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Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Michigan. The ''Glacial Lake Missoula National Natural Landmark'' is located about 68 miles northwest of Missoula, Montana at the north end of the Camas Prairie Valley, just east of Montana Highway 382 and Macfarlane Ranch. It was designated as a National Natural Landmark in 1966 because it contains the great ripples, (often measuring high and long), that served as a strong supporting element for J Harlen Bretz's contention that Washington State's Channeled Scablands were formed by repeated cataclysmic floods over only about 2,000 years, rather than through the millions of years of erosion that had been previously assumed. The lake was the result of an ice dam on the Clark Fork caused by the southern encroachment of a finger of the Cordilleran Ice Sheet into the Idaho Panhandle (at the present day location of Clark Fork, Idaho at the east end of Lake Pend Oreille). The height of the ice dam typically approached , flooding the valleys of western Montana approximately eastward. It was the largest ice-dammed lake known to have occurred. The periodic rupturing of the ice dam resulted in the Missoula Floods – cataclysmic floods that swept across Eastern Washington and down the Columbia River Gorge approximately 40 times during a 2,000 year period. The cumulative effect of the floods was to excavate of loess, sediment and basalt from the channeled scablands of eastern Washington and to transport it downstream. These floods are noteworthy for producing canyons and other large geologic features through cataclysms rather than through more typical gradual processes. ==See also== * Missoula Floods * Glacial lake outburst flood * Giant current ripples * Ice Age Floods National Geologic Trail * List of prehistoric lakes 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lake Missoula」の詳細全文を読む スポンサード リンク
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