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Elkhorn Mountains
The Elkhorn Mountains are a mountain range in southwestern Montana, part of the Rocky Mountains and are roughly 300,000 acres (1200 km²) in size. It is an inactive volcanic mountain range with the highest point being Crow Peak at , right next to Elkhorn Peak, . The range is surrounded by the cities of Helena, Montana City, Townsend, Whitehall, and Boulder and is part of the Helena National Forest in Montana's Jefferson County.
==Geology==
The rocks of the Elkhorns were formed about 74 to 81 million years ago (Late Cretaceous time) as a result of the Farallon tectonic plate subducting beneath western North America and allowing magma to rise to the surface. The Elkhorn Mountains Volcanics are extrusive rocks related to the plutonic granites of the Boulder Batholith. Volcanic flows, lahars, and ash falls from sources in the Elkhorn Mountains reach as far as Choteau, Montana, but the thickest deposits lie within a radius of about from the Elkhorns.〔(Elkhorn Mountains Volcanoes )〕 The volcanics probably originally covered an area of about . Mineral deposits associated with the Elkhorn Mountains Volcanics include those mined at Elkhorn, Montana, now a ghost town, and gold at the Golden Sunlight Mine near Whitehall, which is associated with a breccia pipe in the volcanics.
The mountain range seen today is related to regional structural uplift dating mostly to Oligocene time.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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