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Lake Toba ((インドネシア語:Danau Toba)) is a large natural lake occupying the caldera of a supervolcano. The lake is about 100 kilometres long, 30 kilometres wide, and up to 505 metres (1,666 ft) deep. Located in the middle of the northern part of the Indonesian island of Sumatra, with a surface elevation of about , the lake stretches from to . It is the largest lake in Indonesia and also the largest volcanic lake in the world.〔(Worldlakes.org )〕 Lake Toba is the site of a massive supervolcanic eruption estimated at VEI 8 that occurred 69,000 to 77,000 years ago,〔(Global Volcanism Program page on Toba )〕〔 representing a climate-changing event. It is the largest known explosive eruption on Earth in the last 25 million years. According to the Toba catastrophe theory, it had global consequences for human populations: it killed most humans living at that time and is believed to have created a population bottleneck in central east Africa and India, which affects the genetic make up of the human world-wide population to the present. It has been accepted that the eruption of Toba led to a volcanic winter with a worldwide decrease in temperature between , and up to in higher latitudes. Additional studies in Lake Malawi in East Africa show significant amounts of ash being deposited from the Toba eruptions, even at that great distance, but little indication of a significant climatic effect in East Africa. ==Geology== The Toba caldera complex in Northern Sumatra, comprises four overlapping volcanic craters that adjoin the Sumatran "volcanic front." The fourth and youngest caldera is the world's largest Quaternary caldera () and intersects the three older calderas. An estimated of dense-rock equivalent pyroclastic material, known as the youngest Toba tuff, was released during one of the largest explosive volcanic eruptions in recent geological history. Following this eruption, a resurgent dome formed within the new caldera, joining two half-domes separated by a longitudinal graben. At least four cones, four stratovolcanoes, and three craters are visible in the lake. The Tandukbenua cone on the northwestern edge of the caldera has only sparse vegetation, suggesting a young age of several hundred years. Also, the Pusubukit (Hill Center) volcano (1971 metres above sea level) on the south edge of the caldera is solfatarically active and is a Geology Sanctuary.〔(【引用サイトリンク】title=Gunung Pusukbuhit )〕 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 Toba」の詳細全文を読む スポンサード リンク
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