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Pahvant Butte or Pavant Butte is a butte formed by a dormant volcano in the west-central portion of Utah. It is located in the Sevier Desert in the Pahvant Valley south of Delta and five miles east of Clear Lake and the Clear Lake Wildlife Management Area.〔''Delta, Utah,'' 30x60 Minute Topographic Quadrangle, USGS, 1989〕 The butte has two peaks. The north peak has an elevation of and the south peak reaches . The peaks are about 1000 feet above the surrounding valley floor. The butte is about in diameter at the base.〔''Pahvant Butte North, Utah'' and ''Pahvant Butte South, Utah,'' 7.5 Minute Topographic Quadrangles, USGS, 1971〕 It formed in an active area of volcanism on top of pahoehoe and aa lavas. Originally a subaqueous volcano, it erupted out of the floor of glacial Lake Bonneville approximately 15,500 years ago. == Geography and geology == Part of the Black Rock Desert volcanic field of the Pleistocene-Holocene age, Pahvant Butte formed above older pahoehoe and aa lavas of the Pahvant field. The volcano was originally a subaqueous volcano formed under Lake Bonneville by a large eruption about 15,500 years ago. The water depth at the time of eruption is estimated to have been . This eruptive activity probably ejected steam, ash, and other materials out of the lake, enveloping the surrounding area with ash and spawning large waves in the lake. The eruption released particles of basaltic lava into the air, which fell back to form tuff. A raised beach, or lacustrine terrace, formed by waves surrounds most of the volcano's lower rock. A vertical cliff, known as the Lace Curtain, is present on the north flank of the volcano, formed as a result of storm wave action. This name originated from the distinct white, lace-like pattern seen on the cliff face, caused by partial cementation of the tuff by minerals deposited by groundwater.〔 Pahvant Butte was overlapped by the lava flows of the Ice Springs eruption between 1140 and 1440 AD. 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「Pahvant Butte」の詳細全文を読む スポンサード リンク
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