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The Toba supereruption was a supervolcanic eruption that occurred some time between 69,000 and 77,000 years ago at the site of present-day Lake Toba (Sumatra, Indonesia). It is one of the Earth's largest known eruptions. The Toba catastrophe hypothesis holds that this event caused a global volcanic winter of 6–10 years and possibly a 1,000-year-long cooling episode. In 1993, science journalist Ann Gibbons suggested a link between the eruption and a population bottleneck in human evolution, and Michael R. Rampino of New York University and Stephen Self of the University of Hawaii at Manoa gave support to the idea. In 1998, the bottleneck theory was further developed by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign. Both the link and global winter theories are highly controversial. The Toba event is the most closely studied super-eruption.〔 , p. 200; , p. 174; , pp. 1593–1594; 〕〔(【引用サイトリンク】title=The Toba Supervolcano And Human Evolution )〕 ==Supereruption== The ''Toba eruption'' or ''Toba event'' occurred at the present location of Lake Toba, in Indonesia, about Before Present (BP).〔.〕〔.〕 This eruption was the last and largest of four eruptions of Toba during the Quaternary period, and is also recognized from its diagnostic horizon of ashfall, the youngest Toba tuff (''YTT'').〔, p. 200; , p. 174; , pp. 1593–1594; 〕〔, p. 913; .〕 It had an estimated volcanic explosivity index of 8 (described as "apocalyptic"), or a magnitude ≥ M8; it made a sizable contribution to the 100×30 km caldera complex.〔, p. 1593.〕 Dense-rock equivalent (DRE) estimates of eruptive volume for the eruption vary between and – the most common DRE estimate is (about ) of erupted magma, of which was deposited as ash fall.〔, p. 174; , p. 913.〕 The erupted mass was 100 times greater than that of the largest volcanic eruption in recent history, the 1815 eruption of Mount Tambora in Indonesia, which caused the 1816 "Year Without a Summer" in the northern hemisphere.〔, p. 114; , p. 837.〕 Toba's erupted mass deposited an ash layer approximately 15 centimetres (6 inches) thick over the whole of South Asia. A blanket of volcanic ash was also deposited over the Indian Ocean, and the Arabian Sea and South China Sea.〔, p. 173〕 Deep-sea cores retrieved from the South China Sea have extended the known reach of the eruption, suggesting that the calculation of the erupted mass is a minimum value or even an underestimation.〔, p. 174; . pp. 1593–1596.〕 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「Toba catastrophe theory」の詳細全文を読む スポンサード リンク
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