Tag Archives: geology

Rapidly Inflating Volcano Creates Growing Mystery

Rapidly Inflating Volcano Creates Growing Mystery – Yahoo! News.

Yeah, just ’cause it’s growing a cubic meter per second, and it explodes every 300k years or so, and it’s been 300k years since the last one, no, there’s no reason to get excited, we don’t expect it to explode.

WTF??

Should anyone ever decide to make a show called “CSI: Geology,” a group of scientists studying a mysterious and rapidly inflating South American volcano have got the perfect storyline.

Researchers from several universities are essentially working as geological detectives, using a suite of tools to piece together the restive peak’s past in order to understand what it is doing now, and better diagnose what may lie ahead.

It’s a mystery they’ve yet to solve.

Uturuncu is a nearly 20,000-foot-high (6,000 meters) volcano in southwest Bolivia. Scientists recently discovered the volcano is inflating with astonishing speed.

“I call this ‘volcano forensics,’ because we’re using so many different techniques to understand this phenomenon,” said Oregon State University professor Shan de Silva, a volcanologist on the research team. [See images of the inflating volcano here.]

Researchers realized about five years ago that the area below and around Uturuncu is steadily rising — blowing up like a giant balloon under a wide disc of land some 43 miles (70 kilometers) across. Satellite data revealed the region was inflating by 1 to 2 centimeters (less than an inch) per year and had been doing so for at least 20 years, when satellite observations began.

“It’s one of the fastest uplifting volcanic areas on Earth,” de Silva told OurAmazingPlanet.”What we’re trying to do is understand why there is this rapid inflation, and from there we’ll try to understand what it’s going to lead to.”

The  peak is perched like a party hat at the center of the inflating area. “It’s very circular. It’s like a big bull’s-eye,” said Jonathan Perkins, a graduate student at the University of California, Santa Cruz, who recently presented work on the mountain at this year’s Geological Society of America meeting  in Minneapolis.

Scientists figured out from the inflation rate that the pocket of magma beneath the volcano was growing by about 27 cubic feet (1 cubic meter) per second.

“That’s about 10 times faster than the standard rate of magma chamber growth you see for large volcanic systems,” Perkins told OurAmazingPlanet.

However, no need to flee just yet, the scientists said.

“It’s not a volcano that we think is going to erupt at any moment, but it certainly is interesting, because the area was thought to be essentially dead,” de Silva said.

Uber-Uturuncu?

Uturuncu is surrounded by one of the most dense concentrations of supervolcanoes on the planet, all of which fell silent some 1 million years ago.

Supervolcanoes get their name because they erupt with such power that they typically spew out 1,000 times more material, in sheer volume, than a volcano like Mount St. Helens. Modern human civilization has never witnessed such an event. The planet’s most recent supervolcanic eruption happened about 74,000 years ago in Indonesia. [Related: The 10 Biggest Volcanic Eruptions in History]

“These eruptions are thought to have not only a local and regional impact, but potentially a global impact,” de Silva said.

Uturuncu itself is in the same class as Mount St. Helens in Washington state, but its aggressive rise could indicate that a new supervolcano is on the way. Or not.

De Silva said it appears that local volcanoes hoard magma for about 300,000 years before they blow — and Uturuncu last erupted about 300,000 years ago.

“So that’s why it’s important to know how long this has been going on,” he said.

To find an answer, scientists needed data that stretch back thousands of years — but they had only 20 years of satellite data.

Volcano rap sheet

“So that’s where we come in as geomorphologists — to look for clues in the landscape to learn about the long-term topographic evolution of the volcano,” Perkins said.

Perkins and colleagues used ancient lakes, now largely dry, along the volcano’s flanks to hunt for signs of rising action.

“Lakes are great, because waves from lakes will carve shorelines into bedrock, which make lines,” Perkins said.

If the angle of those lines shifted over thousands of years  — if the summit of the mountain rose, it would gradually lift one side of the lake — it would indicate the peak had been rising for quite some time, or at least provide a better idea of when the movement began.

The local conditions, largely untouched by erosion or the reach of lush plant and animal life, lend themselves to geological detective work, Perkins noted.

“It’s a really sparse, otherworldly landscape,” Perkins said. “Everything is so well preserved. There’s no biology to get in the way of your observations.”

Perkins said that surveys conducted on the lakes last autumn didn’t indicate long-term inflation. However, tilting lakes are only one indicator of volcano growth, he said.

De Silva said the geological detective team is working to combine data from a number of sources — seismic data, GPS data, even minute variations in gravity — to pin down when and why the mountain awoke from its 300,000-year-long slumber, and better predict its next big move.

This story was provided by OurAmazingPlanet, a sister site to LiveScience. You can follow OurAmazingPlanet staff writer Andrea Mustain on Twitter: @andreamustain. Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

Earth's time bombs may have killed the dinosaurs

Earth’s time bombs may have killed the dinosaurs – environment – 27 July 2011 – New Scientist.

THE fate of the dinosaurs may have been sealed half a billion years before life even appeared, by two geological time bombs that still lurk near our planet’s core.

A controversial new hypothesis links massive eruptions of lava that coincided with many of Earth’s largest extinctions to two unusually hot blobs of mantle 2800 kilometres beneath the crust. The blobs formed just after the Earth itself, 4.5 billion years ago. If the hypothesis is correct, they have sporadically burst through the planet’s crust, creating enormous oceans of lava which poisoned the atmosphere and wiped out entire branches of the tree of life.

Debates still rage over what caused different mass extinctions, including the one that wiped out the dinosaurs. An asteroid that smashed into Earth 65 million years ago is no doubt partially to blame for the Cretaceous giants’ demise. But a less-known school of thought has it that this and other extinctions occurred when cracks in the crust let huge amounts of lava gush from the bowels of the Earth. Each event flooded at least 100,000 square kilometres, leaving behind distinct geological regions known as large igneous provinces (LIPs), such as India’s Deccan traps, formed when the dinosaurs went extinct (see map). “There is an amazing correlation between mass extinctions and LIPs,” says Andrew Kerr at the University of Cardiff, UK.

Now Matthew Jackson at Boston University, and colleagues, claim to have found evidence that LIPs are fed by 4.5-billion-year-old stores of mantle.

Most of the mantle has been modified by plate tectonics since then (see “Diamonds and the birth of plate tectonics”). But last year Jackson’s team found that 62-million-year-old basalts from the North Atlantic LIP contain isotopes of helium, hafnium and lead in ratios that reflect the chemistry of early Earth’s mantle.

They have now found similar lead isotope ratios in other LIP rocks, and say that LIPs in general may have an ancient source. Their analysis suggests this mantle contains an abundance of radioactive, heat-producing elements, making it unusually hot and potentially more likely to form the large quantities of lava needed to create LIPs (Nature, DOI: 10.1038/nature10326).

The ancient stores might still exist. Studies to probe the mantle’s structure with seismic waves have revealed two unusual areas some 2800 kilometres down, beneath Africa and the Pacific Ocean. Trond Torsvik of the University of Oslo, Norway, and colleagues recently showed that most LIPs formed while one of these two areas lay directly beneath them.

“It’s an interesting idea – that a giant blob of hot magma might burp from near Earth’s core every now and then, causing havoc for life,” says Gerta Keller at Princeton University, but adds more work is needed to support the hypothesis.

Kerr agrees: “This will be controversial – it flies in the face of much of the research from the last 30 years.” Conventional wisdom, he points out, suggests LIPs have a more prosaic source – young mantle formed when oceanic crust returns to the mantle through subduction.

But Torsvik is enthused. Having spent 10 years collecting evidence that his two mantle blobs have been stable for at least 540 million years, the idea that they contain primordial mantle is “like music to my ears”, he says.

Diamonds and the birth of plate tectonics

The inside of our planet is a magma-churning power house. As a result, very little remains from the millennia just after Earth formed. The two blobs of ancient magma that may be responsible for several mass extinctions are an exception.

Some diamonds, it turns out, may also serve as time capsules. A new study suggests that locked inside them is the secret of when the continents formed.

We knew that plate tectonics have been pushing new bits of crust into existence and engulfing old chunks back into the mantle for hundreds of millions of years. What we didn’t know is when it all started. Stephen Richardson at the University of Cape Town, South Africa, and Steven Shirey of the Carnegie Institution for Science in Washington DC collected thousands of ancient diamonds from around the world. Gems considered to be flawed by the jewellery industry can contain tiny clumps of minerals from the rocks in which they formed. Some clumps are made of peridotite, others of the rarer eclogite, which is only formed when volcanic rocks from the surface are forced deep into the mantle and crushed in the immense pressure and heat there. To get eclogite, you need plate tectonics.

When Richardson and Shirey dated the mineral clumps, they found that the peridotite ranged from 2 to 3.5 billion years old, but the oldest eclogite was 3 billion years old (Science, DOI: 10.1126/science.1206275). This, say the researchers, proves that plate tectonics cannot have been active before then. Michael Marshall

Are we entering an age of major earthquakes?

Are we entering an age of major earthquakes? – CSMonitor.com.

A study of more than a century of global seismic records has prompted some scientists to say that major earthquakes have tended to occur in clusters. Others disagree.

Japan Ground Self-Defense Force members search in the rain for victims’ belongings in a devastated area in Minami Soma, northeastern Japan, Tuesday.

Hiro Komae/AP

By Charles Q. Choi, OurAmazingPlanet Contributor / April 20, 2011

A number of devastating quakes have struck across the globe in recent years — from Japan to Chile to Haiti — sparking fears that our planet is due to experience even more catastrophic temblors in the near future.

Skip to next paragraph

Three research teams have now combed through 110 years’ worth of global seismic records to see if we might be caught in a global trend of giant earthquakes.

Some say we are; others disagree.

Megaquake clusters

One pair of researchers found clusters of what they called “megaquakes,” earthquakes of magnitude 9.0 or greater.

One cluster involved three such quakes between 1952 and 1964, including the magnitude 9.5 Chile quake of 1960, the largest earthquake ever recorded on Earth. Another, larger, cluster of magnitude 8.6 and higher temblors happened between 1950 to 1965, said Charles Bufe and David Perkins, seismologists with the U.S. Geological Survey in Golden, Colo. They speculate that the magnitude 8.4 Peru quake in 2001 could mark the beginning of a new global sequence of major quakes that we are currently experiencing.

“This isn’t doomsday — I don’t think large earthquakes will occur over a long period of time — but we’re saying there seems to be a cluster right now with a higher than normal probability for large quakes,” Bufe told OurAmazingPlanet. “I don’t know how long this cluster might last — if we don’t get another large earthquake in maybe the next 10 or 12 years, I would say we’re probably out of the cluster.”

Bufe suggested that by sending seismic waves traveling around and around the planet’s surface, very large earthquakes might weaken fault zones that are already very close to failure. “I think there’s a more than 50 percent chance we’ll see another magnitude 9 quake sometime in the next decade or so,” he said.

Just chance?

On the other hand, this apparent recent spike in large quakes could just reflect random fluctuations in global patterns of seismic activity. A statistical study from U.S. Geological Survey researcher Andrew Michael at Menlo Park, Calif., suggests this seeming cluster pattern disappeared once local aftershocks of the large earthquakes are taken into account.

“The most important lesson is that random doesn’t mean uniformly distributed in time — instead, random processes create apparent clustering and it is important to carefully consider whether apparent clusters, or times of less activity, go beyond what is expected from a simple random process,” Michael told OurAmazingPlanet. “So far, my results show that the apparent clustering is consistent with a random process.”

If the apparent clustering of these quakes is a matter of chance, then seismologists can’t say whether or not another huge temblor is likely to erupt anytime soon.

“The recent spate of great earthquakes can be explained as a random fluctuation without predictive power for the future,” Michael said. He added that global predictions of earthquakes and the damage they inflict should use the longest possible historical record for an area “rather than focusing on the recent past.”

Long-term record

Seismologist Richard Aster at the New Mexico Institute of Mining and Technology and his colleagues looked at historical catalogs of earthquakes along with more recent findings to create a long-term record of the cumulative size of earthquakes around the world.

They suggest there were relatively low rates of big earthquakes during the periods 1907 to 1950 and 1967 to 2004. However, they found the rate of large earthquakes increased substantially during the period 1950 to 1967 and appears to be on the rise again since 2004, since the devastating magnitude 9.1 to 9.3 earthquake that struck Indonesia and generated a massive tsunami late that year.

Still, this finding “is not statistically differentiable from randomness,” Aster told OurAmazingPlanet.

Progress into understanding whether there are ages of major quakes or not may be slow “because we just don’t get that many great earthquakes to produce a better sampling of this natural process,” Aster said.

“We only get a few magnitude 9-plus earthquakes per century, for example — fortunately for earthquake risks around the world, these events are rare,” Aster said. “There are only 14 earthquakes in the past 111 years greater than magnitude 8.5.”

Michael agreed. “The main limitation is that we don’t have enough data,” he said. “We can’t say that clustering doesn’t exist. We can only say that the data doesn’t let us reject the hypothesis that the data is random. If there was more data, then the results could change — but that will take decades to occur.”

The scientists detailed their findings on April 14 at the Seismological Society of America meeting in Memphis, Tenn.

Yellowstone Has Bulged as Magma Pocket Swells

Yellowstone Has Bulged as Magma Pocket Swells.

Steam rising from Castle Geyser in Yellowstone National Park.

Steam rises from Castle Geyser in Yellowstone National Park (file photo).

Photograph by Mark Thiessen, National Geographic

Brian Handwerk

for National Geographic News

Published January 19, 2011

Yellowstone National Park‘s supervolcano just took a deep “breath,” causing miles of ground to rise dramatically, scientists report.

The simmering volcano has produced major eruptions—each a thousand times more powerful than Mount St. Helens’s 1980 eruption—three times in the past 2.1 million years. Yellowstone’s caldera, which covers a 25- by 37-mile (40- by 60-kilometer) swath of Wyoming, is an ancient crater formed after the last big blast, some 640,000 years ago.

(See “When Yellowstone Explodes” in National Geographic magazine.)

Since then, about 30 smaller eruptions—including one as recent as 70,000 years ago—have filled the caldera with lava and ash, producing the relatively flat landscape we see today.

But beginning in 2004, scientists saw the ground above the caldera rise upward at rates as high as 2.8 inches (7 centimeters) a year. (Related: “Yellowstone Is Rising on Swollen ‘Supervolcano.'”)

The rate slowed between 2007 and 2010 to a centimeter a year or less. Still, since the start of the swelling, ground levels over the volcano have been raised by as much as 10 inches (25 centimeters) in places.

“It’s an extraordinary uplift, because it covers such a large area and the rates are so high,” said the University of Utah’s Bob Smith, a longtime expert in Yellowstone’s volcanism.

Video: Yellowstone—World’s First National Park.

Scientists think a swelling magma reservoir four to six miles (seven to ten kilometers) below the surface is driving the uplift. Fortunately, the surge doesn’t seem to herald an imminent catastrophe, Smith said. (Related: “Under Yellowstone, Magma Pocket 20 Percent Larger Than Thought.”)

“At the beginning we were concerned it could be leading up to an eruption,” said Smith, who co-authored a paper on the surge published in the December 3, 2010, edition of Geophysical Research Letters.

“But once we saw [the magma] was at a depth of ten kilometers, we weren’t so concerned. If it had been at depths of two or three kilometers [one or two miles], we’d have been a lot more concerned.”

Studies of the surge, he added, may offer valuable clues about what’s going on in the volcano’s subterranean plumbing, which may eventually help scientists predict when Yellowstone’s next volcanic “burp” will break out.

Yellowstone Takes Regular Breaths

Smith and colleagues at the U.S. Geological Survey (USGS) Yellowstone Volcano Observatory have been mapping the caldera’s rise and fall using tools such as global positioning systems (GPS) and interferometric synthetic aperture radar (InSAR), which gives ground-deformation measurements.

Ground deformation can suggest that magma is moving toward the surface before an eruption: The flanks of Mount St. Helens, for example, swelled dramatically in the months before its 1980 explosion. (See pictures of Mount St. Helens before and after the blast.)

But there are also many examples, including the Yellowstone supervolcano, where it appears the ground has risen and fallen for thousands of years without an eruption.

According to current theory, Yellowstone’s magma reservoir is fed by a plume of hot rock surging upward from Earth’s mantle. (Related: “New Magma Layer Found Deep in Earth’s Mantle?”)

When the amount of magma flowing into the chamber increases, the reservoir swells like a lung and the surface above expands upward. Models suggest that during the recent uplift, the reservoir was filling with 0.02 cubic miles (0.1 cubic kilometer) of magma a year.

When the rate of increase slows, the theory goes, the magma likely moves off horizontally to solidify and cool, allowing the surface to settle back down.

Based on geologic evidence, Yellowstone has probably seen a continuous cycle of inflation and deflation over the past 15,000 years, and the cycle will likely continue, Smith said.

Surveys show, for example, that the caldera rose some 7 inches (18 centimeters) between 1976 and 1984 before dropping back about 5.5 inches (14 centimeters) over the next decade.

“These calderas tend to go up and down, up and down,” he said. “But every once in a while they burp, creating hydrothermal explosions, earthquakes, or—ultimately—they can produce volcanic eruptions.”

Yellowstone Surge Also Linked to Geysers, Quakes?

Predicting when an eruption might occur is extremely difficult, in part because the fine details of what’s going on under Yellowstone are still undetermined. What’s more, continuous records of Yellowstone’s activity have been made only since the 1970s—a tiny slice of geologic time—making it hard to draw conclusions.

“Clearly some deep source of magma feeds Yellowstone, and since Yellowstone has erupted in the recent geological past, we know that there is magma at shallower depths too,” said Dan Dzurisin, a Yellowstone expert with the USGS Cascades Volcano Observatory in Washington State.

“There has to be magma in the crust, or we wouldn’t have all the hydrothermal activity that we have,” Dzurisin added. “There is so much heat coming out of Yellowstone right now that if it wasn’t being reheated by magma, the whole system would have gone stone cold since the time of the last eruption 70,000 years ago.”

The large hydrothermal system just below Yellowstone’s surface, which produces many of the park’s top tourist attractions, may also play a role in ground swelling, Dzurisin said, though no one is sure to what extent.

“Could it be that some uplift is caused not by new magma coming in but by the hydrothermal system sealing itself up and pressurizing?” he asked. “And then it subsides when it springs a leak and depressurizes? These details are difficult.”

And it’s not a matter of simply watching the ground rise and fall. Different areas may move in different directions and be interconnected in unknown ways, reflecting the as yet unmapped network of volcanic and hydrothermal plumbing.

The roughly 3,000 earthquakes in Yellowstone each year may offer even more clues about the relationship between ground uplift and the magma chamber.

For example, between December 26, 2008, and January 8, 2009, some 900 earthquakes occurred in the area around Yellowstone Lake.

This earthquake “swarm” may have helped to release pressure on the magma reservoir by allowing fluids to escape, and this may have slowed the rate of uplift, the University of Utah’s Smith said. (Related: “Mysterious ‘Swarm’ of Quakes Strikes Oregon Waters.”)

“Big quakes [can have] a relationship to uplift and deformations caused by the intrusion of magma,” he said. “How those intrusions stress the adjacent faults, or how the faults might transmit stress to the magma system, is a really important new area of study.”

Overall, USGS’s Dzurisin added, “the story of Yellowstone deformation has gotten more complex as we’ve had better and better technologies to study it.”

Months of geologic unrest signaled reawakening of Icelandic volcano

Months of geologic unrest signaled reawakening of Icelandic volcano.

ScienceDaily (Nov. 18, 2010) — Months of volcanic restlessness preceded the eruptions this spring of Icelandic volcano Eyjafjallajökull, providing insight into what roused it from centuries of slumber.

An international team of researchers analyzed geophysical changes in the long-dormant volcano leading up to its eruptions in March and April 2010 that suggest that magma flowing beneath the volcano may have triggered its reawakening. Their study is published in the Nov. 18 issue of the journal Nature.

“Several months of unrest preceded the eruptions, with magma moving around downstairs in the plumbing and making noise in the form of earthquakes,” says study co-author Kurt Feigl, a professor of geosciences at the University of Wisconsin-Madison. “By monitoring volcanoes, we can understand the processes that drive them to erupt.”

With funding from a RAPID grant from the U.S. National Science Foundation, Feigl and collaborators from Iceland, Sweden, and the Netherlands used a combination of satellite imaging and GPS surveying to watch the volcano’s edifice as it deformed. They found that the volcano swelled for 11 weeks before it began to erupt in March 2010 from one flank.

“If you watch a volcano for decades, you can tell when it’s getting restless,” Feigl says.

In late summer 2009, a subtle shift at a GPS station on Eyjafjallajökull’s flank prompted the study’s lead author, Freysteinn Sigmundsson, and his colleagues to begin monitoring the mountain more closely. Then, in early January 2010, the rate of deformation and the number of earthquakes began to increase. As the deformation and seismic unrest continued, the researchers installed more GPS stations near the mountain. Just a few weeks later, the instruments detected more rapid inflation, indicating that magma was moving upwards through the “plumbing” inside the volcano.

By the time the volcano began to erupt on March 20, the volcano’s flanks had expanded by more than six inches as magma flowed from deep within the Earth into shallow chambers underneath the mountain.

Surprisingly, the rapid deformation stopped as soon as the eruption began. In many cases, volcanoes deflate as magma flows out of shallow chambers during an eruption. Eyjafjallajökull, however, maintained basically the same inflated shape through mid-April, when the first eruption ended.

Artist’s conception illustrating the three-dimensional geometry of the plumbing (left) and timing of events (right column) at Eyjafjallajökull volcano in Iceland. The complicated plumbing inside the volcano consists of inter–connected conduits, sills, and dikes that allow magma to rise from deep within the Earth. The first three panels in the time series show distinct episodes of magmatic intrusions that caused measurable deformation and seismic events in 1994, 1999, and in the first several months of 2010. No eruptive activity occurred during this period of unrest. Each intrusive episode inflated a different section of the plumbing, drawn and modeled as sills at approximately 5 km depth. The fourth panel illustrates the first eruption, between 20 March and 12 April 2010, when basaltic magma (orange) erupted onto the Earth’s surface on the flank of the mountain. The fifth panel shows the second eruption, between 14 April and 22 May, when a different type of magma (trachyandesite, shown in red), erupted explosively at the ice-capped summit (1600 m elevation). The interaction of magma and ice initially increased the explosive activity, generating a plume of particles that rose as high as the 30,000-foot flight level and disrupted air traffic across Europe for weeks. (Credit: Illustration by Zina Deretsky, U.S. National Science Foundation)

After a two-day pause, the volcano began to erupt again on April 22. This time, the lava broke out through a new conduit under the ice on the summit of the mountain, causing an explosive reaction as water flashed to steam and gas escaped from bubbles in the magma. The resulting “ash” plume rose high into the atmosphere, disrupting air traffic over Europe for weeks and stranding millions of travelers.

Why did Eyjafjallajökull erupt when it did? The geologic processes that trigger an actual eruption are not yet well understood, says Feigl. “We’re still trying to figure out what wakes up a volcano.”

To begin to answer this question, the scientists suggest that a magmatic intrusion deep within the volcano may have triggered the eruption, but this hypothesis remains to be tested at other volcanoes.

They are also studying the structures inside the volcano, such as magma chambers and intrusive conduits, by extracting information from the sensors installed around Eyjafjallajökull.

“The explosiveness of the eruption depends on the type of magma, and the type of magma depends on the depth of its source,” Feigl says. “We’re a long way from being able to predict eruptions, but if we can visualize the magma as it moves upward inside the volcano, then we’ll improve our understanding of the processes driving volcanic activity.”

Satellite radar images were obtained from TerraSAR-X, a satellite operated by the German Space Agency (DLR). Funding was provided by the National Science Foundation, Icelandic Research Fund, University of Iceland, and the Icelandic government.

Yellowstone Hot Spot Shreds Ancient Pacific Ocean

Yellowstone Hot Spot Shreds Ancient Pacific Ocean : Discovery News.

Analysis by Michael Reilly
Thu Sep 2, 2010 05:15 PM ET
3 Comments | Leave a Comment

If you thought the geysers and overblown threat of a supervolcanic eruption in Yellowstone National Park were dramatic, you ain’t seen nothing: deep beneath Earth’s surface, the hot spot that feeds the park has torn an entire tectonic plate in half.

The revelation comes from a new study in the journal Geophysical Research Letters that peered into the mantle beneath the Pacific Northwest to see what happens when ancient ocean crust from the Pacific Ocean runs headlong into a churning plume of ultra-hot mantle material.

Geologically speaking, the Pacific Northwest is a peculiar place. Hot spots usually sit way out on their own in the middle of a tectonic plate (think Hawaii or the Galapagos). Not Yellowstone — it pokes its way to the surface just a few hundred miles from the edge of the North America plate, where a giant trench sends the Juan de Fuca tectonic plate sliding underneath Washington, Oregon, and northern California.

YellowstoneHotspot

Peering into the middle of this tectonic traffic jam is a tricky business. So scientists, led by Mathias Obrebski of the University of California, Berkeley, had to build an image from seismic waves bouncing around inside the mantle. What they found was a subterranean world filled with violence.

The original data figures are a little hard to look at, but the team built a cartoon representation of what they think is going on down there. Around 19 million years ago, the Yellowstone hot spot first ascended from deep within the mantle. As it neared the surface, it ran into the subducting Juan de Fuca plate.

YellowstoneSlab2 But the Juan de Fuca plate was itself young at the time (there’s a mid-ocean ridge just off the coast of Oregon that forms brand new crust to this day), so it hadn’t had the chance fully harden yet. When the crust and hot spot met, the hot mantle plume to found a weakness in the plate — perhaps a pre-existing fracture — and punched a giant hole through it.

So, who cares? The encounter has had several amazing consequences. First, and most obvious, it resurfaced much of northern Nevada, Idaho, and Wyoming over the last several million years in basalt through a series of massive volcanic eruptions. Then there were the tremendous supervolcanic explosions, which coated much of the western U.S. in thick blankets of ash and made the Yellowstone park region what it is today.

Second, the team points out that the rise of the Yellowstone plume also coincided with a large change in the rate at which the crust of the Pacific Ocean dives beneath North America. It’s possible that the shattered underlying plate simply didn’t pull as much weight anymore, and the subduction zone slowed down.

It’s a new chapter in what we know about Yellowstone’s legendary power to change the landscape. Not only did its massive eruptions coat North America in ash from Idaho to the Mississippi River, and south almost to the Gulf of Mexico, but its deep plume sent a ripple effect through the very roots of the continent and the Pacific Ocean that fundamentally altered the coastline of the Pacific Northwest.