Mount Hampton
Shield volcano in Antarctica
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Geography and geology
Mount Hampton is the northernmost volcano of the Executive Committee Range in Marie Byrd Land, Antarctica. It has the form of a symmetrical uneroded shield volcano with an "impressive" appearance and an ice-filled 6.5-by-5.5-kilometre-wide (4.0-by-3.4-mile) caldera. Like other volcanoes in the Executive Committee Range, it is a paired volcano with the northwesterly 3,003-metre-high (9,852-foot) Whitney Peak and the southeasterly 3,323-metre-high (10,902-foot) Marks Peak, which is the main summit of Mount Hampton. The northwesterly summit is associated with its own caldera, which is partly cut by the Mount Hampton caldera on the southeastern flank and buried by the lava flows from the latter. The centres of the two calderas are about 8 kilometres (5.0 mi) apart. Based on outcrops, it appears that most of the volcano is formed by flow rocks, but cinder and lava bombs occur at parasitic vents.
The mountain rises about 1 kilometre (0.62 mi) above the surface of the West Antarctic Ice Sheet, which buries most of the edifice, and moraine ridges are found at its base on the ice sheet. Owing to climate conditions, the persistence of permanent ice atop of the mountain is unlikely over the long term; erosion there appears to have been episodic with maxima during interglacials, and there is no evidence of cirque formation. Lichens have been found on the mountain.
Composition
The volcano is formed by phonolite rocks, but parasitic vents have also erupted basanite, and Whitney Peak also erupted trachyte and benmoreite. Hawaiite has been reported as well. The volcanic rocks contain augite and feldspar; further, spinel-containing lherzolite xenoliths have been found. In general, composition is unique for each volcano in the Executive Committee Range.
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Eruption history
Mount Hampton is one of the oldest volcanoes of Antarctica and was active during the Miocene. Despite this, it is less eroded than some younger volcanoes in the region; in general, the ages of the Marie Byrd Land volcanoes are not correlated to their erosion status. It appears that Whitney Peak is the older half of the edifice and that volcanic activity then migrated to Mount Hampton. More generally, volcanism in the Executive Committee Range migrated southwards over time at an average rate of 0.7 centimetres per year (0.28 in/year), although Mount Hampton and its southern neighbour Mount Cumming were simultaneously active 10 million years ago.
Last parasitic eruptions took place around 11.4 million years ago, and the youngest radiometric dates are 8.3 million years. As at other volcanoes of Marie Byrd Land, the parasitic activity at Mount Hampton occurred after a long period of dormancy. However, the presence around the caldera rim of snow-covered inactive 10–20-metre-high (33–66-foot) ice towers indicate that the mountain is geothermally active and may have erupted during the Holocene. Later research suggested that the ice towers were actually formed by wind-driven erosion of snow and ice. There is no evidence of geothermal processes, and seismic activity recorded at the volcano may be due to volcano-tectonic processes or due to ice movement.