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Lake Vostok ((ロシア語:Озеро Восток), ''Ozero Vostok'', lit. "Lake East") is the largest of Antarctica's almost 400 known subglacial lakes. Lake Vostok is located at the southern Pole of Cold, beneath Russia's Vostok Station under the surface of the central East Antarctic Ice Sheet, which is at above mean sea level. The surface of this fresh water lake is approximately under the surface of the ice, which places it at approximately below sea level. Measuring long by wide at its widest point,〔 and covering an area of and an average depth of , it has an estimated volume of . The lake is divided into two deep basins by a ridge. The liquid water over the ridge is about , compared to roughly deep in the northern basin and deep in the southern. The lake is named after Vostok Station, which in turn is named after the ''Vostok'' (Восток), a sloop-of-war ship, which means "East" in Russian. The existence of a subglacial lake in the Vostok region was first suggested by Russian geographer Andrey Kapitsa based on seismic soundings made during the Soviet Antarctic Expeditions in 1959 and 1964 to measure the thickness of the ice sheet.〔〔 The continued research by Russian and British scientists〔 led by 1993 to the final confirmation of the existence of the lake by J.P. Ridley using ERS-1 laser altimetry.〔 The overlying ice provides a continuous paleoclimatic record of 400,000 years, although the lake water itself may have been isolated for 15 to 25 million years. On 5 February 2012, a team of Russian scientists completed the longest ever ice core of and pierced the ice shield to the surface of the lake. The first core of freshly frozen lake ice was obtained on 10 January 2013 at a depth of . However, as soon as the ice was pierced, water from the underlying lake gushed up the borehole, mixing it with the Freon and kerosene used to keep the borehole from freezing.〔〔 A new "clean" borehole was drilled and an allegedly pristine water sample was obtained in January 2015.〔 The Russian team plans to eventually lower a probe into the lake to collect water samples and sediments from the bottom. It is hypothesized that unusual forms of life could be found in the lake's liquid layer, a fossil water reserve. Lake Vostok contains an environment sealed off below the ice for millions of years, in conditions which could resemble those of the ice-covered ocean of Jupiter's moon Europa, and Saturn's moon Enceladus. ==Discovery== Russian scientist Peter Kropotkin first proposed the idea of fresh water under Antarctic ice sheets at the end of the 19th century.〔"Research on the Ice age", ''Notices of the Imperial Russian Geographical Society'', 1876.〕 He theorized that the tremendous pressure exerted by the cumulative mass of thousands of vertical meters of ice could increase the temperature at the lowest portions of the ice sheet to the point where the ice would melt. Kropotkin's theory was further developed by Russian glaciologist I.A. Zotikov, who wrote his Ph.D. thesis on this subject in 1967.〔 Russian geographer Andrey Kapitsa used seismic soundings in the region of Vostok Station made during the Soviet Antarctic Expedition in 1959 and 1964 to measure the thickness of the ice sheet. Kapitsa was the first to suggest the existence of a subglacial lake in the region, and the subsequent research confirmed his hypothesis. When British scientists in Antarctica performed airborne ice-penetrating radar surveys in the early 1970s, they detected unusual radar readings at the site which suggested the presence of a liquid freshwater lake below the ice. In 1991, Jeff Ridley, a remote sensing specialist with the Mullard Space Science Laboratory at University College London, directed the ERS-1 satellite to turn its high-frequency array toward the center of the Antarctic ice cap. The data from ERS-1 confirmed the findings from the 1973 British surveys, but these new data were not published in the ''Journal of Glaciology'' until 1993. Space-based radar revealed that this subglacial body of fresh water is one of the largest lakes in the world, and one of some 140 subglacial lakes in Antarctica. Russian and British scientists delineated the lake in 1996 by integrating a variety of data, including airborne ice-penetrating radar imaging observations and space-based radar altimetry. It has been confirmed that the lake contains large amounts of liquid water under the more than thick ice cap. The lake has at least 22 cavities of liquid water, averaging each. The lake is named after Vostok Station, which in turn is named after the ''Vostok'' (Восток), the 900 ton sloop-of-war ship sailed by one of the discoverers of Antarctica, Russian explorer Admiral Fabian von Bellingshausen.〔 The word Bосток means "East" in Russian, and the name of the station and the lake also reflects the fact that they are located in East Antarctica. In 2005 an island was found in the central part of the lake. Then, in January 2006, the discovery of two nearby smaller lakes under the ice cap was published; they are named 90 Degrees East and Sovetskaya.〔Robin Bell and Michael Studinger, Geophysical researchers from Columbia University, published in ''Geophysical Research Letters''〕 It is suspected that these Antarctic subglacial lakes may be connected by a network of subglacial rivers. Centre for Polar Observation & Modelling glaciologists propose that many of the subglacial lakes of Antarctica are at least temporarily interconnected.〔 Because of varying water pressure in individual lakes, large subsurface rivers may suddenly form and then force large amounts of water through the solid ice.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lake Vostok」の詳細全文を読む スポンサード リンク
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