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15 Modern-Day Signs of the Ice Age

Picture this: A massive sheet of ice completely buries Manhattan. It happened 20,000 years ago during one of the Earth’s many ice ages. As heavy glaciers—in some places nearly two miles thick—flowed across the land, they pummeled mountains and scoured rock. Out of this chaos were born some of the world’s most well-known natural features: Loch Ness, Walden Pond, Plymouth Rock, and more.

We’re still in an ice age, technically speaking, though we’re in a warmer period called an interglacial. The glaciers have mostly melted back. But, like bad houseguests, they’ve left a huge mess behind. Here are 15 amazing signs of past glaciation. 

1. THE GREAT LAKES

Ice created the Great Lakes. Here’s how: As an ice sheet flowed along, it carved humongous, deep scars in the bedrock. Once the climate warmed, the melting glaciers filled up the basins with water and sediments. And voilà—giant lakes!

They’re not the only well-known water bodies excavated by glaciers. Flowing ice enlarged stream valleys and made them into New York’s Finger Lakes. It also created one of the most famous lakes of all time …

2. LOCH NESS 

The fabled home of Nessie is also the product of glaciers. When the ice from the most recent glaciation rolled over Scotland, it hit a weak spot in the rock. This vulnerable area was, hundreds of millions of years ago, much like the modern San Andreas Fault, where two plates were rubbing against each other. The glacier picked away at the weak point and dug out Loch Ness and other nearby lochs.

3. WALDEN POND

In 1845, Henry David Thoreau headed into the forest to write his famous book Walden; or, Life in the Woods. The setting was Walden Pond—and it was created by a huge chunk of ice that fell off a glacier.

As the glacier melted, the fallen chunk became buried in dirt and debris. And, as the climate got even toastier, the ice chunk melted, leaving a deep hole full of water. The result was a pond so pristine that it became a symbol of nature.

This kind of water body is called a kettle hole. Sometimes, special wetlands called bogs form in kettle holes. Incidentally, bogs are tough places for plants, since they’re not connected to the nutrient-rich flow of a stream, and some bog plants compensate for the lack of nutrients by eating animal flesh.

4. ANCIENT ROADS

How does a two-mile-thick sheet of ice melt? Enormous streams of meltwater flow through it. And, as in all rivers, these ice-encased waterways carry rocks and other debris. Once the ice sheets melt away, that debris remains in the form of raised gravel beds that snake across the landscape. These are called eskers—and people have been using them as natural roads for centuries.

The ancient Celts crossed Ireland along an esker system called An Slí Mór (Irish for The Great Highway). And you can drive atop an esker on the Denali Highway in Alaska or on Route 9 in Maine.

5. GEIRANGER FJORD

Fjords are some of the ice sheets’ most amazing creations. A fjord is a U-shaped valley that was excavated by a glacier and usually filled with seawater. Norway boasts many of the most spectacular fjords, and in fact, the word fjord comes from Old Norse. One of these natural monuments is the beautiful Geiranger Fjord, a UNESCO World Heritage Site. 

6. RISING GROUND

If you’re standing on a place that was once weighed down by a glacier, then the land below you might be rising. 

Sit in a soft chair and you’ll feel the cushion sink under your weight. When you get back up, it’ll (hopefully) spring back into shape. The land reacts in the same way to the heavy weight of an ice sheet—it squishes down up to a half kilometer (.3 miles), then rises slowly once the ice has melted.

This recovery is so slow that the land is still rising after the last glacial period. And that spells trouble for some people, such as those on the U.S. East Coast. Canada and parts of Greenland—which were weighted down by ice sheets during the end of the last Ice Age—are rising like a seesaw, pushing the East Coast downward. This raises the sea level, which is especially alarming when combined with sea level rise from climate change. 

7. PLYMOUTH ROCK

Legend holds that the pilgrims of the Mayflower landed at Massachusetts’ Plymouth Rock in 1620. It’s an important story in the colonial history of the United States, though the Pilgrims may not have actually landed at that particular rock. But this much is true: Plymouth Rock is in Plymouth because of glaciers.

Glaciers are pretty dirty. As they move along, they pick up dirt and debris, including huge boulders, and dump it elsewhere. Once the glaciers are gone, those large rocks sit alone on the landscape, making people wonder, “How on Earth did this thing get here?” These “things” are called glacial erratics.

Plymouth Rock isn’t the only famous erratic. Pictures of Kummakivi in Finland sometimes go viral with a caption declaring that the rock is a scientific mystery (it’s not). There’s also England’s Merton Stone, Canada’s Okotoks or Big Rock, and many more. 

8. FARMS THAT GROW ROCKS 

Glaciers leave behind smaller stones and gravel, too, in a jumbled mix of rubble called glacial till. That’s why the soil in many previously glaciated places is rocky. And every year, as the soil freezes and thaws, more rocks are pushed to the surface. This leads farmers to say that their fields “grow rocks.”

9. SCARS ON ROCKS 

Skreeeeech! It’s worse than nails on a chalkboard. A hulking, weighty glacier drags along loose pieces of rock, grinding them against the bedrock and carving long scratches. These markings, called glacial striations, show us the direction of a glacier’s flow. In some places, you can even track successive glacial movements through overlapping scratches.

10. WORM-FREE WOODS 

In many places where glaciers roamed, the native worms disappeared completely. All of that scouring wiped away plants, soil, and even earthworms, leaving the land pretty barren. Once the ice melted, the forests that sprung back up in the rubble were earthworm-free.

In colonial times, however, people shipped over plants—and earthworms—from Europe. Those imported wrigglers have infiltrated forest soils. They devour the top layer of material, making it hard for certain types of plants to grow. It’s not clear how forests will change long-term as those worms continue to munch. 

11. LONG ISLAND 

Imagine a bulldozer pushing up some dirt, then backing away, leaving that pile of soil behind. Glaciers do essentially the same thing. They create piles of debris called terminal moraines. Long Island is one such feature, and it marks the end point of a glacial advance. Compared to Manhattan, Long Island doesn’t have many big, tall buildings, and that’s partly because it’s built on unstable rubble. Cape Cod, Martha’s Vineyard, and other famous coastal features are also moraines.

12. CHANNELED SCABLANDS

This landscape in Washington State doesn’t have the most appealing name. It’s a scarred place with little soil. That’s because it was scoured clean by a cataclysmic flood.

Glaciers often blocked up rivers, creating dams of ice that led to the formation of enormous lakes. But as the planet warmed, those ice dams broke—often catastrophically. One ice-dammed lake was glacial Lake Missoula. During the dam's most catastrophic failure 20,000 years ago, water rushed out at 10 times the combined flow of all the rivers in the world. When the water rushed across dry land, the result was the Channeled Scablands. 

13. ANIMALS IN WEIRD PLACES 

Ice sheets change the landscape so much that animals wind up in strange places. For example, fish that normally spend part of their lives in the ocean can become permanently trapped in lakes, as is the case of the Killarney shad in Kerry Lake, Ireland.

And in Canada’s St. Lawrence River, there’s a remnant population of an Arctic whale—the beluga. During the last glaciation, ice sheets blanketed much of the beluga’s northern range, pushing the species southward. As things warmed up, a few whales decided to stay.

14. PLANTS IN WEIRD PLACES

There’s something strange about the plants along parts of Lake Champlain, a huge body of water that sits between New York and Vermont. Wander along its shores and you might see certain plants that really belong at the seaside, such as the beach-pea. These are leftovers of a time when the ocean reached much farther inland. As the glaciers melted back, the land in that region was squished down so much that a tongue of ocean flooded in, creating a nice home for seashore plants. 

15. BUNKER HILL

The Battle of Bunker Hill was the American Revolution’s first major battle—and it took place on a glacial hill.

In 1775, American colonial militiamen and British soldiers battled near Boston. Though the British won the fight, they were stunned by the colonists’ ferocity. It was an important fight that helped set the tone for the rest of the Revolutionary War.

The battle is named for Bunker Hill, but here’s a bit of trivia: Most of the fighting took place at nearby Breed’s Hill. Both of these landforms are glacial features called drumlins. They’re teardrop-shaped hills, and we’re still not exactly sure how they form. One thing is clear: The glaciers of the distant past shaped some of the most important events in human history.

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15 Explosive Facts About Volcanoes
U.S. Geological Survey via Getty Images
U.S. Geological Survey via Getty Images

On May 3, the Kilauea volcano erupted on Hawaii's Big Island. Since then, 18 fissures have opened in the earth, some hundreds of feet long. The USGS's Hawaii Volcano Observatory reports that some of these fissures are producing "lava fountaining, explosion of spatter bombs hundreds of feet into the air, and several advancing lava flow lobes." More than 2000 people have evacuated, and dozens of structures and vehicles have been destroyed. Five earthquakes have rattled the island as well.

Volcanoes are amazing portals to the hot, living interior of the Earth, but they're also dangerous. Even small-ish ones can have a global impact. Here are 15 explosive facts about volcanoes.

1. THE VOLCANIC EXPLOSIVITY INDEX MEASURES THE STRENGTH AND SIZE OF ERUPTIONS.

Created in 1982 by Chris Newhall of the United States Geological Survey and Stephen Self of the University of Hawaii, the VEI quantifies the strength of volcanic eruptions by measuring the volume of pyroclastic material spewed by a volcano, including volcanic ash, tephra (fragments of volcanic rock and lava), pyroclastic flows (fast-moving currents of gas and tephra), and other debris. The height and duration of the eruption are also factored in. The scale ranges from 1 to 8, and each step indicates a tenfold increase of ejecta. Fortunately, there hasn’t been a VEI-8 eruption in the past 10,000 years.

2. "WAH WAH SPRINGS" SOUNDS KIND OF FUN. IT WAS ACTUALLY DEVASTATING.

One of the biggest eruptions ever occurred about 30 million years ago in what is today eastern Nevada and western Utah, when a supervolcano exploded 3500 cubic kilometers of magma over an area of about 12,000 square miles. The eruption left behind deposits of debris 13,000 feet deep. Consider that the 1883 eruption of Krakatau, in Indonesia, was heard thousands of miles away—and yet it was a minor burp compared to Wah Wah Springs, a VEI-8 eruption.

3. LAVA IS THE LEAST OF YOUR WORRIES.

Garden of the Fugitives, Pompeii
Garden of the Fugitives, Pompeii

Lava generally moves too slowly to be the biggest threat from an eruption—but that’s not the case with pyroclastic flows. These super-hot, fast-moving currents of gas and tephra did in history’s most famous volcano victims: the residents of Herculaneum and Pompeii. The flow that hit Herculaneum was as hot at 500 degrees—enough to boil brains and vaporize flesh—while the later, cooler wave that hit Pompeii “cooked” people’s flesh, as the BBC puts it, but left their bodies intact; they were preserved by the falling volcanic ash.

4. JUST FOR FUN, THERE ARE 10 WAYS AN ERUPTION CAN KILL YOU.

As Io9 recounts, flying shrapnel, scalding-hot seawater, falling into a lava tube, poisonous gases, and volcanic smog, or vog, can also do you in.

5. THERE ARE THREE TYPES OF VOLCANIC ERUPTIONS.

Magmatic eruptions involve the decompression of gas within magma that propels it forward. Phreatic eruptions are driven by the heat from magma creating superheated steam. Phreatomagmatic eruptions are caused by the interaction of water and magma.

6. VOLCANOLOGISTS ARE CONTINUOUSLY KEEPING TABS ON ACTIVITY ALL OVER THE WORLD.

One of the many initiatives tracking potentially dangerous activity is the Global Volcanism Program of the Smithsonian National Museum of Natural History. It also puts out a weekly report in conjunction with the USGS that features a map. The International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) especially monitors the so-called Decade Volcanoes—16 volcanoes that are potentially hazardous due to their history of large, destructive eruptions and proximity to populated areas. Among them are Rainier, Sakurajima, Vesuvius, and Santorini.

7. THERE ARE VOLCANOES ON OTHER PLANETS AND MOONS IN OUR SOLAR SYSTEM.

Plumes on Io captured by the Galileo spacecraft
Plumes on Io captured by the Galileo spacecraft
NASA/JPL/University of Arizona

That Jupiter’s moon Io is volcanically active has been known since 1979, when Voyager 1 imaging scientist Linda Morabito discovered the first evidence of active volcanism on a body other than Earth. But it’s far from alone. For instance, while Mars’s volcanoes appear to be either dormant or extinct, recent evidence from the Venus Express spacecraft suggests that many of Venus’s volcanoes are active.

8. SHARKS HANG OUT IN ONE VOLCANO.

Scientists recently recorded video of sharks happily swimming around in the acidic, hot, ash- and gas-filled waters near the Kavachi underwater volcano in the Solomon Islands, which is a mere 66 feet below the surface. This suggests extremophiles may be even more diverse than we thought.

9. THE USGS’s ALL-TIME BEST-SELLING MAP FEATURES VOLCANOES.

"This Dynamic Planet" is now in its third edition. This map [PDF] features more than 1500 volcanoes, 44,000 earthquakes, and 170 impact craters, as well as the major, minor, and micro tectonic plates whose movement creates these features. About 60 of Earth’s 550 historically active volcanoes blow every year.

10. AN EARLY 19TH-CENTURY ERUPTION IN THE PACIFIC WAS WORLD CHANGING.

Gillen D’Arcy Wood argues in his book Tambora: The Eruption That Changed the World that the 1815 eruption of the volcano on the Indonesian island of Sumbawa, which created a massive sulfate dust cloud that fundamentally altered the planet’s climate for three years, led to such diverse impacts as the first worldwide cholera pandemic, expanded opium markets in China, the U.S.’s first economic depression—and Mary Shelley’s Frankenstein.

11. A VOLCANO STAMP SOLD CONGRESS ON THE PANAMA CANAL.

Before the Panama Canal opened in 1915, rival proposals for an Atlantic–Pacific link included a plan to carve a canal through Nicaragua, which had a lot more fresh water and much less deadly malaria than Panama. It also has significant volcanic activity, and in the early 20th century, one of its stamps featured an erupting volcano. In 1902, just before a U.S. congressional vote, a pro-Panama Canal French engineer sent this stamp to all 90 senators to hype the volcanic threat in Nicaragua. Panama got the vote by a slim margin. Today Nicaragua says it’s building the canal with help from a Chinese funder.

12. SPEAKING OF NICARAGUA’S VOLCANOES—YOU CAN SURF ONE.

Cerro Negro, a new and very active volcano that first erupted in 1850—and has blown 23 times since, most recently in 1999—has black pebble-covered slopes you can surf down on a metal-bottomed wood board, if you're adventurous and also kind of insane. Intrigued? Here’s our 7-point guide to surfing volcanoes.

13. THE MOST VOLATILE AREA ON EARTH IS THE RING OF FIRE.

Located at the rim of the Pacific Basin, the so-called Ring of Fire is a nearly continuous chain of oceanic trenches and hundreds of volcanoes spanning some 25,000 miles that’s home to 75 percent of the world’s volcanic activity, with some 452 volcanoes (active and dormant), 90 percent of the world's earthquakes, and 22 of the 25 biggest volcanic eruptions in the last 11,700 years.

14. THERE ARE MANY WARNING SIGNS OF VOLCANIC ACTIVITY.

According to the USGS’s Volcano Hazards Program, volcanologists keep an eye out for ground movements caused by magma forcing its way upward through solid rock, earthquakes resulting from this heaving, and changes in heat output and volcanic gases. Other indicators include cracks in the ground, small steam explosions, melting snow, and the appearance of new hot springs.

15. YOUR EUROPE FLIGHT WAS DELAYED IN 2010 BECAUSE OF AN ICELANDIC ERUPTION.

The Eyjafjallajökull volcano began erupting on April 14, 2010 and didn’t stop for six weeks, spewing magma, ash, and gas. Planes were grounded across Europe. Though the eruption was a small one, it had an outsized impact because it spread unusually far and stayed for an unexpectedly long time in the atmosphere thanks to the irregular shape of the tiny porous ash grains, as LiveScience reports.

BONUS: NASA IS TRAINING FOR LIFE ON MARS ON THE SLOPES OF AN ACTIVE VOLCANO.

For several years, NASA has been simulating life on Mars through a simulation on the slopes of Hawaii's Mauna Loa volcano, one of the Decade Volcanoes. Each year, a small team of adventurers who meet the basic qualifications for the NASA astronaut program live in a solar-powered geodesic dome. If they want to go outside, they have to put on space suits. Still beats trying to escape poisonous gases and pyroclastic flows.

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9 'Scientific Mysteries' the Internet Loves, Debunked
John Fielding, Flickr // CC BY 2.0
John Fielding, Flickr // CC BY 2.0

Whether it involves aliens, moving rocks, or crop circles, no one loves a scientific mystery like the internet—even if that "mystery" was solved years ago using all of the rigors of science. Here are 10 so-called mysteries that the global online community can't bear to part with, debunked once and for all (we hope).

1. KUMMAKIVI BALANCING ROCK // RUOKOLAHTI, FINLAND

The "Mystery": This so-called "strange rock" is a balancing act comprised of two rocks, one teetering precipitously on top of the other. Locals of ancient yesteryear, apparently perplexed to discover that the top rock was in no danger of sliding off the bottom rock despite the extremely small point of contact between them—and was, in fact, too heavy to be moved at all—decided giants tossing boulders explained the phenomenon. "And it's true," one theorist wrote: "There is still no exact scientific explanation, but contrary to the laws of physics, the stone stands quite firmly and human strength is not enough to move it."

Science Says: It's not true, actually. Geologists put forward a much more likely cause for this balancing rock and the countless others that exist worldwide: Melting glaciers deposited them where they currently squat.

2. FAIRY CIRCLES // NAMIBIA

geographic features called fairy circles in namibia, created by termites and plants
iStock

The "Mystery": Are they footprints of the gods? Barren patches caused by a dragon's fiery breath? Marks left behind by UFOs? All of these ideas were perpetuated by the internet after tour guides in the region passed them on to tourists, according to The New York Times. The scientific community was pretty sure the dirt circles found in the Namib Desert were none of those things, even though they were hard-pressed to come up with a more logical explanation—until recently.

Science Says: Research published in 2017 suggests that they're the work of colonies of termites, which clear circular patches around their nests; the barrenness of these shapes is possibly enhanced by plants as they stretch their roots to reach scarce water—which prevents other plants from growing in the process.

3. KLERKSDORP SPHERES // OTTOSDAL, SOUTH AFRICA

klerksdorp sphere
Robert Huggett

The "Mystery": These grooved spheres have been the subject of many strange theories, most revolving around the existence of intelligent aliens who made the pod-like trinkets—which apparently can rotate on their axes—using intelligent alien technology and otherworldly metals some 3 billion years ago. Virtuescience.com has proposed a whole host of theories about the spheres' uses, including ancient ammunition, messages from space, and currency.

Science Says: Geologists have a more tempered explanation for how the spheres came to be: They're concretions—little balls of rock that have grown around a core object—of the minerals hematite, wollastonite, or pyrite that have hardened over time in nests of volcanic ash or sediment. The myth of alien metalworking skills was debunked back in 1996, but it still resurfaces every once in a while.

4. WEBDRIVER TORSO // YOUTUBE

The "Mystery": The Webdriver Torso YouTube account has been freaking out the internet with its videos for several years. Commentors posited that the videos—which were usually 11 seconds long and featured colored rectangles moving around on a white screen—were spy code, alien code, or recruitment searches for expert hackers. At the channel's peak, videos were uploaded as often as every two minutes.

Science Says: Google revealed in 2014 that they were simply video clips the company had created to test the quality of YouTube videos. "We're never gonna give you uploading that's slow or loses video quality, and we're never gonna let you down by playing YouTube in poor video quality," the company told Engadget in a statement/Rickroll. "That's why we're always running tests like Webdriver Torso." Conspiracy theorists, however, pointing out that videos had been uploaded elsewhere before Google took credit for the channel, continued to suspect darker intentions. One reddit user posited in 2015 that Google "could … have a secret agenda." Maybe Google wants this chatter to continue: Even today, googling "Webdriver Torso" will yield an easter egg.

5. SAILING STONES // DEATH VALLEY NATIONAL PARK, CALIFORNIA

Sailing stones of Death Valley National Park
Thomas Hawk, Flickr // CC BY-NC 2.0

The "Mystery": Known alternately as sliding, walking, or moving rocks, for more than 100 years these so-called "living stones" have seemingly slid across the floor of a dry lake bed all on their own, leaving trails of their movements—and causing plenty of speculation. Magnetic force is one popular theory, along with psychic energy and the interventions of alien spacecraft. Some claim a 700-pound stone named Karen disappeared for two years, only to somehow reappear again.

Science Says: In 2014, scientists studied the situation and discovered that the stones move when the lake bed they rest on becomes covered with rainwater that freezes overnight into a sheet of ice; when the ice melts, it pushes the rocks here and there—assisted by Death Valley's powerful winds. (No word on what Karen's been up to, though.)

6. NAZCA LINES // NAZCA, PERU

Aerial view of a geoglyph representing a Duck or a Dinosaurius at Nazca Lines
Martin Bernetti, AFP/Getty Images

The "Mystery": If conspiracy theorists like aliens, they love ancient aliens. When it comes to the Nazca lines, they speculate that ancient astronauts from outer space drew almost 1200 geometric, animal, and plant shapes in a vast, arid plateau on Peru's Pampas de Jumana. Ranker.com also purports that the designs were made by humans, "most likely to signal extraterrestrials," and possibly to provide a runway for their space ships.

Science Says: The truth—which has been known since at least the 1940s—is that the figures were created 1500 to 2000 years ago by the Nazca people, who removed rocks and/or a portion of topsoil to create an image in negative. At first, scientists believed the figures were astronomical symbols, or an early sort of calendar, but later research indicated the drawings were used ritualistically, in ceremonies involving the quest for scarce water.

7. BERMUDA TRIANGLE // ATLANTIC OCEAN

aerial view of bermuda

Peter Burka, Flickr // CC BY-SA 2.0

The "Mystery": Three hundred ships and planes, all supposedly sunk or gone missing in the same general area in the middle of the Atlantic Ocean: The Bermuda Triangle (so-named by pulp writer Vincent Gaddis in 1964) has had conspiracy theorists of all stripes spouting endless theories for years. Atlantis! Alien interventions! An opening in the fabric of the universe! Attack by sea monsters! A popular theory in the 1970s involved magnetism wreaking havoc on navigational devices, and one more recent theory suggested that bursting bubbles of methane gas were responsible for missing craft. Online speculations, like this one from BuzzFeedBlue, attempt to stoke the (nonexistent) fire.

Science Says: This has been settled for decades—there is no mystery. In 1975, librarian turned investigative author Larry Kusche unearthed the actual facts: Some "missing" vessels were simply made up; some sank far from the Triangle; and others along the route—which is still heavily trafficked today—fell prey to the region's frequent bad storms.

8. CROP CIRCLES // BRITAIN

The "Mystery": A lot of otherworldly meaning has been ascribed to these designs squished into fields of wheat, rapeseed, and barley. Once again, aliens—mathematical-genius aliens this time—are said to be responsible for them, hiding complicated messages in the circles' sometimes intricate imagery. Others suggest they're spiritual centers that beam energy. In the video above, a farmer who found an intricate crop spiral in his field says, "I don't know what caused it, but I'm not sure that it was made by people."

Science Says: The truth is simple, and perhaps disappointing, which may explain why the alien theory never seems to die: The circles are made under cover of darkness by people, sometimes with the permission of the farmers whose land they're created on. They use measuring devices, rollers, and other low-tech gear to push patterns into grain.

9. ATA THE MUMMY // ATACAMA, CHILE

The "Mystery": When a small, oddly shaped, strangely featured mummy was discovered in Chile's Atacama Desert in 2003, some on the internet called it proof that beings from space had once lived among humans—and perhaps even mated with them. The mummy had 10 ribs instead of the typical 12; a strangely sloped head; and at just 6 inches long, was fetus-sized, but its bones were as dense as a child's. Some thought that the 9 percent of the mummy's DNA that didn't match the human DNA they compared it to was further evidence of its non-human origins. As UFO/ET conspiracy theorist Steven Greer says in the above clip, "Is that all computer read error? Maybe. Is it what's called DNA junk? Perhaps. We don't know."

Science Says: Testing of Ata's genome destroyed these theories, proving that Ata was 100 percent human and died, likely in utero, from genetic defects. Many of these mutations related to bone development, explaining her missing ribs and thick bones. Exposure to nitrate-contaminated drinking water may have been a factor in her deformations as well. And that 9 percent genetic difference? Standard contamination of a mummy that was exposed to the open air.

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