Profile of Lake Toba

Lake Toba is made up of four overlapping volcanic craters that adjoin the Sumatran volcanic front. The youngest one is the world’s largest Quaternary caldera, with a length of 86.15 kilometers (53 mi) and a width of 30 kilometers (18.6 mi), intersecting the other three. Below is a summary of the lake’s geological profile.

NAME Lake Toba (Danau Toba)
COUNTRY Indonesia
SURFACE AREA 1,130 km2 (436 sq mi)
MAXIMUM DEPTH 529 m (1,736 ft)
AVERAGE DEPTH 213 m (699 ft)
LAKE TYPE Volcanic
LENGTH 86.15 km (53 mi)
WIDTH 30 km (18.6 mi)
CATCHMENT AREA 3,726 km2 (1,439 sq mi)
ALTITUDE 900 m (2,953 ft)
VOLUME 240 km3 (57.6 cu mi)
OUTFLOWS Asahan River
ISLANDS Samosir
SHORE LENGTH 464 km (288 mi)
AGE 10,000 – 100,000 years
MIXING TYPE Homogeneous
FROZEN Never freezes
RESIDENCE TIME 20,777 days
FISH SPECIES Catfish, tilapia
TROPHIC STATE Oligotrophic (nutrient-poor)
ORIGIN Volcanic
AVERAGE DISCHARGE 134 m3 / sec.

Source: Lakepedia.com

See also History of Lake Toba.