Lake Toba or Danau Toba is a massive natural lake situated in the caldera of a super-volcano. Lake Toba stretches to a length of up to 62 miles and spans a width of around 19 miles. Regarding depth, Lake Toba reaches depths of 1,657 feet. The lake is situated in the northern sections of the Island of Sumatra in Indonesia, is the biggest lake in Indonesia, and the largest of its kind (volcanic) in the globe.
Formation of Lake Toba
The crater that Lake Toba occupies was formed as a result of huge super-volcanic eruption that researchers estimate happened between 69,000 and 77,000 years ago, in what was a climate changing eruption. Modern techniques have narrowed down the estimated time to 74,000 years ago. The eruption, the largest the earth has ever experienced in the past 25 million years, caused massive loss of human life and property damage. The historic eruption deposited a layer over all of South Asia that was at least 6 inches thick. In some parts of India and Malaysia, the ash from Toba measured 20 feet and 30 feet respectively. The collapse that happened after the eruption formed the massive caldera that Lake Toba currently occupies. A resurgent dome at the center of the lake has formed a small island.
Effects of the Eruption
The eruption that occurred changed the climate of the world itself. Researchers estimate that a volcanic winter was formed after the eruption. During that winter, the temperature of earth dropped by 5.4 to 9.0° F in lower altitudes while higher elevations had a drop of up to 27° F. The eruption was so huge that traces of ash from it were found all the way in Lake Malawi in Africa. However, East Africa was not affected as much.
Secondly, some people argue that the loss of life causes a genetic bottleneck, that is, a sudden reduction in the population size. This bottleneck massively reduced the diversity of the human species. If it were not for the bottleneck, the human species would have had a higher level of diversity. However, this argument is a bit tenuous because similar bottlenecks in animal species have not affected diversity as much.
Habitat of the Caldera
The caldera that Lake Toba occupies is made up of four volcanic craters overlapping one another. The youngest and the fourth is the largest Quaternary caldera in the world. Visible in the lake are four stratovolcanoes, four cones, and three craters. Based on the evidence, the youngest cone is the Tandukbenua cone. The Pusubukit, with an elevation of approximately 6,400 feet, is solfatarically active.
Plant life in the lake consists of several types of phytoplankton, macrophytes (emerged, floating, and submerged), while rainforests dominated the areas around Lake Toba. The fauna consists of plenty of zooplankton species and benthic animals. Since the lake is nutrient-poor, or oligotrophic, fish populations are very low. Examples of the native fish include the Batak fish and Betta taeniata. The low fish populations are further threatened by deforestation which causes pollution, water level changes, and siltation.