http://standeyo.com/NEWS/08_Earth_Ch...olc.erupt.html
PUZZLE: Is there a common thread or were events just coincidence?
October 11, 2008
Anchorage Daily News
How likely is it that three neighboring volcanoes would all erupt at the same time -- as the Kasatochi, Okmok and Cleveland volcanoes in the Aleutians did this summer?
About as likely as a storm that only appears once in a thousand years, says Anchorage volcanologist Peter Cervelli, who'll deliver a paper on the subject this winter to the American Geophysical Union.
In other words, seldom enough that Cervelli is now exploring the question of whether Alaska's triple eruption was only a coincidence involving three independent volcanoes or whether it was triggered by some common mechanism.
There's no question that the volcanoes are related in a broad geological sense, says Comelli, a numerical modeler at the Alaska Volcano Observatory. That's because all 40 active volcanoes in the Aleutian Arc -- a 1,500-mile-long necklace of volcanic peaks that stretch from Kiska Island in the west to Mount Spurr near Anchorage in the east -- owe their existence to the deep, subterranean collision of two tectonic plates.
As the northward moving Pacific plate, consisting of dense material from the ocean floor, dives beneath the North American plate, consisting of lighter material from the continent, friction between the two melts rock, which turns to magma, which eventually shoots skyward through a relief-valve network of volcanoes.
One of them focuses on the fact that all three volcanoes lie within the rupture zone of the 1957 "Great Aleutian Earthquake," a magnitude 8.3 tremor that generated a tsunami that damaged buildings in far-off Hawaii. Because there was so much disruption of earth along the quake's fault line, Cervelli said, the ground around it was drastically distorted and compressed.
"That could create conditions that are favorable for eruption," he said. "That's speculative ... but certainly it makes some degree of sense."
cont.on link above.