Is Yellowstone's 'super volcano' about to blow up?

Is Yellowstone's 'super volcano' about to blow up?

14th January 2009, Comments 0 comments

The super volcano in Yellowstone Park, which includes parts of the states of Wyoming, Idaho and Montana, is making its presence felt.

On New Year's Day, the situation was so alarming that geologists called for an immediate evacuation of an area within a radius of 325 kilometres around the national park. At a rate of four tremors per hour, an eruption appeared imminent. The tremors have subsided slightly since 1 January, but it would appear the beast is slowly coming awake.

The volcano's caldera, which accounts for much of the park's terrain, measures about 40 by 60 kilometres. About 10 kilometres beneath the surface, a giant reservoir is slowly filling up with magma. Through cracks and fissures, some of its heat rises to the surface in the form of steam and gas, creating the geysers the park is so famous for.

Photo © Image-Editor

 Left: The Yellowstone River flowing through Hayden Valley in the northeastern part of the Yellowstone Caldera, Yellowstone National Park, Wyoming, USA.
The caldera rim can be seen in the distance.

Right: A magnitude 5.1 earthquake at 8:32 a.m. PDT on May 18, 1980 caused the entire weakened north face of Mount St. Helens to slide away, suddenly exposing the partly molten, gas- and steam-rich rock in the volcano to lower pressure and triggering a major pumice and ash eruption. Photo Credits: Yellowstone Caldera: Ed Austin and Herb Jone, National Park Service

Since a few days ago, it has become abundantly clear this volcano is no longer dormant. Geologist Jan Nieuwenhuis of the Technical University in Delft explained what fate would await the planet if a super volcano like the one below Yellowstone were to explode:

"It would create a hole about 30 kilometres deep and 30 kilometres across. Most of the debris would be blasted into the stratosphere, which means minute particles would be distributed all across the higher layers of the atmosphere. This would obscure the sun and effect global temperatures, which could easily drop by several degrees Celsius. At the site of the explosion, the edges of the huge crater created by the blast could collapse, triggering earthquakes strong enough to destroy the entire United States."

A drop in global temperatures of just a few degrees may not sound catastrophic but would have far-reaching consequences. The 1883 eruption of the Indonesian volcano Krakatau sparked a ten-year period of global crop failures. And compared to the Yellowstone super volcano, Krakatau is what a tea-warmer is to a blast furnace.

Extremely dangerous

A subterranean volcano may be tucked away far below the surface, but that does not make it any the less dangerous. This is what geologist Jan Nieuwenhuis has to say on the subject:

"Yellowstone sits atop a reservoir filled with a highly viscous sort of magma, which can not simply flow away through cracks, which means that the gases produced by the magma cannot escape and the pressure keeps building. Also, the magma wants to rise up; after all, the gases it contains reduce its specific gravity, and at some point in time the layers of rock on top the reservoir will simply be blown away in a gigantic explosion."

Caldera Rim -  Photo © RNW It's about the time the Yellowstone volcano blew up. It 'explodes' about once every 600,000 to 700,000 years and the previous eruption occurred 650,000 years ago. This means it could blow up at any moment now. Christopher Sanders, the US geologist who wanted to evacuate the area on New Year's Day, did not exactly mince his words:

"We have all of the early warning signs of a major eruption from a super volcano. - I want everyone to leave Yellowstone National Park and for 200 miles around the volcano's caldera."So what were the early warning signs Mr Sanders was talking about? In the week prior to 28 December, the number of tremors in the area steadily increased to a maximum of 103 a day. In the week after, the number was still 10 a day. Park rangers and visitors could feel the tremors for miles around.

Not for the first time...
Similar series of tremors have been registered before. In 1985, and also in 2004, the tremors came so hard and so fast, they were nearly impossible to count, and the ground in the park was so hot, that it melted the soles on people's shoes. Three thousand moose did not live to tell the tale. But the tremors eventually subsided.

The next major alert was raised in 2007: the bottom of the volcano's bowl-shaped caldera was rising by seven centimetres a year, clear evidence of mounting pressure in the magma chamber underneath.

Geologist around the globe are keeping a close eye on the old volcano, but even they have to admit that, in geology, time is measured in millennia rather than days.

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Thijs Westerbeek van Eerten
Radio Netherlands


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