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Beaverhead is an impact structure in central Idaho and western Montana in the United States. Estimated at in diameter, it is one of the largest impact craters on Earth. Its age is estimated to be about 600 million years (late Neoproterozoic). The structure is named after the area in southwest Montana where evidence of an impact was first discovered in 1990. Other than the original shatter cones found on the perimeter, there is little visible evidence of the structure. ==References== * Carr, J and Link, PK, 1999, Neoproterozoic conglomerate and breccia in the formation of Leaton Gulch, Grouse Peak, northern Lost River Range, Idaho: Relation to Beaverhead Impact Structure, in Hughes, S.S., and Thackray, G.D., eds., ''Guidebook to the Geology of Eastern Idaho'': Pocatello, Idaho Museum of natural History, p. 21-29. *(Aerial Exploration of the Beaverhead crater ) 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「Beaverhead crater」の詳細全文を読む スポンサード リンク
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