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Mount Wrangell, in Ahtna K’ełt’aeni or K’ełedi when erupting, is a massive shield volcano located in Wrangell-St. Elias National Park and Preserve in southeastern Alaska, United States. The shield rises over above the Copper River to its southwest. Its volume is over , making it more than twice as massive as Mount Shasta in California, the largest stratovolcano by volume in the Cascades. It is part of the Wrangell volcanic field, which extends for more than 250 km across Southcentral Alaska into the Yukon Territory, and has an eruptive history spanning the time from Pleistocene to Holocene. ==Description== Modern Mount Wrangell, built upon the remnants of a mid-Pleistocene volcano, has an eruptive history spanning from 750,000 years ago to minor phreatic eruptions in 1884.〔Volcanoes of North America, Wood and Kienle〕 The shield volcano features an ice-filled caldera in diameter at the top of Wrangell's broad summit. The caldera was apparently formed by subsidence rather than large explosive eruptions. The caldera is in turn rimmed by three small craters, which often display fumarolic activity with steam plumes that can sometimes be seen from a distance. The main summit is on the north side of the caldera, while the west summit rises to . The summit region above in elevation is over in size. A very large cinder cone, Mount Zanetti, rises nearly above the northwest flank of Wrangell and is the source of some lava flows.〔Richter ''et al'', pp. 11–13〕 Wrangell is unusual in that despite being a shield volcano, it is made mainly of andesite rather than basalt, which forms most shield volcanoes in other parts of the world. A few other volcanoes in the Wrangell Volcanic Field also share this feature. Andesite is a volcanic rock found mainly in stratovolcanoes and tends to form short, stubby flows. How Wrangell grew into a shield volcano is poorly understood, but its lava flows appear to have been voluminous and were also probably generated by high eruption rates.〔 Mount Wrangell is almost entirely covered by an icefield that persists from year to year. The largest glacier on Wrangell is Nabesna Glacier, the source of the Nabesna River.〔 Other glaciers on Mount Wrangell include Cheshnina Glacier, Chetaslina Glacier, Chichokna Glacier, Dadina Glacier〔(【引用サイトリンク】url=http://www.avo.alaska.edu/images/dbimages/1121192360__17.jpg )〕 and Copper Glacier. Wrangell was the first high volcano in the Wrangell range to be climbed. Its summit can be visited by ski-equipped airplane.〔 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「Mount Wrangell」の詳細全文を読む スポンサード リンク
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