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Lake Toba

Lake Toba, the largest lake in South East Asia, and the deepest in the world, was formed 75,000 years ago after an earth splitting volcano eruption. It is the largest and deepest volcanic crater lake in the world. It's 906 meters above sea level with an average depth of 450m. The lake has an island in the middle called Samosir.

According to the Toba catastrophe theory, 70,000 to 75,000 years ago a supervolcanic event at Lake Toba, on Sumatra, reduced the world's human population to 10,000 or even a mere 1,000 breeding pairs, creating a bottleneck in human evolution. The theory was proposed in 1998 by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign

Extract from "Journal of Human Evolution" [1998] 34, 623-651

The last glacial period was preceded by 1000 years of the coldest temperatures of the Late Pleistocene, apparently caused by the eruption of the Mount Toba volcano. The six year long volcanic winter and 1000-year-long instant Ice Age that followed Mount Toba's eruption may have decimated Modern Man's entire population. Genetic evidence suggests that Human population size fell to about 10,000 adults between 50 and 100 thousand years ago. The survivors from this global catastrophy would have found refuge in isolated tropical pockets, mainly in Equatorial Africa. Populations living in Europe and northern China would have been completely eliminated by the reduction of the summer temperatures by as much as 12 degrees centigrade.

Volcanic winter and instant Ice Age may help resolve the central but unstated paradox of the recent African origin of Humankind: if we are all so recently "Out of Africa", why do we not all look more African?

Because the volcanic winter and instant Ice Age would have reduced populations levels low enough for founder effects, genetic drift and local adaptations to produce rapid changes in the surviving populations, causing the peoples of the world to look so different today. In other words, Toba may have caused Modern Races to differentiate abruptly only 70,000 years ago, rather than gradually over one million years.

Volcanic Winter

The Mount Toba eruption is dated to approximately 71,000 years ago. Volcanic ash from Mount Toba can be traced north-west across India, where a widespread terrestrial marker bed exists of primary and reworked airfall ash, in beds that are commonly 1 to 3, and occasionally 6 meters [18 feet] thick.

Tambora, the largest known historic eruption, displaced 20 cubic kilometres of ash. Mount Toba produced 800 cubic kilometres.* It was therefore forty times larger than the largest eruption of the last two centuries and apparently the second largest known explosive eruption over the last 450 million years.





Volcanic Winter, and Differentiation of Modern Humans

Mount Toba's eruption is marked by a 6 year period during which the largest amount of volcanic sulphur was deposited in the past 110,000 years. This dramatic event was followed by 1000 years of the lowest ice core oxygen isotope ratios of the last glacial period. In other words, for 1000 years immediately following the eruption, the earth witnessed temperatures colder than during the Last Glacial Maximum at 18-21,000 years ago.

For the volcanic aerosols to be effectively distributed around the earth, the plume from the volcanic eruptions must reach the stratosphere, a height greater than 17 kilometres. Mount Toba's plume probably reached twice this height. Most solar energy falls at low latitudes between the Tropics of Cancer and Capricorn, so eruptions that happen near the Equator cause much more substantial cooling due to the reflection of solar energy. Toba lies 2 degrees north of the Equator, on the Island Sumatra.

The reduction in atmospheric visibility due to volcanic ash and dust particles is relatively short-lived, about three to six months. Longer-term global climatic cooling is caused by the highly reflective sulphuric acid haze, which stays suspended in the upper atmosphere for several years.

Ice core evidence implicates Mount Toba as the cause of coldest millennium of the late Pleistocene. It shows that this eruption injected more sulphur that remained in the atmosphere fo a longer time [six years] than any other volcanic eruption in the last 110,000 years. This may have caused nearly complete deforestation of southeast Asia, and at the same time to have lowered sea surface temperatures by 3 to 3.5 degrees centigrade for several years.

If Tambora caused the " The year without a summer" in 1816, Mount Toba could have been responsible for six years of relentless volcanic winter, thus causing a massive deforestation, a disastrous famine for all living creatures, and a near extinction of Humankind.

The Volcanic Winter/Weak Garden of Eden model proposed in this paper. Population subdivision due to dispersal within African and other continents during the early Late Pleistocene is followed by bottlenecks caused by volcanic winter, resulting from the eruption of Toba, 71 ka. The bottleneck may have lasted either 1000 years, during the hyper-cold stadial period between Dansgaard-Oeschlger events 19 and 20, or 10ka, during oxygen isotope stage 4. Population bottlenecks and releases are both sychronous. More individuals survived in Africa because tropical refugia were largest there, resulting in greater genetic diversity in Africa.



Samosir Island

Samosir Island is the island in the middle of Lake Toba in northern Sumatra, Indonesia. It is located more or less at the centre of the lake. Samosir Island is believed to be the largest island within an island, and the fifth largest lake island. At 630 sq km, Samosir is just slightly smaller than Singapore, which is 714 sq km.

Samosir Island is believed to have been created 30,000 years ago during a massive eruption. Lake Toba itself was created earlier, 75,000 years ago, in what is believed to be the biggest eruption ever known. During the eruption that created Samosir Island, a peninsula was also formed on the Sumatra mainland, where the small town of Prapat is now located.

Samosir Island is today a major tourist destination in Indonesia, attracting mostly local tourists as well as visitors from neighboring Malaysia and Singapore. Western tourist also come to Samosir Island usually for extended relaxing holidays. Most of the tourist attractions on Samosir Island are connected to its Batak heritage. The main town on the island is Tomok. This is where the tomb of King Sidabutar is located.

The current estimated population of Samosir is 120,000. Including Lake Toba there are six major Batak regions - Toba Batak, Karo Batak, Kakpak/Dairi Batak, Simeulungun Batak, Angkola Batak and Sipirko Batak. Around 1.5 Million Batak live amongst these regions. The Karo Batak and centered around Berastagi.

On the island there are waterfalls and hot volcanic springs (Air Panas). In the dry season most of the waterfalls stop flowing.

Three megalithic sites on Samosir bear witness to the glory - and horror - of Batak history. The three consist of 300-year-old stone seats and benches arrayed in a circle. The first set of ruins was used as a conference area for Batak kings. At the second site, the rajas would sit in judgment of a criminal or enemy prisoner. If the accused were found guilty, the assembly would move to the third set, which features the ghastly addition of a central stone execution block.

There is a regular ferry service, every half hour, between Tuk-Tuk on Samosir Island to Parapat. The ferry runs between 7.30am and 7.30pm during peak tourist seasons. During off peak times the last ferry back from Parapat is 6pm. The cost of the ferry is 7000Rp. Buy your ticket on the boat. At the ferry wharf and on the ferry you will be approached by many of the local young men trying to persuade you to go to the hotel they are affiliated with. These guys are mostly harmless and just trying to make a living guiding tourists. They can be a good resource for information. There is no harm in going and checking their hotel out and if you're not happy with that hotel move on to the ones close by. Tuk-tuk is not that large so the hotels are close. See the list of hotels at the bottom of this page.

How To Get There

The nearest international airport is Polonia Medan (North Sumatra).
Lake Toba is about 4 hours drive by car from Medan City. You can travel by public bus which may take longer to about 6 hours. The usual stop is the town of ” Pematang Siantar ” halfway to Lake Toba for a toilet break.