Yellowstone Needs Tums
[My news story on Yellowstone's bulge. In case you were looking for something else to worry about.]
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 cauldron.
The central region of the park has been rising the last 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 at Yellowstone. Scientists see no sign that Yellowstone is about to blow its top.
"There's no evidence of eruption," said Robert Smith, a University of Utah geologist and co-author of a new report on Yellowstone's unusual behavior, published on-line today by the journal Science. The park's recent rise is "just part of the natural process."
That said, the scientists are watching Yellowstone very closely. This latest glimpse of Yellowstone's 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, on the island of Java, may be on the verge of a major eruption. Climate scientists who try to understand global warming are trying to put volcanic eruptions into their models. Volcanic ejecta can block sunlight and temporarily cool a planet, even though a volcano also produces prodigious amounts of greenhouse gases. In 1815, the eruption of 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. Seismic activity, for example, has actually been lower in the last three years. There's nothing unusual happening with the hydrothermal system -- no strange geysers popping up, no 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.
Although the "rapid period of ground uplift," as the report puts it, has elevated portions of the Yellowstone plateau by roughly three inches in a single year, such activity pretty much goes with the territory when it comes to calderas. They go up and then they go down. 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, since 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 big, 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 a thousand cubic kilometers of material into the atmosphere, burying much of the American West and the Great Plains in a layer of hot ash. By comparison, Mount St. Helens in 1980 spewed forth only about one cubic kilometer 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.
There are a couple of dozen active calderas around the world, but it has been 26,000 years since the last super-eruption, in New Zealand. There has been speculation that the eruption of the Toba caldera on the island of Sumatra some 74,000 years ago may have caused global climate changes that led to a die-off of most human beings on the planet, with only a couple of thousand surviving.
A report from the U.S. Geological Survey earlier this year tried to calibrate the volcanic hazards at Yellowstone.
"Depending on the nature and magnitude of a particular hazardous event and the particular time and season when it might occur, 70,000 to more than 100,000 persons could be affected; the most violent events could affect a broader region or even continent-wide areas," the USGS concluded.
The report, authored by USGS volcanologist Robert L. Christiansen, said the most serious short-term hazard comes from hydrothermal explosions, events in which subsurface steam breaks through the surface and forms a crater. In the 126 years since records have been kept at the park, 26 such explosions have been observed. Since the retreat of the last ice sheet some 16,000 years ago, 18 huge hydrothermal explosions have left Yellowstone pocked with craters larger than 100 meters across.
But the same report argued that a super-eruption is essentially not worth worrying about. The magma chamber below Yellowstone is now "largely crystallized mush."
Yellowstone's hot spot is caused by a plume of magma rising through the Earth's mantle. Over the past 16 million years, the North American tectonic plate has been sliding to the west across the plume. The hot spot has, in turn, bubbled up further to the east from a starting point in eastern Oregon. From a geological perspective, Yellowstone is not so much a permanent place on the map as it is a kind of migratory surface feature of the West.
Volcanologists will readily confess that their field is full of unknowns, and that the geological processes of the Earth are more chaotic than linear. Volcanic eruptions, like earthquakes, aren't predictable, and large calderas are a particular enigma, with no known major eruptions in recorded human history.
"We get better at it as we go along," said Christiansen in an interview. "I can't say we can predict specific events at this point. We keep learning."
Jacob Lowenstern, the scientist in charge at Yellowstone Volcano Observatory, said that with new technology, "We're all kind of viewing the patient for the first time."
[Here's the USGS story on the bulge.]
Check out the Yellowstone Volcano Observatory. Here's their latest report:
During the month of October 2007, 34 earthquakes were located in the Yellowstone Region. The largest of these shocks was a magnitude 2.1 on October 17, 2007 at 6:39 AM MDT, located about 26 miles Southeast of West Thumb, WY. There were no swarms and no earthquakes were reported felt during October.
Earthquake activity in the Yellowstone region is at low background levels.
Ground Deformation Summary: Through October 2007, continuous GPS data show that most of the Yellowstone caldera continued moving upward at similar to slightly lower rates as the past year. The maximum measured ground uplift over the past 36 months is ~17 cm at the White Lake GPS station. An example can be found at: http://pboweb.unavco.org/shared/scripts/stations/?checkkey=WLWY&sec=timeseries_plots×eries=raw
The general uplift of the Yellowstone caldera is scientifically interesting and will continue to be monitored closely by YVO staff.
An article on another recent uplift episode at Yellowstone and discussion of long-term ground deformation at Yellowstone and elsewhere can be found at: http://volcanoes.usgs.gov/yvo/2006/uplift.html
Check out this insane building under construction in Beijing. Would you work there? That is, if not specifically ordered to do so? Or would you choose the re-education camp option?
[Very interesting column by Wilbon today.]
[Beatle Paul hanging with Tony Soprano???]
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