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Lake Toba is a large lake, 100km long and 30km wide, in the middle of the northern part of the Indonesian island of Sumatra.1 Geology
In 1949 the Dutch geologist Rein van Bemmelen reported that Lake Toba was surrounded by a layer of ignimbrite rocks, and was a large volcanic caldera. Later researchers found rhyolite ash similar to that in the ignimbrite around Toba in Malaysia and India, 3000km away. Oceanographers discovered Toba ash on the floor of the eastern Indian OceanThe Indian Ocean is the third-largest body of water in the world, covering about 20% of the Earth's water surface. It is bounded on the north by southern Asia (the Indian Sub-continent); on the west by the Arabian Peninsula and Africa; on the east by the and the Bay of BengalThe Bay of Bengal is a sea that forms the northeastern part of the Indian Ocean. It resembles a triangle in shape, and is bordered on the east by the Malay Peninsula, and on the west by the Indian subcontinent. On the northern tip of the "bay" lie the Ind.
The Toba eruption, dated at 73,000 ± 4000 years ago, was the most recent eruption of a " supervolcanoA supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruptions on earth. The actual explosivity of these eruptions varies, but the sheer volume of extruded magma is immense enough to radically alter the landscape and s." Bill Rose and Craig Chesner of Michigan Technological UniversityMichigan Technological University is an institution of higher learning with its main campus in Houghton, Michigan. It also maintains the Ford Forestry Center and Research Forest, located in Alberta, Michigan. Michigan Tech was founded in 1885 as the Michi deduced that the total amount of erupted material was about 2800km3 -- around 800km3 of ignimbrite that flowed over the ground and around 2000km3 that fell as ash, with the wind blowing most of it to the west. Such a huge eruption probably lasted nearly two weeks. Very few plants or animals in Indonesia would have survived, and it is possible that the eruption caused a planet-wide die-off. There is some evidence, based on mitochondrial DNAMitochondrial DNA mtDNA is DNA which is located not in the nucleus of the cell but in the mitochondria. Mitochondria are parts of the cell that generate fuel in the form of adenosine triphosphate (ATP), which drives the varied machinery of the cell. Unlik, that the human race was reduced to only a few thousand individuals by the Toba eruption (see Toba catastrophe theoryThe Toba catastrophe theory is a theory of how modern human evolution was affected by a recent large volcanic event. It was proposed by Stanley H. Ambrose, of the University of Illinois at Urbana-Champaign. Knowledge of human prehistory is largely theoret).
A large area collapsed after the ejection of that amount of subsurface material, forming a caldera, which filled with water creating Lake Toba. Later, the floor of the caldera uplifted to form SamosirSamosir is a large volcanic island in Lake Toba. Lake Toba is located on the north of the island Sumatra in Indonesia. It is a popular tourist resort due to the fantastic vistas it offers. The tourist resorts are concentrated in the Tuktuk area; some of t, a large island in the lake. Such uplifts are common in very large calderas, apparently due to the upward pressure of unerupted magma. Toba is probably the largest resurgent caldera on Earth.
There have been no historic eruptions at Toba, but large earthquakes have occurred, the most recent in 1987 along the southern shore of the lake. On Sumatra as a whole large earthquakes are very common--several higher than 7.0 on the Richter scale since 1995.
