Английская Википедия:Hudson Mountains

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Шаблон:Good article Шаблон:Short description Шаблон:Use dmy dates Шаблон:Infobox mountain Шаблон:Infobox mountain The Hudson Mountains are a mountain range in western Ellsworth Land just east of Pine Island Bay at the Walgreen Coast of the Amundsen Sea. They are of volcanic origin, consisting of low scattered mountains and nunataks that protrude through the West Antarctic Ice Sheet. The Hudson Mountains are bounded on the north by Cosgrove Ice Shelf and on the south by Pine Island Glacier. The mountains were volcanically active during the Miocene and Pliocene, but there is evidence for an eruption about two millennia ago and uncertain indications of activity in the 20th century.

Geography and geomorphology

The Hudson Mountains rise in western Ellsworth LandШаблон:Sfn of West AntarcticaШаблон:Sfn and were discovered in 1940 by the United States Antarctic Service Expedition.Шаблон:Sfn The mountains lie at some distance from the Amundsen Sea's Walgreen Coast,Шаблон:Sfn facing Pine Island Bay.Шаблон:Sfn The Cosgrove Ice Shelf lies north of the Hudson Mountains.Шаблон:Sfn The mountains are remote and visits are rare.Шаблон:Sfn In 1991, they were prospected as a potential aircraft landing site.Шаблон:Sfn

The mountains are a volcanic field formed by parasitic vents and stratovolcanoesШаблон:Sfn covered in snow and ice,Шаблон:Sfn forming a cold desert landscapeШаблон:Sfn with an area of about Шаблон:Convert.Шаблон:Sfn About 20 mountains emerge above the Antarctic Ice Sheet in the form of nunataks,Шаблон:SfnШаблон:Sfn with the largest rocky outcrops found at Mount Moses and Maish Nunatak.Шаблон:Sfn The stratovolcanoes Mount Manthe, Mount Moses, and Teeters Nunatak constitute the bulk of the volcanic field and are heavily eroded. Better preserved are some parasitic cones and volcanic cratersШаблон:Sfn which appear to have formed on these three volcanoes.Шаблон:Sfn To their south lies the Pine Island Glacier, while the Larter Glacier traverses the Hudson Mountains between Mount Moses and Mount MantheШаблон:Sfn and other glaciers from the Hudson Mountains join the Pine Island Glacier.Шаблон:Sfn The glaciers are rapidly thinning owing to global warming.Шаблон:Sfn

Mount Moses reaches an elevation of Шаблон:Convert above sea level, Teeters Nunatak Шаблон:Convert, and Mount Manthe Шаблон:Convert. Other named structures are:Шаблон:Sfn

The volcanoes are made up by breccia, palagonite tuff,Шаблон:Sfn scoriaceous lava flows and tuffs. At Mount Nickles Шаблон:Sfn and Mount Moses there are pillow lavas. Lava fragments are dispersed on the slopes of Mount Moses.Шаблон:Sfn Volcanic rock sequences that were emplaced under water and under ice are overlaid by volcanic products that were deposed under the atmosphere,Шаблон:Sfn there are deposits of volcanic ash and breccia produced by hydromagmatic activityШаблон:Sfn and tuya-like shapes associated with subglacial growth of the volcanoes.Шаблон:Sfn At Mount Moses, erosion has exposed dykes.Шаблон:Sfn Glaciers have deposited granite boulders and erratic blocks on the Hudson Mountains,Шаблон:Sfn and left glacial striations on the pillow lavas of Mount Moses.Шаблон:Sfn Physical weathering has yielded soils in some areas.Шаблон:Sfn Volcanic glass found in the Pine Island Glacier probably originates in the Hudson Mountains.Шаблон:Sfn

Geology

Neighbouring Marie Byrd Land was volcanically active during the Cenozoic, forming a number of volcanoes, some of which are buried under ice, while others emerge above the ice sheet. The Hudson Mountains are part of the Thurston IslandШаблон:Sfn or Bellingshausen Volcanic Province, and are its largest and best preserved volcanic field.Шаблон:Sfn The volcanism at the mountains may have either been caused by a mantle plume under Marie Byrd Land or by the presence of anomalies (slab windows) in the mantle left over by subduction.Шаблон:Sfn Seismic tomography has found evidence of low velocity anomalies under the Hudson Mountains, which may reflect the presence of the Marie Byrd Land mantle plume.Шаблон:Sfn

The bedrock around the Hudson Mountains lies below sea level.Шаблон:Sfn The basement on which the volcanoes formed is not exposed in the Hudson Mountains, but crops out in the neighbouring Jones Mountains.Шаблон:Sfn It forms the so-called Thurston Island tectonic block.Шаблон:Sfn Below the Hudson Mountains, the crust is about Шаблон:Convert thick.Шаблон:Sfn A proposal by Lopatin and Polyakov 1974 is that east and north-trending fractures have controlled the position of the volcanoes.Шаблон:Sfn

Composition

The main volcanic rocks include alkali basalt,Шаблон:Sfn basalt, hawaiite and tephrite.Шаблон:Sfn They define an alkaline suite, some samples trend towards subalkaline.Шаблон:Sfn Ultramafic nodules have been reported from some rocks.Шаблон:Sfn The magmas erupted by the volcanoes may have originated in a mantle that had been influenced by subduction,Шаблон:Sfn and underwent fractionation of olivine as they ascended.Шаблон:Sfn

Life and climate

Sparse lichens grow on most of the nunataks,Шаблон:Sfn including Usnea species.Шаблон:Sfn Mosses have been found growing in gaps between or cracks in boulders.Шаблон:Sfn Petrels have been observed.Шаблон:Sfn There are no data on the local climate.Шаблон:Sfn An automated weather station was installed on Evans Knoll in 2011 and records air temperatures and wind speeds.Шаблон:Sfn

Geologic history

The volcanoes were active during the late Miocene and Pliocene. Dates range between 8.5±1.0 and 3.7±0.2 million years ago,Шаблон:Sfn an older date is 20±4 million years.Шаблон:Sfn There is no evidence of an age progression in any direction.Шаблон:Sfn

Ice cover was thicker on the Hudson Mountains during the last glacial maximum, perhaps by about Шаблон:Convert.Шаблон:Sfn Retreat commenced about 14,000Шаблон:Sfn-10,000 years ago;Шаблон:Sfn however, glaciers were still thicker than today during the early Holocene and deposited rocks on the Hudson Mountains.Шаблон:Sfn Another thinning step began about 8,000 years ago and was very fast, perhaps lasting only a century.Шаблон:Sfn

Radar data have found a tephra deposit buried under the ice, which may have originated during an eruption of the Hudson Mountains around Шаблон:Val BCE;Шаблон:Sfn the eruption may correspond to an electrical conductivity anomaly in an ice core at Siple DomeШаблон:Sfn and a tephra layer dated to 325 BCE in the Byrd Station ice core. The eruption may have had a volcanic explosivity index of 3-4Шаблон:Sfn and originated in an area east of the main Hudson Mountains.Шаблон:SfnШаблон:Sfn LeMasurier et al. 1990 referenced reports of activity in the Hudson Mountains.Шаблон:Sfn These include a report of steaming at one of the nunataks and of satellite data of a potential eruption in 1985 of Webber Nunatak,Шаблон:Sfn but the report of this eruption is questionable.Шаблон:Sfn There is no evidence of increased heat flow or morphological changes at Webber Nunatak since then,Шаблон:Sfn but anomalies in helium isotope ratios from the Pine Island Glacier ice have been attributed to volcanic activity in the Hudson Mountains.Шаблон:Sfn

References

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Sources

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External links

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