Thursday, August 26, 2004

Permafrost, Permafrost zones

Permafrost is widespread in the northern part of the Northern Hemisphere, where it occurs in 85 percent of Alaska, 55 percent of Russia and Canada, and probably all of Antarctica. Permafrost is more widespread and extends to greater depths in the north than in the south. It is 1,500 metres (5,000 feet) thick in northern Siberia, 740 metres thick in northern Alaska, and thins progressively


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