Scientists forecast
decades of ash clouds Many more of
Iceland’s volcanoes seem to be stirring
THE Icelandic
eruption that has caused misery for air travellers could be part of a
surge in volcanic activity that will affect the whole of Europe for
decades, scientists have warned.They have reconstructed a timeline of 205 eruptions in Iceland,
spanning the past 1,100 years, and found that they occur in regular
cycles — with the relatively quiet phase that dominated the past five
decades now coming to an end.
At least three other big Icelandic volcanoes are building towards an
eruption, according to Thor Thordarson, a volcanologist at Edinburgh
University.
“The frequency of Icelandic eruptions seems to rise and fall in a
cycle lasting around 140 years,” he said. “In the latter part of the
20th century we were in a low period, but now there is evidence that we
could be approaching a peak.”
His findings coincide with new warnings that the eruption of
Eyjafjallajokull, which has disrupted air traffic across Europe for
several weeks, could carry on for many months — and possibly years.
Some geologists have also warned of a serious threat from a fourth
volcano, Katla, which lies 15 miles to the east of Eyjafjallajokull. Two
of its past three eruptions seemed to be triggered by those of its
smaller neighbour and a report issued just before Eyjafjallajokull blew
suggested Katla was “close to failure [eruption]”.
The three other volcanoes cited by Thordarson as being potentially
close to a large eruption are Grimsvotn, Hekla and Askja — all of which
are bigger than Eyjafjallajokull.
In the past, they have proved devastating. Hekla alone has erupted
about 20 times since AD874, pouring out a total of two cubic miles of
lava from a line of fissures that stretches 3Å miles across the
mountain.
There was a minor eruption in 2000 and geologists have reported that
snow is once again melting on Hekla’s summit, suggesting that magma is
rising.
Grimsvotn, another highly active volcano, lies under the huge
Vatnajokull glacier in Iceland’s southeast. An eruption in 1996 saw much
of this glacial ice melt, causing a flood that washed away the
country’s main ring road.
It is linked to the massive Laki fissure volcano whose 1783 eruption
ejected so much ash into the atmosphere that it cooled the entire
northern hemisphere for nearly three years. The resulting low
temperatures caused crop failures and famines that killed 2m people and
helped trigger the French Revolution.
Thordarson believes that the behaviour of the volcanoes is linked to
movements in the earth’s crust which create massive subterranean
stresses over wide areas.
As these stresses build up, more volcanoes erupt and as the stress
disappears, the volcanoes subside again.
The theory is a controversial one. Gillian Foulger, professor of
geophysics at Durham University, suggests that historic clusters of
eruptions could well have occurred by chance. She said: “This needs
rigorous statistical support.”
However, both she and Thordarson agree that Europe needs to take the
threat of further Icelandic eruptions more seriously, including
improving the monitoring of active volcanoes. Foulger is writing to
David Willetts, the new science minister, suggesting Britain could
support Iceland in such a project.
She said: “There are about 35 active [big] volcanoes in Iceland and
if we put a high quality seismograph and some global positioning
equipment on each one we would often be able to tell in advance if an
eruption was coming. The cost is tiny compared with the potential
economic damage from an unexpected eruption.”
The most pressing question for Britain and the rest of Europe is how
long the current eruption will continue.
Professor Stephen Sparks, from the earth sciences department at
Bristol University, said: “Every volcano has its own personality. This
particular volcano has erupted before in 1612 and 1821. When it erupted
in 1821 it continued erupting for 15 months so there is no reason why it
could not last a similar period of time.”
The new rules in place for aviation mean Iceland and Europe can
probably cope with Eyjafjallajokull, but an eruption by Katla could
cause far bigger problems.
Dr Richard Waller, senior lecturer in physical geography at Keele
University, believes the ash cloud could be immense, but for Iceland the
biggest problem would be massive flooding.
“Katla has a crater filled with ice more than 2,000ft thick, which
will all melt,” he said.
Source:
Timesonline.co.uk 
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