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The deposits of an exceptionally large debris avalanche extend from the base of Mount Shasta volcano northward across the floor of Shasta Valley in northern California. The debris-avalanche deposits underlie an area of about 675 square kilometers, and their estimated volume is at least 45 cubic kilometers. Radiometric limiting dates suggest that the debris avalanche occurred between about 300,000 and 380,000 years ago. Hundreds of mounds, hills, and ridges formed by the avalanche deposits are separated by flat areas that slope generally northward at about 5 meters per kilometer.
-- Crandell, 1989
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Map [26K,InlineGIF]
