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HUMANS AND THE TOBA SUPER-ERUPTION 74,000 YEARS AGO: BEFORE AND AFTER THE ‘BIG BANG’

The Toba super-volcano has erupted explosively a number of times over the past 1.2 million years. By far the largest and most destructive of these occurred around 74,000 years ago, and it is this ‘Youngest Toba Tuff’ or YTT eruption that forms the focus of this research project. At least 2800 cubic kilometres of volcanic material was ejected during this super-eruption, dwarfing historical eruptions such as Krakatoa and Pinatubo.

The YTT explosion instantly destroyed all life in its immediate area, with intensely hot flows comprised of billions of tonnes of ash and rock, accompanied by a deafening noise and powerful tsunamis. It also sent hundreds of cubic kilometers of ash and gases high into the atmosphere, even as the volcano itself collapsed inwards to form a huge sunken caldera (now Lake Toba). The gases, including sulfur, circled the globe on air currents, while the ash spread out to the north and west fanned by prevailing winds. When the ash began to fall, it covered the Indian subcontinent and rained down into oceans from the Arabian Sea in the west to the South China Sea in the east (the figure above shows all the locations from which YTT desposits have been recovered to date). Gradually the earth cooled as the sun’s heat was reflected by the suspended gases, affecting rainfall and climates across the globe. Around this time the earth slipped rapidly into a dramatically cold portion of the ice ages, and while this was underway before Toba’s eruption, the super-volcano undoubtedly had an important influence.

Software: Microsoft OfficeAt the time of the Toba eruption 74,000 years ago, humans shared the Earth with a number of similar species, including the cold-adapted Neanderthals and the dwarf Homo floresiensis. All these species made stone tools, gathered plants and hunted animals for their livelihood, and all survived the eruption and its after-effects. Nevertheless, when palaeo-climatic records are combined with genetic data that may indicate an abrupt decline in the number of humans (a genetic ‘bottleneck’) at about the time of Toba’s super-eruption, the possibility that we were driven to the edge of extinction deserves investigation. One of the most critical missing keys in understanding Toba’s impact is a lack of archaeological research looking at the actual remains left by humans who were directly affected by the YTT ashfall, particularly in India. We are not even sure if humans had reached India as part of the ‘Out of Africa’ dispersal by 74,000 years ago, although we do know that either we or a closely-related species watched the ash as it fell across the subcontinent. To resolve this problem, our main field research areas are in the Indian states of Andhra Pradesh (Kurnool District) and Madhya Pradesh (Sidhi District), both of which preserve Toba volcanic deposits along with archaeological evidence of the lives and environment of the people living there from well before until well after Toba’s eruption.

This website is designed to provide an insight into the detailed science required to explore a topic as big as Toba, as well as containing links to publications, media information and educational material. We will be adding to the information here as our studies continue, so please return regularly for updates.

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© 2009 M.Haslam & M.D.Petraglia, University of Oxford