English: Lake Toba is located in the middle of the northern part of the island of Sumatra, occupying the caldera of a supervolcano. The lake is about 100 km (62 mi) long, 30 km (19 mi) wide, and up to 505 m (1,657 ft) deep. It is the largest lake in Indonesia and the largest volcanic lake in the world. Lake Toba is the site of a supervolcanic eruption estimated at a Volcanic Explosivity Index (VEI) of 8, the largest recorded value on the index. Recent advances in dating methods suggest the date was 74,000 years ago and that it represented a climate-changing event. It is the largest-known explosive eruption on earth in the last 25 million years.