Toba Super-Eruption
Saturday, 7. July 2007, 08:35:18
The Toba eruption, in northern Sumatra, was the strongest on earth in the last two million years.
There has been intriguing speculation but unproven as yet that it may have drastically cooled the Earth, killing off most of the human population living at the time. The Indian subcontinent contains extensive
deposits from the eruption, and now a series of stone artefacts unearthed in southern India (Jwalapuram) suggest that local human populations remained in the region after the Toba eruption. The prehistoric tools were found in more than 7.5 m of sedimentary layers sandwiching a layer of ash produced by the Toba eruption, and the tools above were essentially at the same level of evolution as those below. This indicates that the impact of the Toba eruption was not as significant as earlier thought.
The Toba supervolcano-eruption produced the largest known volcanic eruption on earth during the past 2 million years. About 74,000 years ago an estimated minimum of 2800 km3 of magma were erupted, of which at least ca. 800 km3 was transported in atmospheric ash plumes that blanketed an area from the South China Sea to the Arabian Sea. This total volume is even more than the Yellowstone super-volcano eruption, much debated last year, with a volume of an estimated 2500 km3 (See my post on Yellowstone Super-volcano) The eruption led to the final formation of one of Earths largest calderas, the 35x100 km wide Toba caldera (See landsat image).
There have been no eruptions at Toba in historical time. Toba is located near the Sumatra Fracture Zone. I have marked this fracture zone as “Fault Zone” on the landsat image, where it is clearly visible as a light line. On the map it is marked by a stipled line. The movement directions are shown by arrows. Stratovolcanoes in Sumatra are part of the Sunda arc. Volcanism is the result of the subduction of the Indian Ocean plate under the Eurasian plate. The subduction zone is marked by the Java Trench. The geologic symbol for a subduction zone is a line with "teeth" (black triangles). The teeth are on the over-riding plate. The rate of subduction is 6.7 cm per year.
There has been intriguing speculation but unproven as yet that it may have drastically cooled the Earth, killing off most of the human population living at the time. The Indian subcontinent contains extensive
deposits from the eruption, and now a series of stone artefacts unearthed in southern India (Jwalapuram) suggest that local human populations remained in the region after the Toba eruption. The prehistoric tools were found in more than 7.5 m of sedimentary layers sandwiching a layer of ash produced by the Toba eruption, and the tools above were essentially at the same level of evolution as those below. This indicates that the impact of the Toba eruption was not as significant as earlier thought.
- Science of 6 July 2007, pp. 114 - 116. Abstract at http://www.sciencemag.org/cgi/content/abstract/317/5834/114
- http://www.physorg.com/news102867861.html
- http://www.nature.com/news/2007/070702/full/070702-15.html
The Toba supervolcano-eruption produced the largest known volcanic eruption on earth during the past 2 million years. About 74,000 years ago an estimated minimum of 2800 km3 of magma were erupted, of which at least ca. 800 km3 was transported in atmospheric ash plumes that blanketed an area from the South China Sea to the Arabian Sea. This total volume is even more than the Yellowstone super-volcano eruption, much debated last year, with a volume of an estimated 2500 km3 (See my post on Yellowstone Super-volcano) The eruption led to the final formation of one of Earths largest calderas, the 35x100 km wide Toba caldera (See landsat image). There have been no eruptions at Toba in historical time. Toba is located near the Sumatra Fracture Zone. I have marked this fracture zone as “Fault Zone” on the landsat image, where it is clearly visible as a light line. On the map it is marked by a stipled line. The movement directions are shown by arrows. Stratovolcanoes in Sumatra are part of the Sunda arc. Volcanism is the result of the subduction of the Indian Ocean plate under the Eurasian plate. The subduction zone is marked by the Java Trench. The geologic symbol for a subduction zone is a line with "teeth" (black triangles). The teeth are on the over-riding plate. The rate of subduction is 6.7 cm per year.
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