Q. Is Idaho's Magic Valley in Yellowstone National Park’s supervolcano kill zone?
A. “Volcanic eruptions are a little like gifts. Yes, someone could gift you the Palace of Versailles, but it’s probably more likely that you’re going to get a gift certificate to Cracker Barrel,” said Yellowstone Volcano Observatory Scientist-in-Charge Jake Lowenstern. He said about 95 percent of the volcanic eruptions at Yellowstone wouldn’t even be detectable in Twin Falls.
“The last eruption of any kind was 70,000 years ago, which was generally non-explosive,” said Lowenstern. “Everyone has heard about the worst-case scenario at Yellowstone, which happened three times in the last two million years. Could it happen again? Perhaps, but we’re not entirely sure. Volcanoes do die, and Yellowstone has had a long life.”
The National Park Service’s website said given Yellowstone’s past history, the yearly probability of another caldera-forming eruption could be calculated as 1 in 730,000 or 0.00014 percent. However, this number is based simply on averaging the two intervals between the three major past eruptions at Yellowstone.
Lowenstern said, “If it did happen, the effects at Twin Falls would depend a lot on the winds during the eruption. Generally, they would move ash to the east, rather than west, so that you’d receive less than a few inches of ash. You’d survive. Large volcanic eruptions can generate mushroom clouds, which could potentially drop more ash on Twin Falls. However, it’s hard to imagine, even in a worst-case scenario, that Twin Falls would receive enough ash to cause any ‘kill.’”
“Sometimes, you’ll see websites drawing a circle for a three-hundred mile distance around Yellowstone and pronouncing it as a ‘kill zone.’ There is no basis for such a zone. Things are not that simple, and the ‘zone’ is mostly fear-mongering by people who don’t know much about volcanic eruptions,” said Lowenstern.
The website also said there is no evidence that a catastrophic eruption at the nation’s first national park is imminent. Current geologic activity at Yellowstone has remained relatively constant since scientists began monitoring about 30 years ago. Though another caldera-forming eruption is theoretically possible, it’s doubtful to occur in the next thousand or even 10,000 years.
The most probable activity would be lava flows oozing slowly, such as those that occurred after the last major eruption. No scientific evidence indicates this probability will occur soon.
Scientists speculate the buildup prior to a catastrophic eruption would be detectable for weeks and perhaps months to years. Precursors to volcanic eruptions include strong earthquake swarms and rapid ground deformation.
Although with the latest earthquake swarms are elevated, they are not unusual for Yellowstone. Current rates of ground deformation are well within historical norms, said Lowenstern.
A supervolcano is defined as an eruption of magnitude 8 on the Volcano Explosivity Index, meaning more than 1,000 cubic kilometers (240 cubic miles) of magma are erupted. The 1980 Mount St. Helens blast in Washington was the deadliest and most economically destructive volcanic event in the history of the United States, and its VEI was a magnitude 5.
Lowenstern said Craters of the Moon and Yellowstone are two of the most recent volcanoes from the same deep hotspot system that created a series of volcanoes in the Snake River Plain over the past 16 million years.
“Challis is a very long way from Yellowstone,” said Lowenstern. “Activity at the two is connected only in that the tectonic stress of the region can affect them both. The ‘plumbing’ systems of Yellowstone and Craters of the Moon are independent, so an eruption at one place would not cause an eruption at the other.”
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