What an eruption at Yellowstone Super-Volcano would be like: Not so bad?

Lurking beneath Yellowstone National Park is a massive underground reservoir of magma, capped by the park’s famous caldera. 640,000 years ago, a super eruption rocked the region. What would happen if another such event blasted the park today? We asked USGS geologist Jake Lowenstern, scientist-in-charge of the Yellowstone Volcano Observatory.
Photo by Nina B via Shutterstock Most volcanic activity in Yellowstone would not qualify as “super eruptions,” in which 1,000 km3 or more material is ejected from a volcano. Lowenstern told io9 that supervolcanoes are “very large, single eruptions” that usually last for about a week. But, unlike what you’ll see in certain television specials and Hollywood films, even a super eruption at Yellowstone wouldn’t endanger the whole United States. It also wouldn’t cause the kind catastrophe you might expect. Damage from the Super Eruption A super eruption might come fast and the Yellowstone magma source is enormous. But don’t expect walls of lava pouring across the continent. Lava flows would be likely be “within the vicinity of the park,” Lowenstern said, limited to a 30-40 mile radius. When a volcano erupts, he added, at least a third of the liquid rock that’s ejected falls right back into the volcano’s maw. The rest lands nearby, or goes up into the atmosphere.

Most of the real damage comes from ejecta that’s airborne. But it’s not fiery death from above. Instead, most damage would come from “cold ash” and pumice borne on the wind. Lowenstern and his colleagues consider it “disastrous” when enough ash rains down that it creates a layer of 10 or more centimeters on the ground — and that would happen in a radius of about 500 miles or so. This ash might reach so far that you’d see a fine dusting of it on your car in New York. Air traffic would be grounded, of course, as we saw after the 2010 eruption in Iceland. But mostly this ash would pollute farms in the midwest, as well as the Mississippi River. In a sense, it would be like an industrial accident, clogging waterways and agricultural areas with toxic sludge. The worst outcome of this event would be the destruction of our food supplies and waterways.

What would it look like? A super eruption, like all volcanic eruptions, begins with an earthquake. “A lot of earthquakes have to occur to break the rocks and allow magma to get to the surface,” Lowenstern said, adding that we’d need some big ones in the weeks or months leading up to the eruption. That means there would be many warning signs before it happened — this eruption wouldn’t come out of nowhere. Next, enormous vents or fissures in the Earth would break open near the caldera, perhaps in a ring around it or maybe as far as 10 kilometers away. Lava and superheated gasses would shoot out of these vents very rapidly, draining the magma reservoir beneath the caldera. As the the magma quickly drained, the caldera would begin to crumble. Eventually, it would collapse in an oval-shaped sinkhole that might be roughly 50 miles long by 30 miles wide. SExpand After the vents released their gasses and the ground collapsed, it’s likely that we’d see a global effect on temperatures. “Any big eruption causes a cooling of the atmoshpere, especially especially with that much ash,” said Lowenstern. In 1812, the Mount Tambora super volcano eruption in Indonesia lowered global temperatures. A caldera-forming eruption in Yellowstone would be bigger than the one in Tambora, so climate change would almost certainly follow. The cooling, however, would only last for a few years. Lowenstern said there’s no reason to expect that we’ll have an eruption of this size any time soon, especially because the caldera has gone through many regular eruptions that release pressure. “It may be done, or it may move on to another area,” he said. “In a couple million years, [the volcano] might start in the northeast.” As continental plates shift, so too do volcanoes — so the Yellowstone supervolcano might not go off until it’s far beyond the area we call Yellowstone today. “A more likely eruption is going to be a lava flow, a small event,” Lowenstern said. Are there signs of an impending eruption?   Currently, the Yellowstone caldera shows no signs of preparing for a super eruption. That doesn’t mean that there aren’t regular earthquakes in the area — that’s just a natural part of being in a volcanic region. And the caldera itself rises and falls all the time, the ground moving up and down as pressure increases and decreases in the magma reservoir below. “It rose about 27 centimeters max over the past 6 years,” Lowenstern said. “Calderas are big and hot, so they don’t break very easily and they just move up and down. It’s the way heat and gas get out of these deep systems — the system breathes.” He added that if a super eruption were coming, “you’d need extraordinary activity,” something that went way beyond centimeters of movement and a few small quakes. Right now, the Yellowstone caldera is breathing normally, exhibiting behaviors typical of any massive hydrothermal system. Lowenstern and the team of scientists at the Yellowstone Volcano Observatory are constantly studying the caldera, looking for changes and working on projections of what the next eruption might be like. An eruption could “come at any time,” Lowenstern admitted. But would it be a super eruption? Probably not. And even if it were, the damage wouldn’t be the inferno you might be expecting. Instead of fleeing from hell on Earth, you’d just be slogging through lots and lots of ash cleanup. http://io9.com/what-will-really-happen-when-yellowstone-volcano-has-a-508274690

 

Potential for SuperQuakes Underestimated

 

Potential for ‘Superquakes’ Underestimated, Recent Earthquakes Show

Becky Oskin, OurAmazingPlanet Staff Writer –         Feb 04, 2013        04:14 PM ET
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                            A village near the coast of Sumatra lays in ruin, Jan. 2, 2005, as a result of the tsunami that struck South East Asia Dec. 26, 2004. CREDIT: U.S. Navy photo by Petty Officer 2nd Class Philip A. McDaniel

The earthquakes that rocked Tohoku, Japan in 2011, Sumatra in 2004 and Chile in 1960 — all of magnitude 9.0 or greater — should not have happened, according to seismologist’s theories of earthquake cycles. And that might mean earthquake prediction needs an overhaul, some researchers say.

All three earthquakes struck along subduction zones, where two of Earth’s tectonic plates collide and one dives beneath the other. Earlier earthquakes had released the pent-up strain along Chile’s master fault, meaning no big quakes were coming, scientists had thought. Japan and Sumatra both sat above on old oceanic crust, thought to be too stiff for superquakes.

And records of past quakes, combined with measurements of the speed of Earth’s tectonic plates, suggested the Tohoku and Sumatra-Andaman regions couldn’t make quakes larger than 8.4, almost nine times smaller than a magnitude 9.0 temblor.

“These areas had been written off as places incapable of producing a great earthquake,” said Chris Goldfinger, a marine geologist at Oregon State University in Corvallis.

But the events of 1960, 2004 and 2011 showed that these faults were capable of producing some of the most destructive earthquakes in recorded history, suggesting earthquake researchers need to re-think aspects of how they evaluate a fault’s earthquake potential.

“It’s time to come up with something new,” Goldfinger told OurAmazingPlanet.

Faults are like batteries

When two tectonic plates collide, they build up strain where a fault sticks, or locks, together. Earthquakes release this strain, which is a form of energy.

For decades, scientists assumed faults acted like rubber bands, steadily building up strain and then releasing it all at once, Goldfinger said. The longer the time since the last earthquake, the larger the next earthquake would be, the model predicted. [Video: What Does Earthquake ‘Magnitude’ Mean?]

 

The problem was researchers failed to recognize that faults can store energy like a battery, Goldfinger said. And just like batteries, they can discharge energy in small amounts, or all at once, he explained.

Goldfinger and other researchers now think if a “small” quake hits, it may not release all of the accumulated energy in a fault. (On a subduction zone, a small quake can still register in the magnitude-8.0 range, which is devastating to nearby cities.)

Thus, a fault can “borrow” stored energy from previous strain-building cycles, generating larger earthquakes than expected, such as those that hit Sumatra and Tohoku, Goldfinger and his colleagues propose in a study published in the January/February 2013 issue of the journal Seismological Research Letters.

“Those models were already being called into question when Sumatra drove one stake through their heart, and Tohoku drove the second one,” said Goldfinger, the lead author of the study.

Superquakes and supercycles

Goldfinger said scientists’ failure to recognize that faults could store energy comes from a lack of data. Historic earthquake records go back only 100 years, he noted. Geologists are only now getting histories that reach back thousands of years, via techniques that decode evidence of past earthquakes in sediments.

“What is happening on a short-term timescale is actually imposed on a long-term cycle,” he said.

Goldfinger calls these long-term histories supercycles, and the unusually large and rare earthquakes that discharge the battery are superquakes. The sequence, size and location of quakes vary from one supercycle to the next, he said.

Seismologist Marco Cisternas first proposed that faults could store energy in 2005, with a study showing that the magnitude 9.5 Chile earthquake in 1960, the largest on record, released more energy than had been stored since its most recent quake, in 1837. Tsunami deposits in Chile indicate the last superquake occurred in 1575, and smaller quakes since then had only partly released the strain built up on the fault, his study found.

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The Cascadia subduction zone: producer of massive earthquakes. CREDIT: USGS.

In Sumatra, south of the Andaman region, analyses of corals uplifted and killed during earthquakes also indicated that the subduction zone undergoes supercycles, according to a 2008 study led by geologists at the Earth Observatory Institute in Singapore. Each series of quakes in the region lasts between 30 and 100 years, according to the study. The supercycles unfold every 200 years or so.

Forecasting the future

Goldfinger and his colleagues have evidence that the Cascadia Subduction Zone, which stretches from Northern California to British Columbia, is also in the middle of an earthquake supercycle.

Over the past 10,000 years, 19 superquakes and four supercycles have occurred along the zone, Goldfinger said.

“These would typically be of a magnitude from about 8.7 to 9.2, really huge earthquakes,” Goldfinger said. “We’ve also determined that there have been 22 additional earthquakes that involved just the southern end of the fault. We are assuming that these are slightly smaller, more like 8.0, but not necessarily. They were still very large earthquakes that if they happened today could have a devastating impact,” he said.

The present cycle seems like it’s gently ratcheting downward, Goldfinger said. “This would suggest that we’re not due for a giant [quake] anytime soon, but the model has no predictive value,” he said.

The battery model of earthquake energy storage and discharge makes it difficult for scientists to forecast future earthquakes, as there’s no explanation yet for why faults would behave this way, Goldfinger said. Plus, it’s hard to say how much energy a fault’s battery stores. “We haven’t yet figured out how to effectively put a voltmeter on a fault and say how charged it is,” Goldfinger said.

But with more detailed records of past earthquakes, such as those in Sumatra and Cascadia, Goldfinger believes scientists can give better estimates of seismic hazards, and prevent surprises like Sumatra and Tohoku.

“The long records are revealing very useful things,” he said. “We’re not sure what’s driving the long-term cycling, but at least we can tell people what to prepare for,” Goldfinger said.