Gaussberg
Template:Short description Template:Good article Template:Infobox mountain
Gaussberg (or Schwarzen Berg,<ref name="GlaubrechtMaitas2005" /> Mount Gauss) is an extinct, Template: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 historyEdit
Discovered in February 1902 by the German Antarctic Expedition under Erich von Drygalski, who named it after his expedition ship<ref name=gnis/> which in 1902 remained stuck in ice for a year.Template:Sfn The ship in turn was named in honour of the German mathematician Carl Friedrich Gauss.<ref name=gnis/> Drygalski observed the volcano with the help of a tethered balloon.<ref name="Doake1987" />
Owing to its peculiar composition, Gaussberg has been intensively researched.Template:Sfn The mountain was investigated in 1912 by the 1911-1914 Australasian Antarctic Expedition, by the Soviet Antarctic Expedition in 1956–1957,Template:Sfn by Australian expeditions in 1977, 1981,Template:Sfn 1987Template:Sfn and by an expedition linked to an entity "K.D.C" in 1997.Template:Sfn Regional krill stocks in turn were named after the mountain.<ref name="Wright1987" /> Owing to its peculiar composition and isolated location, the volcano has an importance out of proportion to its actual size.<ref name="Smellie2021" /> The mineral gaussbergite is named after the volcano.<ref name="Aodha1989" />
Geography and geomorphologyEdit
The volcano lies in Kaiser Wilhelm II Land, Antarctica,Template:Sfn close to the West Ice Shelf and between the Australian Davis Station and Russian Mirny Station.Template:Sfn It lies on the Davis Sea immediately west of Posadowsky Glacier.<ref name=gnis/> Gaussberg is within the Antarctic territory claimed by Australia,Template:Sfn and the only ice-free outcrop between Mirny Station and the Vestfold Hills.<ref name="Mikhalsky2015" />
It consists of a Template:Convert, Template:ConvertTemplate:Sfn cone located between the East Antarctic Ice Sheet on three sides and the sea on the fourth.Template:Sfn It is the only exposure of rock in the region,Template:SfnTemplate:Sfn with rocky outcrops at the summit and on the northern flank.Template:Sfn The edifice covers an area of about Template:ConvertTemplate:Sfn and has a volume of Template:Convert.Template:Sfn Most of the edifice is made out of pillow lavas with radii of Template:Convert and Template:Convert thick crusts. The volcano is covered with lava fragments resembling lapilli which may have formed through erosion. Gaussberg has no volcanic crater,Template:Sfn rather having a ridge at the summit. The volcano has several terraces of undetermined originTemplate:Sfn and may have formed as a shield volcano with multiple vents.<ref name="Smellie2021" /> The rocks were probably emplaced subglacially, although the occurrence of pahoehoe lava is possible.<ref name="WilliamsCollerson1992" /> There are moraines on the southern, northwestern and northeastern foot of the volcano,Template:Sfn and erratic blocks and glacial striations are evidence that the volcano was formerly glaciated.Template:Sfn
GeologyEdit
Gaussberg is an extremely isolated volcanoTemplate:Sfn although an ice rise a few kilometres southwest of GaussbergTemplate:Sfn and aeromagnetic surveys suggest that within Template:Convert there are other small volcanoes in the area.<ref name="Smellie2021" /> It is the only Antarctic volcano situated on the Antarctic Shield, where the thickest crust of Antarctica is found.Template: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 continentTemplate:SfnTemplate:Sfn<ref name="Panter2021" /> or lateral flow of mantle plume material are possible.Template:Sfn The basement underneath Gaussberg is formed by gneisses of Archean to Proterozoic age.Template:Sfn The lithosphere under Gaussberg is over Template:Convert thickTemplate:Sfn and has an unusually high heat flow.<ref name="Reading2022" />
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",Template:Sfn thus a connection between the two is unproven.Template: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";<ref name="Golynsky2010" /> the volcano rises on a horst on the rift but its relation to the rift is unclear.Template:Sfn Finally, the 90° E Fault that separates regional tectonic structures may have influenced volcanism at Gaussberg.<ref name="Aitken2014" />
CompositionEdit
The volcano has a uniform chemical compositionTemplate:Sfn consisting of lamproite (originally identified as leucitite),Template:Sfn which defines a potassium-rich mafic rock suite.Template:Sfn The rocks are almost free of visible crystalsTemplate:Sfn but contain numerous vesicles. Phenocrysts include clinopyroxene, leucite and olivine,Template:Sfn the latter containing spinel inclusions.Template:Sfn The Gaussberg suite is the youngest lamproite known on Earth.Template:Sfn The rocks are rich in volatilesTemplate:Sfn including carbon dioxide and water.Template:Sfn There are xenoliths, mostly granites coming from the Precambrian basement,Template:Sfn and zircons recovered from the rocks are up to several billion years old.<ref name="Mikhalsky2015" /> Palagonite,Template:Sfn saltTemplate:Sfn and native sulfur deposits have been found.Template: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.Template: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.Template: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.Template:Sfn The Kerguelen plume mayTemplate:Sfn or may not have played a role.<ref name="Smellie2021" />
Eruption historyEdit
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.Template:Sfn Potassium-argon dating has yielded ages of 20 and 9 million years,Template:Sfn with younger dating efforts producing an age of 56,000±5,000 years.Template:Sfn Fission track dating produced ages of 25,000±12,000 years and geomorphologic considerations support a late Pleistocene age.Template: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.Template:Sfn The 56,000±5,000 years age is considered to be more probable than the 20 and 9 million years ones.Template:Sfn
Gaussberg was probably constructed in a single eruptive episodeTemplate:Sfn but there is evidence that the present-day edifice formed on an older, eroded volcano.Template:Sfn Gaussberg formed under much thicker ice than there is today in the area, and the ice deposited moraines on its summit.Template:Sfn There are different views on how erosion affected Gaussberg; some think that it was largely spared<ref name="Grew1982" /> and others that erosion wore down the initially much larger edifice to its current size;Template:SfnTemplate:Sfn the latter theory is the preferred view of the Global Volcanism Program<ref>Template:Cite gvp</ref> and is supported by aeromagnetic data which suggest an initial size of Template:Convert.<ref name="Smellie2021" /> Dust layers in the Siple Dome ice core may come from wind-driven erosion of Gaussberg rocks.<ref name="Koffman2021" />
BiologyEdit
Several moss species were identified at Gaussberg,Template:Sfn as well as a protozoan faunaTemplate:Sfn such as rotifers inhabiting them.<ref name="Murray1907" /> Nematodes<ref name="Yeates1979" /> and tardigrades have been found at Gaussberg.<ref name="MillerMiller1996" /> It was the first place on the Antarctic mainland where lichens were reported.Template:Sfn Emperor penguin rookeries occur at the mountain<ref name="Fuchs1951" /> and snow petrels were observed to breed there,<ref name="CroxallSteele1995" /> but overall there is not much fauna at Gaussberg.Template:Sfn