As Yellowstone Bubbles, Experts Are Calm
Friday, November 9, 2007
Something is stirring deep below the legendary hot springs and geysers of Yellowstone, the first and most famous national park in America -- and home to a huge volcanic caldron.
Parts of the park have been rising the past three years at a rate never before observed by scientists. They believe that magma -- molten rock -- is filling pores in the Earth's crust and causing a large swath of Yellowstone to rise like a pie in the oven.
But that doesn't mean you should cancel any vacation plans. Scientists see no sign that Yellowstone is about to blow its top.
"There's no evidence of eruption," said Robert B. Smith, a University of Utah geophysicist and co-author of a new report on Yellowstone's unusual behavior, published today in the journal Science. The park's recent rise is "just part of the natural process."
That said, scientists are watching Yellowstone very closely. This latest glimpse of its unsettled nature offers a reminder that human-driven climate change is taking place on a planet that isn't an inert bystander.
Several volcanoes are currently rumbling in Indonesia, and one, Mount Kelud, in East Java, could be close to a major eruption. Climate scientists who try to understand global warming are trying to put volcanic eruptions into their models. Material blown high into the atmosphere by volcanoes can block sunlight and temporarily cool the planet, even though a volcano also produces prodigious amounts of greenhouse gases. In 1815, the eruption of Mount Tambora, a volcano in Indonesia, led to the famous "year without a summer," in which crops failed across the Northern Hemisphere.
Yellowstone's behavior of late doesn't match what scientists expect to see before an eruption, however. Seismic activity, for example, has actually been lower in the past three years. And there's nothing unusual happening with the hydrothermal system -- no strange geysers popping up, no weird explosions of steam, no odd gases spewing forth.
"We'd expect lots of earthquakes and deformation going hand in hand. And we're not seeing that at Yellowstone in this particular episode," Smith said.
In recent decades, Yellowstone has had its ups and downs, literally. Yellowstone rose about three feet between 1924 and 1985, then fell for a decade, then rose for a few years, then fell again, and finally in 2004 surged upward once more.
"It's truly breathing. I call it the living, breathing caldera," Smith said.
Yellowstone bears close monitoring, scientists say, because it is prone to hydrothermal explosions, volcanic eruptions (the most recent occurred 70,000 years ago) and, once in a very long while, a super-eruption, a continent-scorching explosion that makes your average volcanic event seem like a hiccup. The most recent super-eruption at Yellowstone, 640,000 years ago, launched 240 cubic miles of material into the atmosphere, burying much of the American West in a layer of hot ash. By comparison, Mount St. Helens in 1980 spewed forth less than a quarter of a cubic mile of material.
A caldera is essentially a collapsed volcano. The overlying material has been blown away or has sunk back into the emptied magma chamber. Although the cool crust of the Earth keeps the caldera's magma from reaching the surface, it heats groundwater that rises to form geysers and hot springs. The best explanation for the recent uplift, the new study concludes, is an infusion of new magma about six miles below Yellowstone's surface.