Lake Toba
The Toba eruption occurred at what is now Lake Toba about 67,500 to 75,500 years ago. It was the last in a series of at least three caldera-forming eruptions at this location, with earlier calderas having formed around 700,000 and 840,000 years ago. This last eruption had an estimated VEI 8, making it possibly the largest explosive volcanic eruption within the last 25 million years.
The subsequent collapse formed a caldera that, after filling with water, created Lake Toba. The island in the center of the lake is formed by a resurgent dome.Evidence from studies of mitochondrial DNA suggests that humans may have passed through a genetic bottleneck around this time that reduced genetic diversity below what would be expected given the age of the species. According to the Toba catastrophe theory, proposed by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign in 1998, the effects of the Toba eruption may have decreased the size of human populations to only a few tens of thousands of individuals. However, this hypothesis isn't widely accepted because similar effects on other animal species have not been observed.
Since the major eruption ~70,000 years ago, eruptions of smaller magnitude have also occurred at Toba. The small cone of Pusukbukit formed on the southwestern margin of the caldera and lava domes. The most recent eruption may have been at Tandukbenua on the northwestern caldera edge, suggested by a lack of vegetation that could be due to an eruption within the last few hundred years.
Most of the people who live around Lake Toba are ethnically Bataks. Traditional Batak houses are noted for their distinctive roofs and their colorful decor.
The flora of the lake includes various types of phytoplankton, emerged macrophytes, floating macrophytes, and submerged macrophytes, while the surrounding countryside is rainforest including areas of Sumatran tropical pine forests on the higher mountainsides.
The fauna includes several species of zooplankton and benthic animals. Since the lake is oligotrophic, the native fish fauna is relatively scarce, and the only endemics are Rasbora tobana (strictly speaking near-endemic, since also found in some tributary rivers that run into the lake) and Neolissochilus thienemanni, locally known as the Batak fish. The latter species is threatened by deforestation (causing siltation), pollution, changes in water level and the numerous fish species that have been introduced to the lake. 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. Among the many introduced species are Anabas testudineus, Oreochromis mossambicus, Oreochromis niloticus, Ctenopharyngodon idella, Cyprinus carpio, Osphronemus goramy, Trichogaster pectoralis, Trichopodus trichopterus, Poecilia reticulata and Xiphophorus hellerii.
| View of the lake with an in the foreground. | example of Batak architecture - |
Related Sites for Lake Toba
- Lake Toba - North Sumatra - Reviews of Lake … read Lake Toba
- Lake Toba Largest Volcanic Lake in the World | Medan Indonesia … read Lake Toba
- Toba: Information from Answers.com - Answers - The Most … read Lake Toba
- Lake Toba, Sumatra | Indonesia Travel Guide read Lake Toba
