Profile of Lake Toba, a UNESCO Global Geopark in Indonesia

Lake Toba is the unifying geosite within the Toba Caldera UNESCO Global Geopark. It is the world’s largest volcanic lake located 120 kilometers (75 mi) south of Medan, Indonesia. It has a surface area of 1,130 square kilometers (436 sq mi) and a body length of 86 kilometers (53 mi). The series of volcanic eruptions with the last one taking place 74,000 years ago left a large caldera that was later filled in with 240 cubic kilometers (57.6 cu mi) of water. The blue water and green vegetation of the lake have attracted inhabitants as well as tourists.

Lake Toba is currently developing into a world-class tourist destination. It ranks 1st on the list of New Bali. Under the New Bali plan, the Indonesian government wants to leverage the success in Bali to boost visitor traffic to a handfull of other destinations, most notably Lake Toba. But the lake has long been a favorite destination for tourists worldwide. The recent development focuses on building new roads, new hotels, new resorts, and new attractions.

New Roads

Land access to the lake area has recently improved with some key road constructions. The roads under construction are the freeways (toll roads) connecting Medan and Parapat. When these are done, the land transfer from the capital city to Lake Toba will reduce from 4 hours to 1.5 hours. To see the current status of ground access to Lake Toba, check it out on the map here.

There is also the preservation and widening work of Jalan Pangururan-Ambarita-Tomok-Onan Runggu (77  km), Jalan Tele-Pangururan-Nainggolan-Onan Runggu (69 km), Jalan Tebing Tinggi-Pematang Siantar-Parapat (110 km). All of these roads are within the lake area. Lake Toba will also see a new Tano Ponggol (currently 95% completed), the only bridge connecting the mainland with Samosir Island.

Samosir Island

There is an island in the middle of the lake called Samosir Island. The island is famous for its Toba culture and tradition. It boasts the history of ancient human whose king would behead criminals and take their blood as his drink. The court chairs from where he would render his decision and the execution table where his men would execute the villains still exist today. Come and enjoy the stunning beauty of the lake and the distinctive culture of its inhabitants (see People and Culture on Lake Toba).

Geological 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
SHORE LENGTH 464 km (288 mi)
AGE 10,000 – 100,000 years
MIXING TYPE Homogeneous
FREEZING Never freezes
RESIDENCE TIME 20,777 days
FISH SPECIES Catfish, tilapia
TROPHIC STATE Oligotrophic (nutrient-poor)
ORIGIN Volcanic
AVERAGE DISCHARGE 134 m3 (4,730 cu ft)/ second


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