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Doubt over 'volcanic winter' after Toba super-eruption

New research from Oxford University casts doubt on the theory that the Mount Toba super-eruption, which took place at the Indonesian island of Sumatra 75,000 years ago, could have plunged the Earth into a volcanic winter leading to the near extinction of early humans.
A fresh analysis of volcanic ash recovered from lake sediment cores in Lake Malawi in East Africa shows that the eruption spewed ash much further than studies have previously found. Other theories have said that the explosive volcanic eruption may have triggered a chain of climatic events resulting in a cooling of temperatures, but this latest study finds no evidence of a significant dip in temperatures in East Africa at the time.
 
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Title: Aerosol size confines climate response to volcanic super-eruptions
Authors: Timmreck, C., H.-F. Graf, S. J. Lorenz, U. Niemeier, D. Zanchettin, D. Matei, J. H. Jungclaus  and T.J. Crowley

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'Pompeii-like' excavations tell us more about Toba super-eruption

Newly discovered archaeological sites in southern and northern India have revealed how people lived before and after the colossal Toba volcanic eruption 74,000 years ago.
The international, multidisciplinary research team, led by Oxford University in collaboration with Indian institutions, unveiled to a conference in Oxford what it calls 'Pompeii-like excavations' beneath the Toba ash.

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Supervolcano eruption in Sumatra deforested India 73,000 years ago
In a new study, scientists have come across what they call incontrovertible evidence that the volcanic super-eruption of Toba on the island of Sumatra about 73,000 years ago deforested much of central India, some 3,000 miles from the epicenter.
Washington, November 24 : In a new study, scientists have come across what they call "incontrovertible evidence" that the volcanic super-eruption of Toba on the island of Sumatra about 73,000 years ago deforested much of central India, some 3,000 miles from the epicenter.
The volcano ejected an estimated 800 cubic kilometres of ash into the atmosphere, leaving a crater that is 100 kilometres long and 35 kilometres wide.
Ash from the event has been found in India, the Indian Ocean, the Bay of Bengal and the South China Sea.

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Mystery of the Mega Volcano
NOVA joins four scientists in their global pursuit of clues to a massive volcanic eruption that appears to have had a devastating impact on the Earth 75,000 years ago.
And if they're right, the ancient supervolcano - and others like it - may someday reawaken, with catastrophic consequences for our modern world. Now, an array of clues - scattered ashes and ice cores, tiny ocean creatures and steaming lakeside rocks - are brought together to solve the "Mystery of the Megavolcano."
The destructive power unleashed by supervolcanoes goes far beyond that of any eruption in recorded human history.

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Title:
Did the Toba volcanic eruption of ~74 ka B.P. produce widespread glaciation?
Authors: Alan Robock, Caspar M. Ammann, Luke Oman, Drew Shindell, Samuel Levis, Georgiy Stenchikov

It has been suggested that the Toba volcanic eruption, approximately 74 ka B.P., was responsible for the extended cooling period and ice sheet advance immediately following it, but previous climate model simulations, using 100 times the amount of aerosols produced by the 1991 Mount Pinatubo eruption, have been unable to produce such a prolonged climate response. Here we conduct six additional climate model simulations with two different climate models, the National Centre for Atmospheric Research Community Climate System Model 3.0 (CCSM3.0) and National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE, in two different versions, to investigate additional mechanisms that may have enhanced and extended the forcing and response from such a large supervolcanic eruption. With CCSM3.0 we include a dynamic vegetation model to explicitly calculate the feedback of vegetation death on surface fluxes in response to the large initial reduction in transmitted light, precipitation, and temperature. With ModelE we explicitly calculate the effects of an eruption on stratospheric water vapour and model stratospheric chemistry feedbacks that might delay the conversion of SO2 into sulphate aerosols and prolong the lifetime and radiative forcing of the stratospheric aerosol cloud. To span the uncertainty in the amount of stratospheric injection of SO2, with CCSM3.0 we used 100 times the Pinatubo injection, and with ModelE we used 33, 100, 300, and 900 times the Pinatubo injection without interactive chemistry, and 300 times Pinatubo with interactive chemistry. Starting from a roughly present-day seasonal cycle of insolation, CO2 concentration, and vegetation, or with 6 ka B.P. conditions for CCSM3.0, none of the runs initiates glaciation. The CCSM3.0 run produced a maximum global cooling of 10 K and ModelE runs produced 8 - 17 K of cooling within the first years of the simulation, depending on the injection, but in all cases, the climate recovers over a few decades. Nevertheless, the "volcanic winter" following a supervolcano eruption of the size of Toba today would have devastating consequences for humanity and global ecosystems. These simulations support the theory that the Toba eruption indeed may have contributed to a genetic bottleneck.

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An ancient volcanic super-eruption, one of the largest known in Earth's history, may not have devastated the world and humanity as much as once thought.
The eruption at what is now Lake Toba in northwestern Sumatra roughly 75,000 years ago was the largest of the last 2 million years.
The gigantic blast released at least 7.7 trillion tons, or 670 cubic miles, of magma, equivalent in mass to more than 19 million Empire State Buildings.


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A stash of ancient tools in India hints that life carried on as usual for humans living in the fall-out of a massive volcanic eruption 74,000 years ago.
Michael Petraglia, from the University of Cambridge, UK, and his colleagues found the stone tools at a site called Jwalapuram, in Andhra Pradesh, southern India, above and below a thick layer of ash from the eruption of the Toba volcano in Indonesia an event known as the Youngest Toba Tuff eruption.
The tools from each layer were remarkably similar, and Petraglia says that this shows that the huge dust clouds from the eruption didn't wipe out the population of tool-using people.

"Whoever was there seems to have persisted through the eruption".

This is the first archaeological evidence associated with the Toba super eruption,  and it contradicts theories that the eruption had a catastrophic effect on the area that its ash blanketed.

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This image of Toba Caldera was captured by NASA’s Terra satellite on January 28, 2006.

toba_lrg
Expand (332kb, 1024 x 768)
Credit NASA

Location: 98°49'24" 2°34'54"

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