Sumatra (Indonesian: Sumatera, is an island in western Indonesia, to the west of the Sunda Islands. It is the largest island that is entirely in Indonesia (two larger islands, Borneo and New Guinea, are shared between Indonesia and other countries) and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538. Its biggest city is Medan with a population of 2,109,330.Sumatra is an elongated landmass spanning a diagonal northwest-southeast axis. The Indian Ocean borders the west, northwest, and southwest sides of Sumatra with the island chain of Simeulue, Nias and Mentawai bordering the southwestern coast. The explorer Marco Polo visited Sumatra in 1292. Sumatra has a huge range of plant and animal species but has lost almost 50% of its tropical rainforest in the last 35 years, and many species are Critically Endangered such as Sumatran Tiger, Sumatran Rhino and Sumatran Orangutan.
- LAKE TOBA
Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano. The lake is 100 kilometres long, 30 kilometres wide, and up to 505 metres (1,666 ft) deep. Located in themiddle 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 2.88°N 98.52°E to 2.35°N 99.1°E. It is the largest lake in Indonesia and 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 world-wide population to the present. This hypothesis is not widely accepted because evidence is lacking for a decline or extinction of other animals, including species that are sensitive to changes in the environment. 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 to 9 °F), and up to 15 °C (27 °F) in higher latitudes.