Антарктида: География, Ледники и Вулканизм

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The geography of Antarctica is dominated by its south polar location and, thus, by ice. The Antarctic continent, located in the Earth's southern hemisphere, is centered asymmetrically around the South Pole and largely south of the Antarctic Circle. It is washed by the Southern (or Antarctic) Ocean or, depending on definition, the southern Pacific, Atlantic, and Indian Oceans. It has an area of more than 14.2 million km2. Antarctica is the largest ice desert in the world. Some 98% of Antarctica is covered by the Antarctic ice sheet, the world's largest ice sheet and also its largest reservoir of fresh water. Averaging at least 1.6 km thick, the ice is so massive that it has depressed the continental bedrock in some areas more than 2.5 km below sea level; subglacial lakes of liquid water also occur (e. g., Lake Vostok). Ice shelves and rises populate the ice sheet on the periphery. The present Antarctic ice sheet accounts for 90 percent of Earth's total ice volume and 70 percent of its fresh water. It houses enough water to raise global sea level by 200 ft. In September 2018, researchers at the National Geospatial Intelligence Agency released a high resolution terrain map (detail down to the size of a car, and less in some areas) of Antarctica, named the "Reference Elevation Model of Antarctica" (REMA).

Physically, Antarctica is divided in two by the Transantarctic Mountains, close to the neck between the Ross Sea and the Weddell Sea. Western Antarctica and Eastern Antarctica correspond roughly to the western and eastern hemispheres relative to the Greenwich meridian. West Antarctica is covered by the West Antarctic Ice Sheet. There has been some concern about this ice sheet, because there is a small chance that it will collapse. If it does, ocean levels would rise by a few metres in a very short period of time.

The definition of Glaciovolcanism is “the interactions of magma with ice in all its forms, including snow, firn and any meltwater.” It defines a special field of volcanic that is specifically centered around ice and ice melt. This field of science is less than 100 years old, and thus continuously makes new discoveries. Glaciovolcanism is characterized by three kinds of eruptions: sub glacial eruptions, supraglacial volcanism, and ice marginal volcanism. The study of glaciovolcanism is vital to the understanding of ice sheet formation. It is also a valuable tool to predict volcanic hazards, such as the ash hazard following the Eyjafjallajökull eruption in Iceland.

The Marie Byrd Land makes up a large portion of West Antarctica, consisting of the Area below the Antarctic Peninsula. The Marie Byrd land is a large formation of volcanic rock, characterized by 18 exposed and subglacial volcanoes. 16 of the 18 volcanoes are entirely covered by the antarctic ice sheet. There have been no eruptions recorded from any of the volcanoes in this area, however scientists believe that some of the volcanoes may be potentially active.

Scientists and researchers debate whether or not the 138 identified possible volcanoes are active or dormant. It is very hard to definitively say, given that many of these volcanic structures are buried underneath several kilometers of ice. However, ash layers within the West Antarctic Ice Sheet, as well as deformations in the ice surface indicate that the West Antarctic Rift System could be active and contain erupting volcanoes. Additionally, seismic activity in the region hints at magma movement beneath the crust, a sign of volcanic activity. Though there are other sources of subglacial water, such as geothermal heat, it almost always is a condition of volcanism. Scientists remain uncertain about the presence of water underneath the West Antarctic Ice Sheet, with some claiming to have found evidence indicating the existence.

In West Antarctica's Marie Byrd Land, volcanoes are typically composed of alkaline and basaltic lava. Sometimes, the volcanoes are entirely basaltic in composition. Due to the geographic similarity of the Marie Byrd Land, it is believed that the volcanoes in the West Antarctic Rift System are also composed of basalt. However, West Antarctic Volcanoes form underneath ice sheets, and are thus categorized as subglacial volcanoes. Subglacial volcanoes that are monogenetic are far more narrow, steeper, flat topped structures. Polygenetic subglacial volcanoes have a wider variety of shapes and sizes due to being made up of many different eruptions. Often, they look more cone shaped, like stratovolcanoes.

Little has been studied about the implications of volcanic ash from eruptions within the Antarctic Circle. It is likely that an eruption at lower latitudes would cause global health and aviation hazards due to ash disbursement. The clockwise air circulation around the low pressure system at the South Pole forces air upwards, hypothetically sending ash upwards towards the Stratospheric jet streams, and thus quickly dispersing it throughout the globe.

Recently, in 2017, a study found evidence of subglacial volcanic activity within the West Antarctic Ice Sheet. This activity poses a threat to the stability of the Ice Sheet, as volcanic activity leads to increased melting. This could possibly plunge the West Antarctic Ice Sheet into a positive feedback loop of rising temperatures and increased melting.

There are three vast canyons that run for hundreds of kilometers, cutting through tall mountains. None of the canyons are visible at the snow covered surface of the continent since they are buried under hundreds of meters of ice. The largest of the canyons is called Foundation Trough and is over 350 km long and 35 km wide. The Patuxent Trough is more than 300 km long and over 15 km wide, while the Offset Rift Basin is 150 km long and 30 km wide. These three troughs all lie under and cross the so called "ice divide" the high ice ridge that runs all the way from the South Pole out towards the coast of West Antarctica.

For a list of all Antarctic islands see List of Antarctic and sub Antarctic islands.

East Antarctica is the larger part of the continent, (50°W – 180°E), both the South Magnetic Pole and geographic South Pole are situated here. Divided into:

For a list of all Antarctic islands see List of Antarctic and sub Antarctic islands.

Seven nations have made official Territorial claims in Antarctica.

Ivanov, L. General Geography and History of Livingston Island. In: Bulgarian Antarctic Research: A Synthesis. Eds. C. Pimpirev and N. Chipev. Sofia: St. Kliment Ohridski University Press, 2015. pp. 17–28.