June 4, 2012 2:03:01 pm
A doomsday volcanic eruption that could wipe out civilisation may not be entirely fictional,as scientists have now warned that so-called supervolcanoes may need far less time than once thought to build up the ammunition for a cataclysmic eruption.
However,this newly discovered short fuse must be put in context – the buildup of a supervolcano toward eruption still may take several hundred or thousands of years,the researchers said.
Previous studies indicated that supervolcanoes – or those that spew out roughly 1,000 times more material than Mount St Helens did in 1980 – need 100,000 to 200,000 years to build up a reservoir of magma before they can unleash a violent eruption.
But the latest research,published in the journal PloS ONE,suggests that these giant magma pools,typically 10 to 25 miles (16 to 40 kilometres) across,exist for only a few thousand to even just a few hundred years before a supervolcano goes off.
Our study suggests that when these exceptionally large magma pools form,they are ephemeral and cannot exist very long without erupting, Guilherme Gualda,an assistant professor of earth and environmental sciences at Vanderbilt University,was quoted as saying by LiveScience.
For their study,Gualda and team studied Bishop Tuff,a plateau in California that is essentially the remains of a supervolcano that erupted about 760,000 years ago.
They used a dating technique that looked at the rate of quartz crystallisation as opposed to a more traditional method that uses the decay of elements such as uranium and thorium in zircon crystals – to determine the lifespan of the magma pool that sparked the massive eruption.
The study yielded compelling evidence that the magma pool may have formed in 10,000 years – and most likely formed in as little as 500 to 3,000 years.
Gualda said that means the world’s supervolcanoes may bear closer scrutiny than they now receive. The fact that the process of magma body formation occurs in historical time,instead of geological time,completely changes the nature of the problem, he said.
The most recent super-eruption occurred at Taupo in New Zealand,about 26,000 years ago; the most dramatic to occur while humans walked the Earth happened 74,000 years ago,in Indonesia,when an eruption at Mount Toba rained ash all over South Asia and filled the atmosphere with so great a load of ash and small particles that it altered global weather for as long as a decade.
There are indications that the eruption took a devastating toll on the world’s human population.
According to the researchers,there are quite a few supervolcanoes around the world,from the one in Yellowstone Park to what could be a new supervolcano in Bolivia.
But none of them appears primed for an eruption and understanding their behaviour illuminates Earth’s past and gives a better picture of the danger they pose,they added.
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