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In Death Valley, ancient volcano gives scientists a surprise

The Ubehebe crater in Death Valley National Park is much younger than previously thought, and represents a more significant volcanic hazard than previously thought, according to a new study.

By Staff writer / January 24, 2012

Ubehebe Craters include over a dozen volcanoes. They were created when magma rising along a fault on the north side of Tin Mountain came in contact with shallow groundwater. The water explosively turned to steam, generating great blasts of rock, and volcanic tuff and ash. The stratigraphic position and lack of erosion on the rocks of Ubehebe Crater (shown here) suggests that the last eruption was in the Holocene, perhaps less than 10,000 years ago.

Courtesy United States Geological Survey

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A half-mile-wide crater in Death Valley National Park may represent a more significant volcanic hazard than previously thought, according to a new study – though not enough to cancel your next visit to the park.

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The crater, Ubehebe, formed in an enormous explosion between 800 and 2,100 years ago, the research team estimates – far more recently than earlier studies suggest.

Moreover, the scientists involved in the work suggest the precursors for an eruption – a supply of magma and an underground source of water the magma could turn to steam in a flash – may still lurk beneath the nearly 800-foot deep crater.

"We were really surprised by the youthfulness of the eruption," says Brent Goerhing, a paleoclimatologist at Purdue University and a member of the team. "We always had in the back of our heads that it could be young, within the past few thousand years. But we didn't think it could be that young."

The results appear in the Jan. 18 issue of the journal Geophysical Review Letters.

Ubehebe is the largest in a grouping of small craters – all thought to have formed the same way: magma rising through the crust to encounter groundwater. The searing magma instantly turned the water to steam, blasting out the crust above it.

The steam and ejected rock would have risen in an expanding column, only to fall back to the valley floor once it ran out of energy to keep rising. The collapse would have sent a hot flow of material with a consistency of just-mixed concrete spreading in all directions at speeds up to 200 miles an hour. Larger rocks the blast lofted would have pummeled the ground.

The best spot for viewing the event would have been several miles away, Dr. Goehring quips.

Death Valley, with its parched climate, represents a prime location for studying the geological forces that shape the continent's basin-and-range region.

The region covers most of the US West, and is characterized by short, generally north-south trending mountain ranges separated by dry valleys.

Into Death Valley rode Goerhing, Columbia University professor Nicholas Christie-Blick, and a group of students in March 2008 on a field trip to use the valley as an outdoor teaching lab.

As the group walked along Ubehebe's rim, they talked about the crater's age and how it formed. How it formed "is pretty well-known," Goehring says. But estimates of its age ranged as far back as 20,000 years. Some researchers had found native American artifacts buried in the explosion's ash fall. That suggested Ubehebe's eruption came no earlier than 10,000 years ago, when humans are thought to have first moved into the valley.

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