Lake Toba (
Indonesian: Danau Toba) is a large natural
lake occupying the
caldera of a
supervolcano. The lake is about 100 kilometres (62 miles) long, 30 kilometres (19 mi) wide, and up to 505 metres (1,657 ft) deep. Located in the middle of the northern part of the
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 to 2°21′N 99°06′E / 2°21′N 99°06′E / 2.35; 99.1. It is the largest
lake in Indonesia and also the largest
volcanic lake in the world.
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 worldwide 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.