There are 35 active volcanoes in Bukit Barisan. The largest volcano is the supervolcano Toba within the 100 km (62 miles) × 30 km (19 miles) Lake Toba, which was created after a caldera collapse (est. in 74,000 Before Present).[3] The eruption is estimated to have been at level eight on the VEI scale, the largest possible for a volcanic eruption.