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    A moon-forming cataclysm could have also triggered Earth’s plate tectonics

    THE WOODLANDS, TEXAS — Vestiges of a moon-forming cataclysm could have kick-started plate tectonics on Earth.

    The leading explanation for the origin of the moon proposes that a Mars-sized planet, dubbed Theia, struck the nascent Earth, ejecting a cloud of debris into space that later coalesced into a satellite (SN: 3/2/18). New computer simulations suggest that purported remains of Theia deep inside the planet could have also triggered the onset of subduction, a hallmark of modern plate tectonics, geodynamicist Qian Yuan of Caltech reported March 13 at the Lunar and Planetary Science Conference.

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    The story offers a cohesive explanation for how Earth gained both its moon and its moving tectonic plates, and it could aid in the search for other Earthlike worlds. But others caution that it’s much too early to say that this is, in fact, what happened.

    Of all the worlds yet discovered, ours is the only one confirmed to have plate tectonics (SN: 1/13/21). For billions of years, Earth’s creeping plates have spread, collided and plunged beneath one another, birthing and splitting continents, uplifting mountain ranges and widening oceans (SN: 4/22/20, SN: 1/11/17). But all this reshaping has also erased most of the clues to the planet’s early history, including how and when plate tectonics first began.

    Many hypotheses have been proposed to explain the initiation of subduction, a tectonic process in which one plate slides under another (SN: 5/2/22; SN: 6/5/19; SN: 1/2/18). Yuan and his colleagues chose to focus on two continent-sized blobs of material in Earth’s lower mantle known as large low-shear velocity provinces (SN: 5/12/16). These are regions through which seismic waves are known to move anomalously slow. Researchers had previously proposed these regions could have formed from old, subducted plates. But in 2021, Yuan and colleagues alternatively proposed that the mysterious masses could be the dense, sunken remnants of Theia.

    Building off that previous work, the researchers used computers to simulate how Theia’s impact, and its lingering remains, would impact the flow of rock inside the Earth.

    They found that once these hot alien blobs had sunk to the bottom of the mantle, they could have compelled large plumes of warm rock to upwell and wedge into Earth’s rigid outer layer. As upwelling continued to feed into the risen plumes, they would have ballooned and pushed slabs of Earth’s surface beneath them, triggering subduction about 200 million years after the moon formed.

    While the simulations suggest the large low-shear velocity provinces could have had a hand in starting subduction, it’s not yet clear whether these masses came from Theia. “The features … are a fairly recent discovery,” says geodynamicist Laurent Montési of the University of Maryland in College Park. “They’re very fascinating structures, with a very unknown origin.” As such, he says, it’s too early to say that Theia triggered plate tectonics.

    “It’s provoking. This material down there is something special,” Montési says of the large low-shear velocity provinces. “But whether it has to be originally extraterrestrial, I don’t think the case is made.”

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    However, if confirmed, the explanation could have implications that reach beyond our solar system. “If you have a large moon, you likely have a large impactor,” Yuan said. Scientists have yet to confirm the discovery of such an exomoon (SN: 4/30/19). But keeping an eye out, Yuan said, could help us uncover another world as tectonically active as our own. More

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    Rare earth mining may be key to our renewable energy future. But at what cost?

    In spring 1949, three prospectors armed with Geiger counters set out to hunt for treasure in the arid mountains of southern Nevada and southeastern California.

    In the previous century, those mountains yielded gold, silver, copper and cobalt. But the men were looking for a different kind of treasure: uranium. The world was emerging from World War II and careening into the Cold War. The United States needed uranium to build its nuclear weapons arsenal. Mining homegrown sources became a matter of national security.

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    After weeks of searching, the trio hit what they thought was pay dirt. Their instruments detected intense radioactivity in brownish-red veins of ore exposed in a rocky outcrop within California’s Clark Mountain Range. But instead of uranium, the brownish-red stuff turned out to be bastnaesite, a mineral bearing fluorine, carbon and 17 curious elements known collectively as rare earths. Traces of radioactive thorium, also in the ore, had set the Geiger counters pinging.

    As disappointing as that must have been, the bastnaesite still held value, and the prospectors sold their claim to the Molybdenum Corporation of America, later called Molycorp. The company was interested in mining the rare earths. During the mid-20th century, rare earth elements were becoming useful in a variety of ways: Cerium, for example, was the basis for a glass-polishing powder and europium lent luminescence to recently invented color television screens and fluorescent lamps.

    For the next few decades, the site, later dubbed Mountain Pass mine, was the world’s top source for rare earth elements, until two pressures became too much. By the late 1980s, China was intensively mining its own rare earths — and selling them at lower prices. And a series of toxic waste spills at Mountain Pass brought production at the struggling mine to a halt in 2002.

    But that wasn’t the end of the story. The green-tech revolution of the 21st century brought new attention to Mountain Pass, which later reopened and remains the only U.S. mine for rare earths.

    Rare earths are now integral to the manufacture of many carbon-neutral technologies — plus a whole host of tools that move the modern world. These elements are the building blocks of small, super­efficient permanent magnets that keep smartphones buzzing, wind turbines spinning, electric vehicles zooming and more.

    Mining U.S. sources of rare earth elements, President Joe Biden’s administration stated in February 2021, is a matter of national security.

    Rare earths are not actually rare on Earth, but they tend to be scattered throughout the crust at low concentrations. And the ore alone is worth relatively little without the complex, often environmentally hazardous processing involved in converting the ore into a usable form, says Julie Klinger, a geographer at the University of Delaware in Newark. As a result, the rare earth mining industry is wrestling with a legacy of environmental problems.

    Rare earths are mined by digging vast open pits in the ground, which can contaminate the environment and disrupt ecosystems. When poorly regulated, mining can produce wastewater ponds filled with acids, heavy metals and radioactive material that might leak into groundwater. Processing the raw ore into a form useful to make magnets and other tech is a lengthy effort that takes large amounts of water and potentially toxic chemicals, and produces voluminous waste.

    “We need rare earth elements … to help us with the transition to a climate-safe future,” says Michele Bustamante, a sustainability researcher at the Natural Resources Defense Council in Washington, D.C. Yet “everything that we do when we’re mining is impactful environmentally,” Bustamante says.

    But there are ways to reduce mining’s footprint, says Thomas Lograsso, a metallurgist at the Ames National Laboratory in Iowa and the director of the Critical Materials Institute, a Department of Energy research center. Researchers are investigating everything from reducing the amount of waste produced during the ore processing to improving the efficiency of rare earth element separation, which can also cut down on the amount of toxic waste. Scientists are also testing alternatives to mining, such as recycling rare earths from old electronics or recovering them from coal waste.

    Much of this research is in partnership with the mining industry, whose buy-in is key, Lograsso says. Mining companies have to be willing to invest in making changes. “We want to make sure that the science and innovations that we do are driven by industry needs, so that we’re not here developing solutions that nobody really wants,” he says.

    Klinger says she’s cautiously optimistic that the rare earth mining industry can become less polluting and more sustainable, if such solutions are widely adopted. “A lot of gains come from the low-hanging fruit,” she says. Even basic hardware upgrades to improve insulation can reduce the fuel required to reach the high temperatures needed for some processing. “You do what you [can].”

    The environmental impact of rare earth mining

    Between the jagged peaks of California’s Clark range and the Nevada border sits a broad, flat, shimmering valley known as the Ivanpah Dry Lake. Some 8,000 years ago, the valley held water year-round. Today, like many such playas in the Mojave Desert, the lake is ephemeral, winking into appearance only after an intense rain and flash flooding. It’s a beautiful, stark place, home to endangered desert tortoises and rare desert plants like Mojave milkweed.

    From about 1984 to 1998, the Ivanpah Dry Lake was also a holding pen for wastewater piped in from Mountain Pass. The wastewater was a by-product of chemical processing to concentrate the rare earth elements in the mined rock, making it more marketable to companies that could then extract those elements to make specific products. Via a buried pipeline, the mine sent wastewater to evaporation ponds about 23 kilometers away, in and around the dry lake bed.

    The pipeline repeatedly ruptured over the years. At least 60 separate spills dumped an estimated 2,000 metric tons of wastewater containing radioactive thorium into the valley. Federal officials feared that local residents and visitors to the nearby Mojave National Preserve might be at risk of exposure to that thorium, which could lead to increased risk of lung, pancreatic and other cancers.

    Unocal Corporation, which had acquired Molycorp in 1977, was ordered to clean up the spill in 1997, and the company paid over $1.4 million in fines and settlements. Chemical processing of the raw ore ground to a halt. Mining operations stopped shortly afterward.

    Half a world away, another environmental disaster was unfolding. The vast majority — between 80 and 90 percent — of rare earth elements on the market since the 1990s have come from China. One site alone, the massive Bayan Obo mine in Inner Mongolia, accounted for 45 percent of rare earth production in 2019.

    Bayan Obo spans some 4,800 hectares, about half the size of Florida’s Walt Disney World resort. It is also one of the most heavily polluted places on Earth. Clearing the land to dig for ore meant removing vegetation in an area already prone to desertification, allowing the Gobi Desert to creep southward.

    In 2010, officials in the nearby city of Baotou noted that radioactive, arsenic- and fluorine-containing mine waste, or tailings, was being dumped on farmland and into local water supplies, as well as into the nearby Yellow River. The air was polluted by fumes and toxic dust that reduced visibility. Residents complained of nausea, dizziness, migraines and arthritis. Some had skin lesions and discolored teeth, signs of prolonged exposure to arsenic; others exhibited signs of brittle bones, indications of skeletal fluorosis, Klinger says.

    The country’s rare earth industry was causing “severe damage to the ecological environment,” China’s State Council wrote in 2010. The release of heavy metals and other pollutants during mining led to “the destruction of vegetation and pollution of surface water, groundwater and farmland.” The “excessive rare earth mining,” the council wrote, led to landslides and clogged rivers.

    Faced with these mounting environmental disasters, as well as fears that it was depleting its rare earth resources too rapidly, China slashed its export of the elements in 2010 by 40 percent. The new limits sent prices soaring and kicked off concern around the globe that China had too tight of a stranglehold on these must-have elements. That, in turn, sparked investment in rare earth mining elsewhere.

    In 2010, there were few other places mining rare earths, with only minimal production from India, Brazil and Malaysia. A new mine in remote Western Australia came online in 2011, owned by mining company Lynas. The company dug into fossilized lava preserved within an ancient volcano called Mount Weld.

    Mount Weld didn’t have anywhere near the same sort of environmental impact seen in China: Its location was too remote and the mine was just a fraction of the size of Bayan Obo, according to Saleem Ali, an environmental planner at the University of Delaware. The United States, meanwhile, was eager to once again have its own source of rare earths — and Mountain Pass was still the best prospect.

    The Bayan Obo mine (shown) in China’s Inner Mongolia region was responsible for nearly half of the world’s rare earth production in 2019. Mining there has taken a heavy toll on the local residents and the environment.WU CHANGQING/VCG VIA GETTY IMAGES

    Mountain Pass mine gets revived

    After the Ivanpah Dry Lake mess, the Mountain Pass mine changed hands again. Chevron purchased it in 2005, but did not resume operations. Then, in 2008, a newly formed company called Molycorp Minerals purchased the mine with ambitious plans to create a complete rare earth supply chain in the United States.

    The goal was not just mining and processing ore, but also separating out the desirable elements and even manufacturing them into magnets. Currently, the separations and magnet manufacturing are done overseas, mostly in China. The company also proposed a plan to avoid spilling wastewater into nearby fragile habitats. Molycorp resumed mining, and introduced a “dry tailings” process — a method to squeeze 85 percent of the water out of its mine waste, forming a thick paste. The company would then store the immobilized, pasty residue in lined pits on its own land and recycle the water back into the facility.

    Unfortunately, Molycorp “was an epic debacle” from a business perspective, says Matt Sloustcher, senior vice president of communications and policy at MP Materials, current owner of Mountain Pass mine. Mismanagement ultimately led Molycorp to file for Chapter 11 bankruptcy in 2015. MP Materials bought the mine in 2017 and resumed mining later that year. By 2022, Mountain Pass mine was producing 15 percent of the world’s rare earths.

    MP Materials, too, has an ambitious agenda with plans to create a complete supply chain. And the company is determined not to repeat the mistakes of its predecessors. “We have a world-class … unbelievable deposit, an untapped potential,” says Michael Rosenthal, MP Materials’ chief operating officer. “We want to support a robust and diverse U.S. supply chain, be the magnetics champion in the U.S.”

    The challenges of separating rare earths

    On a hot morning in August, Sloustcher stands at the edge of the Mountain Pass mine, a giant hole in the ground, 800 meters across and up to 183 meters deep, big enough to be visible from space. It’s an impressive sight, and a good vantage point from which to describe a vision for the future. He points out the various buildings: where the ore is crushed and ground, where the ground rocks are chemically treated to slough off as much non–rare earth material as possible, and where the water is squeezed from that waste and the waste is placed into lined ponds.

    The end result is a highly concentrated rare earth oxide ore — still nowhere near the magnet-making stage. But the company has a three-stage plan “to restore the full rare earth supply to the United States,” from “mine to magnet,” Rosenthal says. Stage 1, begun in 2017, was to restart mining, crushing and concentrating the ore. Stage 2 will culminate in the chemical separation of the rare earth elements. And stage 3 will be magnet production, he says.

    Since coming online in 2017, MP Materials has shipped its concentrated ore to China for the next steps, including the arduous, hazardous process of separating the elements from one another. But in November, the company announced to investors that it had begun the preliminary steps for stage 2, a “major milestone” on the way to realizing its mine-to-magnet ambitions.

    With investments from the U.S. Department of Defense, the company is building two separations facilities. One plant will pull out lighter rare earth elements — those with smaller atomic numbers, including neodymium and praseodymium, both of which are key ingredients in the permanent magnets that power electric vehicles and many consumer electronics. MP Materials has additional grant money from the DOD to design and build a second processing plant to split apart the heavier rare earth elements such as dysprosium, also an ingredient in magnets, and yttrium, used to make superconductors and lasers.

    Like stage 2, stage 3 is already under way. In 2022, the company broke ground in Fort Worth, Texas, for a facility to produce neodymium magnets. And it inked a deal with General Motors to supply those magnets for electric vehicle motors.

    But separating the elements comes with its own set of environmental concerns.

    The process is difficult and leads to lots of waste. Rare earth elements are extremely similar chemically, which means they tend to stick together. Forcing them apart requires multiple sequential steps and a variety of powerful solvents to separate them one by one. Caustic sodium hydroxide causes cerium to drop out of the mix, for example. Other steps involve solutions containing organic molecules called ligands, which have a powerful thirst for metal atoms. The ligands can selectively bind to particular rare earth elements and pull them out of the mix.

    But one of the biggest issues plaguing this extraction process is its inefficiency, says Santa Jansone-Popova, an organic chemist at Oak Ridge National Laboratory in Tennessee. The scavenging of these metals is slow and imperfect, and companies have to go through a lot of extraction steps to get a sufficiently marketable amount of the elements. With the current chemical methods, “you need many, many, many stages in order to achieve the desired separation,” Jansone-Popova says. That makes the whole process “more complex, more expensive, and [it] produces more waste.”

    Under the aegis of the DOE’s Critical Materials Institute, Jansone-Popova and her colleagues have been hunting for a way to make the process more efficient, eliminating many of those steps. In 2022, the researchers identified a ligand that they say is much more efficient at snagging certain rare earths than the ligands now used in the industry. Industry partners are on board to try out the new process this year, she says.

    In addition to concerns about heavy metals and other toxic materials in the waste, there are lingering worries about the potential impacts of radioactivity on human health. The trouble is that there is still only limited epidemiological evidence of the impact of rare earth mining on human and environmental health, according to Ali, and much of that evidence is related to the toxicity of heavy metals such as arsenic. It’s also not clear, he says, how much of the concerns over radioactive waste are scientifically supported, due to the low concentration of radioactive elements in mined rare earths.

    Such concerns get international attention, however. In 2019, protests erupted in Malaysia over what activists called “a mountain of toxic waste,” about 1.5 million metric tons, produced by a rare earth separation facility near the Malaysian city of Kuantan. The facility is owned by Lynas, which ships its rare earth ore from Australia’s Mount Weld to the site. To dissolve the rare earths, the ore is cooked with sulfuric acid and then diluted with water. The residue that’s left behind can contain traces of radioactive thorium.

    Australian company Lynas built a plant near Kuantan, Malaysia, (shown in 2012) to separate and process the rare earth oxide ore mined at Mount Weld in Western Australia. Local protests erupted in 2019 over how the company disposes of its thorium-laced waste.GOH SENG CHONG/BLOOMBERG VIA GETTY IMAGES

    Lynas had no permanent storage for the waste, piling it up in hills near Kuantan instead. But the alarm over the potential radioactivity in those hills may be exaggerated, experts say. Lynas reports that workers at the site are exposed to less than 1.05 millisieverts per year, far below the radiation exposure threshold for workers of 20 millisieverts set by the International Atomic Energy Agency.

    “There’s a lot of misinformation about by­products such as thorium.… The thorium from rare earth processing is actually very low-level radiation,” Ali says. “As someone who has been a committed environmentalist, I feel right now that there’s not much science-based decision making on these things.”

    Given the concerns over new mining, environmental think tanks like the World Resources Institute have been calling for more recycling of existing rare earth materials to reduce the need for new mining and processing.

    “The path to the future has to do with getting the most out of what we take out of the ground,” says Bustamante, of the NRDC. “Ultimately the biggest lever for change is not in the mining itself, but in the manufacturing, and what we do with those materials at the end of life.”

    That means using mined resources as efficiently as possible, but also recycling rare earths out of already existing materials. Getting more out of these materials can reduce the overall environmental impacts of the mining itself, she adds.

    That is a worthwhile goal, but recycling isn’t a silver bullet, Ali says. For one thing, there aren’t enough spent rare earth–laden batteries and other materials available at the moment for recycling. “Some mining will be necessary, [because] right now we don’t have the stock.” And that supply problem, he adds, will only grow as demand increases. More

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    Particles from space provide a new look inside cyclones

    Particles raining down from space offer 3-D views inside swirling tropical storms.

    Muons created from cosmic rays that smash into Earth’s upper atmosphere have revealed the inner workings of cyclones over Japan, researchers report October 6 in Scientific Reports. The new imaging approach could lead to a better understanding of storms, the researchers say, and offer another tool to help meteorologists forecast the weather.

    “Cosmic rays are sustainable natural resources that can be used everywhere on this planet for 24 hours [a day],” says geophysicist Hiroyuki Tanaka of the University of Tokyo, so it’s just a matter of taking advantage of them.

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    Muons offer a glimpse inside storms because variations in air pressure and density change the number of particles that make it through a tempest. By counting how many muons arrived at a detector on the ground in Kagoshima, Japan as cyclones moved past, Tanaka and colleagues produced rough 3-D maps of the density of air inside the storms. The approach gave the team an inside look at the low-pressure regions at the centers rotating storm systems.

    Muons, which are similar to electrons but roughly 200 times as massive, can scatter off molecules in the air. They’re also unstable, which means they break down into electrons and other particles called neutrinos given enough time. As air pressure increases, so does its density. That, in turn, increases the chances that a muon born from a cosmic ray will be bumped off its path on the way toward a detector or get slowed enough that it breaks down before it makes it all the way through the atmosphere.

    For every 1 percent increase in air pressure, Tanaka and colleagues say, the number of muons that survive passage from the upper atmosphere to the ground decreases by about 2 percent.

    Fewer muons make it through the high-pressure portions at the edges of a swirling cyclone (yellow and green in this muograph) than through the low-pressure regions in the center (red), providing a map of conditions inside the storm (illustrated outline). The darkened portion was outside the viewing angle of the muon detector.©2022 H.K.M. Tanaka

    Tanaka has previously used muons from cosmic rays to look inside volcanoes, and he suspects that others have used the particles to study weather (SN: 4/22/22). But, he says, this appears to be the first time that anyone has made 3-D muon scans of the insides of a storm.

    “It is an interesting approach,” says meteorologist Frank Marks of the National Oceanic and Atmospheric Administration’s Atlantic Oceanographic and Meteorological Laboratory in Miami, who wasn’t involved in the research.

    He doesn’t expect muon imaging to replace conventional meteorological measurements, but it’s another tool that scientists could use. “[It] would be complementary to our existing techniques to provide 3-D mapping of the storms with our other traditional observing systems, like satellites and radar.” More

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    Landslides shaped a hidden landscape within Yellowstone

    DENVER — A hidden landscape riddled with landslides is coming into focus in Yellowstone National Park, thanks to a laser-equipped airplane.

    Scientists of yore crisscrossed Yellowstone on foot and studied aerial photographs to better understand America’s first national park. But today researchers have a massive new digital dataset at their fingertips that’s shedding new light on this nearly 1-million-hectare natural wonderland.

    These observations of Yellowstone have allowed a pair of researchers to pinpoint over 1,000 landslides within and near the park, hundreds of which had not been mapped before, the duo reported October 9 at the Geological Society of America Connects 2022 meeting. Most of these landslides likely occurred thousands of years ago, but some are still moving.

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    Mapping Yellowstone’s landslides is important because they can cripple infrastructure like roadways and bridges. The millions of visitors that explore the park each year access Yellowstone through just a handful of entrance roads, one of which recently closed for months following intense flooding.

    In 2020, a small aircraft flew a few hundred meters above the otherworldly landscape of Yellowstone. But it wasn’t ferrying tourists eager for up close views of the park’s famous wolves or hydrothermal vents (SN: 7/21/20, SN: 1/11/21). Instead, the plane carried a downward-pointing laser that fired pulses of infrared light at the ground. By measuring the timing of pulses that hit the ground and reflected back toward the aircraft, researchers reconstructed the precise topography of the landscape.

    Such “light detection and ranging,” or lidar, data reveal details that often remain hidden to the eye. “We’re able to see the surface of the ground as if there’s no vegetation,” says Kyra Bornong, a geoscientist at Idaho State University in Pocatello. Similar lidar observations have been used to pinpoint pre-Columbian settlements deep within the Amazon jungle (SN: 5/25/22).

    The Yellowstone lidar data were collected as part of the 3D Elevation Program, an ongoing project spearheaded by the United States Geological Survey to map the entirety of the United States using lidar.

    Bornong and geomorphologist Ben Crosby analyzed the Yellowstone data — which resolve details as small as about one meter — to home in on landslides. The team searched for places where the landscape changed from looking relatively smooth to looking jumbled, evidence that soil and rocks had once been on the move. “It’s a pattern-recognition game,” says Crosby, also of Idaho State University. “You’re looking for this contrast between the lumpy stuff and the smooth stuff.”

    The researchers spotted more than 1,000 landslides across Yellowstone, most of which were clustered near the periphery of the park. That makes sense given the geography of Yellowstone’s interior, says Lyman Persico, a geomorphologist at Whitman College in Walla Walla, Wash., who was not involved in the research. The park sits atop a supervolcano, whose previous eruptions blanketed much of the park in lava (SN: 1/2/18). “You’re sitting in the middle of the Yellowstone caldera, where everything is flat,” says Persico.

    But steep terrain also abounds in the national park, and there’s infrastructure in many of those landslide-prone areas. In several places, the team found that roads had been built over landslide debris. One example is Highway 191, which skirts the western edge of Yellowstone.

    An aerial image of U.S. Highway 191 near Yellowstone shows barely perceptible signs of a long-ago landslide. But laser mapping reveals the structure and extent of the landslide in much greater detail (use the slider to compare images). It’s one of more than 1,000 landslides uncovered by new maps.

    It’s worth keeping an eye on this highway since it funnels significant amounts of traffic through regions apt to experience landslides, Bornong says. “It’s one of the busiest roads in Montana.”

    There’s plenty more to learn from this novel look at Yellowstone, Crosby says. Lidar data can shed light on geologic processes like volcanic and tectonic activity, both of which Yellowstone has in spades. “It’s a transformative tool,” he says. More

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    Jacky Austermann looks to the solid earth for clues to sea level rise

    It’s no revelation that sea levels are rising. Rising temperatures brought on by human-caused climate change are melting ice sheets and expanding ocean water. What’s happening inside Earth will also shape future shorelines. Jacky Austermann is trying to understand those inner dynamics.

    A geophysicist at Columbia University’s Lamont-Doherty Earth Observatory, Austermann didn’t always know she would end up studying climate. Her fascination with math from a young age coupled with her love of nature and the outdoors — she grew up hiking in the Alps — led her to study physics as an undergraduate, and later geophysics.

    As Austermann dug deeper into Earth’s geosystems, she learned just how much the movement of hot rock in the mantle influences life on the surface. “I got really interested in this entire interplay of the solid earth and the oceans and the climate,” she says.

    Big goal

    Much of Austermann’s work focuses on how that interplay influences changes in sea level. The global average sea level has risen more than 20 centimeters since 1880, and the yearly rise is increasing. But shifts in local sea level can vary, with those levels rising or falling along different shorelines, Austermann says, and the solid earth plays a role.

    “We think about sea level change generally as ‘ice is melting, so sea level is rising.’ But there’s a lot more nuance to it,” she says. “A lot of sea level change is driven by land motion.” 

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    Understanding that nuance could lead to more accurate climate models for predicting sea level rise in the future. Such work should help inform practical solutions for communities in at-risk coastal areas.

    So Austermann is building computer models that reconstruct sea level changes over the last few million years. Her models incorporate data on how the creeping churning of the mantle and other geologic phenomena have altered land and sea elevation, particularly during interglacial periods when Earth’s temperatures were a few degrees higher than they are today.

    Standout research

    Previous studies had suggested that this churning, known as mantle convection, sculpted Earth’s surface millions of years ago. “It pushes the surface up where hot material wells up,” Austermann says. “And it also drags [the surface] down where cold material sinks back into the mantle.”

    In 2015, Austermann and colleagues were the first to show that mantle-induced topographic changes influenced the melting of Antarctic ice over the last 3 million years. Near the ice sheet’s edges, ice retreated more quickly in areas where the land surface was lower due to convection.

    What’s more, mantle convection is affecting land surfaces even on relatively short time scales. Since the last interglacial period, around 130,000 to 115,000 years ago, mantle convection has warped ancient shorelines by as much as several meters, her team reported in Science Advances in 2017.  

    Jacky Austermann builds computer models that reconstruct sea level changes over the last few million years. The work could improve models that forecast the future.Bill Menke

    The growing and melting of ice sheets can deform the solid earth too, Austermann says. As land sinks under the weight of accumulating ice, local sea levels rise. And as land uplifts where the ice melts, water falls. This effect, as well as how the ice sheet tugs on the water around it, is shifting local sea levels around the globe today, she says, making it very relevant to coastal areas planning their defenses in the current climate crisis.

    Understanding these geologic processes can help improve models of past sea level rise. Austermann’s team is gathering more data from the field, scouring the coasts of Caribbean islands for clues to what areas were once near or below sea level. Such clues include fossilized corals and water ripples etched in stone, as well as tiny chutes in rocks that indicate air bubbles once rose through sand on ancient beaches. The work is “really fun,” Austermann says. “It’s essentially like a scavenger hunt.”

    Her efforts put the solid earth at the forefront of the study of sea level changes, says Douglas Wiens, a seismologist at Washington University in St. Louis. Before, “a lot of those factors were kind of ignored.” What’s most remarkable is her ability “to span what we normally consider to be several different disciplines and bring them together to solve the sea level problem,” he says.

    Building community

    Austermann says the most enjoyable part of her job is working with her students and postdocs. More than writing the next big paper, she wants to cultivate a happy, healthy and motivated research group. “It’s really rewarding to see them grow academically, scientifically, come up with their own ideas … and also help each other out.”

    Roger Creel, a Ph.D. student in Austermann’s group and the first to join her lab, treasures Austermann’s mentorship. She offers realistic, clear and fluid expectations, gives prompt and thoughtful feedback and meets for regular check-ins, he says. “Sometimes I think of it like water-skiing, and Jacky’s the boat.”

    For Oana Dumitru, a postdoc in the group, one aspect of that valued mentorship came in the form of a gentle push to write and submit a grant proposal on her own. “I thought I was not ready for it, but she was like, you’ve got to try,” Dumitru says.

    Austermann prioritizes her group’s well-being, which fosters collaboration, Creel and Dumitru say. That sense of inclusion, support and community “is the groundwork for having an environment where great ideas can blossom,” Austermann says.

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    The Tonga eruption may have spawned a tsunami as tall as the Statue of Liberty

    The massive Tonga eruption generated a set of planet-circling tsunamis that may have started out as a single mound of water roughly the height of the Statue of Liberty.

    What’s more, the explosive eruption triggered an immense atmospheric shock wave that spawned a second set of especially fast-moving tsunamis, a rare phenomenon that can complicate early warnings for these oft-destructive waves, researchers report in the October Ocean Engineering.

    As the Hunga Tonga–Hunga Ha’apai undersea volcano erupted in the South Pacific in January, it displaced a large volume of water upward, says Mohammad Heidarzadeh, a civil engineer at the University of Bath in England (SN: 1/21/22). The water in that colossal mound later “ran downhill,” as fluids tend to do, to generate the initial set of tsunamis.

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    To estimate the original size of the mound, Heidarzadeh and his team used computer simulations, as well as data from deep-ocean instruments and coastal tide gauges within about 1,500 kilometers of the eruption, many of them in or near New Zealand. The arrival times of tsunami waves, as well as their sizes, at those locations were key pieces of data, Heidarzadeh says.

    The team analyzed nine possibilities for the initial wave, each of which was shaped like a baseball pitcher’s mound and had a distinct height and diameter. The best fit to the real-world data came from a mound of water a whopping 90 meters tall and 12 kilometers in diameter, the researchers report.

    That initial wave would have contained an estimated 6.6 cubic kilometers of water. “This was a really large tsunami,” Heidarzadeh says.

    Despite starting out about nine times as tall as the tsunami that devastated the Tohoku region of Japan in 2011, the Tongan tsunamis killed only five people and caused about $90 million in damage, largely because of their remote source (SN: 2/10/12).

    Another unusual aspect of the Tongan eruption is the second set of tsunamis generated by a strong atmospheric pressure wave.

    That pressure pulse resulted from a steam explosion that occurred when a large volume of seawater infiltrated the hot magma chamber beneath the erupting volcano. As the pressure wave raced across the ocean’s surface at speeds exceeding 300 meters per second, it pushed water ahead of it, creating tsunamis, Heidarzadeh explains.

    The eruption of the Hunga Tonga-Hunga Ha’apai volcano also triggered an atmospheric pressure wave that in turn generated tsunamis that traveled quicker than expected.NASA Earth Observatory

    Along many coastlines, including some in the Indian Ocean and Mediterranean Sea, these pressure wave–generated tsunamis arrived hours ahead of the gravity-driven waves spreading from the 90-meter-tall mound of water. Gravity-driven tsunami waves typically travel across the deepest parts of the ocean, far from continents, at speeds between 100 and 220 meters per second. When the waves reach shallow waters near shore, the waves slow, water stacks up and then strikes shore, where destruction occurs.

    Pressure wave–generated tsunamis have been reported for only one other volcanic eruption: the 1883 eruption of Krakatau in Indonesia (SN: 8/27/83).

    Those quicker-than-expected arrival times — plus the fact that the pressure-wave tsunamis for the Tongan eruption were comparable in size with the gravity-driven ones — could complicate early warnings for these tsunamis. That’s concerning, Heiderzadeh says.

    One way to address the issue would be to install instruments that measure atmospheric pressure with the deep-sea equipment already in place to detect tsunamis, says Hermann Fritz, a tsunami scientist at Georgia Tech in Atlanta.

    With that setup, scientists would be able to discern if a passing tsunami is associated with a pressure pulse, thus providing a clue in real time about how fast the tsunami wave might be traveling. More

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    The Arctic is warming even faster than scientists realized

    The Arctic is heating up at a breakneck speed compared with the rest of Earth. And new analyses show that the region is warming even faster than scientists thought. Over the last four decades, the average Arctic temperature increased nearly four times as fast as the global average, researchers report August 11 in Communications Earth & Environment.

    And that’s just on average. Some parts of the Arctic Ocean, such as the Barents Sea between Russia and Norway’s Svalbard archipelago, are warming as much as seven times as fast, meteorologist Mika Rantanen of the Finnish Meteorological Institute in Helsinki and colleagues found. Previous studies have tended to say that the Arctic’s average temperature is increasing two to three times as fast as elsewhere, as humans continue causing the climate to change.

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    To calculate the true pace of the accelerated warming, a phenomenon called Arctic amplification, the researchers averaged four sets of satellite data from 1979 to 2021 (SN: 7/1/20). Globally, the average temperature increase over that time was about 0.2 degrees Celsius per decade. But the Arctic was warming by about 0.75 degrees C per decade.

    Even the best climate models are not doing a great job of reproducing that warming, Rantanen and colleagues say. The inability of the models to realistically simulate past Arctic amplification calls into question how well the models can project future changes there.

    It’s not clear where the problem lies. One issue may be that the models are struggling with correctly simulating the sensitivity of Arctic temperatures to the loss of sea ice. Vanishing snow and ice, particularly sea ice, are one big reason why Arctic warming is on hyperspeed. The bright white snow and ice create a reflective shield that bounces incoming radiation from the sun back into space. But open ocean waters or bare rocks absorb that heat, raising the temperature. More