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More Ash Likely, Warn Scientists

Darrien Oliver 06.05.2010 12:43
We can expect more eruptions.

We can expect more eruptions.

The eruption in Iceland has produced ash so fine aircraft instruments are completely unable to detect it.
The near-invisibility of the ash swirling in vast clouds over Britain and Europe has magnified the confusion and trepidation brought about by the eruption of Eyjafjallajokull.
Now the uncertainty is set to increase still further, with scientists warning that, based on the volcano’s historic behavior, the eruption could be “just the beginning”. The mountain may continue to blow out ash sporadically for a year or more.
Even more worryingly, Katla, the neighboring volcano, is groaning from the eruption under pressure equivalent to 3,000 mini-earthquakes a day of up to 3.1 on the Richter scale. Katla is some five times bigger than Eyjafjallajokull and would erupt in a similar way but spewing out far bigger plumes of ash.
This does not mean British airspace will be closed for a year, but it could herald months of repeated bouts of disruption, depending largely on the weather.
Yesterday a British scientist described how even modern aircraft technology cannot detect the clouds of ash.
Guy Gratton, head of Cranfield University’s facility for airborne atmospheric measurement, took a flight with fellow researchers to gather data.
“Speaking as an aeronautical engineer, I would not want to be putting an airliner up there at the moment,” said Gratton.
“There is a lot of fairly nasty stuff there that we were running away from, knowing what we did. We have standard airline instruments on the airplane, we have got a storm scope and we have got a weather radar and they were looking straight through it.
“Neither of those were seeing any of this stuff. It was only our specialist cloud physics instruments that were able to see the particles.”
The ash is formed by the sudden contact between molten rock and ice. As the lava is pushed up through the vent of Eyjafjallajokull at 700-1,100C, it shoots through the glacier of the same name.
A glass-like rind forms but shatters under pressure from below. Jets of steam and gas then carry it into the atmosphere in tiny flakes less than 1mm across.
David Rotherly, a vulcanologist at the Open University, said: “When you put cold on a hot rock it shatters, creating tiny fragments. Also, when water turns to steam there’s a big expansion which propels the particles even higher.”
Jet engines suck in so much air that it carries with it enough ash to wreck the mechanism. Even though the ash becomes invisible as it disperses, planes have to be grounded as has happened regularly during eruptions in Alaska, northern Japan and Sicily.
Ash has been spewing out since March 20, when a 500-yard gash opened on the shoulder of the volcano.
Bjorn Eriksson, who runs the Hotel Ranga in Hella, a few miles southwest, said locals had been expecting it.
“We’ve been experiencing earthquakes since January,” he said. “At first just one or two a day, but increasing rapidly.” A few days after the first opening, another vent broke four miles up the mountain, 600ft beneath the glacial ice cap.
Eyjafjallajokull has erupted twice in the past 1,100 years, the last time in December 1821. That continued for more than a year until January 1823.
Andrew Hooper, an expert on Iceland’s volcanoes at Delft University in Holland, said: “There is a very real possibility that the volcano will continue to erupt on and off for months.
“Eruptions of Eyjafjallajokull in 1821-3 and 1612 were followed in short shrift by eruptions of Katla, with a far greater potential for disrupting travel and the climate.”
Hooper added: “There are no signs yet of the eruption ending, even temporarily.”
In addition, the wind that has been blowing the ash across Europe is not forecast to change, nor is there much sign of heavy rain which would bring a lot down from the sky.
Hooper warned that the eruption may be only a taste of the future if climate change causes ice sheets to melt further. As the last ice age ended, volcanic activity in Iceland increased 30-fold because of reduced pressure on the earth’s mantle.
“Since the 19th century the ice caps in Iceland have been shrinking yet further,” said Hooper. “This will lead to additional magma generation, so we should expect more frequent voluminous eruptions in the future.”

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