domingo, 11 de noviembre de 2012

Scientists Debate Toba Super-Eruption 74,000 Years Ago --Did It Lead to Near Extinction of Homo-Sapiens?


Archaeological sites in southern and northern India revealed how people lived before and after the colossal Toba volcanic eruption 74,000 years ago. Several theories suggested that the Toba eruption plunged the planet into a 6 to 10 year volcanic winter that endangered the world's human population, reducing it to 10,000 or a mere 1,000 breeding pairs. Some researchers argue that the Toba eruption produced a 1,000 year cooling episode. Some studies suggest it was the largest volcanic eruption of the last two million years—an estimated 5,000 times more powerful than Mount St. Helens's 1980 blast.
In 2010, an international, multidisciplinary research team, led by Oxford University in collaboration with Indian institutions, unveiled what it calls 'Pompeii-like excavations' beneath the Toba ash. The seven-year project examined the environment that humans lived in, their stone tools, as well as the plants and animal bones of the time. The team has concluded that many forms of life survived the super-eruption, contrary to other research which has suggested significant animal extinctions and genetic bottlenecks. According to the team, a potentially ground-breaking implication of the new work is that the species responsible for making the stone tools in India was Homo sapiens. Stone tool analysis has revealed that the artifacts consist of cores and flakes, which are classified in India as Middle Palaeolithic and are similar to those made by modern humans in Africa.
Now, a new study published in the journal Climate of the Past based on acid rain-tainted ice cores from Antarctica and Greenland, suggests Toba's wasn't effect quite as catastrophic as might be expected. The Antarctic ice core shows traces of a warming event soon after the Toba eruption in contrast to vivid cooling signs found in the Greenland ice cores.
"That means there's no long-term global cooling caused by the eruption," study co-author Anders Svensson of the Niels Bohr Institute's Centre for Ice and Climate in Copenhagen said. If there had been, you'd expect to see evidence of a chill at both Poles. There may have been shorter cooling of a duration of maybe 10 or 20 years, like we see for more recent and much less powerful volcanoes."
Source: The Daily Galaxy via, and University of Oxford 

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