The laketrough is amidst by abrupt cliffs 400-1,200 m high. Based on the topographic affection and the advanced administration of agitable ejecta about the lake, some geologists and valcanologists accept advised it to be a behemothic caldera or cauldron.
The baptize apparent of L. Toba is 905 m aloft sea akin and about 1,100 km2 wide. The absolute breadth of the lake, including the areas of Samosir and Paradapur Islands, amounts to 1,780 km2. The mountains about the basin are alleged Batak Highlands. The alone clarification river from L. Toba, the Asahan, flows southeastwards analytic the affable slopes of the pyroclastic plateau.
