Lake Toba

Lake Toba is a large lake, 100 km long and 30 km wide, in the middle of the northern part of the Indonesian island of Sumatra.

Lake Toba, the largest year-round lake in Southeast Asia, is located in the province of North Sumatra, Indonesia, approximately 176 km to the west of the provincial capital, Medan.

It is the largest volcanic lake in the world.

Latitude 2° 30' 0" (2.5000)
Longitude 99° 0' 0" (99.0000)


In 1949 the Dutch geologist Rein van Bemmelen reported that Lake Toba was surrounded by a layer of ignimbrite rocks, and was a large volcanic caldera. Later researchers found rhyolite ash similar to that in the ignimbrite around Toba in Malaysia and India, 3000 km away. Oceanographers discovered Toba ash on the floor of the eastern Indian Ocean and the Bay of Bengal.


A large area collapsed after the ejection of so much subsurface material, forming a caldera, which filled with water creating Lake Toba. Later, the floor of the caldera uplifted to form Samosir, a large island in the lake. Such uplifts are common in very large calderas, apparently due to the upward pressure of unerupted magma. Toba is probably the largest resurgent caldera on Earth.

There have been no historic eruptions at Toba, but large earthquakes have occurred, the most recent in 1987 along the southern shore of the lake. The underwater fault off the west coast of Sumatra has had several major earthquakes since 1995, including the ~9.0 2004 Indian Ocean Earthquake and the 8.7 2005 Sumatra earthquake


The lake is among the deepest crater lakes in the world. It rests in the crater of one of Sumatra's many volcanos. The 650 square mile lake is almost 1500 feet deep. Beaches are lined with pine trees. The climate is cool and dry. And steep, scenic mountain slopes surround the lake.

Parapat is the area's main town. Former president Sukarno managed Indonesia's independence movement from here for a time. Today it is mostly a busy, touristy stopover on the way to the lake's real attraction - Samosir Island. Prapat is the embarkation point for ferry's to the island.

Samosir Island is the ancestral home of Sumatra's Toba Batak people. Six Batak tribes live in North Sumarta. Batak culture, arts, and crafts in themselves are an attraction for the region. Samosir Island also provides some excellent trails and paths for trekking and day hikes. Swimming is also an option.

Lake Toba is just over 100 miles (four hours) by road from the North Sumatran port city of Medan. It is possible to fly into Medan from Singapore, Kuala Lumpur, and Penang.

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