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21 October 2011

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Explosion of Mount Toba

Almost Wiped out Humans

 

About 72,000 years ago a volcanic explosion on the island of Sumatra threw so much ash into the atmosphere that all human life may have been threatened

 

Mozpkim

 

According to BBC News (April 2010) “The ‘super-eruption’ of Mount Toba on the Indonesian island of Sumatra is thought by some to have caused a six-year long volcanic winter followed by a 1,000-year-long freeze.”

 

Perhaps the World’s Biggest Volcanic Eruption

Everything about the eruption of Mount Toba challenges the human mind. It is given an 8 on the Volcanic Explosivity Index; that’s the highest rating possible. For comparison, when Mount St. Helens blew its top in May 1980 it was given a rating of 5.

 

However, the Index is logarithmic meaning that Toba’s eruption was several thousand times bigger than Mount St. Helen’s.

 

Volcanologists describe the Mount Toba event as “mega-colossal,” chucking out somewhere around 2,800 cubic kilometres of debris. Another measure of the scale of this eruption is that Mount Toba is now Lake Toba (below), a body of water 100 km long, 30 km wide, and more than 500 metres at its deepest.

 

Bernard Gagnon

 

India Takes a Direct Hit

At the Bradshaw Foundation, Stephen Oppenheimer provides an account of the aftermath of Mount Toba’s huge rumble: “This mega-bang caused a prolonged world-wide nuclear winter and released ash in a huge plume that spread to the north-west and covered India, Pakistan, and the Gulf region in a blanket 1–5 metres (3–15 feet) deep.”

 

India was in the direct line of fire and may have suffered a mass extinction of human and other life. Oppenheimer suggests nobody on the Indian subcontinent would have survived the cataclysm.

 

Mount Toba’s Ash Went Global

In a program aired on the Australian Broadcasting Corporation Science Show, Martin Williams, an emeritus professor at the University of Adelaide, spoke about the worldwide impact of the explosion.

 

The ash and sulphur suspended in the atmosphere filtered out sunlight and caused a dramatic and catastrophic change in climate: “in Greenland associated with it you have a 16-degree drop in temperature, which is quite dramatic...”

 

It’s been estimated that this plunge in temperatures killed off three quarters of the plant life in the Northern Hemisphere with equally dramatic impacts in the southern half of the planet.

 

Human Population Bottleneck

The loss of vegetation meant a shortage of food for all animals including humans and a resulting famine. This prompted anthropologist Stanley Ambrose of the University of Illinois to advance the notion that the human population came close to extinction in the aftermath of the Mount Toba eruption.

 

His theory was reported in an article in ScienceDaily, (September 8, 1998).

 

Geneticists have known for sometime there was a population “bottleneck” during which the number of humans declined rapidly.

 

According to Dr. David Whitehouse at BBC News (September 8, 1998) “Some scientists estimate that there may have been as few as 15,000 humans alive at one time…The rapid decrease, in our ancestors’ populations, in turn, brought about the rapid differentiation - or genetic divergence - of the surviving populations.”

 

Challenge to Near-extinction Theory

Some experts say as few 2,000 humans survived the volcanic winter, but other scientists challenge this. Back at the ABC Science Show, Dr. Martin Williams says “One school says there was no impact whatsoever because when you look at the artifacts in southern India above and beneath the ash they’re the same, they’re…middle stone age, therefore no impact.”

 

This is confirmed by a report in the Sydney Morning Herald written by Science Editor Deborah Smith (July 23, 2007): “Hundreds of sophisticated stone tools have been found in Jwalapuram in southern India by an international team including two Australian researchers, Chris Clarkson and Bert Roberts.”

 

This is taken as tentative proof that at least some people in India survived the after effects Mount Toba’s bout of seismic indigestion, although Clarkson and Roberts are quick to point out more research is needed.

 

Sources

“How Volcanoes have Shaped History.” Dr. David Whitehouse, BBC News, April 15, 2010.

“Eruption of Sumatra’s Mount Toba.” Australian Broadcasting Corporation, September 6, 2008.

“Ancient ‘Volcanic Winter’ Tied to Rapid Genetic Divergence in Humans.” ScienceDaily, September 8, 1998.

“Humans Came ‘Close to Extinction.’ ” Dr. David Whitehouse, BBC News, September 8, 1998.

“Volcano May not Have Blown it.” Deborah Smith Sydney Morning Herald, July 23, 2007.

 

© Canada and the World, April 2011

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THE BIGGEST BANG

 

Jupiter’s moon Io seems to hold the record for the biggest volcanic eruptions in our solar system.

 

No doubt there are bigger ones, yet undiscovered, elsewhere in the Universe.

 

NASA’s Voyager 1 spacecraft observed volcanoes exploding on Io that sent lava plumes 320 km above the surface.

 

The volcanic activity is believed to be caused by the enormous gravitational pull of Jupiter, causing the moon’s liquid core to break through its crust.

 

There is evidence of ancient volcanic activity that dwarfs even Mount Toba.

 

About 132 million years ago volcanic eruptions in Brazil ejected 8,600 cubic kilometres of material, more than three times the amount thrown out by Mount Toba.