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Mount Takahe is a 3,460-metre-high (11,350 ft) snow-covered shield volcano in Marie Byrd Land, Antarctica, 200 kilometres (120 mi) from the Amundsen Sea. It is a c. 30-kilometre-wide (19 mi) mountain with parasitic vents and a caldera up to 8 kilometres (5 mi) wide. Most of the volcano is formed by trachytic lava flows, but hyaloclastite is also found. Snow, ice, and glaciers cover most of Mount Takahe. With a volume of 780 km3 (200 cu mi), it is a massive volcano; the parts of the edifice that are buried underneath the West Antarctic Ice Sheet are probably even larger. It is part of the West Antarctic Rift System along with eighteen other known volcanoes. The volcano was active in the Quaternary period, from 2.5 million years ago to the present. Radiometric dating has yielded ages of up to 300,000 years for its rocks, and it reached its present height about 200,000 years ago. Several tephra layers encountered in ice cores at Mount Waesche and Byrd Station have been attributed to Mount Takahe, although some of them were later linked to eruptions of Mount Berlin instead. The tephra layers were formed by explosive or phreatomagmatic eruptions. Major eruptions took place around 17,700 years ago—possibly forming an ozone hole over Antarctica—and in the early Holocene. Mount Takahe's last eruption occurred about 7,600 years ago, and there is no present-day activity. Geography and geomorphology The mountain's name refers to the takahē, a flightless nearly extinct bird from New Zealand; members of the 1957–1958 Marie Byrd Land Traverse party nicknamed an aircraft that had resupplied them "takahe". It was first visited in 1957–1958 and again in 1968, 1984–1985 and 1998–1999. Mount Takahe is at the Bakutis Coast, eastern Marie Byrd Land, Antarctica. Bear Peninsula and the Amundsen Sea coast are 200 kilometres (120 mi) north of Mount Takahe. It is an isolated mountain, and the closest other volcanoes are Mount Murphy 100 kilometres (62 mi) and Toney Mountain 140 kilometres (87 mi) away. No major air routes or supply roads to Antarctic stations pass close to the mountain, and some parts of the cone are accessible only by helicopter. The volcanic mountain rises 2,100 metres (6,900 ft) above the ice level with maximum elevation 3,460 metres (11,350 ft). It is an undissected nearly perfect cone, a 30-kilometre-wide (19 mi) shield volcano with an exposed volume of about 780 cubic kilometres (190 cu mi). The subglacial part, which might bottom out at 1,340–2,030 metres (4,400–6,660 ft) below sea level, could have an even larger volume and is elongated in an east–west direction. On its summit lies a flat, snow-filled 8-kilometre-wide (5 mi) caldera with a 10-metre-wide (33 ft) and 15-metre-high (50 ft) volcanic neck. A lava dome may crop out inside the caldera. Radial fissure vents are found around the volcano, and vents also occur around the caldera rim. There are at least three parasitic vents with basaltic composition on its lower flanks, with three cinder cones found on the western and southern slopes. One of these cinder cones has been described as a subdued 100-metre-wide (330 ft) vent. The Jaron Cliffs are found on the southern slope. The volcano is largely uneroded, mostly hiding the internal structure which would clarify its history.Only twelve outcrops, with a total area of less than 0.5 square kilometres (0.19 sq mi), emerge from the ice. Based on these outcrops, lava flows with a thickness of 2–10 metres (6 ft 7 in – 32 ft 10 in) appear to be widespread on Mount Takahe, while pyroclastic rocks such as deposits of Strombolian eruptions, lapilli tuffs and lahar deposits are less common. Occurrences of pyroclastic rocks at the summit have been correlated with tephra deposits elsewhere in Antarctica. Additionally, obsidian-bearing and recently erupted lava bomb-and-block units crop out in the caldera rim, at Bucher Rim. Tuyas have been reported. Glaciation Mount Takahe is almost entirely covered by ice of the West Antarctic Ice Sheet, which rises about 1,300 metres (4,300 ft) above sea level. A tributary of the Thwaites Glacier passes close by. There are two small glaciers on the volcano itself, on the southwestern and northern flanks. They are eroding eruption products from the summit area, and moraines have been mapped both on the western flank and in the summit caldera. Glacial erosion is slight, with only a few corries cut into the lower slopes. The ice cover on the mountain includes both snow-covered and ice-covered areas, with sastrugi and other wind-roughened surfaces. The cold dry polar environment retards weathering. Air temperatures are usually below freezing. Some rock units at the foot of the volcano were emplaced underneath ice or water and feature hyaloclastite and pillow lavas. These units rise to about 350–400 metres (1,150–1,310 ft) above the present-day ice level. Some of these units, such as Gill Bluff, Möll Spur and Stauffer Bluff, are "hydrovolcanic deltas" comparable to lava deltas which formed when lava flows or parasitic vents entered the ice, generating meltwater lakes around them. They crop out at the base of the volcano and are well preserved. Ice elevation was not stable during the emplacement of these deltas, and meltwater drained away, leading to the formation of diverse structures within the hyaloclastite deltas. The deltas may have formed during ice highstands 66,000 and 22,000–15,000 years ago. Geology The West Antarctic Rift System is a basin and range province similar to the Great Basin in North America; it cuts across Antarctica from the Ross Sea to the Bellingshausen Sea. The Rift became active during the Mesozoic. Owing to thick ice cover it is not clear whether it is currently active, and there is no seismic activity. Most of the Rift lies below sea level. To the south it is flanked by the Transantarctic Mountains and to the north by the volcanic province of Marie Byrd Land. Volcanic activity in Marie Byrd Land commenced about 34 million years ago, but high activity began 14 million years ago. A major uplifted dome, 1,200 by 500 kilometres (750 mi × 310 mi) in width, is centred on the Amundsen Sea coast and is associated with the Rift. About 18 central volcanoes were active in Marie Byrd Land from the Miocene to the Holocene. Among the volcanic areas in Marie Byrd Land are the Flood Range with Mount Berlin, the Ames Range, the Executive Committee Range with Mount Sidley and Mount Waesche, the Crary Mountains, Toney Mountain, Mount Takahe and Mount Murphy. These volcanoes mainly occur in groups or chains, but there also are isolated edifices. Mount Takahe is located in the eastern Marie Byrd Land volcanic province and with an estimated volume of 5,520 cubic kilometres (1,320 cu mi) could be the largest of the Marie Byrd Land volcanoes, comparable to Mount Kilimanjaro in Africa. Most of these volcanoes are large, capped off by a summit caldera and appear to have begun as fast-growing shield volcanoes. Later, calderas formed. Eventu.... Discover the Ka Moll popular books. Find the top 100 most popular Ka Moll books.