Lake Toba (Indonesian: Danau Toba) is a large natural lake occupying the caldera of a supervolcano. 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. The erupted mass was 100 times greater than that of the largest volcanic eruption in recent history, the 1815 eruption of Mount Tambora in Indonesia, which caused the 1816 "Year Without a Summer" in the northern hemisphere. Toba's erupted mass deposited an ash layer approximately 15 centimetres (6 inches) thick over the whole of South Asia.
Lake Toba is the site of a massive supervolcanic eruption estimated at VEI 8 that occurred 69,000 to 77,000 years ago, representing a climate-changing event. It is the largest known explosive eruption on Earth in the last 25 million years. According to the Toba catastrophe theory, it had global consequences for human populations: it killed most humans living at that time and is believed to have created a population bottleneck in central east Africa and India, which affects the genetic make up of the human world-wide population to the present.
It has been accepted that the eruption of Toba led to a volcanic winter with a worldwide decrease in temperature between 3 to 5 °C (5.4 to 9.0 °F), and up to 15 °C (27 °F) in higher latitudes. Additional studies in Lake Malawi in East Africa show significant amounts of ash being deposited from the Toba eruptions, even at that great distance, but little indication of a significant climatic effect in East Africa.
The Toba caldera complex in Northern Sumatra, comprises 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 estimated 2,800 km3 (670 cu mi) of dense-rock equivalent pyroclastic material, known as the youngest Toba tuff, was released during one of the largest explosive volcanic eruptions in recent geological history. Following this eruption, a resurgent dome formed within the new caldera, joining two half-domes separated by a longitudinal graben.
The Toba eruption has been linked to a genetic bottleneck in human evolution about 50,000 years ago, which may have resulted from a severe reduction in the size of the total human population due to the effects of the eruption on the global climate.
According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to 3,000–10,000 surviving individuals. It is supported by genetic evidence suggesting that today's humans are descended from a very small population of between 1,000 and 10,000 breeding pairs that existed about 70,000 years ago.
 
The exact geographic distribution of human populations at the time of the eruption is not known, and surviving populations may have lived in Africa and subsequently migrated to other parts of the world. Analyses of mitochondrial DNA have estimated that the major migration from Africa occurred 60,000–70,000 years ago, consistent with dating of the Toba eruption to around 66,000–76,000 years ago.
 
However, recent archeological finds have suggested that a human population may have survived in Jwalapuram, Southern India. Moreover, it has also been suggested that nearby hominid populations, such as Homo floresiensis on Flores, survived because they lived upwind of Toba.
Shot on 4x5 inch large format Linhof Technikardan 45s camera
with Nikon Nikkor SW 90mm f/4.5 and Schneider Kreuznach Apo-Symmar 150mm f/5.6 lenses
on Fujifilm Velvia 100F positive film.

 
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