Английская Википедия:Gaussberg

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Gaussberg (or Schwarzen Berg, Mount Gauss) is an extinct, Шаблон:Convert high volcanic cone in East Antarctica fronting on Davis Sea immediately west of Posadowsky Glacier. It is ice-free and conical in nature, having formed subglacially about 55,000 years ago. The current edifice is thought to be the remains of a once-larger mountain that has been reduced by glacial and subaerial erosion. The volcano has produced lamproite magmas, and is the youngest volcano to have produced such magmas on Earth.

Research history

Discovered in February 1902 by the German Antarctic Expedition under Erich von Drygalski, who named it after his expedition ship which in 1902 remained stuck in ice for a year.Шаблон:Sfn The ship in turn was named in honour of the German mathematician Carl Friedrich Gauss. Drygalski observed the volcano with the help of a tethered balloon.

Owing to its peculiar composition, Gaussberg has been intensively researched.Шаблон:Sfn The mountain was investigated in 1912 by the 1911-1914 Australasian Antarctic Expedition, by the Soviet Antarctic Expedition in 1956–1957,Шаблон:Sfn by Australian expeditions in 1977, 1981,Шаблон:Sfn 1987Шаблон:Sfn and by an expedition linked to an entity "K.D.C" in 1997.Шаблон:Sfn Regional krill stocks in turn were named after the mountain. Owing to its peculiar composition and isolated location, the volcano has an importance out of proportion to its actual size. The mineral gaussbergite is named after the volcano.

Geography and geomorphology

The volcano lies in Kaiser Wilhelm II Land, Antarctica,Шаблон:Sfn close to the West Ice Shelf and between the Australian Davis Station and Russian Mirny Station.Шаблон:Sfn It lies on the Davis Sea immediately west of Posadowsky Glacier. Gaussberg is within the Antarctic territory claimed by Australia,Шаблон:Sfn and the only ice-free outcrop between Mirny Station and the Vestfold Hills.

Файл:Gaussberg Drygalski 14157.jpg

German map of Gaussberg

It consists of a Шаблон:Convert, Шаблон:ConvertШаблон:Sfn cone located between the East Antarctic Ice Sheet on three sides and the sea on the fourth.Шаблон:Sfn It is the only exposure of rock in the region,Шаблон:SfnШаблон:Sfn with rocky outcrops at the summit and on the northern flank.Шаблон:Sfn The edifice covers an area of about Шаблон:ConvertШаблон:Sfn and has a volume of Шаблон:Convert.Шаблон:Sfn Most of the edifice is made out of pillow lavas with radii of Шаблон:Convert and Шаблон:Convert thick crusts. The volcano is covered with lava fragments resembling lapilli which may have formed through erosion. Gaussberg has no volcanic crater,Шаблон:Sfn rather having a ridge at the summit. The volcano has several terraces of undetermined originШаблон:Sfn and may have formed as a shield volcano with multiple vents. The rocks were probably emplaced subglacially, although the occurrence of pahoehoe lava is possible. There are moraines on the southern, northwestern and northeastern foot of the volcano,Шаблон:Sfn and erratic blocks and glacial striations are evidence that the volcano was formerly glaciated.Шаблон:Sfn

Geology

Gaussberg is an extremely isolated volcanoШаблон:Sfn although an ice rise a few kilometres southwest of GaussbergШаблон:Sfn and aeromagnetic surveys suggest that within Шаблон:Convert there are other small volcanoes in the area. It is the only Antarctic volcano situated on the Antarctic Shield, where the thickest crust of Antarctica is found.Шаблон:Sfn Why it formed about 50,000 years ago on a stable continental margin is unclear; either a mantle plume, an instability of the East Antarctic continentШаблон:SfnШаблон:Sfn or lateral flow of mantle plume material are possible.Шаблон:Sfn The basement underneath Gaussberg is formed by gneisses of Archean to Proterozoic age.Шаблон:Sfn The lithosphere under Gaussberg is over Шаблон:Convert thickШаблон:Sfn and has an unusually high heat flow.

Its activity has been related to the Kerguelen Plateau, but the Kerguelen volcanoes have yielded different magma compositions and there is no major geological structure linking the two other than the so-called "Kerguelen-Gaussberg Ridge",Шаблон:Sfn thus a connection between the two is unproven.Шаблон:Sfn A graben system in the region, which may have formed in Gondwana and may be correlated to tectonic structures on the Indian Peninsula, has been christened the "Gaussberg Rift"; the volcano rises on a horst on the rift but its relation to the rift is unclear.Шаблон:Sfn Finally, the 90° E Fault that separates regional tectonic structures may have influenced volcanism at Gaussberg.

Composition

The volcano has a uniform chemical compositionШаблон:Sfn consisting of lamproite (originally identified as leucitite),Шаблон:Sfn which defines a potassium-rich mafic rock suite.Шаблон:Sfn The rocks are almost free of visible crystalsШаблон:Sfn but contain numerous vesicles. Phenocrysts include clinopyroxene, leucite and olivine,Шаблон:Sfn the latter containing spinel inclusions.Шаблон:Sfn The Gaussberg suite is the youngest lamproite known on Earth.Шаблон:Sfn The rocks are rich in volatilesШаблон:Sfn including carbon dioxide and water.Шаблон:Sfn There are xenoliths, mostly granites coming from the Precambrian basement,Шаблон:Sfn and zircons recovered from the rocks are up to several billion years old. Palagonite,Шаблон:Sfn saltШаблон:Sfn and native sulfur deposits have been found.Шаблон:Sfn

The source of the Gaussberg lamproites is unclear, as the processes usually proposed for the formation of such magmas do not easily apply to the Gaussberg rocks.Шаблон:Sfn The magma may have formed through the incomplete melting of phlogopite-rich mantle and further chemical processes such as crystal fractionation that raised the potassium/aluminium ratio above 1.Шаблон:Sfn Deep mantle structures that formed through subduction billions of years ago and remained isolated since then have been proposed as the source of Gaussberg lamproites.Шаблон:Sfn The Kerguelen plume mayШаблон:Sfn or may not have played a role.

Eruption history

Drastically different age estimates have been obtained on Gaussberg. Early research suggested a Pliocene or Miocene age based on a presumed history of the Antarctic Ice Sheet and comparisons between the appearance of Gaussberg with Kerguelen volcanoes.Шаблон:Sfn Potassium-argon dating has yielded ages of 20 and 9 million years,Шаблон:Sfn with younger dating efforts producing an age of 56,000±5,000 years.Шаблон:Sfn Fission track dating produced ages of 25,000±12,000 years and geomorphologic considerations support a late Pleistocene age.Шаблон:Sfn These disagreements between potassium-argon dating and other dating methods may indicate either contamination with older rocks or the presence of non-outgassed argon.Шаблон:Sfn The 56,000±5,000 years age is considered to be more probable than the 20 and 9 million years ones.Шаблон:Sfn

Gaussberg was probably constructed in a single eruptive episodeШаблон:Sfn but there is evidence that the present-day edifice formed on an older, eroded volcano.Шаблон:Sfn Gaussberg formed under much thicker ice than there is today in the area, and the ice deposited moraines on its summit.Шаблон:Sfn There are different views on how erosion affected Gaussberg; some think that it was largely spared and others that erosion wore down the initially much larger edifice to its current size;Шаблон:SfnШаблон:Sfn the latter theory is the preferred view of the Global Volcanism Program and is supported by aeromagnetic data which suggest an initial size of Шаблон:Convert. Dust layers in the Siple Dome ice core may come from wind-driven erosion of Gaussberg rocks.

Biology

Several moss species were identified at Gaussberg,Шаблон:Sfn as well as a protozoan faunaШаблон:Sfn such as rotifers inhabiting them. Nematodes and tardigrades have been found at Gaussberg. It was the first place on the Antarctic mainland where lichens were reported.Шаблон:Sfn Emperor penguin rookeries occur at the mountain and snow petrels were observed to breed there, but overall there is not much fauna at Gaussberg.Шаблон:Sfn

See also

• List of volcanoes in Antarctica

References

Sources

• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite book
• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite journal
• Шаблон:Cite journal