As if Death Valley wasn’t dangerous enough… geologists discover that one of its volcanoes is due to go off
Death Valley in California has plenty of hazards, ranging from searing temperatures to flash floods, rock falls, rattlesnakes and scorpions.
Now geologists say that one of its volcanoes is actually far younger and more active than previously thought and is due to go off, because it last exploded in 1200 and has an eruption cycle of 1,000 years or less.
A team based at Columbia University’s Lamont-Doherty Earth Observatory found that the half-mile-wide Ubehebe Crater, formed by a prehistoric volcanic explosion, was created just 800 years ago – and not 6,000 years ago as previously estimated.
Explosive: The half-mile-wide Ubehebe Crater in Death Valley
The researchers used isotopes in rocks blown out of the 600-foot crater to show that it formed around the year 1200.
That geologic youth means it probably still has some vigour, with the scientists certain that there is still enough groundwater and magma around for another reaction.
Ubehebe is the largest of a dozen such craters, or maars, clustered over about three square kilometres of Death Valley National Park.
The violent mixing of magma and water, resulting in a so-called phreatomagmatic explosion, blew a hole in the overlying sedimentary rock, sending out superheated steam, volcanic ash and deadly gases such as sulphur dioxide.
Study co-author Brent Goehring says this would have created an atom-bomb-like mushroom cloud that collapsed on itself in a donut shape, then rushed outward along the ground at some 200mph, while rocks hailed down.
Any creature within two miles or more would be fatally thrown, suffocated, burned and bombarded, though not necessarily in that order.
‘It would be fun to witness – but I’d want to be 10 miles away,’ said Goehring of the explosion.
Study: Geochemists dated the crater by analysing rocks thrown out when it exploded. Pictured is researcher Peri Sasnett contemplating a sample
The team began its work after Goehring and Lamont-Doherty professor Nicholas Christie-Blick led students on a field trip to Death Valley.
Noting that Ubehebe remained poorly studied, they got permission from the park to gather some three to six-inch fragments of sandstone and quartzite, part of the sedimentary conglomerate rock that the explosion had torn out.
They pinpointed the dates to when the stones were unearthed to between 800 and 2,100 years ago and noted that this happened in clusters.
The scientists interpreted this as signalling a series of smaller explosions, culminating in the big one that created the main crater around 1200.
A few other dates went back 3,000 to 5,000 years – these are thought to have come from earlier explosions at smaller nearby craters.
Christie-Blick said the dates make it likely that magma is still lurking somewhere below.
He pointed out that recent geophysical studies by other researchers have spotted what look like magma bodies under other parts of Death Valley.
‘Additional small bodies may exist in the region, even if they are sufficiently small not to show up geophysically,’ he said.
He added that the dates give a rough idea of eruption frequency – about every thousand years or less, which puts the current day within the realm of possibility.
‘There is no basis for thinking that Ubehebe is done,’ he said.
The scientists stress that there are currently no signs of it waking up, which would be preceded by shallow earthquakes and the opening of steam vents, events that could go on for years before anything bigger happened.
The study appears in the current issue of the journal Geophysical Research Letters.
Minor damage (fallen stones, objects etc)
Quake, tsunami debris threaten coastlines
AuroraMAX / Canadian Space Agency
Bjorn Jorgensen
Chad Blakley / Lights Over Lapland
