What Would Happen if Mount Saint Helens Erupted Again

If the supervolcano underneath Yellowstone National Park always had another massive eruption, it could spew ash for thousands of miles across the United States, damaging buildings, smothering crops, and shutting down ability plants. Information technology'd be a huge disaster.

Just that doesn't mean nosotros should all start freaking out. The odds of that happening are thankfully pretty low. The Yellowstone supervolcano — thousands of times more powerful than a regular volcano — has only had three truly enormous eruptions in history. One occurred 2.ane million years agone, one 1.3 million years agone, and one 664,000 years ago.

And despite what yous sometimes hear in the printing, there's no indication that we're due for some other "super-eruption" anytime before long. In fact, it'southward even possible that Yellowstone mightnever have an eruption that large over again.

However, the Yellowstone supervolcano remains an countless source of apocalyptic fascination — and it's not hard to see why. In September 2014 , a squad of scientists published a paper in Geochemistry, Geophysics, Geosystems exploring what a Yellowstone super-eruption might actually look like.

Among other things, they institute the volcano was capable of burial states like Wyoming, Montana, Idaho, and Colorado in three feet of harmful volcanic ash — a mix of splintered rock and glass — and blanket the Midwest. That much ash could kill plants and animals, crush roofs, and short all sorts of electrical equipment:

Ash, ash, everywhere

An example of the possible distribution of ash from a month-long Yellowstone supereruption. (United states of america Geological Survey)

When I called up one of the study's co-authors, Jacob Lowenstern of the Usa Geological Survey, he stressed that the paper wasnot whatsoever sort of prediction of the futurity. "Even if Yellowstone did erupt again, yous probably wouldn't become that worst-instance scenario," he says. "What's much, much more mutual are modest eruptions — that'southward a point that frequently gets ignored in the printing." (And even those pocket-size eruptions are very rare.)

Lowenstern is the Scientist-In-Charge of the Yellowstone Volcano Observatory in Menlo Park, California. Then I talked to him further about what we actually know about the Yellowstone supervolcano, what its eruptions might expect like, and why the odds of disaster are low.

What is the Yellowstone supervolcano?

(National Park Service)

Lurking beneath Yellowstone National Park is a reservoir of hot magma 5 miles deep, fed by a gigantic feather of molten rock welling up from hundreds of miles below. That heat is responsible for many of the park'due south famous geysers and hot springs. And as magma rises up into the chamber and cools, the ground above periodically rises and falls.

On rare occasions throughout history, that magma chamber has erupted. The vast, vast bulk of those eruptions in Yellowstone take been smaller lava flows — with the last occurring at Pitchstone Plateau some 70,000 years ago.

But the reason why Yellowstone gets so much attention is the remote possibility of catastrophic "super-eruptions." A super-eruption is anything that measures magnitude 8 or more on the Volcano Explosivity Alphabetize, in which at least 1,000 cubic kilometers (or 240 cubic miles) of material gets ejected. That's enough to bury Texas five feet deep.

These super-eruptions are thousands of times more powerful than even the biggest eruptions nosotros're used to. Hither's a chart from USGS comparison the Yellowstone super-eruptions with the Mt. St. Helens eruption of 1980. The difference is staggering:

Super-eruptions vs ordinary eruptions

(US Geological Survey)

Yellowstone has had iii of these really massive eruptions in its history — 2.1 meg years ago, 1.iii 1000000 years ago, and 664,000 years agone. The last of those, at Yellowstone Lava Creek, ejected so much material from beneath that it left a 34-mile-by-l-mile depression in the footing — what we meet today as the Yellowstone Caldera:

Location of past Yellowstone super-eruptions

(National Park Service)

It'due south worth noting that Yellowstone is hardly the but supervolcano out at that place — geologists have found testify of at least 47 super-eruptions in Earth'due south history. The most contempo occurred in New Zealand'southward Lake Taupo some 26,000 years ago.

More dramatically, in that location was the gargantuan Toba eruption 74,000 years ago, acquired past shifting tectonic plates. That triggered a dramatic 6- to 10-year global winter and (according to some) may have most wiped out the nascent human race .

On average, the Globe has seen roughly one super-eruption every 100,000 years, although that's not an ironclad law.

Then what would a Yellowstone eruption wait like?

Allow's reiterate that the odds of whatsoever sort of Yellowstone eruption, big or small, are very low. Just if we're speaking hypothetically…

The most likely eruption scenario in Yellowstone is a smaller issue that produced lava flows (like to what'southward happening at Iceland's Bárðarbunga right now) and possible a typical volcanic explosion. This would likely exist precipitated by a swarm of earthquakes in a specific region of the park as the magma made its way to the surface.

Now, in the unlikely result of a much bigger super-eruption, the warning signs would be much bigger. "We'd likely kickoff meet intense seismic activeness beyond the entire park," Lowenstern says. It could have weeks or months for those earthquakes to break up the rocks above the magma earlier an eruption.

And what if nosotros did get a super-eruption — an event that was 1,000 times more than powerful than a regular volcanic eruption, ejected at least 240 cubic miles of material, and lasted weeks or months? The lava flows themselves would be contained within a relatively minor radius within the park — say, 40 miles or and then. In fact, only about 1-third of the fabric would actually brand it up into the atmosphere.

The main impairment would come from volcanic ash — a combination of splintered rock and glass — that was ejected miles into the air and scattered around the country. In their new newspaper, Lowenstern and his colleagues looked at both historical ash deposits and advanced modeling to conclude that an eruption would create an umbrella deject, expanding even in all directions. (This was really a surprising finding.)

A super-eruption could conceivably bury the northern Rockies in three feet of ash — devastating large swaths of Wyoming, Idaho, Colorado, Montana, and Utah. Meanwhile, the Midwest would get a few inches of ash, while both coasts would run across even smaller amounts. The verbal distribution would depend on the time of yr and weather condition patterns:

Modeling the spread of ash from a Yellowstone super-eruption

(Mastin et al 2014)

Whatever of those scenarios would be terrible news. That much volcanic ash is capable of killing people, plants, and animals and burdensome buildings.Even a few inches of ash (which is what much of the country can go) can destroy farms, clog roadways, cause serious respiratory problems, cake sewer lines, and even curt out transformers. Air travel would have to close down beyond much of North America.

A volcanic eruption that large would also have major effects on the global climate. Volcanoes can emit sulfur aerosols that reflect sunlight back into the temper absurd the climate. These particles are short-lived in the atmosphere, then the outcome is just temporary, simply it can still be dramatic.

When Pinatubo erupted in 1991, it cooled the planet by near one°C (1.8°F) for a few years. The Tambora eruption in 1815 cooled the planet enough to damage crops around the world — mayhap leading to famines in some areas. And those were relatively tiny eruptions compared to what a supervolcano is, in theory, capable of.

Yikes! So what are the odds of a Yellowstone super-eruption?

Very, very low. In fact, it's fifty-fifty possible Yellowstone might never erupt again.

Right now, in that location's no sign of a pending eruption. Yellowstone park does continue to go earthquakes, and the ground continues to rise and fall, just that'south nil out of the ordinary. "Yellowstone is behaving as it has for the past 140 years," the USGS points out. "Odds are very high that Yellowstone will be eruption-free for the coming centuries."

The USGS likewise notes that, if y'all simply took the by 3 eruptions, the odds of Yellowstone erupting in any given year are0.00014 pct — lower than the odds of getting hit by a civilization-destroying asteroid. But fifty-fifty that's not a expert estimate, since it's not at all certain that Yellowstone erupts on a regular cycle or that it's "overdue" for some other eruption. In fact, in that location might never be a large eruption in Yellowstone again.

"The Earth volition see super-eruptions in the hereafter, but will they come in Yellowstone? That's not a sure thing," says Lowenstern. "Yellowstone's already lived a good long life. It may non even run into a fourth eruption."

Volcanoes, after all, exercise die out. The magma chamber below Yellowstone is being affected by two opposing forces — the heat welling upwards from below and the relative cold from the surface. If less heat comes in from below, and then the sleeping room could conceivably freeze, eventually turning into a solid granite body.

It's too worth noting that the volcanic hotspot underneath Yellowstone is slowly migrating to the northeast (or, more accurately, the North American tectonic plate above the hotspot is migrating southwest). You can see the migration below:

The volcanic hotspot is sloooooowly moving northeast

(USGS)

On a long enough time scale, the hotspot will movement out from under Yellowstone — and the Yellowstone supervolcano would, presumably, die out. Of class, information technology'southward possible that another supervolcano could emerge further in the northeast, but the hotspot would offset have to oestrus up and melt the cold chaff first. And that process could have a million years or longer.

"It's difficult to go our minds around something like a million years," Lowenstern says. "Humans are a relatively brand-new species. Only Earth's been around a very long time, and these systems take a long time to exercise what they do."

Further reading

-- The US Geological survey has an excellent FAQ on the Yellowstone supervolcano.They also take a great rundown of the near contempo paper modeling a super-eruption.

-- Here's a fascinating (and very accessible) paper Lowenstern wrote in 2006 explaining how scientists actually monitor the Yellowstone volcanic system. A key line: "One obstacle to authentic forecasting of large volcanic events is humanity's lack of familiarity with the singals leading up to the largest class of volcanic eruptions."

-- In the New Yorker, George Black wrote a fun slice about how unhinged fears (and misinformation) almost the Yellowstone supervolcano go along going viral.

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Source: https://www.vox.com/2014/9/5/6108169/yellowstone-supervolcano-eruption