Lake Toba
Caldera Lake
Location
The Lake Toba volcano- tectonic located in a boiler burglary, 77 km south of the provincial capital of Medan. The level of the lake is 905 meters above sea level, the shoreline is 294 km. With a total area of 1776.5 km ² (compared to Constance 536 km ² ), including 647 km ² peninsula Samosir, it is the largest crater lake on earth. Prapat on the east bank is the largest and most important city on the lake. More important for the infrastructure of cities around the lake, in the northeast of Berastagi, Pematang Siantar the east and Sibolga the Indian Ocean.
The longitudinally extending through Sumatra Barisangebirge is a plate tectonic folding, formed by the pressing of the approach of the southwest pushing Indo- oceanic plate. According to the Dutch geologists Reinout Willem van Bemmelen emerged in this process between the Pliocene and the Pleistocene in the area and in the area of present-day Lake Toba a dome-shaped, up to 2000 m high bulge, which he gave the name " Batak tumor ". The extent of this bulge goes far beyond the lake today's addition: The length along the longitudinal axis of Sumatra is 275 km, the width up to 150 km. During the bulge created by and for ever larger and deeper strain cracks until about 74,000 years through these cracks the gas-rich magma of only little deeper batholiths found its way into a gigantic eruption.
At Lake Toba dormant volcanoes Dolok Pusukbukit limits ( in the west) and Dolok Tandukbenua (north - west). Lake Toba is drained by the 150 km long river Asahan, in the extreme southeast of the Bay of Porsea. Downstream breaks through the Asahan with an up to 300 m deep canyon the eastern edge of the mountains boiler burglary. As a result of this erosion, the low level of the lake has decreased by about 250 m.
Eruption
The result of the boiler of the Lake Toba is by the eruption of the Toba super volcano 73,880 years ago ± 320 cal BP. It is believed that it has traded the largest volcanic eruption of the past two million years. Volcanic ash from the eruption can be found throughout the Indian Ocean and in large parts of India. It was next to the Oruanui eruption of Taupo in New Zealand 26,500 years ago, the only eruption that reached in the same period Vulkanexplosivitätsindex ( VEI ) of 8. It is estimated that 2,800 cubic kilometers of volcanic material ( including 800 km ³ of ash) were hurled down to 80 km altitude and distributed in the atmosphere. This was followed by a cooling of the global climate, known as a volcanic winter. Estimates speak of 3 to 5 ° C cooling. Model calculations showed that depending on the selection of the input values for the model, the cooling reproached several decades and at the beginning of this period of cold weather, the cooling could have even be 8 to 17 ° C. The outbreak could therefore have caused the coldest years of the Würm.
Toba catastrophe theory
The Toba catastrophe theory of the anthropologist Stanley Ambrose According to the eruption to depletion of - led then still living exclusively in Africa ancestors of modern humans (Homo sapiens) at 1,000 to 10,000 individuals, what this type to the edge - according to Ambrose have brought the extinction. Ambrose tries with his theory to explain why comparative analyzes of mitochondrial DNA suggest a genetic bottleneck in human development from this era. However, this is contradicted by that stone tools were found both below as well as above the Tuffschicht in southeast India, which suggest a continuity of settlement in this region. Climate simulations of the research group of Alan Robock at Rutgers University in New Jersey, however, point out that the climatic effects have entailed severe impairments of living conditions by themselves. Living in Europe and Asia to Siberia, Neanderthals and living in Asia Homo erectus survived this natural disaster and died out until much later.