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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.
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 At
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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