Wednesday, April 6, 2005

An explosive neighbor

Docu-drama explores the supervolcano known as Yellowstone


By
An explosive neighbor

Excelsior Geyser erupted in a series of violent hydrothermal explosions in the 1880s and early 1890s; one of these eruptions is shown in this colorized postcard made from a photograph. These were the largest such events to occur in the Yellowstone region in historical times. Original photograph by F. Jay Haynes, 1888

Next time you step into the deliciously hot water of one of the areas many hot springs, ask yourself this; why is it hot? "Supervolcano"—the somewhat gulp-worthy factual film to be aired this Sunday, April 10, at 6 p.m. on the Discovery Channel—may give you some clues, albeit slightly horrifying ones.

Just to the east of us in northwest Wyoming sits Yellowstone National Park, which in turn sits atop a subterranean chamber of molten rock and gasses so vast that the entire region is arguably one of the largest active volcanoes in the world.

Now this is not your typical volcano, either in scale (it's huge), appearance (it's a vast depression, not a single mountain) or frequency of eruption. But it is active, and the evidence is everywhere.

"A relatively close-to-the-surface magma chamber—as close as five miles underground in some spots—fuels thousands of spewing geysers, hissing steam vents, gurgling mud pots and steaming hot springs that help make Yellowstone such an otherworldly and popular tourist attraction," writes Larry O'Hanlon, a science writer and geologist on Discovery's Web site.

This is not a volcano like Mount St. Helens in eastern Washington's Cascade Mountains, her crater is about two square miles. The Yellowstone "caldera"—a depression in the Earth equivalent to a crater top—is 1,500 square miles, big enough to swallow Tokyo, the largest city in the world.

The 1980 Mount St. Helens eruption blew 1,300 vertical feet off the mountain, sent an eruption column 80,000 feet high in 15 minutes, ejected 1.4 billion cubic yards of ash detectable over 22,000 square miles, and killed 57 people. The last major eruption at Yellowstone, some 640,000 years ago, ejected 8,000 times the ash and lava of Mount St. Helens.

"Yellowstone is much larger than any other volcanic feature in North America," says geophysicist Bob Smith, of the Yellowstone Volcano Observatory and the University of Utah. One that has experienced three supervolcanic eruptions in the ancient past: 2.1 million years ago, 1.3 million years ago and 640,000 years ago. Disturbingly, this cycle of approximately 600,000-700,000 years suggests another eruption could be brewing.

The force of a supervolcanic eruption at Yellowstone would be the equivalent of 1,000 Hiroshima bombs exploding every second. It would obliterate the national park and nearby communities (such as the Wood River Valley).

A super-eruption at Yellowstone would eject over 2,000 million tones of sulfuric acid into the stratosphere. This would form a veil around the earth that would deflect sunlight, triggering a catastrophic volcanic winter. Temperatures would drop by up to 12 degrees in the Northern Hemisphere and up to 16 degrees in the Southern Hemisphere, causing mass starvation, as the life-giving monsoon rains would fail. The total worldwide death toll from a Yellowstone super-eruption has been estimated at 1 billion.

The good news, however, is that volcanologists with the U.S. Geological Survey believe that supervolcanoes are likely to give decades—even centuries—of warning signs before they erupt.

The scientists think those signs would include lots of earthquakes, massive bulging of the land, an increase in small eruptions, "swarms" of earthquakes in specific areas and, possibly, large-scale cracking of the land. Good news then.

None of those indicators are present at Yellowstone—yet—says Smith, who describes the potential effects in detail in his book "Windows Into the Earth," published in 2000.

Discovery's "Supervolcano" is a true story then, just one that hasn't happened yet. Along the lines of their successful "Pompeii: The Last Day" docu-film aired earlier this year, "Supervolcano" is a factually based drama that charts the possible consequences of this most cataclysmic of events.

The film draws on scientific evidence available from the previous eruptions at Yellowstone as well as research from major scientific bodies, including the United States Geological Survey, Yellowstone Volcano Observatory, the Federal Emergency Management Agency, the UK Met Office and NOAA (The National Oceanic and Atmospheric Administration). The characters in "Supervolcano" are based on the people who work for these organizations.

You have been warned.






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