## Lake Toba: ERS-SAR Mosaic

Lake Toba is a complex and very large tectonic-volcanic depression. The past volcanoes of the area erupted several times releasing huge quantities of ash which has deposited a special type of rock called ignimbrite in this area. The eruptions were so large that Toba ash has been found as far west as Sri Lanka and India. Violent eruptions and tectonic collapses created the huge depression which later was filled up with water to form Lake Toba. One of the eruptions which took place about 73 000 years ago was gigantic. In this super-eruption an estimated 2800 km3 of material was released. In contrast, Mount St. Helens in 1980 and Pinatubo in 1991 ejected 0.35 km3 and 5 km3 of material respectively.

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