-wide tsunami, Blakeman said. 

"This is a strike-slip earthquake," meaning that two sides of the fault move sideways relative to each other. "So, you don't get the vertical movement you need," Blakeman said.

Original article on Live Science.

A powerful 7.8-magnitude earthquake struck New Zealand early Monday (Nov. 14) local time, triggering a tsunami that hit the coast a couple of hours later, according to New Zealand's WeatherWatch. Aftershocks are still being felt across the country, and officials say at least two people were killed by the natural disaster.

New Zealand's South Island was hit by the 7.8-magnitude earthquake at 12:02 a.m. local time Monday (6:02 a.m. Sunday EST), the U.S. Geological Survery (USGS) said. The quake's epicenter was northeast of Christchurch, but it was felt as far away as New Zealand's capital of Wellington, located 120 miles (200 km) away, on the North Island, the BBC reports.

Tsunami waves over 7 feet tall (2 meters) hit the coast about 2 hours after the main earthquake, WeatherWatch said. Although authorities have now lifted the tsunami alert, the BBC reports that officials are still asking residents to stay away from the shore. Following the initial earthquake and subsequent tsunami, the island nation has experienced hundreds of aftershock temblors, including a 6.3-magnitude quake, according tothe BBC. [Image Gallery: This Millennium's Destructive Earthquakes]

The town nearest to the earthquake epicenter, Kaikoura, has been cut off after the quake triggered landslides and a large river dammed up, the BBC reports. More than 1,000 people are still stranded in the town, and military helicopters and a navy ship are being sent to evacuate the remaining residents.

In 2011, New Zealand experienced a devastating magnitude-6.3 quake, also centered very close to Christchurch. The earthquake killed 185 people and damaged or destroyed 100,000 buildings, and was the costliest disaster ever to strike New Zealand, according to New Zealand government officials.

The lethal 2011 earthquake was the aftershock of a magnitude-7.1 temblor that struck 172 days earlier (in 2010), according to the USGS. This initial quake caused millions of dollars in damage to bridges and buildings, and seriously injured two people. Though stronger than the aftershock, the 2010 temblor occurred farther away from any city, the USGS said.

Original article on Live Science.

A magnitude-7.0 earthquake struck southern Japan today, less than two days after a 6.2-magnitude temblor rocked the same region, triggering tsunami advisories in the area.

The most recent earthquake struck the Kumamoto region on Japan's Kyushu Island early Saturday (April 16) at 1:25 a.m. local time (12:25 p.m. ET on April 15), according to the U.S. Geological Survey (USGS). The smaller 6.2-magnitude quake on Thursday (April 14) killed nine people and injured hundreds more, reported CBS News.

With residents of the Kumamoto region reeling from two sizable earthquakes in as many days, and with memories of the massive 9.0-magnitude earthquake and tsunami that devastated Tohoku, Japan, in 2011 not far from people's minds, what is it about this part of the world that makes it so seismically active? [The 10 Biggest Earthquakes in History]

For starters, Japan is located along the so-called Pacific Ring of Fire, which is the most active earthquake belt in the world. This "ring" is actually an imaginary horseshoe-shaped zone that follows the rim of the Pacific Ocean, where many of the world's earthquakes and volcanic eruptions occur.

Within the Ring of Fire, several tectonic plates — including the Pacific Plate beneath the Pacific Ocean and the Philippine Sea Plate — mash and collide.

"The Earth's surface is broken up into about a dozen or so major chunks that are all moving around. Where they all interact at their edges, interesting things happen," said Douglas Given, a geophysicist with the USGS in Pasadena, California.

Today's earthquake seems to have been caused by the Philippines Sea Plate diving underneath the Eurasia Plate, according to Paul Caruso, a geophysicist with the USGS.

While Japan is no stranger to earthquakes, the 7.0-magnitude temblor is one of the largest ever recorded in this part of southern Japan, Caruso told Live Science.

"The second-largest was probably on March 20, 1939 — there was a magnitude-6.7 in this area. And we've had magnitude-6.5 and magnitude-6.3 earthquakes, but this is the largest quake that has been measured in that vicinity," he said.

A tsunami advisory was issued after today's earthquake, but it was subsequently lifted by the Japan Meteorological Agency, and there are currently no major tsunami warnings or advisories in effect.

Not all earthquakes trigger tsunamis, Caruso said. In general, there are three key ingredients that can produce a dangerous earthquake-tsunami combination, he added. First, the earthquake must be at least a magnitude-7 temblor. Second, the quake's epicenter has to be underneath the ocean, Caruso said. And finally, the earthquake has to be shallow.

"We have quakes around Fiji all the time, but those are sometimes 400 miles [640 kilometers] underground, so they aren't going to generate a tsunami," he said.

Today's earthquake was shallow — about 6 miles (10 km) underground — but the epicenter was on land, meaning there aren't likely to be any dangerous tsunamis as a result, Caruso said.

Given said he hasn't seen many damage reports yet, but Japanese authorities and scientists at the USGS will be monitoring the area for potentially dangerous aftershocks, which are smaller quakes that follow the largest event in a series and that generally decrease in strength.

"This seems to be a pretty energetic sequence, and there are lots of large aftershocks," Given told Live Science. "And of course, after a large earthquake, structures are often weakened as a result. Additional damage can be expected."

Residents of the area should expect more shaking in the coming days, according to Caruso.

"We can say for certain that there are going to be more aftershocks in this area," he said. "Exactly when and how big they're going to be is difficult to say, though. No one can predict that."

Follow Denise Chow on Twitter @denisechow. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

A 7.8-magnitude earthquake struck off the coast of Sumatra, an island in western Indonesia, according to the U.S. Geological Survey (USGS).

The quake happened at 7:49 p.m. local time on March 3 (7:49 a.m. ET on March 2), about 500 miles (800 kilometers) southwest of Sumatra. The temblor occurred as a result of two tectonic plates sliding against each other — what's known as strike-slip faulting — within the ocean lithosphere of the Indo-Australia plate, according to the USGS.

The earthquake's epicenter was located 500 miles southwest of the city at Padang, at a depth of about 15 miles (24 km), according to the USGS. Indonesian authorities issued a tsunami warning following the quake, but that notice has since been lifted, reported Bloomberg. Similarly, Australian officials canceled tsunami warnings for Cocos Island and Christmas Island in the Pacific Ocean, according to news reports.

"The plate boundary southwest of Sumatra is part of a long tectonic collision zone that extends over 8,000 km [4,970 miles] from Papua in the east to the Himalayan front in the west," USGS officials wrote in their preliminary report of the quake.

In 2004, a massive 9.1-magnitude undersea earthquake struck off the coast of Sumatra, triggering a deadly tsunami that killed more than 230,000 people and destroyed coastlines along the Indian Ocean.

Follow Denise Chow on Twitter @denisechow. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Everyone dies of something, but after slogging through the daily news, you'd think most people die from terrorism, shark attacks and gas explosions. But are these tragedies — not to mention deaths from lightning strikes, plane crashes and tsunamis — actually top killers in the United States?

Not really.

Even combined, these incidents killed far fewer people than the most deadly illness — heart disease, which took the lives of more than 614,000 people in the United States in 2014, accounting for about 23 percent of all deaths in the country, according to the Centers for Disease Control and Prevention (CDC).

To separate the deaths that make headlines from those that are far more common, Live Science investigated the odds of dying from various causes. We used the CDC's Wonder database for 2014 data and other sources, and found that you're more likely to die of Alzheimer's disease (about 29 deaths per 100,000 people in the U.S.) than you are from contact with a venomous snake or lizard (there were just five such deaths in 2014).

In total, about 2.6 million people died in the United States in 2014, according to the CDC. To put this number into perspective, that means about 824 people died for every 100,000 people in the country. (Keep this statistic in mind, as we'll be giving death rates per 100,000 people throughout this article.) Worldwide, an estimated 56 million people died in 2012, the most recent year for which numbers on worldwide deaths are available from the World Health Organization (WHO).

Although Hollywood advised us (in no fewer than five of its blockbusters) to "Die Hard," there are a ton of ways to die. Here's a look at how many people die from common, unexpected and even theoretical events, and the science behind those numbers. [9 Healthy Habits You Can Do in 1 Minute (Or Less)]

Ways to Die 

1. Top 2 Deadly Diseases
2. Top Killers
3. Respiratory Diseases & Accidents
4. More Diseases
5. Drug Overdoses
6. Animal Attacks
7. Transportation
8. Terrorism & Homicides
9. Other Scary Ways to Die
10. Natural Disasters

Top 2 Deadly Diseases

In decades past, infectious diseases were the No. 1 killer, "but with the advent of antibiotics and treatment of infectious diseases, people started to live longer," said Dr. Maan Fares, a staff cardiologist at Cleveland Clinic. With many infections now conquered, people's lifestyle choices — including whether they smoke, how they eat and how much they exercise — are catching up with them, and causing conditions such as diabetes, high blood pressure and high cholesterol, Fares told Live Science.

So, it may come as no surprise that the top two killers — heart disease and cancer — account for roughly half of all deaths in the United States. About 193 per 100,000 people died from cardiovascular problems, such as heart attacks, in the United States in 2014. Worldwide, cardiovascular diseases killed 17.5 million people, accounting for 3 of every 10 deaths in 2012, the WHO reported.

People's risk of heart disease rises with smoking, sedentary lifestyles and poor sleep. To lower your risk of dying of heart disease, you can exercise, eat colorful fruits and vegetables (and fiber), and drink less alcohol.

Cancer placed second, with about 186 deaths per 100,000 people in the United States. Some cancers took more lives than others. The top killers, lung and bronchial cancers, killed about 155,000 people in 2014, or about 49 deaths per 100,000 people. Colon and rectal cancers claimed about 16 lives per 100,000 people, and breast cancer took about 13 lives per 100,000 people. Pancreatic cancer and prostate cancer followed, with about 12.7 and 9 deaths per 100,000 people, respectively. [7 Cancers You Can Ward Off with Exercise]

"We still don't know what causes cancer, but we do realize that each cancer is different, and the risk factors associated with each is very different," said Dr. Rupal O'Quinn, a cardio-oncologist at the University of Pennsylvania. People with cancer are living longer and sometimes even beating their diagnosis, largely thanks to cancer screenings, organ transplants and targeted therapies (newer drugs that aim to specifically kill cancer cells, rather than the broader approach of chemotherapy drugs), O'Quinn said.  

There were 3 million cancer survivors in the country in 1971, and more than 12 million in 2012, according to a study in the International Journal of Medical Sciences. But there is still much to be learned about cancer, she said. Screening cannot look for every type of cancer, such as ovarian cancer, which may explain why some cancers claim more lives than others, O'Quinn said.

A person's cancer risk may also vary according to region. For instance, esophageal cancer kills about 4 per 100,000 people a year in the United States, but about 140 per 100,000 people in Central Asian countries such as Pakistan, according to a 2004 study in the journal Annals of Oncology.

The reason? Researchers suspect that the higher rates of esophageal cancer in Central Asia are linked to the use of chewing tobacco — a habit common in Pakistan — as well as the "drinking of very hot beverages such as tea and Kawa [or kahwa], which are again, extremely common in Pakistan," the researchers wrote in the study. (Drinking scalding-hot beverages is linked to an increased risk of esophageal cancer, a 2009 study in northern Iran found.)

People's risk of cancer generally rises the longer they live, but also with smoking, using tanning beds and sitting too much. To lower your risk of dying of cancer, you can get recommended screenings, exercise and eat a healthy diet.

Top Killers

The first eight diseases listed in the table below were the top eight killers in the United States in 2014, whereas the rest are shown for comparison purposes.

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Respiratory Diseases & Accidents

In the U.S., after cancer, the next two largest killers are respiratory diseases and accidents. Respiratory diseases such as bronchitis, emphysema and asthma killed about 46 per 100,000 people in 2014, the CDC found. People may lower their respiratory risk by kicking their cigarettes to the curb. Moreover, some evidence suggests that asthma may be prevented in young children if they live with a dog or are exposed to allergens early in life.

Avoiding accidents is a whole other ball game. Accidents include a whole range of unintentional injuries and accounted for about 43 deaths per 100,000 people, or about 5 percent of all deaths in the United States in 2014, the CDC reported. A word to the wise: Remember to take off your headphones if you're walking around town (it can distract you from cars), and don't speed while driving.

The fifth top killer in 2014 was cerebrovascular disease (strokes), which claimed about 42 lives per 100,000 people in the United States.

More Diseases

Other health conditions also took a toll. Influenza and pneumonia (the two conditions are lumped together in CDC statistics) killed about 17 per 100,000 people in the United States, or about 55,000 people in total. Of those, about 23,700 were people age 85 or older, and 186 were infants younger than 1 year old. But many cases of flu can be prevented through vaccination. The 2014 flu shot decreased people's chances of getting the flu by only 19 percent, but the vaccines developed between 2012 and 2013 decreased their chances by 56 percent, Live Science found.

Suicide took the lives of about 42,700 individuals in 2014, meaning that there were about 13 suicides per 100,000 people in the United States that year. It was the 10th leading cause of death in the United States, topping death by assault, which took about 13,000 lives that same year. The number for the suicide hotline is (800) 273-8255.

On other fronts, modern medicine is helping people manage their maladies. Human immunodeficiency virus (HIV) disease killed about 6,700 people in the United States in 2014, or about 2 per 100,000 people. That's substantially fewer deaths than the virus caused in 1999 (the first year listed in CDC Wonder), when HIV took the lives of about 14,800 people, or about 5 per 100,000 people. [Extending Life: 7 Ways to Live Past 100]

Worldwide, about 1.2 million people, including 150,000 children younger than age 15, died of HIV-related causes in 2014, WHO reported. That's about a 57 percent decrease from 1999, when about 2.8 million people worldwide died of the disease, according to the Joint United Nations Programme on HIV/AIDS. The drop is largely due to increased access to a drug regimen called antiretroviral therapy (ART), which keeps the virus at low levels within the body, and fewer people contracting the disease, the WHO said.

Other diseases that plague the world are very uncommon in the United States. For instance, malaria killed eight people in the U.S. in 2014 but caused 584,000 deaths worldwide, 90 percent of them in Africa, according to the WHO. Moreover, tuberculosis killed 493 people in the United States, or 0.2 per 100,000 people in 2014. Worldwide, the respiratory disease killed 1.5 million people, the WHO found.

Drug Overdoses

A total of 47,055 people died of drug overdoses in the United States in 2014, or 14.7 deaths per 100,000 people. The number is alarming, as it represents an increase of 6.5 percent over the previous year, the CDC said.

"More persons died from drug overdoses in the United States in 2014 than during any previous year on record," the CDC wrote in a Jan. 1 report. "In 2014, there were approximately one and a half times more drug overdose deaths in the United States than deaths from motor vehicle crashes." Deaths from opioids (including opioid pain relievers and heroin) came in at 9 deaths per 100,000 people in 2014 — a 14 percent increase from 2013. In fact, 61 percent of drug overdose deaths included some type of opioid, the CDC said.

Animal Attacks

Many people automatically think of sharks when they imagine deadly animals, but they're far from a leading cause of death. CDC Wonder doesn't always mention the exact animal, but it noted that nobody in the U.S. died from "contact with a marine animal" such as a whale or a shark in 2014 (although three people died in this category in 2013).

However, in 2014, six people died after being bitten or stung by a nonvenomous insect, 36 people died after being bitten or mauled by a dog and 83 died after being struck by a mammal (not including dogs), such as a cow or a horse. But rest assured — no one in the U.S. reportedly died from rat bites or crocodile or alligator attacks in 2014. Furthermore, there were no deaths from "contact with plant thorns and spines and sharp leaves," though it's good to know that's a category the CDC can use just in case. [In Photos: The 10 Deadliest Animals]

Worldwide, the deadliest animal (after the mosquito, which kills people with the illness-causing pathogens it carries) is perhaps the snake. Snakebites kill 20,000 people globally each year, according to a 2008 study published in the journal PLOS Medicine.

Transportation

In the United States, people are much more likely to die while walking on a roadway than from tuberculosis or getting mauled by an animal, the odds show. In the United States, there were about 37,000 deaths from "transport accidents" (including car, train, motorcycle and boat accidents). This number includes 6,200 pedestrians who died in transportation collisions — such as crashes with cars, trucks, bikes and trains — meaning that 2 pedestrians died per 100,000 people.

In fact, more pedestrians died in the United States than motorcyclists (about 4,100 deaths) and bicyclists (about 900 deaths) combined, according to CDC Wonder. But death rates from vehicle accidents are still the highest: More than 7,800 people died in a car, pickup truck, van, heavy transport vehicle (such as a semitruck) or bus accident in 2014. That's 2.5 per 100,000 people, according to CDC Wonder.

Of the deaths due to traffic accidents in the U.S., 31 percent were due to alcohol, according to the National Highway Traffic Safety Administration (NHTSA). Of the motor-vehicle-related deaths, speeding accounted for 28 percent, distracted driving for 10 percent and drowsy drivers for almost 3 percent, the NHTSA said.

Terrorism & Homicides

In 2014, there were more than 32,700 deaths related to terrorism worldwide, according to the U.S. Department of State. (The department has yet to post data from 2015, and undoubtedly, these numbers have increased due to the conflicts in Syria and elsewhere.)

More than 6,200 of the 32,700 people (19 percent) killed were perpetrators. These people died after committing suicide, by accident or from security forces or victims responding to the attacks, the department reported. The terrorist attacks happened in 95 countries, but 78 percent of all terrorism fatalities took place in Iraq, Nigeria, Afghanistan, Pakistan and Syria, the department said.

Large attacks increased from 2013 to 2014. In 2013, there were two attacks that killed more than 100 people, but in 2014, there were 20 attacks of this size. Moreover, the death count increased by 81 percent in 2014 compared to in 2013, largely because of terrorist activities in Iraq, Afghanistan and Nigeria, the department reported.

Of course, it's hard to define terrorism, but the department makes an attempt. Terrorism is a violent act "aimed at attaining a political, economic, religious or social goal" that seeks to "coerce, intimidate or convey some other message to a larger audience," according to the report. Terrorism also breaks international humanitarian law by targeting "noncombatants," or innocent people.  

In the United States, about another 10,900 people died from an assault by a handgun, rifle, shotgun, larger firearm or unspecified firearm discharge in 2014, accounting for 3.4 deaths per 100,00 people, the CDC reported. (In this case, "firearm assaults" do not include suicides, unintentional shootings, shootings of undetermined intent, justifiable shootings, war or terrorism.)

Other Scary Ways to Die

For comparison, the table below lists the deaths caused by some of the more sensationalized means, also in 2014. These figures tend to vary significantly from year to year, and in the case of some — like deaths from venomous spiders — can be just a handful, or zero. They tend to be so low that when the rate of deaths per 100,000 people is calculated, the result is insignificantly tiny.

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Natural Disasters

Preparedness can make a world of difference when natural disasters strike. Take tsunamis, for instance. Since 2000 B.C., there have been about 2,400 tsunamis that have killed at least 500,000 people, according to the National Oceanic and Atmospheric Administration (NOAA). But the 2004 Sumatra and 2011 Tohoku (Fukushima) tsunamis were the deadliest waves in recent history. [Fukushima Radiation Leak: 5 Things You Should Know]

About 300,000 people were in danger during each of these disasters. But about 230,000 people died in the Sumatra tsunami, whereas an estimated 16,000 died in Japan, according to Vasily Titov, an oceanographer at the NOAA Center for Tsunami Research in Seattle. The difference came down to tsunami education programs and warning systems in Japan, Titov said. "About the same amount of people were exposed for both events, but 10 percent of them died in Japan and about 90 percent were killed in Sumatra," Titov told Live Science.

Fewer people died in Japan because "everyone is very much in tune with the tsunami hazard," and hundreds of thousands of people evacuated to shelters during and after the catastrophe, he said.

Tsunami readiness may help save lives in the future. Nowadays, people who live on the coastlines of large bodies of water, especially the Pacific and Indian oceans, are at risk, and these populations are only growing. In 2000, about 625.2 million people worldwide lived in low-elevation coastal zones, according to a 2015 study published in the journal PLOS ONE. The researchers estimated that between 879 million and 949 million people will live in these low-elevation areas by 2030, making tsunami education and warning systems paramount.

But preparedness appears to be paying off. In 2010, an 8.8-magnitude earthquake in Chile triggered a tsunami, and together, the earthquake and tsunami killed about 500 people. The tsunami was responsible for fewer than 200 of the deaths, Titov said. In 2015, an 8.3-magnitude earthquake in Chile also triggered a tsunami, but the country immediately evacuated about 1 million people away from the coastline, and only five people died in the catastrophe, Titov said.

To survive a tsunami, create a safety kit and plan, so you and your family know where to meet and how to evacuate to higher ground, Ready.gov advises. Also — needless to say — stay away from the beach.

Unlike for tsunamis, there is no warning system for earthquakes. But few large tremblors have struck populated areas of the United States in recent years. A total of eight people died from earthquakes from 1999 to 2014 in the United States, the CDC reported. Worldwide, earthquakes have killed tens of thousands of people. An estimated 629 people died from earthquakes in 2012; about 22,000 in 2011; and 320,120 in 2010, largely from the 7.0-magnitude earthquake in Haiti, according to the U.S. Geological Survey.

Avalanches and landslides also caused havoc. A total of 549 people died in these natural disasters from 1999 to 2014 in the United States. The deadliest year was 2014, with 85 deaths, including 43 from the catastrophic landslide in Oso, Washington.

Earth could also experience extraterrestrial threats from asteroids. After all, an asteroid is thought to have wiped out 75 percent of all species (including the dinosaurs) about 65 million years ago, at the end of the Cretaceous period. But no human death ever recorded was due to an asteroid, so it's hard to give the odds of dying from one of these space rocks, said Lindley Johnson, NASA's planetary defense officer. (A meteorite was thought to have killed a man in southern India on Feb. 6, 2016, but NASA has since reported the event was more consistent with a land-based explosion than a space rock.) [When Space Attacks: The 6 Craziest Meteor Impacts]

"It is so rare, there has never been a scientifically confirmed report of someone being killed by a meteorite impact in recorded history," NASA's Planetary Defense Officer Lindley Johnson told Live Science in February. "There have been reports of injuries, but even those were extremely rare before the Chelyabinsk event three years ago."

Lightning is far more deadly, with 25 people getting zapped by a bolt in the United States in 2014. Cataclysmic storms (such as hurricanes, tornadoes, dust storms and tidal waves — which are shallow water waves) are even worse, killing 61 people in the country in 2014.

So take precautions, caring for your health and your safety, lest you become a statistic. But don't stress about the freak events — odds are, you'll die of something much more mundane.

Editor's Note: This story was first published in 2005 and has been updated with the most recent data. Live Science will continue to update the odds of dying as new numbers are released.

Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Massive undersea earthquakes off the coast of California could send a tsunami crashing into Los Angeles or San Diego, new research suggests.

As the North American and Pacific tectonic plates grind past each other, large chunks of Earth's crust wedged between them get squeezed and twisted off Southern California and Baja California in Mexico. This logjam of crust could cause catastrophic ruptures at two faults along this boundary, setting off undersea temblors of magnitude 7.9 or 8.0, according to new research published April 25 in the Journal of Geophysical Research: Earth Surface.

"We're dealing with continental collision," Mark Legg, a geologist at Legg Geophysical, a geoexploration and hazard assessment company in Huntington Beach, California, said in a statement. "That's fundamental. That's why we have this mess of a complicated logjam." [In Photos: This Millennium's Most Destructive Earthquakes]

Network of faults

The San Andreas Fault — which snakes about 800 miles (1,300 kilometers) from Mendocino in northern California to the Salton Sea in the southern part of the state — gets most of the attention. But a network of faults also lurks off California's coasts.

These faults have formed because huge chunks of Earth's crust are being smashed and twisted between the  North American plate and the Pacific, which is sliding northwest, away from California. This pileup of crust spans from the San Andreas Fault inland to a region between about 90 and 125 miles (150 and 200 km) off the coast. This area of Earth's crust, called the California Continental Borderland, sits partially under the Channel Islands, the most accessible of which are a few hours' boat ride from Santa Barbara, California.

To understand the threat posed by this crustal compression, Legg and his co-authors analyzed older images of the seafloor, data from earthquakes that have occurred in the region, and floor-depth measurements (called "seafloor bathymetry").

The researchers found several troubling issues. Several rifts, ridges and valleys had formed along the Santa Cruz-Catalina Ridge Fault — an indication that the fault was building up seismic stress, they said. In fact, chunks of the California Continental Borderland crust are slipping sideways and being pulled upward — collateral damage from the collision of two continental plates.

Farther offshore, one side of the Ferelo Fault had thrust upward because the Pacific Plate is dragging the wedged chunks of crust northward. Those chunks are then crashing into Transverse Mountain Range, which runs east to west and lies north of Los Angeles.

That seismic stress could lead to a dangerous fault rupture, just like the one likely to hit the San Andreas Fault in the next several decades, the researchers said.

"Such large faults could even have the potential of a magnitude-8 quake," Christopher Sorlien, a geologist at the University of California, Santa Barbara who was not involved in the study, said in a statement.

If those faults were to rupture in certain locations, they could send tsunami waves crashing into Los Angeles or San Diego, the researchers suggested.

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

This article was originally published on The Conversation. The publication contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

Ten years ago we witnessed one of the worst natural disasters in history, when a huge earthquake off the coast of Sumatra triggered a devastating tsunami which swept across the Indian Ocean.

An estimated 230,000 people lost their lives, and 1.6 million people lost their homes or livelihoods.

The impact was greatest in northern Sumatra because of its proximity to the earthquake. Catastrophic shaking was followed within minutes by the full force of the tsunami.

Avoidable deaths

Thousands of people were also killed in distant countries, where the earthquake could not be felt. If they had received a warning of the approaching tsunami, they could have moved inland, uphill or out to sea, and survived. Tsunami take several hours to cross an ocean, becoming much larger and slower as they reach the coast.

Back in 2004 there were long-established tsunami warning systems in the Pacific Ocean, which has many subduction zones – places where two tectonic plates collide – capable of generating huge earthquakes or volcanic eruptions.

Other regions, including the Indian Ocean, did not have a warning system. The probability of a major tsunami was judged to be too low to justify the cost, especially for poorer countries.

The Boxing Day 2004 disaster changed all that.

Progress in the past decade

In early 2005, the UN agreed to develop an international warning system including regional systems in the Indian Ocean, North East Atlantic & Mediterranean, and Caribbean. The Indian Ocean tsunami warning system was developed between 2006 and 2013, at a total cost of at least $19 million.

In the three years prior to October 2014, bulletins were issued about 23 Indian Ocean earthquakes, resulting in a small number of potentially life-saving coastal evacuations. Most of these 23 earthquakes did not actually generate a threatening tsunami because they did not cause significant uplift or subsidence of the seafloor. But false alarms can provide reassurance that communications work well, or highlight weaknesses.

Communications and evacuation procedures are also regularly tested by international mock drills, often based on worst case scenarios.

How do tsunami warning systems work?

All warning systems work in the same general way. First, a network of broadband seismometers detects the seismic waves generated by an earthquake, which travel at speeds of several kilometres per second. When several seismometers have detected the seismic waves, the location and approximate magnitude of the earthquake can be computed. If the epicentre is under water and the magnitude large (greater than 6.5 on the Richter, or moment magnitude, scale) a tsunami bulletin, watch or warning is issued to local communication centres, ideally within three minutes of the earthquake. If the epicentre is nearby and the probability of a tsunami is high, evacuation procedures will be initiated immediately.

Otherwise, local centres will standby for confirmation of whether a tsunami has actually been generated. Confirmation comes within about 30-60 minutes, using a network of tsunami buoys and seafloor pressure recorders. These detect the series of waves (usually less than a couple of metres high and travelling at about 800 km/h) in the open ocean, and transmit the data by satellite to a regional control centre.

Tsunami warnings reach the public via TV, radio, email, text messages, sirens and loudspeakers. You can sign up to receive tsunami alerts anywhere in the world by SMS on your mobile phone, thanks to a not-for-profit humanitarian service called CWarn.org.

Many high-risk areas also have signage to alert people to “natural” warnings (such as strong shaking or a sudden withdrawal of the sea), and direct them to higher ground.

Limitations of warning systems

The Pacific and Japanese warning systems helped to ensure the major tsunami generated off the coast of Japan on 11 March 2011 caused far fewer deaths (15,000) than the 2004 disaster. However, it showed that even a wealthy and well-prepared nation such as Japan cannot fully protect people from extreme hazards, and that warning systems can sometimes lead to a false sense of security.

The slow rupture of the subduction zone near Japan meant the initial warnings underestimated the magnitude of the earthquake and resulting tsunami. Many people did not move to higher ground in the vital few minutes after receiving the warning, because they wrongly assumed the tsunami would be stopped by 5-10 m high sea walls.

Japan has learned from this tragedy and, among other things, made changes to tsunami warning messages, improved coastal defences, and installed more seismometers and tsunami buoys.

Will more tsunami disasters occur?

It is impossible to predict exactly when or where the next major tsunami will occur. They are very rare events in our limited historical record. But by dating prehistoric tsunami deposits, we can see that major tsunamis happen on average every few hundred years in many coastal regions.

Future tsunami disasters are inevitable, but with better technology, education and governance we can realistically hope that a loss of life on the scale of the 2004 tsunami disaster will not happen again.

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.

This story was updated Oct. 21 at 2:15 p.m. EDT.

A powerful earthquake in Alaska sent towering waves up to 30 feet (9 meters) tall crashing down on Hawaii about 500 years ago, leaving behind fragments of coral, mollusk shells and coarse beach sand in a sinkhole located on the island of Kauai, new research finds.

The quake, likely a magnitude 9.0, sent the mighty waves toward Hawaii sometime between 1425 and 1665, the study found. It's possible that another large Alaskan earthquake could trigger a comparable tsunami on Hawaii's shores in the future, experts said.

The tsunami was at least three times the size of the damaging 1946 tsunami, which was driven by an 8.6-magnitude earthquake off the Aleutian Islands. Mammoth tsunamis, like the one described in the study, are rare, and likely happen once every thousand years. There's a 0.1 percent chance it could happen in any given year, the same probability that northeastern Japan had for the 9.0-magnitude 2011 Tohoku earthquake and related tsunami, said Gerard Fryer, a geophysicist at the pacific Tsunami Warning Center in Ewa Beach, Hawaii, who was not involved in the study. [Waves of Destruction: History's 8 Biggest Tsunamis]

Results of the study have already prompted Honolulu officials to revise their tsunami evacuation maps, Fryer said. The new maps, which will affect nearly 1 million people who live in Honolulu County, would include more than twice the area of evacuation in some areas, Fryer said in a statement. County officials hope to distribute the new maps by the end of 2014, Fryer said.

"You're going to have great earthquakes on planet Earth, and you're going to have great tsunamis," said the study's lead researcher, Rhett Butler, a geophysicist at the University of Hawaii at Manoa. "People have to at least appreciate that the possibility is there."

Evidence of the colossal tsunami surfaced in the late 1990s during the excavation of the Makauwahi sinkhole, a collapsed limestone cave on the south coast of Kauai. About 6.5 feet (2 meters) below the surface, study researcher David Burney found a bounty of old debris that must have come from the ocean.

Curiously, the sinkhole's mouth is 328 feet (100 m) away from the present-day shore, and 23 feet (7 m) above sea level, suggesting the enormous quantities of corals and shells were probably carried there by a gigantic wave, Burney, a paleoecologist at the National Tropical Botanical Garden in Kalaheo, said. But he needed more evidence to back up his claim.

Tsunami surge

The debris remained a mystery until the 2011 Tohoku earthquake hit Japan. The earthquake triggered a rapid surge of water that stood 128 feet (39 m) above sea level and pummeled the Japanese coast. Soon after, researchers revisited Hawaii's tsunami evacuation maps. The maps are largely based on the 1946 tsunami, which caused water to rise 8 feet (2.5 m) up the side of the Makauwahi sinkhole.

"[The Japan earthquake] was bigger than almost any seismologist thought possible," Butler said. "Seeing [on live TV] the devastation it caused, I began to wonder, did we get it right in Hawaii? Are our evacuation zones the correct size?"

Butler and his colleagues assembled a wave model to predict how a tsunami might flood Kauai's coastline. They simulated earthquakes ranging between magnitudes 9.0 and 9.6 along the Aleutian-Alaska subduction zone, a 2,113-mile-long (3,400 kilometers) ocean trench where the Pacific tectonic plate slips under the North American plate.

In the aftermath of a large earthquake, the eastern Aleutians' distinctive geography could send a large tsunami toward Hawaii, the researchers found. In fact, a magnitude- 9.0 earthquake in just the right spot could easily direct water levels of 26 to 30 feet (8 to 9 m) high toward Kauai, carrying debris into the Makauwahi sinkhole, they found. [Photos: Tsunami Debris & Trash on Hawaii's Beaches]

The researchers also looked for tsunami evidence in other places. Radiocarbon dating showed that the marine deposits in the sinkhole, on Sedanka Island off the coast of Alaska and along the west coasts of Canada and the United States all date back to the same time period, and may have come from the same tsunami.

"[The researchers] stitched together geological evidence, anthropological information as well as geophysical modeling to put together this story that is tantalizing for a geologist, but it's frightening for people in Hawaii," Robert Witter, a geologist at the U.S. Geological Survey in Anchorage, Alaska, who was not involved in the study, said in the statement.

More evidence is needed to determine whether the deposits came from the same tsunami, Witter said. For instance, radiocarbon dating, which the study researchers relied on, only gives a rough time estimate. It's possible that multiple tsunamis between 350 and 575 years ago deposited the debris at the three locations, he said.

But the sinkhole debris may be evidence enough that a huge tsunami hit Hawaii hundreds of years ago, he added. "An important next thing to do is to look for evidence for tsunamis elsewhere in the Hawaiian island chain," Witter said.

Researchers will likely find more evidence of the giant tsunami, Fryer added. "I've seen the deposit, " Fryer said. "I’m absolutely convinced it's a tsunami, and it had to be a monster tsunami."

The study was published Oct. 3 in the journal Geophysical Research Letters.

Editor's Note: This story was updated to fix the spelling of Gerard Fryer's first name. 

Follow Laura Geggel on Twitter @LauraGeggel and Google+. Follow LiveScience @livescience, Facebook & Google+. Originally published on Live Science.

How unusual slow earthquakes can spawn powerful tsunamis is a long-standing mystery that researchers may have finally solved.

Called "tsunami earthquakes," these slow quakes are capable of creating huge waves that can cause serious damage to coastal cities. Tsunami earthquakes are not like typical earthquakes. They happen slowly and don't generate the same kind of violent shaking as typical earthquakes — the tell-tale sign that it's time to evacuate.

Scientists first discovered tsunami earthquakes 35 years ago and they happen so rarely there has been little opportunity to study them since. Now, a new study suggests that tsunami earthquakes happen when two sections of Earth's crust, called tectonic plates, get hung up on extinct volcanoes on the ocean floor, called seamounts. The seamounts act like tread on a tire and make tectonic plates stick. [The 10 Biggest Earthquakes in History]

The research team realized these extinct volcanoes sometimes get squashed in subduction zones. A subduction zone is where one tectonic plate is sliding under the other plate.  

The researchers propose that two tsunamis that struck New Zealand in 1947 were caused by tsunami earthquakes that struck in a zone near two sunken volcanoes off the country's northern coast. The earthquake happened when the Pacific tectonic plate slid under the New Zealand tectonic plate, releasing a massive buildup of energy. However, the actual rupture of tsunami earthquakes is slow compared with regular earthquakes. The rupture happens at 335 to 670 mph (539 to 1,078 km/h). In regular earthquakes that rupturing can happen two or three times faster. The slow rupture allows time for huge waves to swell.

Bell and the team estimate the tsunamis might have reached 43 feet (13 meters). Since the New Zealand tsunami earthquake, scientists think there have been nine other tsunami earthquakes. In 1992, a magnitude-7.2 earthquake off the coast of Nicaragua created a wave 26 feet (8 m) tall that killed 170 people. In 2006, an earthquake off the coast of Indonesia with the same magnitude created a wave 23 feet (7 m) tall that drowned 637 people.

Researchers arrived at this conclusion by studying eyewitness accounts from the earthquakes. Witnesses did not report any violent shaking associated with regular earthquakes. Instead they reported feeling the ground "rolling" and feelings of seasickness. After analyzing data originally collected for oil and gas deposit searches, the researchers were able to locate two extinct volcanoes off the coast that likely caused the tsunamis.

By understanding the geologic causes of tsunami earthquakes, scientists hope to pinpoint the areas most at risk for the mysterious slow earthquakes. The scientists hope the new research will help raise awareness among people living in coastal regions who are at risk for tsunami earthquakes.

"These tsunami earthquakes create very little ground shaking, but they shake the ground gently for a long time," lead researcher Rebecca Bell from Imperial College London, told Live Science. "The best warning for residents living close by is that if they feel a very prolonged earthquake, even if the shaking is gentle, they should evacuate to high ground. New tsunami warning signs in New Zealand now use the tag line 'Long, strong, gone'."

Despite a network of seismometers (instruments that measure ground motion, which is then used to measure earthquake size) across the globe that allows geologists to detect very low magnitude underwater quakes, scientists are unsure which quakes have the potential to generate tsunami waves. For now, the researchers think teaching people living in tsunami-risk areas to watch for prolonged shaking will be the most effective way to keep people safe.

The new study was published on May 5 in the journal Earth and Planetary Science Letters.

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

This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

The old German saying Stadt Luft Macht Frei (“urban air makes you free”) is the defining injunction of modernity. Modern western cities were launched as the vessels of liberation from a human era darkened by power and enchantment.

The link between the urban and the urge for emancipation goes back to much earlier times. And to other parts of the globe, what we know today as the Middle East and the Indian subcontinent. In its primordial, post-Neolithic forms the city was the expression of that most basic freedom, from natural necessity, from subsistence and endless toil. City walls protected, and thus freed, their populations from wilder human compulsions, for acquisition, dominance – for war.

Later, in Classical Antiquity (the ancient Greek and Roman eras), the city expressed a deepening political imagination and a strengthening instinct for collective expression and development, res publica. New cultural flows followed the courses of urbanisation. In Marx and Engels' memorable words, cities “rescued a considerable part of the population from the idiocy of rural life".

The city was the escape raft from a life of servitude and grubbing. Modernisation has, however, failed miserably on many accounts and in many quarters.

For the German sociologist Ulrich Beck and his colleague Edgar Grande, globalised modernity hums with urban disenchantment, especially amongst “those for whom cosmopolitanism is not a lifestyle choice, but the tragic involuntary condition of the refugee or otherwise dispossessed”.

The “wild impulses” of market expansion, political ambition, and cultural aspiration have driven an ever urbanised modernity towards the precipices of risk, uncertainty and self-doubt. Second modernity is nothing less than “a historically new, entangled Modernity which threatens its own foundations.”

Disasters show cities are vulnerable

The city, a powerful beacon of hope and opportunity through modernisation, is now indissolubly linked to natural risk and human endangerment. Urban sustainability researchers Mike Hodson and Simon Marvin of the University of Salford highlight the “dual and ambivalent role of the city, as both a victim and cause of global ecological change."

A series of natural and human catastrophes in recent years have underlined the vulnerability of cities to sudden endangerment. The sources of urban crisis are both endogenous and exogenous – a tsunami or flood being an instance of the former; a resource system failure (water, power) representing the latter.

The 2011 tsunami that devastated Japan’s highly urbanised coast exemplified how endangerment can unfold in a series of catalysing exogenous (tsunami inundation) and endogenous (nuclear plant failure) shocks that drive human threats to precarious scales – especially when potentially lethal technological systems are disrupted. Global warming will vastly increase the tempo and power of these natural furies.

Following Hurricane Katrina in 2005, New Orleans, mythically loved city in the world’s richest nation, descended into anarchy — no less than a time of civic terror. The internal fragility of western modernity is tested further by enemies that wage their war from within. Second modernity is countered by Islamist (and other) counter-modernities that use cities as terrifying stages to attack Western assertion.

Cities in the Anthropocene

The urban age defines what some scientists now call the Anthropocene – an epoch dominated in its latter stages by modern Prometheanism.

The Slovenian cultural critic Slavoj Žižek rejects the naturalism inherent in many scientific renderings of the Anthropocene; viz., the idea that “because humans constitute a particular kind of species they can, in the process of dominating other species, acquire the status of a geologic force."

He counters that “this shift from Pleistocene to Anthropocene is entirely due to the explosive development of capitalism and its impact.“ It is the universal threat to existence that now binds humanity for the first time as a "species”, not the potency that generated the crisis.

Beck and Grande offer: “When a world order collapses, that’s the moment when self-reflection should begin.” Reflexivity is taken as birth cry of the second modernity. And yet, this compelling injunction of the time echoes wordlessly in a post-political age. No common cause, or new dispensation, has emerged to arrest epochal decline or to assay global threat.

It seems evident that rapid, epochal global change is not conducive to human deliberation about “common dangers”. At least not to now. Where are the stirrings of the “natality” that the influential political theorist Hannah Arendt has promised us? What stands against the tide of endangerment? It is surely collective will that must arrest the slide to disaster. In the face of power and its many arrogations, the human right to a good destiny must be reasserted.

But cities our only hope

The city, the new human heartland, is where this battle for human renewal must be joined. It can and must be won. The consequences of loss are unthinkable, indeed as yet unknowable. The city air must once again nurture the cause of human realisation. To restore human prospect, Homo urbanis must dismantle its own work, the material and ideological apparatuses of Promethean modernity.

They must be held to account through critical scientific interrogation and brought to heel by politics. Where to begin? So much of contemporary modernity seems like dangerously flailing pieces of machinery, uncoupled to wild play by a disintegrating industrialism.

The collapsing natural order surely points to first priority, a political economy that is hard wired for growth. It is a death machine that endangers Homo urbanis and all that depends upon us.

This article is an adapted extract from The Urban Condition by Brendan Gleeson.

Brendan Gleeson receives funding from the Australian Research Council.

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.

Tsunamis are not only some of the most powerful natural disasters in the world; they are also some of the most unpredictable. Because of that unpredictable nature, knowing what to do before, during and after a tsunami can be the key to your survival chances. With that in mind, here is what you need to know when a tsunami warning is issued. 

Everyone knows just how destructive the ocean can be, but that amazing power is never more on display than when there is a tsunami. These awe-inspiring displays of Mother Nature's fury can reshape coastlines while leaving a wide trail of destruction and death. Although they are not very common, tsunamis have made quite an impact in recent years. Here is everything you need to know about the destructive power of tsunamis. 

Related: No, You Can't Outrun a Tsunami

Additional Information:

Red Cross Tsunami Page 

A strong aftershock rattled northern Chile late Wednesday night (April 2), a day after an earthquake of magnitude 8.2 triggered a tsunami in the region, according to the U.S. Geological Survey (USGS).

The temblor, which measured 7.6 in magnitude, originated 12 miles (19 kilometers) south of the Chilean port city of Iquique. Its epicenter was 24.9 miles (40 km) deep, and it struck at 11:43 p.m. Tuesday local time (2:43 UTC April 3), the USGS reports.

A tsunami alert prompted the evacuation of low-lying areas along the country's long Pacific coastline, but no new major damage or casualties were reported, according to the Associated Press.

The earthquake was just one of at least 47 aftershocks following the 8.2-magnitude event, which killed six people and set off a tsunami nearly 7 feet (2 meters) high along the coasts of southern Peru and northern Chile.

Chile is no stranger to large tremors, as it sits near a so-called subduction zone, where the Nazca tectonic plate is squeezing under the South America plate. In February 2010, an 8.8-magnitude earthquake — the fifth largest ever measured — struck off Chile's southern Pacific coast, leveling buildings, killing more than 500 people and moving the city of Concepción at least 10 feet (3 m) to the west. The largest earthquake on record, measuring 9.5 in magnitude, ruptured nearby in May 1960, killing 5,700 people.

But the earthquake that hit this week ripped along a stretch of Chile's northern coastline that had been quiet for more than a century. The last big quake to strike near Iquique happened in 1877. Decades' worth of built-up stress set off the recent swarm of earthquakes, with a 6.7 tremor on March 16 kicking off the foreshock sequence near the epicenter of the April 1 earthquake.

The damage caused by any single earthquake depends on the quake's depth and proximity to populated areas, as well as the building standards in the region and the type of earthquake. The USGS frequently updates the magnitude of an event after more data is analyzed.

An earthquake's magnitude is a measure of the energy released at the source. It is just one predictor of the shaking that may ensue, which is affected by local and regional geology. Scientists know in a general sense what causes earthquakes but are unable to predict specific quakes.

This article will be updated if significant additional information becomes available. Find more earthquake news here.

Follow Megan Gannon on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Scientists had been waiting for this one.

The 8.2-magnitude earthquake that rumbled off the northern coast of Chile on Tuesday (April 1) was located along the Pacific Ring of Fire, where plate boundaries grind past each other, producing tremors all the time.

But this particular quake struck smack in the middle of a 320-mile (500 kilometers) stretch of Chile's coast that had been alarmingly quiet for more than a century, said Rick Allmendinger, a geologist at Cornell University. [The 10 Biggest Earthquakes in History]

"The last earthquake in this segment was in 1877," Allmendinger told Live Science. That 19th-century temblor, estimated to have been 8.5 in magnitude, triggered a tsunami nearly 80 feet (24 m) high and caused fatalities as far away as Hawaii and Japan.

Tuesday's event was much less devastating. There were six reported deaths, a tsunami that rose to 8 feet (2.5 meters), and some landslides, power failures and property damage, according to the Associated Press. 

Despite the decades' worth of built-up stress that was released in Tuesday's earthquake, there could be more energy stored along the plate boundary, ready to unleash aftershocks or even a bigger quake, Allmendinger said. It's possible that this tremor was a "foreshock," like the strong rumblings that led up to the 9.5-magnitude quake that ripped along the coast of southern Chile on May 22, 1960 — the biggest earthquake on record.

"The longer you go without earthquakes, the more likely it is that it will occur in the future," Allmendinger said. "That was the case in this particular segment."

Earthquakes greater than 8 in magnitude don't occur every year. Georgia Institute of Technology earthquake researcher Andrew Newman said they happen, on average, every 2.5 years. 

The first signs of trouble started a few weeks ago, Allmendinger said. A magnitude-6.7 earthquake struck in the region on March 16, and it was followed by more than 60 earthquakes greater than magnitude 4, and 26 earthquakes greater than magnitude 5, according to the U.S. Geological Survey. But then the spot was quiet for about week before the 8.2-magnitude quake hit on Tuesday, about 59 miles (95 km) northwest of the port city of Iquique.

As a scientist, Allmendinger said he is interested in this pattern of seismicity, because it also has some resemblance to the lead up to the devastating 2011 Tohoku earthquake and tsunami in Japan.

"We may be able to learn quite a lot about it," he told Live Science.

Other researchers, too, are poring over data from Tuesday's event, looking for connections that could help them explain or predict the probability of big earthquakes. Newman, for example, said the tremor might demonstrate how interconnected earthquakes are in this region.

Tuesday's Iquique earthquake occurred about 13 years after a 8.4-magnitude earthquake struck immediately north of it, off the coast of southern Peru, Newman said. This pattern mirrors the 1877 Iquique earthquake, which occurred nine years after the 1868 Arica earthquake off the coast of southern Peru, thought to have been at least 8.5 in magnitude, Newman said.

In other words, one big earthquake could increase the pressure in another part of the plate boundary, triggering another big earthquake years later.

"These earthquakes seem to have really strong interdependence," Newman told Live Science.

Perhaps strangely, Tuesday's quake is the third greater than 8 in magnitude to occur on an April 1, but Newman said he doesn't make much of this April Fools' anomaly.

"Maybe Mother Nature's playing a joke on us," he said.

Follow Megan Gannon on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

A powerful 8.2-magnitude earthquake that rocked Chile Tuesday night (April 1) originated in a seismic hotspot that has produced some of the world's strongest tremors in history.

Given the size and strength of the jolt, the current death toll of six seems rather modest. The tsunami it generated was relatively localized, too. One of the worst-hit areas, Iquique, a port city in northern Chile, about 60 miles (96 kilometers) from the earthquake's epicenter, was hit by a tsunami wave of nearly 7 feet (2.1 meters). For comparison, the 9.0-magnitude earthquake that struck Japan in March 2011 caused a massive tsunami wave that reached heights of up to 133 feet (40.5 m).

Even when they don't cause widespread damage, tsunami waves can travel far. Through a network of sensors at the bottom of the ocean and sophisticated computer models, scientists can measure the ripples of these huge waves thousands of miles from their origin. [The 10 Biggest Earthquakes in History] 

How the earthquake created a tsunami

Tuesday's earthquake occurred along a so-called subduction zone, where one tectonic plate plows beneath another. Off the Pacific coast of South America, the Nazca Plate is squeezing under the South America plate.

While some earthquakes originate from side-to-side sliding along a crack like the San Andreas Fault in California, subduction zone tremors are associated with vertical plate movement. And when one plate sinks, water is displaced and a deep ocean wave is generated, said Michael Angove, the National Oceanic and Atmospheric Administration's (NOAA) tsunami program manager.

What sets a tsunami apart from others waves is the way it hits the bottom of the ocean, Angove said.

"Its wavelength goes through the whole length of the ocean," Angove told Live Science.

To track these big waves, NOAA manages a network of 39 sensors anchored to the seafloor at a depth of 13,000 feet to nearly 20,00 feet (4,000 to 6,000 meters). These devices are linked to a surface platform that acts as a receiver and transmitter, beaming data to satellites overhead.

These so-called DART stations (short for deep-ocean assessment and reporting of tsunami) line the Pacific "Ring of Fire," where most of the world's earthquakes and volcanic eruptions occur. While most sensors in this network are operated by the United States, other countries — including Australia, Ecuador, Japan and Russia — have contributed their own stations.

In the last two years, the Chilean government added two of its own stations off the country's northern coast, Angove said, and this is the first seismic event in which those new trackers were really put to use.

Effects of the tsunami

The earthquake that shook Chile Tuesday didn't produce enough energy to trigger a severely threatening tsunami outside of the Pacific coast of South America, Angove said. Nonetheless, a tsunami advisory was in place for Hawaii, where strong currents could pose risks for swimmers, boaters and surfers.

"In Hawaii, oftentimes we'll see surfers who think this is like Christmas," said Susan Buchanan, a NOAA spokeswoman. "They often underestimate the power of the current, but it's very dangerous for them to be the water."

Indeed, Angove noted that the currents could be as strong as 3 to 4 knots.

But for a truly damaging tsunami originating from Chile to hit Hawaii and the western coast of the United States, the earthquake might have to be at least 8.5 in magnitude, Angove said. 

That's not to say that an earthquake of smaller magnitude couldn't produce a devastating tsunami. There are earthquakes that scientists call "tsunami earthquakes" that shake out much more slowly than a normal earthquake. They tend to occur in the shallowest portion of a subduction zone, and they produce waves much bigger than their magnitude would suggest, said Georgia Institute of Technology earthquake researcher Andrew Newman.

"Tsunami earthquakes are a third as fast — they take three times as long to rupture," Newman told Live Science. "They still do just as good of a job at moving that mass that's creating the tsunami wave."

Follow Megan Gannon on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Oftentimes earthquakes hit with little to no warning. 

So, do you know what to do when the Earth starts to shake? 

For some help, check out this infographic.  

Additional Information:

Red Cross Earthquake Website

Red Cross Earthquake App

This article was provided by AccuWeather.com.

Researchers are examining a possible meteotsunami that may have hit the coast of New Jersey June 13. The Tsunami Warning Center relayed an account of the events as seen by Brian Cohen, who was out spear fishing in the Barnegat Inlet in Ocean County when he saw waves that were approximately 6 feet peak-to-trough spanning across the inlet.

"Earlier in the day around noon, thunderstorms had moved through the area. By 3:30 p.m. [EDT] the weather was overcast with a light east wind. At approximately 3:30 [p.m. EDT], the outgoing tide was amplified by strong currents which carried divers over the submerged breakwater (normally 3-4 feet deep). This strong outrush continued for 1-2 minutes and eventually the rocks in the submerged breakwater were exposed. Brian backed his boat out before being sucked over as well."

The low-end derecho that pushed from Chicago to Washington, D.C., on June 13 may have sparked the possible meteotsunami on the New Jersey coast, said Paul Whitmore, Director of the Tsunami Warning Center.

"The first impulse was to see this as meteorologically driven, but once a system gets over the [continental] shelf, we lose data," he said. "It makes it hard to confirm."

It could take months before the event is officially confirmed one way or the other, but it seems likely at this time that the derecho may have caused the tsunami-like waves.

A meteotsunami differs from a tsunami because it is caused by a weather event rather than by seismic activity. Most tsunamis are created by volcanic eruptions or earthquakes, which gives researchers a fixed point to work off of. When the waves are created by a weather event like a derecho, it requires more, exact elements to come together for its creation. These elements are harder to track because they are occurring above the Earth's surface.

Related: What Are Shelf Clouds?

Tsunamis and meteotsunamis are more than just large waves; wave frequency and speed are more emphasized factors in labeling a tsunami. So far, the waves that hit New Jersey seem to be in line with the qualifications for a meteotsunami.

At over 30 gauges the indications were recorded for a tsunami in its strength and wave frequencies. According to Whitmore, shelf clouds off the New Jersey coast are conducive to such events occurring.

On occasion, large complexes of thunderstorms have caused tsunami-like waves on the Great Lakes.

According to Expert Senior Meteorologist Alex Sosnowski, "A strong downward rush of air can get the lakes rocking back and forth, or simply push water away for a brief time, before it sloshes back."

The wind-driven phenomenon on the Great Lakes is known as a seiche.

© AccuWeather.com. All rights reserved. More from AccuWeather.com.

Death by drowning was the biggest killer in the 2011 Japan earthquake and tsunami.

Since the disaster, scientists have analyzed the massive Tohoku earthquake and tsunami, seeking better ways to predict these dangerous waves. Based on computer modeling, scientists at Stanford University now think sound waves from big earthquakes such as Japan's could provide 15 to 20 minutes of advance notice before a tsunami hits, according to a study published in the June 2013 issue of the journal the Bulletin of the Seismological Society of America. (Some towns on the Japan coastline had just 10 minutes to flee before the tsunami arrived.)

Along with seismic shaking, undersea earthquakes also produce low-frequency sound waves that travel through the ocean. The size of the sound signal is linked to the earthquake's magnitude. The U.S. National Oceanic and Atmospheric Administration (NOAA) uses a network of underwater microphones called hydrophones to listen for offshore earthquakes and volcanic eruptions.

The size of tsunami waves also appears to be linked to the acoustic signals produced by earthquakes, according to the new study.

"We've found that there's a strong correlation between the amplitude of the sound waves and the tsunami wave heights," co-author Eric Dunham, a Stanford geophysicist, said in a statement. "Sound waves propagate through water 10 times faster than the tsunami waves, so we can have knowledge of what's happening a hundred miles offshore within minutes of an earthquake occurring. We could know whether a tsunami is coming, how large it will be and when it will arrive."

The Japan Meteorological Agency issued a tsunami warning three minutes after the 2011 earthquake struck, but the agency underestimated the height of the waves. A revised warning of the bigger tsunami was sent out within minutes, but some residents did not hear or heed the new alert. In March, the country unveiled a new tsunami warning system with upgraded seismic sensors and offshore buoys to better track incoming waves. [Infographic: How Japan's 2011 Earthquake Happened]

The researchers said the varying orientation of faults offshore of tsunami-prone regions, such as Alaska, Chile and the Pacific Northwest, means the model's telltale acoustic signal could vary from region to region.

"The ideal situation would be to analyze lots of measurements from major events and eventually be able to say, 'This is the signal,'" lead author Jeremy Kozdon, a mathematician at the Naval Postgraduate School, said in the statement.

The U.S. tsunami warning system detects and locates potential tsunami-triggering earthquakes with seismic monitors and ocean-bottom pressure sensors, and uses computer models to predict the impact of incoming waves. Countries such as Chile are also exploring GPS-based tsunami alert systems, which provide more accurate estimates of ground movement than do seismic monitors (seismometers).

Tsunamis occur when earthquakes or undersea landslides suddenly displace the ocean floor and the sea above it, triggering a wave.

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