[3][4][5] Lake Toba is the site of a supervolcanic eruption estimated at VEI 8 that occurred 69,000 to 77,000 years ago,[6][7][8] representing a climate-changing event.

[11] It was also suggested that the eruption of the Toba Caldera led to a volcanic winter with a worldwide decrease in temperature between 3 and 5 °C (5.4 and 9.0 °F), and up to 15 °C (27 °F) at higher latitudes.

An estimated 2,800 km3 (670 cu mi) of dense-rock equivalent pyroclastic material, known as the youngest Toba tuff, was released during one of the largest explosive volcanic eruptions in recent geological history.

The Tandukbenua cone on the northwestern edge of the caldera has only sparse vegetation, suggesting a young age of several hundred years.

Also, the Pusubukit (Hill Center) volcano (1,971 m (6,467 ft) above sea level) on the south edge of the caldera is solfatarically active.

[15] It was the last in a series of at least four caldera-forming eruptions at this location, with the earlier known caldera having formed around 1.2 million years ago.

The pyroclastic flows of the eruption destroyed an area of least 20,000 km2 (7,700 sq mi), with ash deposits as thick as 600 m (2,000 ft) by the main vent.

[20] The eruption lasted perhaps two weeks, and the ensuing volcanic winter resulted in a decrease in average global temperatures by 3.0 to 3.5 °C (5 to 6 °F) for several years.

Ice cores from Greenland record a pulse of starkly reduced levels of organic carbon sequestration.

[24] However, this hypothesis is not widely accepted because similar effects on other animal species have not been observed, and paleoanthropology suggests there was no population bottleneck.

[28] Some parts of the caldera have shown uplift due to partial refilling of the magma chamber, for example, pushing Samosir Island and the Uluan Peninsula above the surface of the lake.

Large earthquakes have recently occurred in the vicinity of the volcano, notably in 1987 along the southern shore of the lake at a depth of 11 km (6.8 mi).

Traditional Batak houses are noted for their distinctive roofs (which curve upwards at each end, as a boat's hull does) and their colorful decor.

[35] Other native fishes include species such as Aplocheilus panchax, Nemacheilus pfeifferae, Homaloptera gymnogaster, Channa gachua, Channa striata, Clarias batrachus, Barbonymus gonionotus, Barbonymus schwanenfeldii, Danio albolineatus, Osteochilus vittatus, Puntius binotatus, Rasbora jacobsoni, Tor tambra, Betta imbellis, Betta taeniata and Monopterus albus.

Ignoring overloading on the vessel and operating in rough weather conditions were concluded to be the main reasons leading to the disaster.