Yellowstone supereruption would send ash across North America

Aug 27, 2014
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 cloud known as an umbrella, which expands evenly in all directions, sending ash across North America.

A supereruption is the largest class of , 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 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 '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

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User comments : 10

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sean_smith_7967
1 / 5 (6) Aug 27, 2014
Heading to a national park this summer? Take this with you. bit.ly/coltershell
carl_mennare
1.8 / 5 (6) Aug 27, 2014
Dumb, the author minimalizes the article by stating that another eruption will be unlikely. It has erupted 3 times in the past and it will erupt again, the author would have been correct to state that it is unlikely that an eruption will happen in our lifetimes. Europe already knows and is properly concerned about this eruption because they admit that it will impact them in a negative manner. There have been several documentaries from European scientists and they all agree that the ash cloud released from this volcano will affect the planet, first it will be picked up by the jet stream and unevenly distributed across the US and into Europe, then our plants and livestock will start to die off. Lastly us, unless we figure out how to move indoors at the first sign of rumbling.
drloko
2 / 5 (5) Aug 27, 2014
Seriously, is this the Onion? A super volcano erupts in the middle do the US and the bad effect you point out is that the ash might cause roads to be slippery?

Can we get a refund on this study?
Bob Osaka
1.7 / 5 (3) Aug 28, 2014
What did Ben Franklin say? "It is better to remain silent and be thought a fool.....?" forget the rest. The problem with computer models are that they are more akin to neat video games than messy reality. Can anyone answer the question: What exactly is going on deeper than 100km below the crust? Surely, someone who thinks themselves an expert is about to open their mouths.
The article mentions three previous eruptions. Three? Sure about that? On average Yellowstone erupts every 600,000 years. If that's the case it's 40,000 years overdue, minuscule in geological timeframes. It's not like we're talking about Ol' faithful here.
Believe the more correct answer they're searching for is: "Don't know, yet."
There have been much older slide rule based studies which have surmised everything within 1,000 miles will be vaporized by the blast and yards of molten debris and ash will cover the Eastern seaboard. Waiting to see who is right.
alfie_null
4 / 5 (4) Aug 28, 2014
No thanks for the awkward metric to imperial conversions liberally applied throughout the article.
howhot2
3 / 5 (2) Aug 28, 2014
Wow, ashes to ashes, dust to dust after that thing blows.
MosaicDude
1 / 5 (2) Aug 29, 2014
Would a nuclear strike on Yellowstone provoke an eruption?
howhot2
5 / 5 (1) Aug 29, 2014
Having backpacked all through the back country of Yellowstone it is an amazing volcano and an amazing park. I think a better place for a nuclear strike is right on the top of MosaicDude and see what kind of eruption that will provoke.
zorro6204
5 / 5 (1) Aug 30, 2014
There's something seriously wrong with this model. I was in Idaho during the Mt. St. Helen's eruption, and we had nearly a foot of ash 250 miles from the volcano. It's my understanding the a Yellowstone super eruption would be several orders of magnitudes larger, 1000-2500 km3. St. Helens was a tiny fraction of that.
Nik_2213
5 / 5 (2) Aug 30, 2014
http://www.usarray.org/

Their work shows the Yellowstone 'plume' is coming up from a break in the subducted Farallon plate. That should give a deeper (pun) understanding and rather more warning than just watching the caldera 'breathe'.

IIRC, the St Helens eruption was atypical because the paroxysmic flank collapse made it erupt 'sideways' with a 'super' pyroclastic flow. Most of that stuff would otherwise have gone upwards, to drift on the wind. Compare Pinatubo...