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The Tseax Cone ( ), also called the Tseax River Cone or alternately the Aiyansh Volcano, is a young cinder cone and adjacent lava flows associated with the Nass Ranges and the Northern Cordilleran Volcanic Province. It is located east of Crater Creek at outlet of Melita Lake, southeast of Gitlakdamix and north of Terrace, British Columbia, Canada. The volcano is situated in a valley above and east of the Tseax River, about south of the river's junction with the larger Nass River. The Tseax Cone is one of the most accessible volcanic centres in British Columbia.〔 ==Geology== The Tseax Cone is located in the southern part of the Northern Cordilleran Volcanic Province and is therefore part of the Ring of Fire. It has been the site of some of the youngest volcanic eruptions in Canada. It has been active at least twice in the past few hundred years and other remnants of lava flows exist in the area. It is in diameter at its base and rests on the remnants of an earlier and somewhat larger, dissected, diameter cone.〔 The volcano is made of volcanic bombs and cinders with a crater at its summit where a churning lava lake ponded and overflowed its rim during the 18th century.〔(Nisga'a Memorial Lava Beds Provincial Park ) Retrieved on 2008-02-13〕 Volcanism at the Tseax Cone is caused by the rifting of the Earth's crust where two parts of the North American Plate are breaking apart. The rifting is the result of the Pacific Plate sliding northward along the transform Queen Charlotte Fault, on its way to the Aleutian Trench.〔(Catalogue of Canadian volcanoes – Stikine volcanic belt ) Retrieved on 2008-02-13〕 The lava emitted in eruptions at the Tseax Cone is fluid. Its lavas are made of basalt, a common grey to black or dark brown extrusive volcanic rock low in silica content (the lava is mafic) that is usually fine-grained due to rapid cooling of lava on the Earth's surface. Pāhoehoe is found at the volcano, which has a smooth, billowy, undulating, or ropy surface. A pāhoehoe flow typically advances as a series of small lodes and toes that continually break out from a cooled crust.〔(Basaltic Lava ) Retrieved on 2008-02-13〕 It also forms lava tubes where the minimal heat loss maintains low viscosity. However, there is also basaltic lava at the volcano characterized by a rough or rubby surface composed of clinker called ʻaʻā. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface.〔 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「Tseax Cone」の詳細全文を読む スポンサード リンク
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