November 23, 2009
Toba Supervolcano Deforested India 73,000 Years Ago

About 73,000 years ago (74,000 by some estimates) a massive volcano on the Indonesia island of Sumatra erupted with a volcanic explosivity index (VEI) of 8. Such an eruption is so severe in its effects it basically would cause the deaths of billions of people today. New evidence finds that Toba's eruption caused deforestation in what is now central India.

CHAMPAIGN, Ill. A new study provides "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, researchers report.

The 800 cubic kilometers of ash ejected by Toba compares with the mere 160 cubic kilometers ejected by the 1815 Tambora eruption. The larger Toba eruption caused an ice age that lasted 1,800 years.

The volcano ejected an estimated 800 cubic kilometers of ash into the atmosphere, leaving a crater (now the world's largest volcanic lake) that is 100 kilometers long and 35 kilometers wide. Ash from the event has been found in India, the Indian Ocean, the Bay of Bengal and the South China Sea.

The bright ash reflected sunlight off the landscape, and volcanic sulfur aerosols impeded solar radiation for six years, initiating an "Instant Ice Age" that according to evidence in ice cores taken in Greenland lasted about 1,800 years.

During this instant ice age, temperatures dropped by as much as 16 degrees centigrade (28 degrees Fahrenheit), said University of Illinois anthropology professor Stanley Ambrose, a principal investigator on the new study with professor Martin A.J. Williams, of the University of Adelaide. Williams, who discovered a layer of Toba ash in central India in 1980, led the research.

We are not prepared for such an event today. Even 5 or 10 years to prepare could at most save a small fraction of the human race.

The 1815 Tambora VEI 7 eruption caused crop failures for 2 years. Imagine that happening today with nearly 7 billion humans using a much larger fraction of total planetary biomass. If a VEI 7 eruption could somehow be predicted several years in advance then industrialized nations could stockpile enough food to make it thru the crop failures. But poorer nations would face starvation on a scale not seen in the last 100 years.

Since geologists can't predict VEI 7 and up eruptions years in advance I do not expect we'll possess the ability to handle such an eruption until nanotechnology enables such huge increases in living standards that it becomes possible to very cheaply produce huge amounts of excess food and very cheap ways to store it for years.

Share |      Randall Parker, 2009 November 23 08:58 PM  Dangers Natural Geological

Bruce said at November 24, 2009 6:52 AM:

One word ... Yellowstone.

"The volume of volcanic rock produced by the first Yellowstone caldera eruption was about 600 cubic miles-about 17 times more than Tambora"

It erupts every 600,000 years or so and last one was 640,000 years ago.

Randall Parker said at November 24, 2009 9:16 AM:


Yellowstone's last eruption was 1000 cubic kilometers versus 800 for Toba. So, yes, really big.

I figure if I live until Actuarial Escape Velocity is achieved and then I survive the Singularity then I'm going to construct a place that can allow my cybernetic self to survive the next VEI 8 eruption.

random said at November 24, 2009 9:27 AM:

Another possible use for nanotechnology would be collection of the ash particles from the atmosphere after an event such as this.

Nick G said at November 24, 2009 2:45 PM:

I saw the following claim:

" Newer evidence indicates that after populating much of Europe and Asia there was a dieoff (likely climatic) and all modern humans can trace their genetic ancestry to a fairly small group of early humans who survived at the southern tip of Africa around 70'000 years ago. Supervolcano Toba in Indonesia exploded around 73,000 thousand years ago. It killed almost all humans. Less than 10,000 survived in Africa.

No references...

Randall Parker said at November 24, 2009 4:40 PM:

Nick, A die-off caused by Toba has been much debated by anthropologists. I'm not surprised there isn't a cite. I could ask an anthropologist for a sense of where the debate is if you are interested.

Lono said at November 25, 2009 7:37 AM:


I would be curious too - regarding that claim - as I have heard much the same and thought it was generally accepted now as a major incident in our ancestry.

Of all the natural disaster scenarios - I must admit - Volcano's scare the crap outta me - it certainly seems like we should be putting more resources into how to prevent (or at least predict) such a large scale calamity...

Maybe we should force all banking instutions to have their headquarters within potentially active volcanic zones - if they want to maintain their tax breaks - and before long the govt. will be pouring taxpayer money into investigating the problem.

What a rediculous, short sighted, species we still are...

Randall Parker said at November 25, 2009 8:57 AM:


Banks obviously do not believe that reckless policies are anything to worry about. Why would you expect them to worry about volcanoes? I'm sure the top execs would think they'll be long retired by the time of the next eruption.

Lono said at November 25, 2009 9:51 AM:

Heh Heh - Touche'!

Seriously though - not being a geologist - is their any force or action of man that can potentially dampen or reroute the erruption of a volcano - yet alone a super volcano?

Don't they usually (and paradoxically) use nukes in the movies to prevent these disasters?

Randall Parker said at November 25, 2009 11:30 AM:


I've yet to read about a serious way to stop or reduce a volcanic eruption. Nukes? I have no idea. Haven't seen geophysicists propose this. Only saw it in Hollywood movies.

I'm curious to know what could be done.

I'm also curious to know what happens when a VEI 8 happens in the ocean. Better or worse than on land?

Dr Cornelius Vanderbilt said at June 12, 2011 3:13 AM:

Either of the two events can wipe out most of the humanity: Collision and Eruption. We are utilizing more resources on Collision and comparatively little on Eruption. It is a matter of head you win, tail I loose. Both are imminent and both are Apocalyptic. Diverting a large incoming object appears more difficult than dealing with an Eruption.
Eruption: Forget the past. Learn from it and prepare for the future. The only solution is to dig and release the pressure under controlled conditions. It might be a blessing to have so much energy from Yellowstone. Russians have already gone to over 12km deep in Sakhalin. Earth's crust is around 30km thick. World should join Russians in their efforts to bore deeper.
If past eruption of Yellowstone is any guideline, the next one shall be 3,000 km e3 with a plume higher than 30,000 m. You can say good bye to a very very large area of up to 3,000km in radius. It shall be Apocalypse. Toba would look like a firecracker for children at 800 km e3. It is exponential. A modern pocket calculator can do the rest.
Temperatures deeper than the crust, at the upper surface of Magma are not that high: 600C. Surface density of the crust is around 5.36g/cm e3. It gets denser to around 14g/cm e3 at the thickest then it becomes lesser and lesser to reach the semi liquid state of Magma. The deepest borehole dug in 2011 by Russians to 12,345 metres (40,502 ft) at Sakhalin-I Odoptu OP-11 Well is a good omen. Such technology should be used to defuse small volcanoes already making a mess, like in Iceland.

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