Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano, 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 2°53′N 98°31′E / 2.88°N 98.52°E / 2.88; 98.52 to 2°21′N 99°06′E / 2.35°N 99.1°E / 2.35; 99.1.
It is the largest volcanic lake in the world. In addition, it is the site of a supervolcanic eruption that occurred 74,000 years ago, a massive climate-changing event. The eruption is believed to have a VEI intensity of this eruption, believed to have been the largest anywhere on Earth in the last 25 million years, may have had catastrophic consequences globally; some anthropologists and archeologists believe that it killed most humans then alive, creating a population bottleneck in Central Eastern Africa and India that affected the genetic inheritance of all humans today.
The Toba eruption (the Toba event) occurred at what is now Lake Toba about 67,500 to 75,500 years ago. It had an estimated Volcanic Explosivity Index of toba (described as "mega-colossal"), making it possibly the largest explosive volcanic eruption within the last twenty-five million years. It had a volume 300 cubic km greater than the Island Park Caldera supereruption (2500 cubic km) of 2.1 million years BP.
Bill Rose and Craig Chesner of Michigan Technological University have deduced that the total amount of erupted material was about 2,800 km3 (670 cu mi) — around 2,000 km3 (480 cu mi) of ignimbrite that flowed over the ground, and around 800 km3 (190 cu mi) that fell as ash, with the wind blowing most of it to the west. The pyroclastic flows of the eruption destroyed an area of 20,000 square kilometres (7,722 sq mi), with ash deposits as thick as 600 metres (1,969 ft) by the main vent. By contrast, the 1980 eruption of Mount St. Helens ejected around 1.2 km3 (0.29 cu mi) of material, whilst the largest volcanic eruption in historic times, at Mount Tambora in 1815, emitted the equivalent of around 100 km3 (24 cu mi) of dense rock and created the "Year Without a Summer" as far away as North America. The eruption was also about three times the size of the latest Yellowstone eruption of Lava Creek 630,000 years ago.
The Toba eruption was the latest of a series of at least three caldera-forming eruptions which have occurred at the volcano. Earlier calderas were formed around 700,000 and 840,000 years ago.
To give an idea of its magnitude, consider that although the eruption took place in Indonesia, it deposited an ash layer approximately 15 centimetres (6 in) thick over the entire Indian subcontinent; at one site in central India, the Toba ash layer today is up to 6 metres (20 ft) thick and parts of Malaysia were covered with 9 m of ashfall. In addition it has been calculated that 1010 metric tons of sulphuric acidwas ejected into the atmosphere by the event, causing acid rain fallout.
The subsequent collapse formed a caldera that, after filling with water, created Lake Toba. The island in the center of the lake is formed by a resurgent dome.
Though the year may never be precisely determined, the season can: only the summer monsoon could have deposited Toba ashfall in the South China Sea, implying that the eruption took place sometime during the northern summer.
The eruption lasted perhaps two weeks, but the ensuing "volcanic winter" resulted in a decrease in average global temperatures by 3 to 3.5 degrees Celsius for several years. Greenland ice cores record a pulse of starkly reduced levels of organic carbon sequestration. Very few plants or animals in southeast Asia would have survived, and it is possible that the eruption caused a planet-wide die-off. There is some evidence, based on mitochondrial DNA, that the human race may have passed through a genetic bottleneck around this time, reducing genetic diversity below what would be expected from the age of the species. According to the Toba catastrophe theory proposed by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign in 1998, human populations may have been reduced to only a few tens of thousands of individuals by the Toba eruption.People
Most of the people who live around Lake Toba are ethnically Bataks. Traditional Batak houses are noted for their distinctive roofs (which curve upwards at each end, as a boat's hull does) and their colorful decor.
Flora and fauna
Lake Toba offers a nurturing environment for fish such as the tilapia mossambica, aplocheilus pachax, lebistes reticulatus, osphronemus goramy, trichogaster trichopterus, channa striata, chana gachua, clarias batrachus, clarias nieuhofi, clarias. sp., nemachilus fasciatus, cyprinus carpio, puntius javanicus, puntius binotatus, osteochilus nasselti, lissochilus sp., labeobarbus sora, and rasbora sp.
Many other types of plants and animals live within the boundaries of Lake Toba. Flora organisms include various types of phytoplankton, emerged macrophytes, floating macrophytes, and submerged macrophytes. Fauna include several variations of zooplankton and benthos.
source : wikipedia