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The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over northwest of the city of Vancouver and about west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The caldera is one of the largest of the few calderas in western Canada, measuring about long (north-south) and wide (east-west).〔 Mount Silverthrone, an eroded lava dome on the caldera's northern flank that is high may be the highest volcano in Canada. The main glaciers in the Silverthrone area are the Pashleth, Kingcome, Trudel, Klinaklini and Silverthrone glaciers. Most of the caldera lies in the Ha-Iltzuk Icefield, which is the largest icefield in the southern half of the Coast Mountains; it is one of the five icefields in southwestern British Columbia that thinned between the mid-1980s and 1999 due to global warming.〔 Nearly half of the icefield is drained by the Klinaklini Glacier, which feeds the Klinaklini River.〔(【引用サイトリンク】url=http://wayback.archive.org/web/20081219153707/http://www.igsoc.org/journal/54/186/j07J029.pdf )〕 The Silverthrone Caldera is very remote and rarely visited or studied by geoscientists, such as volcanologists. It can be reached by helicopter or — with major difficulty — by hiking along one of the several river valleys extending from the British Columbia Coast or from the Interior Plateau.〔 ==Geology== Silverthrone is part of the Pemberton Volcanic Belt, which is circumscribed by a group of epizonal intrusions. At another deeply eroded caldera complex called Franklin Glacier Volcano, the Pemberton Volcanic Belt merges with the Garibaldi Volcanic Belt, a northwest-trending belt of volcanic cones and fields extending from near the Canada–United States border east of Vancouver on the British Columbia Coast. The intrusions are thought to be subvolcanic bodies associated with a volcanic front that was active in the Miocene, during early stages of subduction of the Juan de Fuca Plate.〔(【引用サイトリンク】url=http://journals.hil.unb.ca/index.php/GC/article/viewFile/1120/1469 )〕 With the notable exception of King Island, all the intrusive and eruptive rocks are calc-alkaline, mainly granodioritic bodies and dacite ejecta.〔 On a broader scale, the intrusive and eruptive rocks are part of the Coast Plutonic Complex, which is the single largest contiguous granite outcropping in North America.〔(【引用サイトリンク】url=http://www.washington.edu/burkemuseum/geo_history_wa/Coast%20Range%20Episode.htm )〕 The intrusive and metamorphic rocks extend approximately along the coast of British Columbia, the Alaska Panhandle and southwestern Yukon. This is a remnant of a once vast volcanic arc called the ''Coast Range Arc'' that formed as a result of subduction of the Farallon and Kula Plates during the Jurassic-to-Eocene periods.〔 In contrast, Garibaldi, Mount Meager, Mount Cayley and Silverthrone areas are of recent volcanic origin. 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「Silverthrone Caldera」の詳細全文を読む スポンサード リンク
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