Heaven Lake is a crater lake at the top of Mount Changbaishan (also called Changbai Mountain) — a colossal, dormant volcano on the border between China and North Korea that formed through successive eruptions over the past 2.6 million years.

Known in China as Tianchi, the lake is the highest and largest crater lake in Northeast Asia, according to UNESCO. It is also the deepest lake in China, according to a study published in March. The lake sits at an elevation of around 7,200 feet (2,200 meters), covers roughly 3.6 square miles (9.2 square kilometers), and has a maximum depth of 1,224 feet (373 m), according to the study.

Heaven Lake is surrounded by 16 peaks that belong to Mount Changbaishan. The lake fills a caldera created by past eruptions, the biggest of which was the "millennium eruption" that took place in A.D. 946 and remains one of the largest eruptions in modern history.

Water started to pool on Mount Changbaishan's summit after the prehistoric Tianwenfeng eruption, which scientists dated to between 70,000 and 40,000 years ago. Heaven Lake has periodically emptied and refilled since then due to precipitation, snowmelt, and an active geothermal system beneath the volcano that forces water up through fault lines.

Although hundreds of reports in the early 2000s claimed there was a creature with a head shaped like that of a horse living in the water, scientists have repeatedly said they are skeptical that any large creature could survive in Heaven Lake.

Mount Changbaishan is one of the best-preserved stratovolcanoes from the past several million years, according to UNESCO. Stratovolcanoes, also known as composite volcanoes, are volcanic mountains built from alternating layers of solidified lava, volcanic ash and rocky debris. Mount Changbaishan is an "open-air classroom for volcanism" because it recorded the different stages of multiple eruptions in astounding detail.

In North Korea, Mount Changbaishan is known as Mount Paektu or Paeku Mountain, meaning "white-topped mountain." The volcano's Chinese name means "forever white mountain."

China, North Korea and South Korea have clashed over the volcano in the past, as the mountain holds cultural and geopolitical significance for the three countries. Two border treaties between China and North Korea in 1962 and 1964 divided the volcano and Heaven Lake roughly down the middle, with North Korea securing 54.5% of the lake.

In the 2000s, China moved to develop the region around the volcano, opening the Mount Changbai Airport and the Mount Changbai Eastern Railroad to connect the region with the rest of the country.

A geological park surrounding the Chinese site of the volcano was officially designated a UNESCO Global Geopark in 2024.

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The Socotra Archipelago is a cluster of four islands and two rocky islets belonging to Yemen. It is nicknamed the "Galápagos of the Indian Ocean" due to its staggering biodiversity, which includes hundreds of species that aren't found anywhere else in the world.

Located about 250 miles (400 kilometers) south of the Arabian Peninsula and 140 miles (220 km) east of the Horn of Africa, the Socotra Archipelago is home to around 60,000 people. As of 2023, visitors could reach it only via a weekly flight from Abu Dhabi, United Arab Emirates, that had to be booked through WhatsApp and was often canceled without reason.

The archipelago has one main island, Socotra, which makes up 95% of the landmass, along with three smaller islands and two islets. The main island hosts snow-white sand dunes, a central mountain range, and limestone plateaus peppered with drought-resistant cucumber trees (Dendrosicyos socotranus) and umbrella-shaped dragon's blood trees (Dracaena cinnabari) that do not exist elsewhere on Earth. The dragon's blood tree gets its name from its crimson resin, which is used for natural medicine and as a pigment.

Socotra was recognized as a UNESCO World Heritage Site in 2008, thanks to its unique plants and animals, which have evolved in isolation for at least 15 million years. Socotra is a leftover fragment from when Arabia and Africa pulled apart around 30 million years ago. The split opened the Red Sea and the Gulf of Aden, which connects the Red Sea and the Arabian Sea.

More than one-third of Socotra's plants, 90% of its reptiles and 95% of its land snail species are found exclusively in the archipelago, according to UNESCO. The marine life in Socotra is also incredibly diverse; it includes sea turtles, whale sharks (Rhincodon typus) and more than 250 species of reef-building corals.

The archipelago is tricky to get to, and pirates sometimes hijack vessels in the surrounding seas. Due to Yemen's ongoing civil war, many governments, including the U.S., advise against all travel to the country, including Socotra, citing threats of terrorism, unrest, crime, health risks, kidnapping and landmines.

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Fingal's Cave is a sea cave in Scotland whose walls are made of hexagonally joined basalt columns. These structures may have formed within the same lava flow that shaped the Giant's Causeway, a geological formation in Northern Ireland composed of more than 40,000 interlocking basalt pillars.

Fingal's Cave extends 230 feet (70 meters) deep and 60 feet (18 m) high inside the small, uninhabited island of Staffa, located in Scotland's Inner Hebrides. It was carved by a volcanic eruption sometime during the Paleocene epoch (66 million to 56 million years ago).

As giant lava flows from this eruption began to cool and solidify, their top and bottom parts contracted and fractured into hexagonal shapes similar to those formed by desiccation cracks in muddy sediments. Eventually, these fractures extended and combined in the center of the flow, forming hexagonal pillars whose sides were later revealed by waves eroding the margins of the flow, according to the National Trust for Scotland.

The cave gets its name from an Irish myth about a warrior called Fionn Mac Cumhaill. According to the legend, Fionn — whose full name was shortened to Fingal, meaning "white stranger" — built the Giant's Causeway across the sea to Scotland to fight a rival called Benandonner, and Fingal's Cave is what remains of Fionn's path over the ocean on the Scottish side.

The 18th-century Scottish writer James Macpherson popularized the name Fingal's Cave with a book titled "Fingal, an Ancient Epic Poem in Six Books" that was published in 1762. Then, after visiting the cave in 1829, the Romantic composer Felix Mendelssohn wrote an overture — a musical introduction to a ballet or opera — known as the "Hebrides Overture" or "Fingal's Cave Overture."

Mendelssohn was inspired by the natural acoustics and eerie echoes inside Fingal's Cave, according to the National Trust for Scotland. A nod to these unique sounds is also found in the cave's Gaelic name, "Uamh-Binn," meaning "cave of melody" or "musical cave." Mendelssohn's overture established Fingal's Cave as a tourist destination, and other famous visitors include the authors Jules Verne and Robert Louis Stevenson, the poets John Keats and Lord Alfred Tennyson, and Queen Victoria.

The cave can still be visited today through organized sightseeing cruises that take tourists inside the cathedral-like cavern when ocean conditions are calm enough.

The National Trust for Scotland owns Fingal's Cave as part of a nature reserve that was established in 2001. The cave and its surroundings host several types of birds and marine animals, including puffins, fulmars, basking sharks, dolphins, gray seals, minke whales and pilot whales.

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Don Juan Pond is a lake in Antarctica's extremely cold McMurdo Dry Valleys region that has a salinity above 40%, making it one of the saltiest bodies of water on Earth. The pond contains so much salt, it has a syrupy consistency that never freezes, even though temperatures in the Dry Valleys often fall to minus 58 degrees Fahrenheit (minus 50 degrees Celsius).

Don Juan Pond is 4 inches (10 centimeters) deep and slightly smaller than the total area of six football fields. It is named after two U.S. Navy helicopter pilots, Donald Roe and John Hickey, who spotted the pond during a reconnaissance expedition in 1961. There are other lakes in the Dry Valleys ‪—‬ but none are as salty as Don Juan Pond, so they stay frozen solid for most of the year.

Scientists are fascinated by Don Juan Pond because the harsh conditions in the McMurdo Dry Valleys resemble those on Mars, according to NASA. The Red Planet is bitterly cold and dry, rich in a variety of salts, and potentially hosts water. There is evidence for microbial life near Don Juan Pond, and it's possible that some organisms survive in the brine. If life can persist in the Dry Valleys, then life may exist, or may have once existed, in hypersaline features on Mars.

Don Juan Pond has elevated levels of calcium chloride, which is a highly soluble salt that lowers the pond's freezing temperature by keeping apart water molecules that would otherwise bond to make ice crystals. At 40% salinity, Don Juan Pond is much saltier than the Dead Sea, which has a salinity of 34%, and it is 12 times saltier than Earth's oceans, which have a salinity of 3.5%.

Scientists have been studying Don Juan Pond for more than 60 years, but they still aren't sure where the water and calcium chloride come from. Since the lake's discovery, the dominant hypothesis has been that Don Juan Pond is fed by groundwater bubbling to the surface. But in a 2013 study, Brown University geologists reported that the water is moisture from the atmosphere that is trapped by salts in the soil and eventually trickles down into the Upper Wright Valley, where Don Juan Pond is located.

The researchers took thousands of time-lapse photographs of the pond and the Upper Wright Valley's steep slopes. The images showed dark streaks near Don Juan Pond that the team argued were wet, salt-rich sediments funneling water toward the pond. Similar streaks, known as recurring slope linear features, occur on Mars' surface, hinting that a corresponding process may have once taken place on the Red Planet.

However, this hypothesis was contradicted by a 2017 study that revived the groundwater theory. That research, which was based on model simulations, indicated that the only way Don Juan Pond could have acquired its unique chemical makeup is if the water source were a deep groundwater system.

"If we accept that the deep groundwater theory is true, then what we're seeing could be part of a bigger process that involves quite an extensive aquifer," first author Jonathan Toner, an astrobiologist and research assistant professor at the University of Washington, said in a statement in 2017. "When thinking about the implications for a similar environment on Mars, that's much more exciting than just a localized surface phenomenon."

However, the source of water at Don Juan Pond is still debated.

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Thríhnúkagígur is a dormant volcano near Reykjavík whose last eruption 4,500 years ago left a hollow magma chamber with bronze-and-indigo-colored walls. It's the only place in the world where people can climb into a volcano's plumbing system and explore the cavern that held sizzling molten rock before an eruption.

Since 2012, visitors have been allowed to enter Thríhnúkagígur's magma chamber via an open cable elevator that was built in 2010 for scientists. The chamber is about 700 feet (210 meters) deep, or more than double the height of the Statue of Liberty with the pedestal. Visitors are lowered to the bottom of the cave in a metal cage, and then they are free to roam the 33,600-square-foot (3,120 square meters) cave floor.

Volcanoes don't usually have empty magma chambers beneath them. Typically, during an eruption, there comes a point when the pressure in the chamber isn't high enough to eject any more liquid. The leftover magma slowly solidifies inside the chamber, filling the ground beneath the volcano.

Thríhnúkagígur is an exception, but researchers don't really understand why. The magma that fed the most recent eruption seems to have disappeared, and scientists think it may have been sucked back down into Earth's crust.

"It's like somebody came and pulled the plug and all the magma ran down out of it," Haraldur Sigurdsson, a volcanologist and professor emeritus of marine geology and geophysics at the University of Rhode Island, told Inside the Volcano, a company that organizes tours of Thríhnúkagígur.

The colors inside the chamber are attributed to microbes, but not much is known about the organisms that live there. Sulfur-rich gases likely painted some parts of the cave yellow and orange, while rocks falling off the walls formed the indigo and blue patches. Visitors occasionally see puffs of steam rising from corners of the chamber, but these are caused by water dripping onto lamps that illuminate the cave and are not signs of an impending eruption.

Evidence suggests Thríhnúkagígur has erupted three times over the past 50,000 years. The volcano presents three peaks at the surface — hence its name, which translates to "Three Peaks Crater." They are similar in height ‪—‬ about 115 feet (35 m) tall ‪—‬ and they form a line, with about 660 feet (200 m) between each peak.

The youngest peak dates to the eruption 4,500 years ago. At the top sits the opening where scientists and tourists start their journey into the heart of the volcano. The next peak in the line formed 5,000 years ago, and it is partly encircled with solidified lava from the most recent eruption, according to Inside the Volcano. The oldest peak formed 50,000 years ago, when Iceland was covered with a thick ice sheet. It is composed of hyaloclastite, a volcanic rock characterized by sharp, glassy fragments that appear when lava comes into contact with water and ice.

It's unlikely that Thríhnúkagígur will erupt anytime soon, even though the volcano sits within the Mid-Atlantic Ridge, a tear in Earth's crust where the Eurasian and North American tectonic plates are separating, according to Inside the Volcano.

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Aoshima is a tiny, 0.2-square-mile (0.5 square kilometers) Japanese island in the Seto Inland Sea that is home to around 80 feral cats and three elderly people. It is the best known of 11 "cat islands" in Japan where felines easily outnumber humans.

Due to a lack of economic opportunities and the island's aging human population, it's possible that Aoshima will be completely abandoned by people and inhabited only by cats within the next five years, although the cat population is also in decline.

A decade ago, there were about 200 cats on the island, but a mass spaying-and-neutering program in 2018 reduced the number of cats by more than half, and no kittens are known to have been born there since then. All of the remaining cats are older than 7, and a third have diseases caused by decades of inbreeding, according to The Guardian.

"We just take it one day at a time," Naoko Kamimoto, a resident of the island who is in her 70s and known locally as the "cat mama," told The Guardian in 2024. "But the day will come when there are no people left, and no cats. All we can do is make sure we look after them for as long as we're here."

Aoshima was settled in the 17th century and grew into a sardine fishing community with almost 900 inhabitants. Fishers brought a handful of cats to the island to kill rodents that were destroying fishing nets and increasingly becoming pests. But a decline in the fishing industry in the 20th century forced people to leave Aoshima and relocate to the mainland. Many left their cats behind, and the felines reproduced.

Aoshima's cats are fed by food donations from people around Japan. The felines also eat small animals on the island, but their impact on local wildlife is unclear.

The cats occupy abandoned houses and buildings that have crumbled over the years due to weather events such as typhoons and storms. Kamimoto looks after the cats, feeding them twice per day and administering medication.

"People see images online and think they're being neglected, but nothing could be further from the truth," she said. "Some are blind, some are really thin, and others look normal. But that's the reality for wild animals in a place like this."

A 2023 study analyzed the cats' genetic makeup and found significant differences in their coat-color genes compared with cats on other Japanese islands, explaining why most cats on Aoshima are ginger or tortoiseshell. The research showed that Aoshima's cats are descended from a small founder population, confirming that the felines are likely suffering from the effects of inbreeding.

If humans abandon the island, locals are confident that volunteers and shelters will adopt the cats, The Guardian reported. But for now, the felines are a tourist attraction, with visitors taking day trips to the island by boat and helping to feed the cats.

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Cat quiz: Can you get a purr-fect score?

Lençóis Maranhenses is a national park on Brazil's northeast coast that is famous for its white sand dunes peppered with thousands of temporary, crystal-clear lagoons.

The lagoons form every year during the wet season, between January and June, when rainwater collects in natural basins between the dunes. A compact, impermeable sediment layer prevents the water from draining, thereby creating freshwater pools that vary in shape, size, depth and color, according to UNESCO, which designated Lençóis Maranhenses National Park as a World Heritage Site in 2024.

Sand dunes cover about two-thirds of Lençóis Maranhenses, which spans 580 square miles (1,500 square kilometers) within a transition area between the Brazilian Amazon, the Cerrado ecoregion and the Caatinga ecoregion. The Cerrado features tropical savannas, wetlands and abundant biodiversity, and it's one of the best carbon sinks in the world. The Caatinga, meanwhile, is a semiarid landscape covered in dry forests with thorny shrubs and stunted trees. The name Caatinga comes from the term "ka'atinga," which means "white forest" or "white vegetation" in the Tupi language.

Lençóis Maranhenses does not belong to any of those ecoregions. Instead, it forms its own unique landscape that, in some places, looks like a desert but isn't one.

The remaining third of Lençóis Maranhenses is home to mangrove swamps and lush vegetation. Rare and endangered species live these ecosystems, including the neotropical otter (Lontra longicaudis); the West Indian manatee (Trichechus manatus); the scarlet ibis (Eudocimus ruber); and the oncilla (Leopardus tigrinus), a type of small, spotted cat.

The national park includes 50 miles (80 kilometers) of coastline, with a dry plain separating the beach from the sand dunes. Sand is dumped ashore by the tides and then eroded by winds and transported across the plain to the dunes. This action shapes the dunes into huge crescents, also known as barchans, that grow taller the farther inland they are, because the farthest dunes from the beach are those that have been around the longest and accumulated the most sand via wind deposition. The dunes that hug the plain are up to 3.3 feet (1 meter) high, while those farthest inland can measure up to 100 feet (30 m) tall, according to UNESCO.

Lençóis Maranhenses is surrounded by a large buffer zone to protect it from human activities. The best time to visit the national park is between June and September, when the lagoons are full. Lagoa da Gaivota, Lagoa Azul and Lagoa Bonita are some of the largest lagoons in the national park.

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Sørvágsvatn, also called Leitisvatn, is a 1.3-square-mile (3.4 square kilometers) lake in the Faroe Islands that appears to float above the sea.

The optical illusion is visible from a limited number of angles along the lake's southern tip.

The trick functions because the lake sits 105 feet (32 meters) above sea level at the top of a cliff that slopes slightly inland toward the lake. Therefore, from a point a few hundred feet out, it looks like the lakeshore reaches all the way to the edge of the cliff, creating the illusion that the water extends over the sea.

Locals disagree about the name of the lake, hence why there are two. The inhabitants of Sørvágur, a village to the west of the lake on the island of Vágar, prefer the name Sørvágsvatn, which means "the lake by Sørvágur." People living in Miðvágur and Sandavágur to the east of the lake on Vágar call it Leitisvatn, or "the lake by Leiti," in reference to a territory in the east of the Faroe Islands.

The village of Miðvágur is closer to the lake than Sørvágur is, but the latter is thought to have been settled earlier during the ninth century, complicating the picture. Another argument in favor of calling the lake Sørvágsvatn is that the Faroe Islands' first settlers divided Vágar into three equal regions — and the lake is situated in the same region as Sørvágur.

But to avoid this debate, locals mostly refer to the lake as Vatnið, meaning simply "the lake."

The lake is surrounded by cliffs, which creates the impression that it is higher above the waves than it actually is. This is especially the case on either side of the lake's primary outlet, a 100-feet-high (30 m) waterfall called Bøsdalafossur, meaning "the waterfall at Bøsdal," referring to the area near the settlement of Bøur.

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The Bandera Volcano Ice Cave is a hollow in the ground in New Mexico where temperatures never exceed 31 degrees Fahrenheit (minus 0.6 degrees Celsius).

The cave formed roughly 10,000 years ago, when the nearby Bandera Volcano violently erupted, spewing lava that solidified at the surface while caverns formed in the layers below. The cave's unusual geology has preserved frigid conditions, which have caused ice to form inside it for at least 3,400 years.

The ice inside the Ice Cave is up to 20 feet (6 meters) thick on the floor year-round. Due to the freezing conditions, Arctic algae have colonized the cave, growing on top of the ice to form a blue-green, living blanket, according to the Ice Cave's website.

The cave is "one of New Mexico's weirdest spots, where it's both hot and cold all at the same time," Paul Mauermann, an environmental educator and director of New Mexico's Sandia Mountain Natural History Center, said in a video.

The Ice Cave is freezing because it is nestled inside a collapsed lava tube. Lava tubes are natural tunnels that form beneath surface lava flows during volcanic eruptions. Because surface flows are in contact with air, they cool and solidify more quickly than the lava flowing closer to the ground. As a result, when a volcano stops erupting, the core of a lava flow drains away while the outside hardens, leaving an empty conduit, or cave.

The Ice Cave has porous walls and an opening that's just the right shape to trap cold air inside the lava tube while keeping the warm air outside. This "natural icebox" is continually replenished through rainfall and snowmelt that freeze upon contact with the icy floor, according to the Ice Cave's website.

Bandera Volcano is also remarkable, as it represents one of the best and most accessible examples of a cinder cone volcanic eruption in North America. This type of eruption is short but explosive, with sprays of lava that crystallize in the air before landing on the ground. This results in steep cones covered in loose fragments that make it hard for anyone to climb some of the volcano's vents.

Bandera is now dormant. One of its vents collapsed during the eruption, forming a 800-foot-deep (240 m) crater that visitors can view from a breach on the south side. Lava likely flowed through this gap and into the valley below, forming a 23-mile-long (37 kilometers) river of molten rock that has since solidified into lava fields, according to the website.

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The Chocolate Hills are a formation made of 1,776 limestone, grass-covered mounds in the Philippines.

This landscape is lush green during the rainy season from February to May, but in the dry season, the hills turn cocoa brown, giving the formation its name.

The Chocolate Hills were designated a national geological monument of the Philippines in 1988 and were granted protection as a natural monument in 1997. There is no other formation quite like them in the world, with just one region in Java, Indonesia, having a similar, but less impressive geology.

The hills are between 100 and 390 feet (30 to 120 meters) tall and have tapering tops. They are examples of what geologists call "mogotes" — steep-sided mounds that occur in tropical karst landscapes, or areas that have a soluble bedrock and host sinkholes and cave systems. Numerous underground caverns and springs have been documented around the Chocolate Hills, according to a 2001 research article, with some caves potentially existing directly beneath the mogotes themselves.

Evidence suggests the Chocolate Hills formed sometime at the start of, or just before, the last ice age (2.6 million to 11,700 years ago), when tectonic processes lifted coral and other marine deposits. These deposits were then exposed to rainfall and erosion, which carved the landscape into regular mounds.

Local myths have tried to explain how the Chocolate Hills formed. According to one legend, the mounds formed after a mud-throwing fight between two giants. Another tale says the region was once inhabited by giant children, who, while competing to make the most mud cakes, baked them under coconut half shells that eventually became the Chocolate Hills.

The land between the hills is flat and cultivated with rice and other crops. When the Chocolate Hills were declared a natural monument in the late 1990s, farmers, small-scale miners and landowners rose up against the government because they feared environmental protections would curb their property rights and livelihoods.

These protests escalated into violent conflicts between the military and a guerilla group dubbed the "Chocolate Hills Command," according to the 2001 article. Two armed fights broke out, one of which caused 10 deaths in October 1999.

Balancing the diverse and sometimes conflicting needs of environmental protection, tourism and local residents still poses a challenge today; the construction of a resort in the middle of the Chocolate Hills sparked public outcry in 2024.

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As its name suggests, the Avenue of the Baobabs is a road in Madagascar that’s lined with towering baobab trees. The trees are the remnants of a tropical forest that once sprawled across the island, and in the modern era they are listed as a natural monument by Madagascar's government.

The Avenue of the Baobabs is made up of endangered Grandidier's baobabs (Adansonia grandidieri) — one of six endemic baobab species in Madagascar. The trunks of Grandidier's baobabs typically grow around 80 feet (24 meters) tall and 10 feet (3 m) wide, but the biggest specimen ever recorded was a 98-foot (30 m) giant with a diameter of 36 feet (11 m), according to the plant sciences faculty at the University of California, Davis.

Grandidier's baobabs have such huge trunks because they store water. However, water doesn't gush out if you drill a hole into a baobab; rather, the trees store water in their cells, in order to grow new leaves and maintain their structure, according to the Baobab Foundation.

The Avenue of the Baobabs is an unpaved road between Morondava and Belo Tsiribihina, two towns close to Madagascar's west coast. About 20 to 25 Grandidier's baobabs line a short stretch of the road, but 25 more trees of the same species grow scattered among rice paddies and meadows just a short distance away — and there are hundreds of baobabs in the surrounding landscape.

Baobabs evolved in Madagascar between 41 million and 21 million years ago, a 2024 study found. Most of the baobab species that exist today remain in Madagascar, but two species — A. digitata and A. gregorii — are found in continental Africa and Australia, respectively. It's unclear how the baobabs got there, but researchers have proposed that the fruits may have crossed the oceans on currents or been transported by humans.

In Madagascar, baobabs are called "renala" or "reniala," meaning "mother of the forest." The name points to evidence suggesting that the baobabs that give their name to the Avenue of the Baobabs only recently became isolated trees; thousands of years ago, they stood in a dense tropical forest.

Today, baobabs in Madagascar face extinction threats from illegal logging, fires and climate change. Nevertheless, the trees play a central role in Malagasy culture, featuring in local legends such as that of the "Baobab Amoureux," or "Loving Baobabs" — two intertwined trees that are said to embody a pair of star-crossed young lovers who were forced to marry other people.

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Spotted Lake — also known as Khiluk Lake in the local Indigenous Nsyilxcən language — is a soda lake named after strange circles that appear on its surface in the summer.

The lake is incredibly rich in minerals, including sodium sulfates, calcium, magnesium sulfate — which is also known as Epsom salt — and trace amounts of silver and titanium. As temperatures rise every spring and summer, most of the water in the lake evaporates and minerals that were dissolved precipitate, leaving a pitted, white crust that looks like a giant doily.

The mineral crust exists year-round and can be seen beneath the water outside of summer, but the best time to see it is in the hotter months. Spotted Lake has no outlet, meaning evaporation is the only process that removes water from the lake. Precipitation and runoff from the surrounding hills increase the water level periodically, which also brings more minerals that crystallize into the crust.

Spotted Lake is a soda lake, meaning it is extremely salty and alkaline. Soda lakes typically form in closed basins, where minerals leach from surrounding rocks and become highly concentrated.

The lake is 2,300 feet (700 meters) long and 820 feet (250 m) wide. The darker spots in the mineral crust are shallow brine pools, beneath which there are more solidified minerals. These pools can appear blue, green or yellow, depending on the light, the makeup of the crust underneath, and the presence of algae. They can also change size and shape as the crust crystallizes and dissolves.

Geologist Olaf Pitt Jenkins described the texture and smell of the brine at Spotted Lake in a 1918 paper, writing: "The brine itself in the pools was so strong that it was very heavy and very slimy like the white of an egg, and had an offensive odor."

Jenkins visited Spotted Lake because, starting in 1916, the lake's minerals were extracted to make ammunition during World War I. However, Spotted Lake's history and cultural significance goes back much further than that.

For centuries, the Syilx People of the Okanagan Nation have considered Spotted Lake a sacred place of healing. According to their belief, each circle in the lake has unique medicinal properties.

After World War I, the land where the lake sits was acquired and privately owned for about 40 years. But in 2001, the federal government bought back the land for the benefit of the Okanagan Nation. The Syilx People still protect Spotted Lake today, and access to the water is restricted for the general public. A viewing area guarantees good views of the lake, however.

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Colombia's Coconucos volcanic chain is a high mountain ridge pockmarked with at least 14 volcano craters. These craters form a line that runs northwest-to-southeast, offering striking aerial views and images.

Twelve volcanoes in the Coconucos volcanic chain have summits higher than 13,000 feet (4,000 meters) above sea level. The tallest volcano, at about 15,400 feet (4,700 m) above sea level, is the Pan de Azúcar, which until a few decades ago was permanently covered in snow.

The second-tallest volcano in the chain, known as Puracé, is Coconucos's only active volcano and one of the most active volcanoes in Colombia. Puracé, meaning "fire mountain" in the Quechua family of languages, stands 15,260 feet (4,650 m) high and sits at the northwesternmost end of the chain. Its last eruption was in early December 2025, when the volcano spewed gas and ash up to 3,000 feet (900 m) into the sky and showered nearby areas with fine debris. Colombian authorities issued an alert on Nov. 29 and the outburst continued Monday (Dec. 15).

Puracé showed signs of activity in 2022 and 2023, but the volcano's last recorded eruption before the most recent one was in 1977. The last measurements before the 2025 eruption showed that Puracé's crater has a diameter of 1,640 feet (500 m).

The Coconucos volcanic chain is located in Puracé National Park in the Andes mountains. The region is a misty grassland ecosystem known as páramo, with temperatures ranging between 37 and 65 degrees Fahrenheit (3 to 18 degrees Celsius). Snow was widespread on mountain tops in Puracé National Park until a century ago, but this is rare nowadays, according to Colombia's national parks website.

Several of Colombia's most important rivers originate in Puracé National Park, including the Cauca, Magdalena, Patía and Caquetá. The national park is peppered with sulfur springs and clear lagoons, attracting tourists and hikers.

The Coconuco people have traditionally inhabited, and continue to live in, the region.

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China's "Great Green Wall" is a huge ecological engineering project to slow the expansion of the Gobi and Taklamakan deserts in the country's north.

Since 1978, China has planted more than 66 billion trees along its borders with Mongolia, Kazakhstan and Kyrgyzstan — and Chinese authorities plan to plant 34 billion more over the next 25 years. If they succeed, the Great Green Wall will increase Earth's forest cover by 10% since the late 1970s.

The Great Green Wall, formally known as the Three-North Shelter Forest Program, is designed to slow soil erosion and sand deposition that has been increasing since the 1950s due to huge urbanization and farmland expansion. These changes exacerbated the region's already dry conditions, which in turn created the conditions for more sandstorms. Sandstorms blow away the top layer of soil and deposit sand, degrading the land and increasing particulate matter pollution in cities.

Northern China was dry before the urbanization boom of the 1950s, because the Himalayas create a rain shadow over the country's border with Mongolia that limits precipitation in the region. This is why the Gobi and Taklamakan deserts are so enormous; combined, they cover 618,000 square miles (1.6 million square kilometers), which is slightly smaller than Alaska, according to the Royal Geographical Society.

Despite China's efforts over the past five decades, the Gobi and Taklamakan are still expanding. The Gobi Desert, for instance, swallows around 1,400 square miles (3,600 square km) of China's grassland every year. Desertification is ruining ecosystems and agricultural land, but it's also making pollution in cities like Beijing worse, according to the Royal Geographical Society.

Last year, government representatives announced China had finished encircling the Taklamakan with vegetation, which has helped stabilize sand dunes and grow forest cover from about 10% of China's area in 1949 to more than 25% today. Tree planting will continue around the Taklamakan to maintain and enlarge the forest, the representatives said.

If everything goes to plan, the Great Green Wall will be 2,800 miles (4,500 kilometers) long by 2050. The "wall" is the world's largest seeded forest — but it's still unclear just how effective it is at slowing desertification.

While some studies suggest the Great Green Wall has reduced the frequency of sandstorms, others argue this decrease is mostly due to climatic factors.

Critics say the survival rate of planted trees and shrubs is too low to show robust results, possibly because huge swathes of the wall encompass only one or two tree species — mostly poplar and willow, according to the Royal Geographical Society — making the wall susceptible to disease. For example, in 2000, 1 billion poplar trees were lost to a single pathogen in the Ningxia province.

Tree mortality is also high because China is planting trees in places that don't have enough water to grow them. Without constant human intervention, many of the trees don't survive.

"People crowded into the natural sand dunes and the Gobi to plant trees, which have caused a rapid decrease in soil moisture and the groundwater table," Xian Xue, a leading expert on erosion-driven desertification at the Chinese Academy of Sciences, told National Geographic in 2017. "Actually, it will cause desertification [in some regions]."

Because it is a monoculture, the Great Green Wall also doesn't promote biodiversity in the same way that a more diverse mix of indigenous plants would. Nevertheless, the program inspired Africa's Great Green Wall, which will be a 5,000-mile-long (8,000 km) tree belt across the continent to slow land degradation and desertification.

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Sistema Ox Bel Ha, meaning "three paths of water" in the local Mayan language, is a gigantic submerged labyrinth that runs for at least 326 miles (524 kilometers) underground, according to the Investigation Center of the Aquifer System of Quintana Roo (CINDAQ). This makes it the longest submerged system and the second-longest cave system in the world, after the 426-mile-long (686 km) Mammoth Caves in Kentucky.

The Yucatán Peninsula is home to several massive cave systems because it has a thin layer of top soil covering limestone, which is soluble, enabling rain water to quickly pass through into caverns below the surface, according to a 2020 study. This is also the reason why the region has few rivers or streams.

The caverns form through a process called karstification, in which rain water dissolves calcium carbonate from the limestone. In the case of Ox Bel Ha, this process is supercharged as the fresh water meets salt water that's entered the system from the ocean.

The fresh and salt water form distinct layers and meet at a point in the cave water called the halocline. This line varies in Ox Bel Ha, varying from 33 feet (10 meters) near the coast, where there is more salt water, to 66 feet (20 m) deep further inland. CINDAQ estimated that 27% of the system is salt water and 73% fresh water. This fresh water feeds the vast Maya aquifer, which is the only source of drinking water in the region.

The karstification process can cause cavern roofs to collapse, creating an exposed pool or sinkhole, known as a cenote. Ox Bel Ha has at least 160 cenotes, and they are important water sources for animals and ecosystems, according to CINDAQ. The organization has recently recorded a number of species around the cenotes, such as cougars (Puma concolor), jaguars (Panthera onca) and various deer and other animals.

The system also supports a range of creatures below the surface. In 2018, scientists discovered that the subterranean system supports its ecosystem with methane. Methane forms below the jungle floor and then migrates down into the caves, where microbes and bacteria consume it. These in turn become food for cave-dwelling crustaceans as well as several species of fish, including an eyeless albino cave fish.

Ox Bel Ha runs near the historical Maya town of Tulum. The ancient Maya believed that cenotes were gateways to Xibalba, the Maya underworld, and these pools, along with those of the nearby Sistema Sac Actun, have yielded a number of important archaeological finds.

Most notably, researchers found the remains of a 25- to 30-year-old woman, named Eve of Naharon, whose remains may date to 13,700 years ago — potentially making these the oldest human remains found in the Americas. However, a 2021 review noted that this date has not been replicated or verified. Evidence suggests the woman was deliberately placed on the cave floor, which wasn't flooded at that point, although this also isn't clear, a 2020 study noted.

Ox Bel Ha's system is under threat from construction and developments, including the Maya Train and Tulum International Airport, and it already runs under a number of urban areas, CINDAQ said. This makes studying and mapping the vast underwater system critically important, CINDAQ added.

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Triple Divide Peak is a mountain in Montana's Glacier National Park where a drop of water could flow into one of three oceans: the Pacific, the Atlantic or the Arctic Ocean.

Other triple divides — also known as "hydrological apexes" — exist in the world, but Triple Divide Peak is the only place on Earth that links three oceans rather than three seas or a mix of seas and oceans. However, some experts dispute this.

Snowmelt from the peak can travel west through the Columbia River drainage basin and end up in the Pacific Ocean, or it can ride along the Missouri and Mississippi rivers and into the Atlantic, according to the National Park Service. Alternatively, meltwater or raindrops landing on Triple Divide Peak can flow into Hudson Bay via the Saskatchewan River.

The International Hydrographic Organization considers Hudson Bay to be part of the Arctic Ocean, so by that reckoning, Triple Divide Peak feeds three separate oceans.

The peak sits on North America's Continental Divide, an imaginary line that runs through the Rocky Mountains and separates major river systems flowing to the Pacific, Atlantic and Arctic oceans. Triple Divide Peak is one of just two hydrological apexes on the Continental Divide and across North America, the other one being Snow Dome in Canada.

Meltwater from Snow Dome can flow into the Pacific Ocean via the Columbia River, into the Arctic Ocean via the Mackenzie River or into Hudson Bay via the Nelson River. Some scientists argue that Hudson Bay is part of the Atlantic Ocean, so in their view, Snow Dome is the only triple divide on Earth that connects three oceans. For them, water on Triple Divide Peak only flows into either the Pacific or the Atlantic Ocean.

Triple Divide Peak and Snow Dome also sit on other "great divides," with these divides marking out different watersheds. As well as the Continental Divide, Triple Divide Peak sits on the Laurentian Divide, which separates the Hudson Bay watershed to the north from the Gulf of Mexico watershed to the south. Snow Dome, meanwhile, sits on the Arctic Divide, which separates the Arctic Ocean watershed to the northwest from the Hudson Bay watershed to the southeast.

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Eternal Flame Falls is a waterfall in New York State that houses one of the world's few natural "eternal" flames.

The waterfall is about 30 feet (9 meters) tall and consists of two tiers; one at the top measuring 8 feet (2.5 m) high and the other at the base making up the remaining height. The cascade flows over an outcrop of shale, a type of sedimentary rock made of compacted clay, silt, mud and organic matter.

As its name suggests, Eternal Flame Falls features a fire that burns uninterrupted behind the waterfall. The small blaze grows up to 8 inches (20 centimeters) tall, protected from any spray and wind by the walls of a small grotto around it.

The air surrounding Eternal Flame Falls is filled with a smell like rotten eggs, according to the website NY Falls, which publishes guides to waterfalls in New York. That's because the cascade is surrounded by natural gas seeps that release hydrogen sulfide, methane and other gases into the atmosphere. And the biggest of these seeps is located directly beneath the eternal flame.

Gases like methane are highly flammable. Thanks to the shelter of the small grotto, the natural gas escaping from this seep can be ignited with a match or lighter and burn permanently. Other seeps around Eternal Flame Falls aren't protected in the same way, so lighting them would not produce a lasting fire. These seeps are invisible, unless they are located at the bottom of the stream and pools near the waterfall, in which case the gas can be seen bubbling up, according to NY Falls.

The natural gas at Eternal Flame Falls originates from decomposing organic matter in buried layers of shale. Specifically, the gas comes from a geological formation called the Hanover Shale that dates to the Devonian period (419.2 million to 358.9 million years ago). Organic matter breaking down in this 90-foot-thick (27.5 m) formation releases gases that accumulate underground. As the pressure builds, these gases escape via fissures in the rock and soil above, giving rise to seeps at the surface.

The best time to visit Eternal Flame Falls is in early spring, when the waterfall and eternal flame look the most impressive, according to NY Falls. The waterfall is highly dependent on meltwater and rainfall, so it usually dries up in the summer and fall. The flame, meanwhile, relies on relatively dry conditions. It burns stronger in the summer but looks better in the spring, because the waterfall diffuses the light like a lampshade, creating an otherworldly glow.

Eternal Flame Falls is fed by the Shale Creek, which joins another waterway called Eighteenmile Creek about 2 miles (3 kilometers) away, according to NY Falls. The water then empties into Lake Erie.

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The Coral Triangle is a tropical marine region between the Pacific and Indian oceans where 76% of Earth's coral species are found. It encompasses 2.3 million square miles (6 million square kilometers) of ocean around the Philippines, Indonesia and Papua New Guinea, and stretches south to Timor-Leste and as far east as the Solomon Islands.

Biodiversity in the Coral Triangle is much higher than in other regions with coral reefs, such as the Caribbean Sea and the southwest Pacific Ocean. Around 605 reef-building coral species inhabit the Coral Triangle — 10 times the number in the Caribbean Sea, according to an article from the U.K.'s Natural History Museum (NHM).

These corals provide a home for six of the world's seven sea turtle species and 37% of the world's coral reef fish species, as well as marine mammals like dolphins, dugongs, blue whales and sperm whales, according to the NHM article. This incredible array of species has earned the Coral Triangle the nickname the "Amazon of the sea."

"This part of the world contains the highest diversity of marine species," Nadia Santodomingo, a coral expert and marine biologist at the NHM, said in the article. "Scientists have been trying to understand why it's so diverse for a very long time." In fact, British naturalist and explorer Alfred Russel Wallace was working there when Charles Darwin was alive, trying to solve the same problem, she added.

Wallace traveled through the Malay Archipelago between mainland Southeast Asia and Australia, collecting specimens and developing theories regarding the region's staggering biodiversity. He came up with what scientists call the "Wallace Line" — a gigantic biological boundary that separates the Oriental and Australian faunal regions — and proposed the theory of evolution by natural selection around the same time as Darwin.

Scientists today have more tools at their disposal to understand the region, with evidence suggesting that murkier conditions in the Coral Triangle compared with other shallow tropical waters may provide a haven for different species. The Coral Triangle has been a biodiversity hotspot for at least the past 20 million years, and this is partly thanks to a huge variety of habitat types and optimal conditions for larvae that ride on ocean currents, according to the nongovernmental organization Blue Corner Marine Research.

Research also suggests that the Coral Triangle has a plethora of species simply because diversity built up over time. Unlike temperate and polar marine regions that have undergone glaciations, tropical regions like the Coral Triangle have remained relatively stable. And what sets this region apart from other tropical seas is its unique, platform-like geology and location at the intersection between two oceans, researchers say.

Like other coral reef regions, the Coral Triangle is vulnerable to overfishing, pollution from coastal development, and ocean acidification linked to climate change — although scientists think its murky conditions may shield it somewhat.

"Corals living under continuous sediment stress seem to be more resilient, as the mud may block light, which in turn alleviates bleaching stress induced by high temperatures," Kenneth Johnson, a paleobiologist and principal researcher at the NHM, said in the article.

Nevertheless, it's important to protect this patch of ocean, Johnson said. "Nobody really thinks about these reefs," he said, "but they might be the ones we really want to protect."

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The Cairo Fossil Forest is a unique collection of 385 million-year-old trees preserved in an abandoned quarry in upstate New York. The forest holds some of the oldest trees in the world, as well as the oldest known examples of trees with leaves and thick, woody trunks, researchers say.

"The Cairo site is very special," Christopher Berry, a paleobotanist at the University of Cardiff in the U.K., told Science Magazine when the discovery was announced in 2019. "Standing on the quarry surface we can reconstruct the living forest around us in our imagination," Berry, who was one of the scientists that found the site in 2009, added.

The remains of ancient trees are buried beneath the quarry floor, but they form patterns on the surface that reveal where tree trunks and roots once anchored into the ground. Some of the fossilized roots are almost 6 inches (15 centimeters) thick, Science Magazine reported, and the biggest root networks stretch 36 feet (11 meters) away from the trunks.

The trees likely belong to Archaeopteris, an extinct group of trees with fern-like leaves that is related to modern trees. Research suggests Archaeopteris trees grew more than 66 feet (20 m) tall toward the end of the Devonian period (419.2 million to 358.9 million years ago), which is also known as the "age of fishes" due to the huge diversification that happened in this animal group.

The first Archaeopteris trees marked a turning point in Earth's history, because they helped to suck up and lock away carbon dioxide (CO₂) from the air, shifting the composition of the planet's atmosphere. These plants also accelerated a process called weathering, which occurs when roots jumble and break up rocks, exposing them to air and triggering a chemical reaction that turns CO₂ into carbonate ions. These ions eventually end up in the ocean and bind together to form limestone, experts told Science Magazine.

Before the Cairo Fossil Forest discovery, the oldest found Archaeopteris trees were 365 million years old, Berry said. The discovery of the Cairo Fossil Forest in 2009 suggests these prehistoric trees evolved at least 20 million years earlier than that, but it's still unclear exactly when they first appeared on Earth.

Related: 23 million-year-old petrified mangrove forest discovered hiding in plain sight in Panama

Despite being the earliest example of leaves and thick trunks appearing in trees, the Cairo Fossil Forest isn't the oldest in the world. In 2024, scientists discovered 390 million-year-old plant fossils in the southwest of England that dethroned the Cairo Fossil Forest as the earliest known forest. These older fossils belong to an extinct type of plant that looked like palm trees and are thought to be closely related to ferns and horsetails.

"They've got a long central stem and what look like palm fronds coming off, but those palm fronds aren't really leaves — they're actually just lots of twiglets," Neil Davies, a professor in the Department of Earth Sciences at the University of Cambridge in the U.K., told Live Science at the time.

Similar plants to those found in southwestern England have been discovered just 25 miles (40 kilometers) away from the Cairo Fossil Forest in Gilboa, New York. The Gilboa Fossil Forest is 382 million years old and was first excavated in the 1800s. It held the title of "world's oldest forest" until researchers discovered the forest in Cairo.

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The Narusawa Ice Cave is a lava tube that is brimming with icicles and ice pillars at the base of Mount Fuji in Japan.

Lava tubes are natural tunnels that form beneath solidified lava flows after a volcanic eruption. Lava hardens faster in the top layers of a lava flow, where the molten rock comes into contact with cool air, than in the middle layers, where it stays red hot and fluid. As a result, when a volcano stops erupting, the core of a lava flow drains away while the outside hardens, leaving an empty conduit, or cave.

The Narusawa Ice Cave is one of several caves that formed during a violent eruption of Mount Fuji in A.D. 864. The eruption took place on the northeast side of the volcano, with lava spewing from a new vent called Mount Nagao rather than from Mount Fuji's central summit crater.

The eruption lasted 10 days and created the large lava plain that's now covered by the Aokigahara Forest, a dense woodland also known as the "Sea of Trees." The blast also split a lake in half, carving out two of the five Fuji volcanic lakes.

The ice cave is one of the three largest caves in this area, along with Fugaku Wind Cave and Lake Sai Bat Cave (also called Lake Saiko Bat Cave). Narusawa Ice Cave is 490 feet (150 meters) long and up to 12 feet (3.6 m) high, according to Wind Cave & Ice Cave, the company that manages and offers tours of the cave. The average temperature in the cave is only slightly above 37 degrees Fahrenheit (3 degrees Celsius) due its particular geology, meaning that any moisture is likely to freeze, especially in the winter.

Water that drips from the ceiling of the cave forms stalactites and stalagmites that meet in the middle during the coldest months. The best time to visit Narusawa Ice Cave is in winter or early spring, when these ice pillars can reach up to 1.6 feet (0.5 m) thick and 10 feet (3 m) tall, according to Wind Cave & Ice Cave.

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The cave is a tourist attraction, but historically, it was used to keep seeds and silkworm cocoons cool. People carved rectangular blocks out of the ice pillars, which they then stacked to create an icebox or refrigerator of sorts, according to Wind Cave & Ice Cave.

"To prevent growth of the cocoons and to preserve the quality of seeds and promote budding, they were stored in a refrigerated environment," the company states on its website.

The cave also holds the remains of ancient trees, which were knocked down by lava flows during the A.D. 864 eruption, pictures on the website show.

The Narusawa Ice Cave sits just half a mile (800 m) east of Fugaku Wind Cave, which extends much deeper belowground, boasts impressive lava formations and houses unusual moss colonies, according to the Japan National Tourism Organization. There is no echo in the wind cave because the walls of pure basaltic rock absorb sound — and unlike in the ice cave, there isn't any frozen water for sound waves to bounce off of.

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Loughareema, or The Vanishing Lake, is an ephemeral lake in Northern Ireland with a rare geology that scientists still don't really understand.

Three streams flow into the lake, but the only exit is a drain at the bottom that frequently gets blocked and unblocked, resulting in dramatic changes in the water level.

The Vanishing Lake can be full in the morning and empty by lunchtime due this drain and a puzzling underground drainage system that carries the water to a large spring in the Carey River, 1.6 miles (2.5 kilometers) away, according to The Geological Society. Geologists aren't sure how the drainage system works or when it formed, but it can empty the lake with remarkable efficiency.

"Loughareema is a dynamic landscape and on approach to the lake it's exciting to guess what state it will be in," Paul Wilson, a hydrogeologist at the British Geological Survey in Belfast, Northern Ireland, told The Geological Society. "The water disappears into an underground drainage system, the details of which we currently know very little about."

Related: What's the oldest lake on Earth?

Water flows into the lake, and with it comes debris that sinks to the lake bed and eventually covers the drain. Once the hole becomes completely blocked, the water level rises fast. But when the water reaches a certain level, the pressure it exerts on the drain suddenly unblocks it, so the water level sinks rapidly again until the lake is practically empty.

A small road runs through the middle of The Vanishing Lake, but today it is elevated enough that cars can pass even when the water level is high. The lake is in a remote location, surrounded by a blanket bog — a treeless, peatland habitat characterized by waterlogged ground and foggy conditions.

Legend has it that at some point in the 19th century, people on a horse-drawn carriage traveling along the road tried to cross The Vanishing Lake in the dead of night and drowned. According to folklore, the carriage and horses still haunt the shoreline now, appearing as ghosts on nights when the lake is full.

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Hin Sam Wan, or Three Whale Rock, is a natural formation in Thailand that is named after its striking resemblance to a family of whales swimming side by side. It consists of three extremely elongated, rounded boulders that look like giant cetaceans floating in a sea of trees.

Three Whale Rock formed about 75 million years ago due to long-term erosion and tectonic uplift. Wind and rain sculpted and smoothed the sandstone in northeastern Thailand into the shapes we see today, with cracks in the rock helping to form the narrow boulders that now look so much like whales.

The formation is situated near the border between Thailand and Laos, in a forest-covered nature reserve called Phu Sing Forest Park. A network of hiking trails leads up to the three whales, but only the bigger "mommy" and "daddy" whales are accessible by foot. The "baby" whale — the smallest of the three — is closed to the public.

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The views from the "backs" of the two biggest stone whales extend to the Mekong River and mountains in Laos' Pakkading district, according to National Geographic. The whales sit on a high ridge and jut out over the forest canopy, which reinforces the illusion that they are sea creatures in their natural habitat.

Three Whale Rock and the surrounding area are part of the Khorat Plateau. This region of uplifted sedimentary rock holds fossils — including evidence of dinosaurs — from the Cretaceous period (145 million to 66 million years ago) and the Cenozoic era (66 million years ago to present).

Phu Sing Forest Park and its stone leviathans are protected as natural and cultural heritage sites.

Mount Thor is a remote mountain in Canada with the largest vertical drop in the world. The mountain is just under 5,500 feet (1,675 meters) tall — but its most striking feature is its west face, which is so steep that it actually curves back on itself.

An object falling from the top of Mount Thor's western cliff would plummet 4,100 feet (1,250 m) before hitting anything. If a human were to jump off the summit and not deploy a parachute, they would remain in the air for a terrifying 26 seconds.

Mount Thor's west face has an average angle of 105 degrees, which means that the mountain has an overhang of 15 degrees. The western face is, as a Facebook post put it, "steeper than vertical" — making the mountain look like it was cleaved unevenly in half.

Mount Thor is named after the Norse god of thunder. It is located on Baffin Island, the largest island in the Canadian Arctic Archipelago.

Related: Savonoski Crater: The mysterious, perfectly round hole in Alaska that scientists can't explain

The mountain sits on the eastern edge of the Canadian Shield, a massive geological formation with rocks that are at least 1 billion years old. But the peak belongs to the Arctic Cordillera mountain range, which stretches from Ellesmere Island to Labrador.

Mount Thor is made of solid granite that formed between 3.5 billion and 570 million years ago. The mountain was carved over millennia by glaciers, whose repeated advance and retreat between 18,000 and 1,500 years ago eroded the west face into the C-shape we see today.

Despite its remote location, Mount Thor is a popular destination for rock climbers. American astrophysicist Lyman Spitzer and his mountaineering partner Donald Morton made the first recorded ascent of Mount Thor in 1965, but the first ascent of the mountain's west face wasn't until 1985 — and that took 33 days.

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Whale Valley is a region of the Egyptian Sahara desert that is peppered with archaic whale skeletons, some of which have feet and toes preserved.

These skeletons and other marine fossils date to the late Eocene epoch (55.8 million to 33.9 million years ago), when present-day Egypt was submerged beneath the Tethys Ocean and whales had just evolved into sea creatures, according to UNESCO.

"These fossils represent one of the major stories of evolution: the emergence of the whale as an ocean-going mammal from a previous life as a land-based animal," UNESCO's website says.

Paleontologists have unearthed more than 400 ancient whale skeletons in Whale Valley since the beginning of the 20th century, according to a UNESCO video. The first such discovery, in 1902, uncovered a never-before-seen whale species called Basilosaurus isis (formerly Zeuglodon isis). This whale grew up to 60 feet (18 meters) long and probably dined on smaller whales, crushing their skulls before gulping them down, according to a 2019 study.

Evidence suggests B. isis "had a long snout and was armed with pointed incisors and sharp cheek teeth," Manja Voss, a marine mammal expert at the Berlin Museum of Natural History and the lead author of the 2019 study, previously told Live Science.

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Researchers have found scores of B. isis skeletons in Whale Valley, but in 1989, paleontologists made a remarkable discovery: A team from the University of Michigan and the Egyptian Geological Museum unearthed B. isis skeletons with hind limbs, feet and toes, according to a 2023 review article.

Modern-day whales lack hind limbs, but still have pelvic bones indicating that they once had them, according to the University of Hawaii. This means the fossils in Whale Valley are some of the oldest known archaeocetes, a group of mammals from the Eocene that later evolved into modern-day whales and dolphins, according to the 2023 review.

In 2005, paleontologists uncovered a stunningly preserved, near-complete B. isis skeleton, prompting UNESCO to list Whale Valley as a World Heritage site. Since then, plenty more fossils have emerged, including the remains of ancient Eocene turtles, bony fishes, sharks, rays, crocodiles, sea cows and shellfish, according to the review.

These fossils have stood the test of time thanks to the region's arid climate since the Pliocene (5.3 million to 2.6 million years ago), according to UNESCO.

Whale Valley operates as an open-air museum, complete with a visitor center and easy access for tourists, but the site is strictly protected. Researchers continue to find new fossils and learn more about the geology of the area, according to the review.

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Taal Lake is a volcanic crater lake in the Philippines with a rare geology of nested islands and water. Researchers think the crater formed after a series of eruptions between 140,000 and 5,380 B.C. — but the landscape has shifted significantly since then.

The lake fills the Taal volcano caldera, a bowl-shaped basin that opened when the top of Taal volcano blew off during one of the prehistoric eruptions. The water came from the sea, traveling via what is now the Pansipit River from modern-day Balayan Bay. The early eruptions also created an island that sits near the center of Taal Lake, called Volcano Island.

Volcano Island is an island within a lake on an island in the sea. But Volcano Island also has a lake, known as Main Crater Lake, which contains its own island, called Vulcan Point. According to UNESCO, this unusual geology, shaped by early volcanic events and subsequent eruptions, is essentially "an island within a lake, within an island within a lake, within an island." The description refers to Vulcan Point, Main Crater Lake, Volcano Island, Taal Lake and Luzon, respectively.

Taal Lake was initially a marine lake, filled with salt water from the West Philippine Sea. That changed after a massive eruption at the Taal volcano in 1754, which dumped so much material into the Pansipit River that the lake was cut off from the sea, according to UNESCO. Taal Lake turned into a catchment area for rainwater and gradually transformed into a freshwater lake, according to the University of the Philippines.

Related: Kawah Ijen: The volcano in Indonesia that holds the world's largest acidic lake at its heart

Species that were trapped in the lake after the 1754 eruption adapted to the freshwater conditions or evolved into new species, according to UNESCO. For example, Taal Lake is home to the only known freshwater sardine in the world (Sardinella tawilis) and gave rise to the Taal Lake snake (Hydrophis semperi), a venomous sea snake not found elsewhere on Earth.

"The transition of Taal Lake from a saltwater to a freshwater environment — in a relatively recent occurrence in the scale of geological processes — fuels the continuous evolution of flora and fauna and presents opportunities for ongoing scientific discoveries," UNESCO states on its website.

Researchers have documented 38 eruptions at Taal volcano over the past 450 years. The most recent eruption occurred in 2020 after 43 years of quiet, prompting evacuations of the surrounding towns and covering Volcano Island and neighboring areas in ash.

With its current geology, Taal Lake is the third largest lake in the Philippines. It is protected as part of the Taal Volcano Protected Landscape, but the ecosystem is threatened by overfishing, tourism and water extraction for irrigation, according to the World Lake Database.

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Lake Natron has a chemical makeup that is so harsh, it is uninhabitable for most creatures. It is a "soda" lake, meaning it has high levels of dissolved sodium and carbonate. Due to this high concentration of salts and minerals, the lake's pH can reach 10.5, which is almost as caustic as ammonia solution — and animals that die on the shores of Lake Natron are preserved as calcified mummies as a result.

Lake Natron sits along the East African Rift System, a divergent tectonic plate boundary that is tearing apart the African Plate. This geology means that Lake Natron is shaped by volcanic processes, which produce large amounts of sodium carbonate and calcium carbonate. These salts and other minerals trickle down into the lake from surrounding hills and enter the water from below via hot springs, Live Science previously reported. The lake does not drain into any river or sea, so the chemical concentration stays high year-round.

Few animals can survive a salt level and pH as high as Lake Natron's, and the water can severely burn the skin and eyes of creatures that try to take a sip or dip. But animals that have adapted to the conditions, including lesser flamingos (Phoeniconaias minor) and tilapia, thrive in and around the lake.

In fact, Lake Natron is the world's most important breeding site for lesser flamingos, with most of East Africa's 1.5 million to 2.5 million lesser flamingos — which represent around 75% of the global population of the species — hatching at the lake, according to the Tanzania Wildlife Management Authority. Lesser flamingos' legs have tough skin and scales that prevent burns from the water. These birds build nests on islands that form in the lake during the dry season, Live Science previously reported, and their babies are safe from most predators thanks to the deadly conditions.

Related: Kilimanjaro's giant groundsels: The strange plants that thrive on Africa's tallest mountain

In addition to being extremely alkaline, Lake Natron is so shallow that its water temperature can reach a scalding 140 degrees Fahrenheit (60 degrees Celsius) during the hottest times of the year, according to NASA's Earth Observatory. The lake is 1.6 feet (0.5 meters) deep and 9 miles (15 kilometers) wide, but it shrinks and expands depending on the weather, with less rainfall and river input during the dry season leading it to contract (and vice versa).

When the lake shrinks, microorganisms that feast on its salts multiply. Haloarchaea (salt-loving organisms that lack a nucleus) and cyanobacteria (blue-green algae) can color the lake different shades of red thanks to pigments in their cells. The same pigments give lesser flamingos their pink hue, according to NASA's Earth Observatory, because these flamingos almost exclusively eat blue-green algae.

Lake Natron made headlines in 2013, when photographer Nick Brandt's images of "stone" animals on the lake's shores were published in the book "Across the Ravaged Land" (Abrams Books, 2013). The pictures showed carcasses of birds and bats that had died on the shores of the lake and were preserved by its sodium carbonate. Brandt positioned them on branches and on the water to look "alive again in death," he wrote in the book.

"I unexpectedly found the creatures — all manner of birds and bats — washed up along the shoreline of Lake Natron," Brandt wrote. "No one knows for certain exactly how they die."

Birds pictured in the book include a dove and a fish eagle. These birds do not feed and breed at Lake Natron, but they live in the salt marshes and freshwater wetlands that make up the surrounding landscape. These ecosystems also host greater flamingos, pelicans, ostriches, buffalo, wildebeest and many other creatures, according to the Tanzania Wildlife Management Authority.

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On the middle-altitude slopes of Mount Kilimanjaro grows a strange plant not found anywhere else on Earth. The giant groundsel, a plant that looks like a pineapple crossed with a saguaro cactus, colonized the flanks of Africa's tallest mountain up to 1 million years ago and has not budged since.

Kilimanjaro's giant groundsels (Dendrosenecio kilimanjari) grow at altitudes of between 9,200 and 13,100 feet (2,800 to 4,000 meters), where they get just enough rainfall to survive, according to the tour operator Tranquil Kilimanjaro. The plants have evolved adaptations to the harsh conditions on the mountain, including water storage systems and a protective jacket of dead leaves.

Located in northeast Tanzania, the base of Mount Kilimanjaro is hot and humid, but temperatures at the summit, which is 19,340 feet (5,895 m) above sea level, can drop to minus 20 degrees Fahrenheit (minus 29 degrees Celsius). The mountain "creates its own weather," according to the tour operator Climbing Kilimanjaro, with baking sunshine, snow, rain and bitter winds all possible at different altitudes at any time of the year.

Giant groundsels have evolved to cope with this variable climate. Their thick stems are topped with a crown of sturdy leaves covered in hairs that limit how much water escapes the plant by evaporation. Both the stem and the leaves store water for when the climate is dry, usually from December to March and June to October.

The plants are also well equipped to survive a wide range of temperatures. When their leaves die, they fold over the stem and create a thick layer of insulation against the cold. Additionally, giant groundsels ooze “antifreeze” substances that enable the plants to grow above the tree line.

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Most giant groundsels aren't much taller than a human, but some can reach 20 to 30 feet (6 to 9 m) tall. Their vertical growth is another adaptation to the conditions on Mount Kilimanjaro, as the plants receive more sunlight the higher they grow, according to the tour operator Altezza Travel.

However, growth takes time. Giant groundsels grow by 1 to 2 inches (2.5 to 5 centimeters) per year, according to tour operators, meaning that the tallest specimens may be at least 100 years old.

According to a genetic study by botanists, published in the journal PNAS, groundsels colonized Kilimanjaro within the past 1 million years and giant groundsels evolved as certain species adapted to the hostile conditions and migrated up the mountain.

Giant groundsels are pollinated by insects, which visit the plants' yellow flowers. After pollination, the flowers turn into fluffy seed heads, and these are carried by the wind to new locations.

Giant groundsels are found on Mount Kilimanjaro's Shira plateau and in the area around Barranco Camp, according to the Kilimanjaro National Park website. The best walking trails to see the plants are the Northern Circuit, the Lemosho route and the Machame route, according to tour operators.

Hikers should be careful not to touch or damage giant groundsels, which provide food and shelter for birds and small mammals. The plants' deep roots also help stabilize the soil, slowing the rate of erosion on Kilimanjaro, according to Tranquil Kilimanjaro.

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North America's "broken heart" is an ancient rift valley in the Midwestern United States. The rifting began roughly 1.1 billion years ago due to tectonic forces pulling what is now the North American continent in opposite directions. Evidence suggests the rifting process stalled about 100,000 years after it began, but scientists aren't sure why.

The rift valley is shaped like a horseshoe, stretching from Kansas north to Lake Superior and south again to Michigan, according to maps from a 2013 article in Nature — although some evidence suggests the rift might extend farther south. Geologists estimate that the rift once measured around 1,900 miles (3,000 kilometers) long and created a basin as wide as the Red Sea, but most of the structure is now buried beneath a thick layer of sediment, according to the National Park Service (NPS).

The only parts of the rift that are visible today are near Lake Superior, where huge blocks of basalt and other rift-related rocks are exposed, according to the NPS. Basalt is a dark, fine-grained — and, therefore, dense — rock formed from rapidly cooling lava. As Earth's crust was ripped apart during the rifting process, magma rose to fill the crack, creating a belt of solidified lava and magma in the valley.

The rift likely opened in what is now the Midwest because Earth's crust was already fragile there — a large blob of magma may have weakened the surface and sealed the region's fate, according to the NPS. As the rifting progressed, molten rock rose and triggered volcanic eruptions, depositing huge amounts of dense material, such as basalt, that caused the rift valley to sink into the crust.

A "spectacular failure"

For reasons that scientists debate, rifting and the eruptions stopped, so sediment settled on top of the volcanic material. But the rift valley didn't stop sinking, because the weight of the sediment pushed the structure deeper into the crust.

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Rifting was followed by a period of compression, in which chunks of crust on each side of the rift valley were squished together. This pushed up the volcanic material and sediment, according to the NPS, exposing sections of the rift valley that were then covered up by sediment.

The cyclical growth and melting of glaciers over the past 2.5 million years removed some of that sediment, which is why parts of the rift are still visible. Near Lake Superior — particularly on northern Michigan's Keweenaw Peninsula — basalt and copper-rich rocks emerged. People have mined this copper for at least 8,000 years — and although the mines closed in the late 20th century, the industry is now seeing a revival.

Why the rifting ended after 100,000 years remains somewhat unclear.

"It's a spectacular failure," G. Randy Keller, a professor emeritus of geophysics at the University of Oklahoma and the director of the Oklahoma Geological Survey, said in the 2013 Nature article. "How that feature could just totally reorganize the crust of the Earth in the Lake Superior region and not manage to break the continent apart is fairly amazing."

Geologists have been exploring this question for more than a decade, with some scientists linking the failure to a mountain-building episode along North America's Atlantic coast. Other researchers reject this theory, proposing instead that the rifting ended when a sea opened between Laurentia and Amazonia — the geologic cores of North and South America.

Meanwhile, sections of the rift valley in Kansas have attracted attention from resource exploration companies. Basalt can react with water to make hydrogen, which is a source of clean energy and an ingredient in key chemicals, Live Science previously reported.

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Jellyfish Lake is a pool of saltwater on Eil Malk island in Palau that is brimming with golden jellyfish — a subspecies not found anywhere else on Earth. The lake typically houses around 5 million jellyfish, according to the Coral Reef Research Foundation (CRRF) — although there have been years, including 2005, when the number of jellies exceeded 30 million.

Jellyfish Lake is highly stratified, meaning it is separated into distinct layers. Golden jellyfish inhabit the top layer, which extends from the surface down to about 43 feet (13 meters) deep. Between 43 and 50 feet (13 to 15 m) deep, the lake contains pink bacteria that prevents light and oxygen from reaching the bottom layer of the lake, which sits between 50 and 100 feet (15 to 30 m) deep.

The lake is connected to the ocean through small cracks in Eil Malk's limestone rock, but it is nevertheless considered an isolated ecosystem, according to CRRF learning resources. Jellyfish Lake formed toward the end of the last ice age, roughly 12,000 years ago, due to ice melt and sea level rise. Sea water filled depressions in Palau's islands and elsewhere, creating three types of lakes: stratified lakes, such as Jellyfish Lake; mixed lakes, which are connected to the ocean via large tunnels; and transitional lakes, which are also connected to the ocean, but via smaller tunnels.

Related: 'A challenge and an opportunity for evolution': The extreme, hidden life thriving in Earth's most acidic and alkaline lakes

Jellyfish Lake's pink layer exists because the conditions in that layer suit a type of bacteria that are pink in color. These bacteria create a barrier between the lake's oxygenated top layer and its oxygen-free bottom layer. This barrier bobs up and down depending on density changes in the water.

The lack of oxygen beneath the pink layer is deadly for most life. What's more, plant and animal decomposition at the bottom of Jellyfish Lake releases poisonous hydrogen sulfide gas, which means only certain microbes can survive there, according to the CRRF.

Jellyfish Lake's endemic golden jellyfish (Mastigias papua etpisoni) population likely evolved from a handful of spotted jellyfish (Mastigias papua) that became trapped when sea levels dropped following the lake's formation. Unique conditions inside the lake forced the jellies to adapt, leading to a new subspecies, which is named after Palau's former president, Ngiratkel Etpison.

Golden jellyfish have a symbiotic relationship with single-celled, photosynthetic algae that give them nutrients in exchange for a place to live. The jellyfish follow an unusual migration pattern that involves swimming towards the sun as it rises and sets, always avoiding the lake's edges where jellyfish-eating sea anemones (Entacmaea medusivora) lurk. These predatory anemones prefer the shadows, so golden jellyfish have evolved to stay in sunlit waters. Every morning, the jellies crowd along the lake's eastern shadow line, and visitors may occasionally see a "wall" of jellyfish forming underwater, according to the CRRF.

While golden jellyfish have stinging cells, the sting is so mild that humans can't feel it. Visitors can safely swim in Jellyfish Lake, but people should take care not to accidentally introduce non-native species to the lake, as these can, and already do, endanger the fragile ecosystem, according to the CRRF.

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Cerro El Cono is a 1,310-foot-tall (400 meters), pyramid-like formation in the Amazon rainforest. It rises steeply from the relatively flat jungle landscape of eastern Peru, making it visible from as far west as the Andes — 250 miles (400 kilometers) away — on a clear day.

The formation, whose name translates to "cone hill," is located in a mountainous region on the border between Peru and Brazil known as the Sierra del Divisor. The mountains are visible in the background of most photographs of Cerro El Cono, but the formation is isolated from the other peaks and has an unusual pyramidal shape, making it stand out from the rest of the mountain range.

The origins of the strange peak have remained mysterious due to its remote location. While some sources suggest that the cone could be an extinct volcano, others say it might simply be an unusual rock formation.

Related: Mount Roraima: The 'lost world' isolated for millions of years that Indigenous people call the 'house of the gods'

Indigenous people have another explanation for the bizarre mountain: According to the Peruvian newspaper La República, Cerro El Cono is a spiritual entity for local tribes and groups, some of which revere the peak as an "Andean Apu" — a sacred mountain god or spirit. In the mythologies of Peru, Bolivia and Ecuador, Apus emerged from Earth to guide and protect the people living close by.

A fourth explanation — one for which there is no evidence — is that Cerro El Cono sits on the ruins of a pyramid built by ancient Indigenous tribes, according to La República.

Cerro El Cono stands adjacent to the Ucayali River, which is a major tributary of the Amazon River. The surrounding jungle is a biodiversity hotspot and home to several vulnerable species, including giant armadillos (Priodontes maximus), jaguars (Panthera onca) and various types of monkeys, according to The Guardian. The peak itself is forested and forms part of a large area that has been considered a biodiversity conservation priority since the 1990s.

Concern that this ecosystem may become degraded by infrastructure, illegal logging and gold mining prompted the creation of the Sierra del Divisor National Park in 2015. But recent surveys indicate that the protected park, which is 1.5 times the size of Yellowstone National Park, has not removed threats from illegal deforestation and wildlife poaching.

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The Corryvreckan whirlpool is a fierce, circular current between the Scottish isles of Jura and Scarba. Nicknamed the "raging cauldron," it almost killed George Orwell and his son Richard in 1947.

The whirlpool is named after the Gulf of Corryvreckan, which, according to tradition, is named after the Norse king Breckan. Legend has it that Breckan anchored his boat in the whirlpool for three days to prove his valor to a Scottish chief whose daughter he wanted to marry. The Norse king used three ropes to anchor his vessel — one woven from hemp, another from wool, and a third from the hair of virgins — but they snapped, drowning him. According to the legend, the virgins' hair should have kept Breckan safe, but one of the women had been unchaste.

"Corry" in "Corryvreckan" is derived from the Gaelic word for cauldron "coire," so the full name means "the cauldron of Breckan."

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The Corryvreckan whirlpool is one of the largest whirlpools in the world. (Others include Saltstraumen in Norway, Old Sow in Canada, and Naruto in Japan.)

The whirlpool is caused by ocean currents that skirt the east and west coasts of Jura before meeting off the island's northernmost tip, in the Gulf of Corryvreckan. The gulf acts like a funnel, forcing waters into the narrow strait between Jura and Scarba and increasing their speed to 8.5 knots (10 mph or 16 km/h), according to the Universities Space Research Association (USRA).

A huge hole in the gulf's eastern end and an underwater basalt-rock pillar directly off Scarba then create a swirling motion by pushing water down and then up. The hole is 720 feet (220 meters) deep, according to the USRA. The pillar — known as the "Old Hag" due to folkloric tales of a witch living there — rises from a depth of 230 feet below the surface to 95 feet below the surface (70 to 29 m).

The whirlpool, located above the Old Hag, is sometimes so strong that its roar can be heard 10 miles (16 km) away, according to BBC Glasgow and West Scotland. Waves can reach up to 30 feet (9 m) high, making the Gulf of Corryvreckan one of the most dangerous passages around the British Isles.

Indeed, Orwell and his son nearly drowned during a boat trip around Jura in 1947. They were living on the island while Orwell wrote his famous novel "1984" and wouldn't have made it back if fishers hadn't saved them from the whirlpool, according to the BBC.

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Iran's folded rocks are rugged mountain ridges and valleys to the southwest of the Caspian Sea. They are an extension of the Greater Caucasus mountain belt, which also stretches along Russia's border with Georgia and Azerbaijan.

The folded rocks sit at the intersection of Asia and Europe, where major tectonic forces converge. The rocks are formed of countless sedimentary layers, which were upturned and creased into the landscape we see today during the initial collision between the Arabian and Eurasian tectonic plates. The timing of this collision is hotly debated, with estimates ranging from 10 million to 50 million years ago.

"A tectonic collision between Eurasia and Arabia over millions of years compressed these colorful rock layers, bending them into large folds," NASA officials wrote on the social platform X in January 2024.

The Arabian and Eurasian plates are still converging, and recent research indicates a chunk of oceanic crust that separated the two plates before they collided is now being torn apart under Iraq and Iran. The Neotethys oceanic plate appears to be pulling the region down from below, resulting in an unusual accumulation of sediment at the surface.

Related: North America is 'dripping' down into Earth's mantle, scientists discover

Iran's folded rocks are colorful, with vibrant terracotta, greenish and blueish bands that are the result of different sedimentary layers deposited over time. These layers were eroded over millions of years after the initial tectonic collision, exposing the underlying rocks' alternating colors and textures.

Satellite images of the folded rocks reveal the extent to which the landscape was bunched together over the eons. Scientists at NASA's Jet Propulsion Laboratory colored one such image with infrared to show the various rock layers, as well as vegetation and the human-built Zanjan-Tabriz freeway, which cuts through the folded rocks and connects the cities of Tehran and Tabriz.

Another satellite image from NASA's Earth Observatory highlights the intricacy of Earth's surface in this region and shows the Qezel Ozan River, which hugs the southeast corner of the folded rocks and supplies water for agriculture in the area.

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The Wilkes Land crater is a hole in the bedrock beneath East Antarctica's ice sheet measuring 315 miles (510 kilometers) across. Researchers have been trying to explain its existence since the 1960s, and the most recent evidence suggests it was born from a cataclysmic meteorite impact.

The crater was first detected as a huge dent in Earth's gravitational field. Initial ground-based seismic and gravity surveys already indicated that the crater was huge — around 150 miles (240 km) across — but newer techniques reveal that it is likely more than double this size.

According to a 2018 study, the Wilkes Land crater sits about 1 mile (1.6 km) beneath the surface of Antarctica's ice sheet. The study showed the crater in more detail than ever before and examined its potential link with southern Australia, which was connected to East Antarctica until around 35 million years ago. While the origin of the crater remains uncertain, the results of the study suggest the event that created the hole likely occurred before the continents separated.

Researchers have proposed several explanations for the Wilkes Land crater, including that it could be a volcanic structure, a sedimentary basin, a deeply eroded valley or a meteor impact crater, according to a 2015 paper. For that paper, scientists used satellite remote sensing techniques to map the crater and determine its physical characteristics. In the middle of the hole in Earth's gravitational field, known as a negative gravity anomaly, they found a positive gravity anomaly, with the ice sheet filling the gap around this central peak like a huge, frosty donut.

Related: Scientists create new map showing ice-free Antarctica in more detail than ever before

The central peak is likely a structure known as a mass concentration, or a "mascon," according to the study. Mascons can occur within meteor impact structures due to the meteor crashing through Earth's crust and affecting the mantle beneath. Following the impact, the mantle may recoil and form a dense plug, resulting in a positive gravity anomaly, the study authors wrote.

The Wilkes Land crater and its mascon aren't perfectly circular and instead form a U-shape, according to the 2018 study, whose results support the conclusion that the crater was caused by a meteor impact. The northern side of the crater is fragmented, perhaps as a result of tectonic processes that ripped Australia and Antarctica apart, the authors noted. Parts of the crater are clearly visible in southern Australia, they added.

If the Wilkes Land crater is an impact crater, then it "would be the greatest impact crater known" on Earth in terms of its size, the authors wrote.

In the 2015 study, researchers found that the crater's diameter matches the speed and size of space rocks that regularly crashed into Earth during its early history between 4.1 billion and 3.8 billion years ago. "The WLA [Wilkes Land Anomaly] could have been created by such bolides," they wrote in the study.

"Nonetheless, because of the constraints imposed by the overlying continental ice sheet, [...], we believe that the other explanations for the subglacial structure remain viable," they added.

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

As the name suggests, China's Rainbow Mountains are multicolored formations in the northwest of the country. The landscape in this region is otherworldly, with vibrant bands that look like they were spray-painted onto the rocks.

The Rainbow Mountains are located in the foothills of the rugged Qilian mountains and likely formed around the same time as the Himalayas, approximately 50 million years ago, according to NASA's Earth Observatory. Land that was once relatively flat was scrunched up and folded into jagged terrain when the Indian tectonic plate collided with the Eurasian plate. This was because these plates have a similar rock density, so neither could slip beneath the other to form a subduction zone, according to the U.S. Geological Survey (USGS).

But the basis for the mountains' rainbow pattern was laid long before the epic collision.

Related: Massive tectonic collision causing Himalayas to grow may also be splitting Tibet apart

The Rainbow Mountains are made of sandstone and siltstone — sedimentary rocks that form when sand and silt, respectively, are compacted and cemented together over long periods of time. These rocks — with their bands of different colors — were deposited before the Himalayas formed.

The colorful bands are the result of iron and other trace minerals in the stone. Each band has a different composition that determines its pigment. For example, the deep red stripes are rich in iron oxides, the yellow layers contain abundant iron sulfide and the green bands hold more chlorite and iron silicates, according to a 2016 article in Forbes.

Iron and other minerals accumulated in the rock while the sand and silt grains were still cementing together. Groundwater circulating in the pore space between the grains deposited the minerals, coating each grain and further gluing the rocks together.

The slanted bands we see on the flanks of the Rainbow Mountains today are upturned layers that would have remained buried and horizontal had the Indian and Eurasian plates not smashed into each other. The bunching of the land by plate tectonics was followed by intense erosion, which wiped away any sediment covering the colorful layers. Luckily for modern visitors, there is no vegetation to obscure the striking rainbow pattern.

The Rainbow Mountains are a popular tourist attraction. They are protected as part of the Zhangye Danxia National Geopark, but visitors can climb to the top of the hills and admire the view using wooden stairs and platforms.

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Lake Salda is a body of water in Turkey that bears a strong resemblance to Mars' Jezero crater. The stunning lake is the only place on Earth with geology and mineralogy comparable to those of the ancient impact structure on the Red Planet. This striking similarity meant scientists flocked to study its shores before the Perseverance rover landed on Mars in 2021.

Lake Salda is one of Turkey's deepest lakes, with a maximum depth of 643 feet (196 meters). Its shores are covered in powdered hydromagnesite, a carbonate mineral that's rich in magnesium and is found in caves and on the shores of certain lakes. Notably, this mineral holds clues about ancient microbial life.

"Carbonates are important because they are really good at trapping anything that existed within that environment, such as microbes, organics, or certain textures that provide evidence of past microbial life," Brad Garczynski, a researcher in planetary geology at Western Washington University, told NASA's Earth Observatory.

Related: NASA Mars rover finds 'first compelling detection' of potential fossilized life on the Red Planet

The hydromagnesite on Lake Salda's shores likely eroded from microbialites, which are rock-like mounds that look similar to coral reefs but are made of microbes. The lake still hosts intact microbialites, but these will eventually be reworked and end up as sand on the shoreline, according to NASA's Earth Observatory.

Using data from NASA's Mars Reconnaissance Orbiter, scientists detected similar minerals along Jezero's western edge in 2019, suggesting the crater once held a lake. These observations have since been confirmed by the Perseverance rover, which found mineral evidence of a lake that existed inside Jezero crater billions of years ago.

Lake Salda and Jezero crater have something else in common: depositional features known as deltas. Deltas are layers of sediment that accumulate in places where rivers flow into lakes and other bodies of water. The features offer tantalizing clues about how water came to fill Jezero, and studying them in Lake Salda has helped scientists narrow down their search to specific locations in the Martian crater.

"One of the great things about visiting Lake Salda is it really gives you a sense of what it would have been like to stand on the shores of ancient Lake Jezero," Horgan said.

The area around Lake Salda is home to more than 300 plant species and 30 waterfowl species, making it a popular destination for nature enthusiasts and hikers, according to CNN. The lake is only a short drive from the Pamukkale travertines — stunning limestone formations with thermal pools.

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The Drake Passage is an ocean channel between the southern tip of South America and the West Antarctic Peninsula. Named after the 16th-century explorer Sir Francis Drake, it is notorious for whipping up wild storms and monster waves up to 80 feet (25 meters) tall.

The passage is "the most dreaded bit of ocean on the globe," Alfred Lansing wrote in his 1959 book "Endurance: Shackleton's Incredible Voyage to the Antarctic." At around 600 miles (965 kilometers) wide, the channel is relatively narrow compared with the ocean around it, meaning currents speed up as they are forced through the passage. The same goes for southern winds, which blow unimpeded from west to east around Antarctica before they reach the Drake Passage.

As winds funnel through the passage, they whisk up huge waves, some of which can be dangerous — and even deadly — for passengers on boats making the 48-hour-long crossing. In the best case, the waves make for a bumpy ride, known as the "Drake shake."

"It's always interesting when you go to dinner and they put sticky mats on all the tables to make sure your plates and things don't slide around," Karen Heywood, a professor of physical oceanography at the University of East Anglia in the U.K. who sailed through the Drake Passage in 2024, told National Geographic.

Related: Mount Washington: Home to 'the world's worst weather' with record wind speeds of 231 mph

The Drake Passage is a "melting pot" of currents from the Atlantic, Pacific and Southern oceans, Heywood said. The waters are so turbulent that the layers which normally make up the seas mix together, meaning the passage draws a lot more carbon down into its depths than other parts of the ocean do.

The world's oceans lock away more than 30% of the carbon humans emit into the atmosphere every year, and the Drake Passage could be one of a handful of places where this activity is particularly pronounced, National Geographic reported.

The passage also keeps Antarctica cold, because it cuts off warm air that would otherwise blow south from South America. Research suggests that when the Drake Passage opened between 49 million and 17 million years ago, it triggered significant cooling in Antarctica and contributed to the growth of giant ice sheets on the continent.

The temperature drop as you traverse the passage is noticeable even for people on ships, Alberto Naveira Garabato, a professor of physical oceanography at the University of Southampton in the U.K., told National Geographic. "Suddenly you are in this icy world," Naveira Garabato said.

So, while extreme winds and currents inside the passage create terrifying conditions for passengers, they also help to maintain Antarctica's frigid climate — although climate change is slowing the system.

Were it not for the Drake Passage and its wild weather, the frozen continent would likely hold much less ice than it currently does.

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Mount Washington is the tallest peak in the Northeast. The mountain is famous for attracting extreme weather, with winds that exceed the force of a hurricane more than 100 days per year.

The mountain is home to "the world's worst weather" for three main reasons. Firstly, at 6,288 feet (1,917 meters) tall, it is the highest mountain in New England. Winds pick up speed when they can blow unobstructed, and the mountain is directly exposed to winds from the west that travel for hundreds of miles without obstruction. The closest mountains of a similar height to Mount Washington along this westerly windpath are the Black Hills of South Dakota about 1,600 miles (2,500 kilometers) away, according to the Mount Washington Observatory.

Not only do these winds hit Mount Washington at full speed but they are also siphoned toward the peak by the surrounding landscape. The mountains to the west of Mount Washington form a 75-mile-wide (120 km) funnel that channels westerly winds toward the mountain, accelerating already-fast winds until they reach breakneck speeds, according to the observatory.

Finally, Mount Washington sits on the confluence of three major storm tracks. Storms hit the summit every three days on average in the winter, bringing high winds and huge amounts of precipitation, according to the observatory. Record levels of precipitation for Mount Washington were measured in 1969, when 4.1 feet (1.3 m) of snow fell within 24 hours.

Related: Record spike in earthquakes at Washington's 'high threat' volcano sends researchers scrambling for answers

As a result of its unique position, Mount Washington is a contender for the world's fastest recorded wind speed. On "calm" summer days, instruments on Mount Washington's summit record wind speeds of 40 mph (65 km/h). But when storms roll in, these winds can whip up gusts exceeding 100 mph (160 km/h).

On April 12, 1934, instruments at the summit measured a record wind speed of 231 mph (372 km/h), which is equivalent to wind speeds inside a level-5 tornado on the Enhanced Fujita Scale. Such winds have the power to level well-constructed buildings, blow away structures with weak foundations and throw cars over large distances. The record still stands today as the second-fastest natural wind gust ever recorded, with the fastest occurring on Barrow Island in Australia on April 10, 1996 and reaching speeds of 253 mph (407 km/h).

Even wind speeds of 100 mph can rip huge chunks of ice off the mountain and the Mount Washington Observatory building at the summit, which poses a severe risk for hikers and climbers in the winter. The observatory has bulletproof windows to mitigate the risk of one of these chunks smashing into the building, according to its website.

As well as flying ice, people climbing Mount Washington in the winter are faced with the risk of avalanches, hypothermia and frostbite. Temperatures on the mountain average 27.1 degrees Fahrenheit (minus 2.7 degrees Celsius), which can create extreme wind chill conditions, according to New Hampshire State Parks.

Several rescue teams monitor Mount Washington, and volunteers regularly save the lives of hikers who get lost or caught out by changing weather conditions.

Mount Roraima is a plateau with near-vertical sides that sits on the triple border point between Brazil, Venezuela and Guyana. The plateau is often encircled by a ring of clouds, which makes the summit look like an island floating in the sky.

The mountain towers 9,219 feet (2,810 meters) above the surrounding savanna, jutting out like a giant tabletop. Geologists call this kind of formation a "tepui," which means "house of the gods" in the language of the Pemon, the local Indigenous people. The Pemon believe tepuis to be sacred, and that Mount Roraima is the stump of a supernatural tree that held all the fruit and vegetables of the world until a mythical figure named Makunaima felled it, according to the International Business Times.

But scientists have another explanation for how Mount Roraima came to be. Tepuis are exclusively found in South America, and specifically in Venezuela and western Guyana, where they number more than 100. According to the Geological Society of London, tepuis are the remnants of a huge block of sandstone that formed in this region around 1.8 billion years ago as large sand dunes slowly solidified into rock.

Over the next 1.5 billion years, other types of rock accumulated on top of the sandstone, but these layers were eroded away roughly 180 million years ago, according to the Geological Society. Wind and water then went to work on the sandstone, carving out the giant, steep-sided plateaus we see today, according to Geology Science. Finally, geologic uplift raised the plateaus to their current height, according to Geology Science.

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Like other tepuis, Mount Roraima's summit harbors a "lost world" ecosystem that has been sheltered from the surrounding region for about 70 million to 90 million years, according to a 2012 study.

Much remains unknown about the way that tepui ecosystems have assembled and evolved, but researchers estimate that a high proportion of the flora and fauna on the summits are endemic, meaning that they aren't found elsewhere. For example, about one-third of the vegetation found at the top of all tepuis, including carnivorous plants and orchids, is endemic, according to the World Wildlife Fund.

However, the 2012 study found that these ecosystems aren't completely isolated. The researchers analyzed the DNA of four tree frog species living on separate tepuis to determine whether these species have had any contact with each other in the past 70 million years. The scientists discovered that the frogs shared a common ancestor as recently as 5.3 million years ago, suggesting that tree frogs — and perhaps other creatures as well — can migrate up and down the cliffs of tepui formations.

Rare nectar-sucking birds and other unusual creatures, such as the Roraima black frog (Oreophrynella quelchii), thrive at the top of Mount Roraima thanks to pools of crystal-clear water and streams that feed waterfalls down the tepui's sides. These cascades are fed by rainwater and include the Crystal Valley Falls and Triple Point Falls.

Mount Roraima's summit and its incredible views are accessible to tourists, but ascending to the top requires a multi-day trek through challenging terrain, according to Geology Science.

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Walvis Bay is a port city on the Atlantic coast of Namibia that is home to an enormous sea salt production plant. The plant has been operating for more than 60 years thanks to the region's arid climate and coastal winds, which are ideal for evaporating seawater containing the salt.

The saltworks are located about 5 miles (8 kilometers) southwest of Walvis Bay city center. The plant covers an area of 12,350 acres (5,000 hectares), according to Walvis Bay Salt Holdings, making it roughly half as big as Disney World in Florida.

Salt production at Walvis Bay relies on Atlantic seawater that is pumped at a rate of 8,500 cubic feet (240 cubic meters) per minute into artificial ponds, according to the guided tour operator Desert, Dunes and Dust Tours. The plant is fed by the Benguela Current — a cold, northward flowing ocean current that forms the eastern limb of the South Atlantic subtropical gyre.

Evaporation via a combination of the sun's warmth and wind increases the salt content in the ponds from about 2.9% to 3.5%, which is still liveable for plankton, algae and small ocean critters. These creatures and microorganisms can turn the ponds so colorful, the plant looks like a tile mosaic from above.

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Pumps transfer the brine resulting from this initial evaporation stage to concentration ponds, where the salt content rises to 25%. Another set of pumps then siphons this water into crystallization ponds that each span about 50 acres (20 hectares) in size, or about 38 football fields.

By the end of the crystallization stage, each pond contains a 4- to 6-inch-thick (10 to 15 centimeters) salt crust, which mechanical harvesters remove and dump into huge bins. A conveyor belt then takes these bins to a facility where the salt crystals are washed with a mixture of seawater and gypsum that dissolves impurities such as magnesium and potassium, while keeping the salt intact.

After washing, the salt is dried in huge piles outside. Around 240 tons (220 metric tons) of salt are washed and dried every hour at Walvis Bay, amounting to a total annual production of more than 1.1 million tons (1 million metric tons) of salt, according to Walvis Bay Salt Holdings.

The company exports chemical-grade salt used in industries like animal feed production, water treatment and pharmaceuticals to Nigeria, Cameroon, South Africa and Europe. It also exports table salt for human consumption to several countries in Africa, including South Africa, Angola and the Democratic Republic of Congo.

Walvis Bay's saltworks are also a feeding ground for shrimp and larval fish, which in turn attracts birds. Together with the nearby Walvis Bay Lagoon and a bird sanctuary, the salt production plant provides coastal wetland habitat for birds like flamingos and pelicans, according to the website Birdingplaces.

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The Savonoski Crater is a round hole in southwestern Alaska that scientists have long struggled to explain due to a lack of geological evidence. However, there is a scientific explanation for this lack of evidence, so we can confidently say that the hole is neither supernatural nor an alien creation.

The crater measures roughly 1,600 feet (500 meters) across and 360 feet (110 m) deep, according to a 1978 article published on the University of Alaska Fairbanks' website. It is half-filled with water from rainfall and snow melt.

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From the air, the Savonoski Crater looks like it could have been created by a meteorite impact. Impact craters are typically circular and deep, so Savonoski fits the bill — but geologists have yet to find proof of a space rock hitting Earth in this location.

Extensive surveys in the 1960s and 1970s failed to find evidence of meteoritic material or any shocked rocks within the crater that would have confirmed an impact-related origin. Researchers also failed to find any rock fragments around the crater to indicate that a meteorite sprayed material away from its landing spot.

Alternatively, the crater could be a volcanic maar — a depression formed when magma rises from deep inside Earth's crust and reaches the water table. The intruding magma brings the water to a boil, and the resulting steam builds up so much pressure underground that it eventually triggers an explosion.

Volcanic maars often leave broad craters that fill up with groundwater. For example, the 330-foot-deep (100 m) eastern Ukinrek maar in Alaska formed during a 10-day-long eruption in 1977 and has since partially filled with water, according to the U.S. Geological Survey.

However, there are no known volcanic landforms in the immediate vicinity of Savonoski Crater and no signs of a magma source beneath the hole, according to the surveys from the 1960s and 1970s. A potential volcanic origin for the crater therefore remains mysterious.

Scientists agree that the Savonoski Crater is either a meteorite impact crater or a volcanic maar, but a definitive answer will only come with much more extensive research, according to the surveys.

The crater has undergone at least one glaciation event since it formed, meaning it was swallowed by an ice sheet when glaciers last covered southwestern Alaska between 23,000 and 14,700 years ago. This glaciation swept away any obvious evidence of the crater's origin, according to the University of Alaska Fairbanks — but clues may still be hidden inside the crater, should scientists decide to drill into its center, researchers noted in the surveys.

Editor's Note: This article was updated Feb. 24 at 6:25 a.m. ET to correct the coordinates of the Savonoski Crater. The previously published coordinates were those of a volcanic crater lake near Mount Katmai.

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Lake Vostok is a giant lake in Antarctica that is similar in size to North America's Lake Ontario. But unlike Lake Ontario, Lake Vostok sits beneath more than 2 miles (3 kilometers) of wind-blown snow and ice.

Once an enormous surface lake, Lake Vostok became buried at least 15 million years ago, with some estimates suggesting it has been continuously covered for much longer — 20 million years or more. As a result of being cut off from light and the atmosphere for so long, the lake harbors a unique ecosystem of extremophiles — creatures that have evolved to thrive in extreme conditions.

Related: Scientists peered into a secret Antarctic lake hidden beneath the ice — and uncovered a never-before-seen ecosystem

Lake Vostok is about 150 miles (240 km) long and 30 miles (50 km) wide. It is the biggest of Antarctica's more than 400 subglacial lakes, which are scattered across the continent because low levels of geothermal heat melt the base of the ice sheet.

The lake is located near Russia's Vostok research station, roughly 800 miles (1,300 km) from the South Pole. Although scientists have occupied Vostok since 1957, they had no idea the lake existed until the 1960s, when a Russian geographer and pilot first noticed the flat, relatively smooth expanse of ice above it from the air.

In 1993, researchers found the lake with satellite-based radar technology capable of penetrating the ice. And in 2012, Vostok scientists finally succeeded in a years-long effort to drill down to the lake through the ice.

Lake Vostok is about 0.6 miles (1 km) deep at its south end and comparatively shallower at its north and southwest corners. Researchers mapped the bottom of the lake and found that the deep and shallow areas are separated by a ridge, which they think might be peppered with hydrothermal vents similar to those in the Pacific Ocean.

The lake's only source of water is the ice sheet above it. The water temperature hovers around 27 degrees Fahrenheit (minus 3 degrees Celsius), but it remains liquid thanks to the crushing pressure of the overlying ice sheet, which lowers the freezing point of the water.

Countless species of microbes inhabit the lake, including marine lifeforms that suggest the water body was once connected to the ocean. Researchers sampled a layer of frozen water called accretion ice that sits on top of the lake and found it contains DNA from more than 3,500 organisms, including fungi and bacteria commonly found in the digestive tracts of fish.

Due to the lack of light blocking photosynthesis, these organisms have evolved to feast on minerals in the water and chemicals produced in the bedrock. Researchers think that further studying them could provide clues about life on other planets and moons, including Jupiter's icy moon Europa.

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Near a village in central Romania sits a cluster of rocks that can grow and reproduce as though they were living. These unusual rocks, known as trovants, simultaneously push out several "babies" that can drop off and mushroom on their own.

Trovants are found almost exclusively in Romania, specifically near the village of Costești, where they are protected by the Trovants Museum Natural Reserve. Rare geologic and mineral conditions that exist in central Romania (as well as in small parts of Russia, Turkey and the U.S.) are needed to form trovants, which are made of a hard stone core surrounded by a sandstone shell, according to the geology website Geology In.

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Trovants grow by about 2 inches (5 centimeters) every 1,000 years by adding to their sandstone shell, which is composed of chunks of rock cemented together with limestone. The shell is so porous, it can absorb minerals like calcium carbonate from rainwater. The shell then acts like a cement mixer, combining minerals with water to produce a substance that oozes from the rocks and adds to their circumference.

As a result of how they grow, trovants are often bulbous and smooth. Lumps can appear on existing trovants if rainwater consistently hits or drips onto one side of the rock, and these lumps may, over thousands of years, give rise to baby trovants. The weight of a baby trovant may cause it to break off from its parent rock, meaning trovants can multiply.

Trovants come in all shapes and sizes, ranging from a few inches to several feet across.

Geologists think trovants first originated in earthquakes more than 5 million years ago, according to BBC Science Focus. Seismic shocks may have compacted sandy sediments from an ancient aquatic environment into spherical rocks. This origin theory is bolstered by bivalve and gastropod fossils that researchers sometimes find inside Romania's trovants, according to the online magazine.

The rocks have inspired fantastical explanations, too. Romanian folklore abounds with tales of the origins of trovants, including a myth that the rocks are giant dinosaur eggs. Another wild theory suggests trovants are plant fossils, while others have proposed alien involvement, both of which, of course, are not true.

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Upheaval Dome is a rock formation in Utah with jagged peaks carved into concentric rings. Astronauts on board the International Space Station photographed the structure in 2007, sparking comparisons between the giant dome and a belly button.

Upheaval Dome stretches 3 miles (5 kilometers) across and 1,000 feet (300 meters) high. Its origin remains somewhat controversial, but the presence of shocked quartz crystals at the site suggests the dome mushroomed after a meteorite smashed into Earth 60 million years ago.

Related: 'Alien plant' fossil discovered near Utah ghost town doesn't belong to any known plant families, living or extinct

Geologists think the meteorite impact initially left a bowl-shaped hollow in the ground, and that the edges of this hollow were unstable and eventually collapsed. Underlying rocks may then have risen to fill the void, creating the ridged structure we see today.

But not everyone agrees with this interpretation. Some scientists believe that Upheaval Dome was formed by a mountain of salt rising beneath southeastern Utah's sandstone layers.

A thick layer of salt originating from ancient landlocked seas sits beneath Canyonlands National Park. Salt is relatively light and can move around in rocks, much like ice can migrate at the bottom of a glacier, according to the National Park Service (NPS).

Salt is also less dense than sandstone, so it could have created a giant "bubble" that shoved the rocks aside as it surged upwards, according to the NPS.

Upheaval Dome is unlikely to be the salt bubble itself covered in sandstone, because erosion probably stripped several layers off the structure over the eons. Instead, the dome's center is considered to be a rocky base that formed beneath the salt bubble due to rocks falling into cracks around the edges of the bubble. These rocks may have rolled down along the sides of the bubble and piled up beneath the salt, creating the craggy feature we see today.

If true, the salt bubble theory would make Upheaval Dome the most deeply eroded salt structure in the world.

But the discovery of the shocked quartz crystals is the last published investigation into the origins of Upheaval Dome. It's unclear whether research is ongoing to settle the case once and for all.

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Pamukkale is a town in Turkey that's famous for its dazzling travertine terraces and thermal water pools. The name, which means "cotton castle" in Turkish, hints at the height and snow-white color of the landmark, which stands in stark contrast to the surrounding arid plain.

Travertine is a type of rock made mostly of calcium carbonate that is deposited from mineral-rich spring water. Pamukkale is home to hot springs that bubble up at the top of a 660-foot-tall (200 meters) cliff overlooking the town. The water drips down over the mountainside, coating the rocks in calcium carbonate that has accumulated over millennia to form a white limestone crust.

The travertines of Pamukkale have grown so thick, they resemble a small glacier from above and afar.

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Pamukkale's travertines may look like a winter wonderland, but they're situated in a warm, sun-kissed part of southwestern Turkey.

The water flowing down the slopes is also warm — between 66 and 135 degrees Fahrenheit (19 to 57 degrees Celsius), according to NASA's Earth Observatory — and can reach boiling temperatures. It collects in basins that have formed within the terraced slopes, creating natural hot tubs and infinity pools. These cascade into each other, with stalactites and other limestone formations growing along ledges up to 20 feet (6 m) tall where water has dripped down for thousands of years.

Pamukkale is listed as a UNESCO World Heritage Site, but the listing highlights far more than the site's effervescent bathing pools. The travertines have drawn visitors since antiquity, with the ancient Greeks, in particular, building thermal baths, monuments and a complex system of canals to bring the spring water to nearby villages and fields.

The Attalid kings of Pergamon — an ancient Greek state that ruled large parts of Asia Minor during the Hellenistic period — established a thermal spa town called Hierapolis near the travertines in the second century B.C., the ruins of which still exist today and are also listed by UNESCO. Previously, the site hosted an ancient cult, according to the U.N. agency.

Hierapolis reached its heyday in the second and third centuries A.D., after the ancient Romans took over and rebuilt the town following an earthquake. Remains dating back to Greco-Roman rule and the later Byzantine period include several baths, a monumental arch, a theater, a necropolis, a nymphaeum (a monument dedicated to water nymphs) and temple ruins.

Notably, some of these monuments, like the Temple of Apollo, stood on top of a geological fault that likely leaked noxious gases into the space between their walls, according to UNESCO.

The ruins at Pamukkale are generally well preserved, but huge numbers of visitors threaten the integrity of the site, according to UNESCO. An area where tourists can swim between ancient columns and marble decorations that collapsed after an earthquake in the seventh century is particularly vulnerable.

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The Bungle Bungles are a collection of sandstone towers with distinctive orange and dark-gray stripes in Western Australia. Although Indigenous people have inhabited the area since time immemorial, the towers only came to the attention of the rest of the world in the 1980s, when filmmakers recorded them while shooting a documentary.

The Bungle Bungles are the main feature of Purnululu National Park, a protected area spanning almost 600,000 acres (240,000 hectares) in the Kimberley region. Due to its areas of "incredible natural beauty" and "outstanding geological value," Purnululu National Park was named a UNESCO World Heritage Site in 2003.

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The sandstone towers at Purnululu National Park (Purnululu means "sandstone" in the local Indigenous language) are a stunning example of cone karst — landscapes made up of beehive-shaped hills and rocky ground connected to form an area structured like an egg box.

They rise about 980 feet (300 meters) above the grassy plains that surround the Bungle Bungles and sit around 6 miles (10 kilometers) southwest of the Piccaninny crater, a meteor impact structure that formed less than 360 million years ago, according to NASA's Earth Observatory.

The sandstone itself was deposited roughly 360 million years ago and eroded through the joint action of wind and water over the past 20 million years to form the relief we see today, according to Western Australia's Department of Biodiversity, Conservation and Attractions (DBCA).

The orange and dark-gray stripes are evidence of the Bungle Bungles' ancient oceanic origins, with each band resulting from a layer of historic seabed. The alternating colors are caused by the presence of either ancient microscopic algae (gray) in moister layers or oxidized iron compounds (orange) in dry layers of rock. In the orange layers, the rock dried out too quickly for the microscopic algae — also known as cyanobacteria, the earliest known form of life on Earth — to grow, according to the DBCA.

The Bungle Bungles are accessible to the public, with several hiking routes available through the gorges between the striped sandstone domes. The landmark is home to 130 bird species and myriad other native animals, including nail-tail wallabies (Onychogalea) and short-eared rock wallabies (Petrogale brachyotis).

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A mountain that's hidden in a sea of snow in Antarctica looks strikingly like an ancient Egyptian pyramid when viewed from above. But no human (or alien) hands were needed to build this peak — it was forged through the slow, grinding process of erosion.

The pyramidal mountain, which doesn't have a formal name, became internet-famous in 2016, but scientists likely knew about it before then, Mauri Pelto, a professor of environmental science at Nichols College in Dudley, Massachusetts, previously told Live Science. A research base for climate scientists sits just south of the mountain in an area called the Patriot Hills, and "you can probably see this mountain from up there," Pelto said.

Related: 'We were in disbelief': Antarctica is behaving in a way we've never seen before. Can it recover?

Antarctica's "pyramid" is about 4,150 feet (1,265 meters) tall, or about one-fifth the height of Denali, the tallest mountain in North America. It has four steep sides and is located in the southern Ellsworth Mountains — a chain of jagged peaks first spotted during a flight by American aviator Lincoln Ellsworth in 1935, according to a U.S. Geological Survey (USGS) research paper published in 2007.

The region is known for holding 500 million-year-old fossils of trilobites and other critters dating to the Cambrian period (541 million to 485.4 million years ago).

The mountain's sides were likely carved and smoothed into a pyramid-like shape by hundreds of millions of years of erosion. Specifically, the rocks may have been subject to freeze-thaw erosion, which is when water and snow fill small cracks during the day and then freeze at night, Pelto said. The water expands in the cracks as it freezes, causing the gaps to grow larger under the resulting pressure and eventually causing large chunks of rock to break off of the mountain.

Three of the pyramidal mountain's sides appear to have eroded at the same rate, while the fourth side — the eastern ridge — formed independently, Pelto said.

Freeze-thaw erosion probably forged other pyramidal mountains, too, such as the Matterhorn in the Swiss Alps, Pelto added.

Various conspiracy theories sprung up to explain the shape of Antarctica's pyramid mountain when it went viral in 2016, with theorists contemplating the involvement of a forgotten civilization or aliens from outer space.

But "this is just a mountain that looks like a pyramid," Eric Rignot, a professor of Earth system science at the University of California, Irvine and senior research scientist at NASA's Jet Propulsion Laboratory, previously told Live Science. "Pyramid shapes are not impossible — many peaks partially look like pyramids, but they only have one to two faces like that, rarely four."

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Antarctica quiz

Tristan da Cunha is a group of islands in the South Atlantic Ocean that is home to the world's most isolated human settlement. Around 250 people holding British Overseas Territories citizenship live on the archipelago's only inhabited island, also called Tristan da Cunha, in a community known as Edinburgh of the Seven Seas.

Tristan da Cunha, or Tristan for short, comprises six volcanic islands that sit 1,500 miles (2,400 kilometers) southwest of St. Helena island, another British outpost in the Atlantic. Together with Ascension Island, Tristan and St. Helena form a British Overseas Territory that spans more than 2,000 miles (3,250 km) of the Atlantic Ocean, from a point west off the coast of Gabon in Africa to a point farther south than the tip of South Africa.

Related: Perilous expedition to uninhabited island in South Atlantic confirms existence of world's 8th lava lake

The main island stretches 7.5 miles (12 km) across and its cone-shaped volcano, called Queen Mary's Peak, rises 6,765 feet (2,062 meters) above sea level. The volcano's central crater is filled with a heart-shaped lake that freezes over in the winter and thaws in the summer, providing a cold bath for hikers that clamber up to the peak. The island is also a wildlife-watcher's paradise, with seals, albatrosses and northern rockhopper penguins (Eudyptes moseleyi) breeding on its shores.

Tristan is accessible only by a six-day boat journey from South Africa, and most of its inhabitants are farmers, according to the BBC.

Evidence of past geologic activity deep in Earth's mantle

Tristan's six islands are evidence of past geologic activity deep in Earth's mantle, each formed from peaks in the oceanic crust. They are located about 250 miles (400 km) east of the mid-Atlantic ridge, where the North and South American plates meet those of Eurasia and Africa. Over time, these plates have slowly moved apart, allowing molten rocks to bubble up into the gaps between them. Tristan's islands are not connected to the ridge, but they similarly formed as a result of magma gushing from deep within Earth's layers.

The archipelago was forged eons ago from what scientists call a hotspot — a large plume of hot material that rises from deep within the mantle, Earth's middle layer, and forms volcanoes in the crust above it. The hotspot in question, known as the Walvis Ridge Hotspot, formed between South America and Africa roughly 132 million years ago, when these continents were breaking up after millions of years spent locked together in the ancient supercontinent Gondwana.

As the continents tore apart and Earth's crust began grinding westward over the Walvis Ridge Hotspot, volcanoes developed one by one in a horizontal line beneath the opening Atlantic Ocean. These volcanoes grew to become islands and eventually went extinct as they drifted farther away from their source of magma (the hotspot).

The main island of Tristan da Cunha is the second-farthest east of the archipelago, meaning it went extinct shortly after four of the islands — Inaccessible, Nightingale, Middle and Stoltenhoff islands — and shortly before the farthest-east island of Gough.

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Kawah Ijen is a giant, active volcano on the island of Java with a crater that contains the world's largest acidic lake. The water has a pH lower than 0.3 in parts of the lake where hydrothermal fluids rise up from inside Earth's crust, filling the water with minerals, as well as sulfuric and hydrochloric acids.

A pH of 0.3 is similar to that of battery acid, a solution that creates and stores electrical energy in cars. For comparison, gastric acid has a pH between 1.5 and 2, and lemon juice scores between 2 and 3. But despite conditions that would dissolve human skin instantly, Kawah Ijen's acidic lake is home to a small community of microbes, according to a 2006 study.

Related: 'A challenge and an opportunity for evolution' — The extreme, hidden life thriving in Earth's most acidic and alkaline lakes

Kawah Ijen crater lake's bluish-green color is so bright, it's visible from space.The minerals and acids in the crater lake give the water its seemingly artificial turquoise color. They originate from a chamber of red-hot magma below the volcano, which last erupted in 1999. The volcano stands 9,085 feet (2,769 meters) tall and the crater measures 2,300 by 2,625 feet (700 by 800 m) wide.

'Bitter water' river

Rain regularly replenishes Kawah Ijen's acidic lake, but the new water immediately turns corrosive due to vents that release gas continuously at the bottom of the lake. When the crater is full, water overflows into a stream on the volcano's west side that feeds into the Banyupahit River basin — the name of the river means "bitter water" in the Javanese language.

If the crater lake's extremely acidic waters weren't eerie enough, Kawah Ijen also emits sulfurous gases that catch fire when they come into contact with oxygen in Earth's atmosphere. When the gases ignite above the volcano, they produce electric blue flames that mostly go unnoticed during the day, but create an astonishing spectacle at night.

Often, the sulfur in these gases condenses after catching light, forming a liquid that flows a short distance along the volcano before solidifying into yellow deposits. Local people mine these deposits, breaking off chunks of sulfur which they sell to a sugar refinery in the area that uses them to remove color impurities from the sugar.

There is considerable risk involved in these mining operations, according to the website Geology.com, including harm from poisonous sulfur gases, regular gas explosions and dangerous paths up and down the volcano.

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The Denmark Strait cataract is a submarine waterfall in the ocean channel between Iceland and Greenland. It is technically the world's largest waterfall, with waters plunging 11,500 feet (3,500 meters) down a slope from the top of the cataract to its bottom.

The waterfall itself is about 6,600 feet (2,000 m) tall, because it lands in a deep pool of cold water that spans the remainder of the slope. That's still double the height of Angel Falls — the tallest waterfall on land — even if the Denmark Strait cataract doesn't look as dramatic as the landmark in Venezuela.

Related: Blood Falls: Antarctica's crimson waterfall forged from an ancient hidden heart

The cataract is as wide as the Denmark Strait, roughly 300 miles (480 kilometers) across, and the seabed drops off over a length of 310 to 370 miles (500 to 600 km). "If we visualize it, it looks like a relatively low-gradient slope," Mike Clare, leader of marine geosystems at the U.K.'s National Oceanography Centre in Southampton, previously told Live Science.

As a result, water gushing down the cataract moves at much slower speeds than those recorded at other waterfalls — 1.6 feet per second (0.5 meters per second) compared with 100 feet per second (30.5 m/s) at Niagara Falls, for example. "If you were down there, you probably wouldn't notice a whole heap going on," Clare said.

Glaciers carved out the Denmark Strait cataract between 17,500 and 11,500 years ago, during the last ice age. The waterfall straddles the Arctic circle and funnels polar waters from the Greenland, Norwegian and Iceland seas into the Irminger Sea, a region of the North Atlantic that is crucial for Atlantic-wide ocean circulation.

The waters north of the cataract are about 1,300 feet (400 m) deep, but only the bottom 660 feet (200 m) cascade down the slope. The top half sits at the surface and mixes with water flowing northward through the strait. After exiting the Denmark Strait, the bottom half continues south along the seabed to the Antarctic, where it enters a global loop of ocean currents called the thermohaline circulation.

None of this is visible above the waves in the Denmark Strait. "At the surface, you have typical sunny Arctic conditions," Anna Sanchez Vidal, a professor of marine science at the University of Barcelona in Spain who led a research expedition to the strait in 2023, previously told Live Science.

The waterfall isn't detectable from space either, she said, except through mapping indicators, such as temperature and salinity.

The Denmark Strait cataract isn't the only known underwater waterfall, although other documented cascades can't compete with it in size. There are features known as knickpoints that often occur along continental margins that look a lot more like waterfalls on land, Clare said, but these are small in comparison to the monstrous cataract.

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The Marble Caves are natural rock formations with curved walls covered in swirling mineral patterns. They sit on the shores of General Carrera Lake, a glacial lake in southern Chile. The lake floods the caverns with turquoise waters, which fill the caves with blue light and give them an ethereal appearance.

The Marble Caves are so smooth, they look like they've been hollowed out with an ice cream scoop. But the caves formed due to the slow action of lake water, which dissolved minerals in the rocks until the walls crumbled. Researchers think this occurred over the past 10,000 to 15,000 years, after glaciers retreated from the region and exposed its stone to weathering.

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"After the glaciers retreated, the lake was created, and that was when the process of sculpting the [caves] began," Francisco Hervé Allamand, a professor of geology at Andrés Bello National University in Chile and an honorary fellow of the Geological Society of America, told the BBC in 2019.

The stone in the caves was originally limestone, a sedimentary rock made of calcium carbonate. But it transformed into marble, which is a metamorphic rock, under high heat and pressure before the caverns opened, Hervé Allamand said. Limestones are some of the most soluble rocks in the world, he said, meaning they are extremely susceptible to erosion from water.

The original limestone formed closer to the equator than Chile sits today and drifted southward millions of years ago as tectonic plates shifted around Earth, Hervé Allamand said. This grinding journey jumbled up Earth's crust and buried rocks so deep that they became exposed to blistering temperatures of 570 to 750 degrees Fahrenheit (300 to 400 degrees Celsius). Together with the pressure from plate movement, this heat recrystallized the limestone into whitish-gray marble and created ripples of brown and yellow rock where impurities were trapped in the limestone.

"When a rock undergoes metamorphosis, new minerals are formed," Hervé Allamand said, referring to brown and yellow veins within the marble.

Reflections off the water in the Marble Caves give rise to stunning images that shift depending on the light and water levels. The water owes its brilliant azure color to glacial silt, which is also known as "rock flour." This fine stone powder absorbs the shortest wavelengths of light — the purples and indigos — and reflects mainly light-blue and green light back to the surface, giving the water a turquoise tint. (Water absorbs longer wavelengths of light that give rise to red, orange and yellow.)

The turquoise water may look like a tropical sea, but its glacial origin means it's freezing.

The Marble Caves are accessible only by water, and they are best explored with kayaks, which enable visitors to wind in and out of the curved walls, according to the travel website Swoop Patagonia.

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