Explosive volcano highlights eruption risk
.The violent eruption of a Patagonian volcano last year has shown the high speed with which magma can burst through the earth’s crust, according to a European study.
The finding has prompted warnings for closer monitoring of potentially active volcanoes around the world.
The unexpected explosive eruption of the Chaiteìn volcano in Chile on 1 May 2008, occurred less than 24 hours after residents in the nearby town of Chaiteìn first began feeling earth tremors.
An examination of the forces behind the eruption published in the journal Nature , shows that the magma travelled at up to one-metre per second.
The force of the eruption resulted in ash being deposited across Chile and large parts of southern Argentina. This compares with the months to years of seismic unrest that precedes most eruptions.
It shot from a depth of more than five kilometres to the surface in about four hours. .
Depending on the nature of the eruption it can form pumice or obsidian on the surface.
Rhyolite is a volcanic material high in silica, which tends to make it very viscous or sticky and prone to explosive eruptions caused by trapped gasses.
Australian geologist, Dr Wally Johnson from Australian National University in Canberra is currently studying a rhyolitic eruption that occurred thousands of years ago at the Rabaul volcano in Papua New Guinea.
– Rare events –
The violent and unexpected nature of the blasts, together with their rarity, means the Chaiteìn eruption is the first rhyolite event to have been scientifically assessed in this way.
Dr Johnson says the last explosive rhyolitic eruption occurred in 1912 when the Novarupta volcano spewed 30 cubic kilometres of magma in 60 hours.
He says the analysis of the Chaiteìn eruption is strong.
“But when they do take place, they’re highly explosive and for anyone living nearby they’re certainly dangerous.
“But when they do take place, they’re highly explosive and for anyone living nearby they’re certainly dangerous.
“They put up a very, very good case for rhyolitic magma ascending very quickly through the crust,” Dr Johnsonsaid.
By documenting the speed with which the magma reached the surface, the researchers have now provided a measure for comparing the activity of other rhyolite volcanoes.”
Dr Johnson says that while rhyolite volcanoes are rare, there should be increased monitoring of potentially active volcanoes, in particular in developing countries, regardless of the magma involved.
“Basically once it starts, it’s on its way and there’s not much chance of getting a reasonably early warning.