If the Yellowstone Supervolcano ever blew its top, this new study shows us what to expect
Thursday, September 11, 2014, 2:04 PM - Some recent scares with the supervolcano that lies under Wyoming's Yellowstone National Park - an unusually strong earthquake and some running bison - caused worry to spread about a possible impending eruption. None of these scares actually represented any real threat, but if this slumbering giant were to erupt, a new study is giving a much clearer, and frightening view of the effects that would be felt right across the U.S. and Canada.
Yellowstone National Park is famous for its hot springs and its geysers, like Old Faithful, but in geologic circles it's famous for something else too - the Yellowstone caldera. This immense supervolcano is one of the largest in the world, capable of spewing out over 250 cubic kilometres of magma (over 1,100 times greater than the flow from Mount St. Helens) and blasting billions of metric tons of ash into the atmosphere. Whereas the magma is definitely a concern for anyone in Wyoming, Idaho and Montana, the ash is considered a far bigger concern, as it has the potential to spread right across the continent, to cover everything from Los Angeles to Vancouver, all the way to Florida and up the east coast to Atlantic Canada.
Since the last eruption at Yellowstone was roughly 70,000 years ago and the other known major eruptions ranged back hundreds of thousands to millions of years ago, much of the evidence for the extent of the ashfalls from these eruptions have been erased by time. Since knowing the potential full extent of a worst-case scenario would be a benefit to any kind of disaster planning, scientists with the US Geological Survey took on the task. Gathering the most recent information on the caldera, and using real-world historic weather data to construct the wind fields that ash would be released into, Larry Mastin, a USGS researcher at the Cascades Volcano Observatory, along with fellow USGS scientists Jacob Lowenstern and Alexa Van Eaton studied just how much ash would fall due to a super-eruption, given different types of ash plumes, and at different times of the year.
After a month of blasting ash into the sky, their models of the worst (read: strongest) eruptions typically resulted in that ash being spread right across the U.S. and through southern parts of Canada. The image below, taken from one of their simulations, shows the full extent of the ashfall if the eruption took place in the month of January, and produced an ash plume that took the form of a 'major umbrella cloud' (which looks just like it sounds, spreading ash in all directions around the volcano).
Credit: US Geological Survey
With the way weather patterns generally move across the continent, this means that ash would spread much farther east than west, but it ends up extending to cover much of the continent.
Although those thicknesses are only being measured in millimetres, that still represents over a metre's worth of ash on the ground closest to the caldera, and up to 5-10 centimetres covering every surface in southeastern Alberta, southern Saskatchewan and southwestern Manitoba, up to a centimetre falling over Toronto, and lower amounts reaching the US East Coast and the Maritimes. And whereas it may look like snow, even the smallest amount of this ash could have serious consequences, not just to the regions it falls over, but for the planet.
The first issue with this ash is that it's a physical problem - covering everything and getting into everything (including engine intakes, A/C systems, etc). Regions closest to the eruption would be buried, rendering much of the area uninhabitable for a significant amount of time. Cleanup of the ash in less-affected areas would still cost millions to billions of dollars.
A second issue is that all the ash in the sky would make air travel anywhere in North America hazardous, as it would coat jet turbines, causing the engines to shut down in mid-flight.
A third issue is that the volcano would be spreading billions of tons of what is essentially particulate matter though the air. Breathing, without some kind of protection, anywhere this ash was falling would be potentially dangerous, especially for those people who already suffer from respiratory problems. Also, it's not just from the physical particulate matter that we'd breathe into our lungs, but there's also the potentially toxic chemicals that could be coating those particles. The effects of this would be worse the closer someone is to the volcano, but as we already monitor for low levels of fine particulate matter in the air and reports have found that no amount in the air is entirely safe, this is a fairly big concern for human and animal health.
Fourthly, the effects on the environment would be potentially disastrous as well. The ash (and any chemicals that came along with it) would contaminate lakes and waterways. Plants would be cut off from the Sun, both by the ash coating them, and the ash plume blocking much of the Sun's rays from even reaching the ground.
Lastly (at least for this look at it), it could have significant impacts on our civilization. As the ash spread on the winds (and the smallest particles can travel all the way around the planet), the highly-reflective sulfur compounds in the ash clouds would cause significant cooling of the planet. This could, potentially, plunge us into a volcanic winter. The impact on agriculture would threaten our food supply and these types of events have been known to touch off ice ages.
This study gives us the latest, best look at that to expect from a Yellowstone super-eruption, but what are the chances that an eruption like this will take place?
In fact, even though it's been around 70,000 years since the last eruption there, so perhaps there's some thought that it's 'overdue' for another, the risk of Yellowstone going through one of these super-eruptions is pretty low.
"Thinking about a Yellowstone supereruption is like imagining a large asteroid hitting the Earth," Lowenstern, who is the USGS Scientist-in-Charge at the Yellowstone Volcano Observatory, told Business Insider. "It could happen, but it's not something you can plan for or worry about, because it's such a low-probability event."
According to Lowenstern, if there is an eruption at Yellowstone, it's more likely to be a moderate one, rather than the worst-case scenarios represented in this study. Even moderate eruptions can be a concern, though, mostly for the cooling effects that the ash can have on our climate.
The study, which includes views of the ashfalls from other runs of their models, is published in the journal Geochemistry, Geophysics, Geosystems (available online, by clicking here). The US Geological Survey has info not only on this study, but also on supervolcanoes and the Yellowstone caldera itself.