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Horror began deep beneath Indian Ocean
http://www.canoe.ca/NewsStand/LondonFreePress/News/2004/12/27/798157-sun.html
LONDON -- The chain reaction that set off enormous, deadly tidal waves that struck six Asian countries yesterday started several kilometers beneath the ocean floor off the tip of the Indonesian island of Sumatra. Geologic plates pressing against each other slipped violently, creating a bulge on the sea bottom that could be as high as 10 metres and as long as 1,200 kilometres, one scientist said.
The quake occurred at a spot where two massive geological plates press against one another with enormous force, Booth said.
The Indian Ocean plate is gradually being forced underneath Sumatra, which is part of the Eurasian plate, at approximately the speed at which a human fingernail grows, he explained.
"This slipping doesn't occur smoothly," he said. Rocks along the edge stick against one another and pent-up energy builds over hundreds of years.
It's "almost like stretching an elastic band, and then when the strength of the rock isn't sufficient to withstand the stress, then all along the fault line the rocks will move."
The quake likely occurred about 10 kilometres beneath the ocean floor, Booth said, causing the huge, step-like protrusion on the sea bed and the resulting tsunami.
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