text: Beneath Yellowstone National Park lies a supervolcano, a behemoth far more powerful than your average volcano. It has the ability to expel more than 1,000 cubic kilometers of rock and ash at once — 2,500 times more material than erupted from Mount St. Helens in 1980, which killed 57 people. That could blanket most of the United States in a thick layer of ash and even plunge the Earth into a volcanic winter. 
   
   Yellowstone’s last supereruption occurred 631,000 years ago. And it’s not the planet’s only buried supervolcano. Scientists suspect that a supereruption scars the planet every 100,000 years, causing many to ask when we can next expect such an explosive planet-changing event. 
   
   To answer that question, scientists are seeking lessons from Yellowstone’s past. And the results have been surprising. They show that the forces that drive these rare and violent events can move much more rapidly than volcanologists previously anticipated. 
   
   The early evidence, presented at a recent volcanology conference, shows that Yellowstone’s most recent supereruption was sparked when new magma moved into the system only decades before the eruption. Previous estimates assumed that the geological process that led to the event took millenniums to occur. ||||| If the supervolcano underneath Yellowstone erupts again, we may have far less advance warning time than we thought. 
   
   After analyzing minerals in fossilized ash from the most recent mega-eruption, researchers at Arizona State University think the supervolcano last woke up after two influxes of fresh magma flowed into the reservoir below the caldera. 
   
   And in an unsettling twist, the minerals revealed that the critical changes in temperature and composition built up in a matter of decades. Until now, geologists had thought it would take centuries for the supervolcano to make that transition. 
   
   Volcanoes 101 Volcanoes are as dangerous as they are majestic. Over 50 eruptions rock our planet every year. This video helps you understand what causes volcanoes to form and erupt—and shows where they are most likely to be found. 
   
   
   
   A 2013 study, for instance, showed that the magma reservoir that feeds the supervolcano is about two and a half times larger than previous estimates. Scientists also think the reservoir is drained after every monster blast, so they thought it should take a long time to refill. Based on the new study, it seems the magma can rapidly refresh—making the volcano potentially explosive in the geologic blink of an eye. 
   
   “It’s shocking how little time is required to take a volcanic system from being quiet and sitting there to the edge of an eruption,” study co-author Hannah Shamloo told the New York Times. 
   
   Still, Yellowstone is one of the best monitored volcanoes in the world, notes Michael Poland, the current Scientist-in-Charge of the Yellowstone Volcano Observatory for the U.S. Geological Survey. A variety of sensors and satellites are always looking for changes, and right now, the supervolcano does not seem to pose a threat. 
   
   "We see interesting things all the time ... but we haven't seen anything that would lead us to believe that the sort of magmatic event described by the researchers is happening," says Poland via email, adding that the research overall is "somewhat preliminary, but quite tantalizing." 
   
   The new paper adds to a suite of surprises scientists have uncovered over the last few years as they have studied the supervolcano. (Also find out about a supervolcano under Italy that has recently been rumbling.) 
   
   Related: Top 5 Must-See Attractions in Yellowstone 
   
   Today, Yellowstone National Park owes much of its rich geologic beauty to its violent past. Wonders like the Old Faithful geyser and the Grand Prismatic Spring are products of the geothermal activity still seething below the park, which is driven in turn by the vast magma plume that feeds the supervolcano. 
   
   About 630,000 years ago, a powerful eruption shook the region, spewing forth 240 cubic miles’ worth of rock and ash and creating the Yellowstone caldera, a volcanic depression 40 miles wide that now cradles most of the national park. 
   
   That eruption left behind the Lava Creek Tuff, the ash deposit that Shamloo and her ASU colleague Christy Till used for their work, which they presented in August at a volcanology meeting in Oregon. The pair also presented an earlier version of their study at a 2016 meeting of the American Geophysical Union. 
   
   Based on fossil deposits like this one, scientists think the supervolcano has seen at least two other eruptions on this scale in the past two million years or so. Lucky for us, the supervolcano has been largely dormant since before the first people arrived in the Americas. While a handful of smaller belches and quakes have periodically filled the caldera with lava and ash, the last one happened about 70,000 years ago. 
   
   In 2011, scientists revealed that the ground above the magma chamber bulged by up to 10 inches in a span of about seven years. 
   
   "It's an extraordinary uplift, because it covers such a large area and the rates are so high," the University of Utah's Bob Smith, an expert in Yellowstone volcanism, told National Geographic at the time. 
   
   The swelling magma reservoir responsible for the uplift was too deep to create fears of imminent doom, Smith said, and instead the caldera’s gentle “breathing” offered valuable insights into the supervolcano’s behavior. 
   
   In 2012, another team reported that at least one of the past super-eruptions may have really been two events, hinting that such large-scale events may be more common than thought. 
   
   But almost everyone who studies Yellowstone’s slumbering supervolcano says that right now, we have no way of knowing when the next big blast will happen. For its part, the U.S. Geological Survey puts the rough yearly odds of another massive Yellowstone blast at 1 in 730,000—about the same chance as a catastrophic asteroid collision. ||||| Beneath America's fourth most-visited national park, the apocalypse waits. There's a supervolcano under Yellowstone, capable of shooting 1,000 cubic kilometers of rock and ash into the air. Enough to cover the entire planet. And now, scientists are learning that the entire process may happen faster than previously expected. 
   
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   At IAVCEI 2017 in Portland, Oregon, researchers presented evidence that such eruptions only need a few decades of gestation before exploding. Considering how such eruptions are relatively rare, geologically speaking—there are only three known explosions in history, the last one occurring 631,000 years ago—there was an expectation that they needed a lot of preparation beforehand. That assumption is proving to be wrong, showing how much left there is to learn about supervolcanoes. 
   
   "If something like this happened today, it would be catastrophic," says Hannah Shamloo, a geologist at Arizona State, speaking to the American Geophysical Union. "We want to understand what triggers these eruptions, so we can set up warning systems. That's the big-picture goal." 
   
   Alongside her Ph.D. adviser at Arizona State, geologist Christy Till, Shamloo examined two specific sorts of crystals known as phenocrysts, which form as magma cools a beneath a volcano. Varying between 1 and 2 millimeters each, these crystals are too large to have formed during the heat of an eruption. Rather, each crystal starts with a core that grows layer upon layer, forming a rough equivalent to the rings of a tree. 
   
   The outer rims of these phenocrysts show a clear change in temperature and composition occurring over a few decades, a geologic snap of the finger. "We expected that there might be processes happening over thousands of years preceding the eruption," Till tells the New York Times. "It's shocking how little time is required to take a volcanic system from being quiet and sitting there to the edge of an eruption," Shamloo says. 
   
   However, there's still a lot of work to be done before Shamloo's dream of a warning system gets put into place. Scientists still need to figure out how these massive buildups transform into supereruptions. Because if one happens, you'll need to run pretty fast if you want to escape it. 
   
   Source: New York Times ||||| An example of the possible distribution of ash from a month-long Yellowstone supereruption. The distribution map was generated by a new model developed by the US Geological Survey using wind information from January 2001. The improved computer model, detailed in a new study published in Geochemistry, Geophysics, Geosystems, finds that the hypothetical, large eruption would create a distinctive kind of ash cloud known as an umbrella, which expands evenly in all directions, sending ash across North America. Ash distribution will vary depending on cloud height, eruption duration, diameter of volcanic particles in the cloud, and wind conditions, according to the new study. Credit: Credit: USGS In the unlikely event of a volcanic supereruption at Yellowstone National Park, the northern Rocky Mountains would be blanketed in meters of ash, and millimeters would be deposited as far away as New York City, Los Angeles and Miami, according to a new study. 
   
   An improved computer model developed by the study's authors finds that the hypothetical, large eruption would create a distinctive kind of ash cloud known as an umbrella, which expands evenly in all directions, sending ash across North America. 
   
   A supereruption is the largest class of volcanic eruption, during which more than 1,000 cubic kilometers (240 cubic miles) of material is ejected. If such a supereruption were to occur, which is extremely unlikely, it could shut down electronic communications and air travel throughout the continent, and alter the climate, the study notes. 
   
   A giant underground reservoir of hot and partly molten rock feeds the volcano at Yellowstone National Park. It has produced three huge eruptions about 2.1 million, 1.3 million and 640,000 years ago. Geological activity at Yellowstone shows no signs that volcanic eruptions, large or small, will occur in the near future. The most recent volcanic activity at Yellowstone—a relatively non-explosive lava flow at the Pitchstone Plateau in the southern section of the park—occurred 70,000 years ago. 
   
   Researchers at the U.S. Geological Survey used a hypothetical Yellowstone supereruption as a case study to run their new model that calculates ash distribution for eruptions of all sizes. The model, Ash3D, incorporates data on historical wind patterns to calculate the thickness of ash fall for a supereruption like the one that occurred at Yellowstone 640,000 years ago. 
   
   The new study provides the first quantitative estimates of the thickness and distribution of ash in cities around the U.S. if the Yellowstone volcanic system were to experience this type of huge, yet unlikely, eruption. 
   
   Cities close to the modeled Yellowstone supereruption could be covered by more than a meter (a few feet) of ash. There would be centimeters (a few inches) of ash in the Midwest, while cities on both coasts would see millimeters (a fraction of an inch) of accumulation, according to the new study that was published online today in Geochemistry, Geophysics, Geosystems, a journal of the American Geophysical Union. 
   
   The figure above shows illustrations of plume shapes that would result from different types of volcanic eruptions. A weak plume (left) typically forms above small eruptions such as the April-May 2010 eruption of the Eyjafjallajökull volcano in Iceland, as shown in this NASA Earth Observatory image. A strong plume with a major umbrella cloud (right) forms during very large eruptions, such as shown in this Japanese Meteorological Agency image of the Pinatubo cloud on June 15, 1991. During superuruptions, umbrella clouds from strong plumes may push their way hundreds or thousands of kilometers upwind, according to a new study published in Geochemistry, Geophysics, Geosystems. Credit: Credit: USGS 
   
   The model results help scientists understand the extremely widespread distribution of ash deposits from previous large eruptions at Yellowstone. Other USGS scientists are using the Ash3D model to forecast possible ash hazards at currently restless volcanoes in Alaska. 
   
   Unlike smaller eruptions, whose ash deposition looks roughly like a fan when viewed from above, the spreading umbrella cloud from a supereruption deposits ash in a pattern more like a bull's eye – heavy in the center and diminishing in all directions – and is less affected by prevailing winds, according to the new model. 
   
   "In essence, the eruption makes its own winds that can overcome the prevailing westerlies, which normally dominate weather patterns in the United States," said Larry Mastin, a geologist at the USGS Cascades Volcano Observatory in Vancouver, Washington, and the lead author of the new paper. Westerly winds blow from the west. 
   
   "This helps explain the distribution from large Yellowstone eruptions of the past, where considerable amounts of ash reached the west coast," he added. 
   
   The three large past eruptions at Yellowstone sent ash over many tens of thousands of square kilometers (thousands of square miles). Ash deposits from these eruptions have been found throughout the central and western United States and Canada. 
   
   Erosion has made it difficult for scientists to accurately estimate ash distribution from these deposits. Previous computer models also lacked the ability to accurately determine how the ash would be transported. 
   
   Using their new model, the study's authors found that during very large volcanic eruptions, the expansion rate of the ash cloud's leading edge can exceed the average ambient wind speed for hours or days depending on the length of the eruption. This outward expansion is capable of driving ash more than 1,500 kilometers (932 miles) upwind – westward—and crosswind – north to south—producing a bull's eye-like pattern centered on the eruption site. 
   
   In the simulated modern-day eruption scenario, cities within 500 kilometers (311 miles) of Yellowstone like Billings, Montana, and Casper, Wyoming, would be covered by centimeters (inches) to more than a meter (more than three feet) of ash. Upper Midwestern cities, like Minneapolis, Minnesota, and Des Moines, Iowa, would receive centimeters (inches), and those on the East and Gulf coasts, like New York and Washington, D.C. would receive millimeters or less (fractions of an inch). California cities would receive millimeters to centimeters (less than an inch to less than two inches) of ash while Pacific Northwest cities like Portland, Oregon, and Seattle, Washington, would receive up to a few centimeters (more than an inch). 
   
   Even small accumulations only millimeters or centimeters (less than an inch to an inch) thick could cause major effects around the country, including reduced traction on roads, shorted-out electrical transformers and respiratory problems, according to previous research cited in the new study. Prior research has also found that multiple inches of ash can damage buildings, block sewer and water lines, and disrupt livestock and crop production, the study notes. 
   
   The study also found that other eruptions – powerful but much smaller than a Yellowstone supereruption—might also generate an umbrella cloud. 
   
   "These model developments have greatly enhanced our ability to anticipate possible effects from both large and small eruptions, wherever they occur," said Jacob Lowenstern, USGS Scientist-in-Charge of the Yellowstone Volcano Observatory in Menlo Park, California, and a co-author on the new paper. 
   
   Explore further: Volcanic eruption begins under Iceland glacier 
   
   More information: onlinelibrary.wiley.com/doi/10 … 014GC005469/abstract 
   
   ||||| Geologists suggest that mixing of magma melt pockets could have caused the explosion a little more than 600,000 years ago. 
   
   Yellowstone National Park is renowned for more than just its hot springs and Old Faithful. The area is famous in the volcanology community for being the site of three explosive supereruptions, the last of which was 631,000 years ago. 
   
   During that eruption, approximately 1000 cubic kilometers of rock, dust, and volcanic ash blasted into the sky. Debris rained across the continental United States, spanning a rough triangle that stretches from today’s Canadian border down to California and over to Louisiana. In places, ash reached more than a meter thick. 
   
   “If something like this happened today, it would be catastrophic,” said Hannah Shamloo, a geologist at Arizona State University’s School of Earth and Space Exploration in Tempe. “We want to understand what triggers these eruptions, so we can set up warning systems. That’s the big-picture goal.” 
   
   Now, Shamloo and her coauthor think they’ve found a clue. By examining trace elements in crystals that they found in the volcanic leftovers of Yellowstone’s last supereruption, they might be able to pinpoint what triggered it. 
   
   Outer Rims 
   
   Just outside Yellowstone National Park is a thick multicolored, multilayered rock formation called the Lava Creek Tuff. Tuffs are igneous rocks formed by the volcanic debris left behind by an explosive eruption. 
   
   Minerals in these tuffs can tell scientists about conditions inside the volcano before it erupted, and identifying these preeruptive conditions may help inform current hazard assessments. 
   
   Shamloo and her Ph.D. adviser at Arizona State University, geologist Christy Till, examined two crystals of feldspar that they found embedded in the tuff. These crystals, called phenocrysts, form as magma cools slowly beneath the volcano. 
   
   These phenocrysts, measuring between 1 and 2 millimeters in diameter, were too large to have formed when hot material was flung up during the eruption. 
   
   Instead, as Shamloo explained, they grew gradually over time in Yellowstone’s magma chamber, each crystal beginning with a core that slowly and steadily enlarged outward, layer upon layer. As surrounding magma conditions—temperature, pressure, and water content— changed, trace elements surrounding the growing phenocrysts also changed and became incorporated into subsequent layers. 
   
   In this way, the differences in chemical composition between the phenocryst core and successive layers serve as a map of changing conditions deep within the volcano over time. What’s more, the phenocrysts’ outermost rims represent the magma that surrounded the crystal right before Yellowstone erupted. 
   
   Thus, by analyzing the outer rims, Shamloo and Till could gather both temperature and trace element information just prior to the massive explosion. 
   
   Bubble, Bubble, Toil and Trouble 
   
   Temperature information locked in a phenocryst’s outer rims can be extracted using a technique called feldspar thermometry. The technique relies on the fact that certain minerals vary their compositions in known ways as temperatures change. Thus, scientists can work backward from the exact compositions of minerals present in these outer rims to estimate the surrounding temperature when the crystal rim formed. 
   
   The duo found signatures in the rims that point to an increase in temperature and uptick in the element barium in the magma just before the eruption. They presented their research on 13 December at the American Geophysical Union’s Fall Meeting in San Francisco, Calif. 
   
   To verify their layer by layer analysis of temperature and chemical composition, Shamloo and Till used MELTS, a software program that models how the crystal composition changed as a function of temperature, pressure, and water content in the magma chamber. They assumed that the magma had the same bulk composition as the Lava Creek Tuff. Their results and the model agreed well but pointed to a low water content for the magma chamber involved in the recent supereruption. In contrast, an older eruption from the Long Valley Caldera that produced the Bishop Tuff had 5% water by weight, 5 times more than the one that produced the Lava Creek Tuff. 
   
   “There are multiple ways to trigger an eruption, but as of now, we’re seeing evidence for a magma injection.” The low water content is surprising, Shamloo explained, because water and steam create pressures that can trigger eruptions. But Shamloo said that the phenocrysts’ story of hotter temperatures and more barium in the magma chamber just prior to the eruption suggests a possible culprit behind the explosion: the mixing of neighboring pockets of semimelted magma, called an injection event. “There are multiple ways to trigger an eruption, but as of now, we’re seeing evidence for a magma injection,” she said. 
   
   Magma, molten or semimolten rock that exists in layers of the Earth’s crust, can also reach the Earth’s surface. Because it is less dense than surrounding rocks, magma can move upward through cracks in the Earth’s crust, but when its motion is stymied, it pools into magma chambers. These chambers expand thanks to magma injections, when hotter material from deeper volcanic reservoirs feeds into shallower ones. This injection of hotter material just before the eruption may explain the temperature increase recorded in the phenocrysts. 
   
   But the presence of barium in the phenocrysts is a smoking gun, said Shamloo. “Barium doesn’t like to be in the crystal. It likes to hang out in the melt, so this tells us the barium must’ve been introduced from a different source.” The duo thinks this source is a deeper reservoir inside the volcano. 
   
   Eric Christiansen, a volcanologist from Brigham Young University in Provo, Utah, who was not involved with the study, was skeptical of Shamloo’s use of the MELTS software and thinks this type of modeling isn’t as reliable as “real experiments with real rocks.” However, he asserted, “her work is sound, and her analysis is solid. She’s got interesting trace element data with the barium, a late addition to the chamber, which suggests it accompanies what triggered the eruption.” 
   
   Geologic Crystal Ball 
   
   “The public is always afraid of the ‘next big one.’ And I like to ask, ‘Can we really forecast that?’” “The public is always afraid of the ‘next big one,’” Shamloo said. “And I like to ask, ‘Can we really forecast that?’” Shamloo and Till hope that they can. 
   
   Knowing the eruption trigger is just the first step, according to Shamloo. The next step is understanding what order of time—days, months, even years—these changes can take before an eruption like the one that produced the Lava Creek Tuff. 
   
   Such information could help Shamloo, Till, and others to correctly read signs of volcanic unrest at Yellowstone and to create a model for predicting future supereruptions. 
   
   —Aylin Woodward (email: [email protected]; @AylinWoodward), Freelance Science Writer
target: – Should it ever erupt, a supervolcano beneath Yellowstone National Park could blanket North America in an ash cloud, wipe out communications, and alter the climate. Given that eruptions of supervolcanoes buried on our planet—and there are several—are thought to occur every 100,000 years or so, however, the likelihood of such an event during your lifetime is small, reports the New York Times. As comforting as that may be, new research out of Arizona State University is far less so. Whereas researchers previously thought such an eruption would be centuries or millennia in the making, an analysis of fossilized ash left over from Yellowstone's last supereruption 630,000 years ago reveals the process could take only decades. Tiny crystals left over from underground magma at Yellowstone show the first sign of the last supereruption was a spike in temperature that coincided with the movement of new magma into the reservoir beneath the supervolcano. The crystals also reveal a supereruption followed much quicker than scientists previously thought—perhaps within decades, or what Popular Mechanics calls "a geologic snap of the finger." This is the first indication that "the conditions that lead to supereruptions might emerge within a human lifetime," which one researcher describes as "shocking," per the Times. For now, though, you can rest easy. The lead scientist at the Yellowstone Volcano Observatory tells National Geographic there's no sign of any "magmatic event" at this time. (You might outrun a supervolcano's lava anyway.)