Senin, 01 Oktober 2012

Lake Toba


Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano. The lake is 100 kilometres long and 30 kilometres wide, and 505 metres (1,666 ft) at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 metres (2,953 ft), the lake stretches from http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/WMA_button2b.png/17px-WMA_button2b.png WikiMiniAtlas2°53′N 98°31′E / 2.88°N 98.52°E / 2.88; 98.52 tohttp://upload.wikimedia.org/wikipedia/commons/thumb/5/55/WMA_button2b.png/17px-WMA_button2b.png WikiMiniAtlas 2°21′N 99°06′E / 2.35°N 99.1°E / 2.35; 99.1. It is the largest lake in Indonesia and the largest volcanic lake in the world.
Lake Toba is the site of a supervolcanic eruption that occurred an estimated 69,000 to 77,000 years ago, a massive, climate-changing event. It is estimated to have been a VEI 8 eruption. It is the largest known explosive eruption anywhere on Earth in the last 25 million years. According to the Toba catastrophe theory, it had global consequences, killing most humans then alive and creating a population bottleneck in Central Eastern Africa and India that affected the genetic inheritance of all humans today. However, this hypothesis is not widely accepted due to lack of evidence for any other animal decline or extinction, even in environmentally sensitive species. However, it has been accepted that the eruption of Toba led to a volcanic winter with a worldwide decline in temperatures between 3 to 5 °C (5 to 9 °F), and up to 15 °C (27.0 °F) in higher latitudes.

Geology

The Toba caldera complex in Northern Sumatra, Indonesia consists of four overlapping volcanic craters that adjoin the Sumatran "volcanic front". The youngest and fourth caldera is the world's largest Quaternary caldera (100 by 30 km (62 by 19 mi)) and intersects the three older calderas. An estimate of 2,800 km3 (670 cu mi) of dense-rock equivalent pyroclastic material, known the Youngest Toba tuff, was blasted from the youngest caldera during one of the largest single explosive volcanic eruptions in geologic history. Following the "Youngest Toba tuff eruption", a typical resurgent dome formed within the new caldera, joining two half-domes separated by a longitudinal graben.
There are at least four cones, four stratovolcanoes and three craters visible in the lake. The Tandukbenua cone on the NW edge of the caldera is relatively lacking in vegetation, suggesting a young age of only several hundred years. Also, the Pusubukit volcano on the south edge of the caldera is solfatarically active.

Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano. The lake is 100 kilometres long and 30 kilometres wide, and 505 metres (1,666 ft) at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 metres (2,953 ft), the lake stretches from http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/WMA_button2b.png/17px-WMA_button2b.png WikiMiniAtlas2°53′N 98°31′E / 2.88°N 98.52°E / 2.88; 98.52 tohttp://upload.wikimedia.org/wikipedia/commons/thumb/5/55/WMA_button2b.png/17px-WMA_button2b.png WikiMiniAtlas 2°21′N 99°06′E / 2.35°N 99.1°E / 2.35; 99.1. It is the largest lake in Indonesia and the largest volcanic lake in the world.
Lake Toba is the site of a supervolcanic eruption that occurred an estimated 69,000 to 77,000 years ago, a massive, climate-changing event. It is estimated to have been a VEI 8 eruption. It is the largest known explosive eruption anywhere on Earth in the last 25 million years. According to the Toba catastrophe theory, it had global consequences, killing most humans then alive and creating a population bottleneck in Central Eastern Africa and India that affected the genetic inheritance of all humans today. However, this hypothesis is not widely accepted due to lack of evidence for any other animal decline or extinction, even in environmentally sensitive species. However, it has been accepted that the eruption of Toba led to a volcanic winter with a worldwide decline in temperatures between 3 to 5 °C (5 to 9 °F), and up to 15 °C (27.0 °F) in higher latitudes.

Geology

The Toba caldera complex in Northern Sumatra, Indonesia consists of four overlapping volcanic craters that adjoin the Sumatran "volcanic front". The youngest and fourth caldera is the world's largest Quaternary caldera (100 by 30 km (62 by 19 mi)) and intersects the three older calderas. An estimate of 2,800 km3 (670 cu mi) of dense-rock equivalent pyroclastic material, known the Youngest Toba tuff, was blasted from the youngest caldera during one of the largest single explosive volcanic eruptions in geologic history. Following the "Youngest Toba tuff eruption", a typical resurgent dome formed within the new caldera, joining two half-domes separated by a longitudinal graben.
There are at least four cones, four stratovolcanoes and three craters visible in the lake. The Tandukbenua cone on the NW edge of the caldera is relatively lacking in vegetation, suggesting a young age of only several hundred years. Also, the Pusubukit volcano on the south edge of the caldera is solfatarically active.

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