Doomsday continued: supervolcanoes

Ordinary volcanic eruptions, like the one at Mt. St. Helens in 1980 or the famous eruption of Vesuvius that buried Herculaneum and Pompeii in 79, or one about to go off in Indonesia any time now, are hardly any threat to human civilization, however horrible they are for the people living nearby.

But supervolcanoes are a whole different phenomenon. They erupt when a massive underground magma pool builds up over hundreds of thousands of years, raising the ground below until a caldera tens or hundreds of miles across suddenly explodes (over a matter of a few days!) and rains debris across continents, even the entire globe. The famous geysers, like Old Faithful, at Yellowstone National Park are not simply a tourist attraction - they are more akin to a hole in the lid of a huge boiling pot, one about to boil over and explode.

Here's how Livescience describes a Yellowstone supervolcano:

"Geologists in the United States detailed a similar scenario in 2001, when they found evidence suggesting volcanic activity in Yellowstone National Park will eventually lead to a colossal eruption. Half the United States will be covered in ash up to 3 feet (1 meter) deep, according to a study published in the journal Earth and Planetary Science Letters.

Explosions of this magnitude "happen about every 600,000 years at Yellowstone," says Chuck Wicks of the U.S. Geological Survey, who has studied the possibilities in separate work. "And it's been about 620,000 years since the last super explosive eruption there.""

Everyone in the surrounding regions and downwind across most of North America would die almost immediately. The resultant horrific weather, akin to the worst nuclear winter scenarios, might do the rest of us in. At the very least, it would destroy our economy and likely the economies of most of the other developed nations. As the author puts it:

"Earth is plunged into a perpetual winter, some models predict, causing plant and animal species disappear forever. "The whole of a continent might be covered by ash, which might take many years -- possibly decades -- to erode away and for vegetation to recover," Sparks said."

The last supervolcano on record was not at Yellowstone, but at Lake Toba (in current day Sumatra) about 74,000 years ago. Genetic studies indicate that at the same time, Homo sapiens went through a 'genetic bottleneck' - for despite having far more members of our species alive right now (almost 7 billion and counting) than any other large mammal, genetic surveys indicate our species evinces far less genetic diversity than any of our relatives - for instance, genetic surveys of chimps

"reveals an almost four-fold higher diversity and a three-fold greater age of the most recent common ancestor of the chimpanzee sequences. Phylogenetic analyses show the sequences from the different chimpanzee subspecies to be intermixed ... These data, as well as preliminary work in the other great apes, indicate that the human genome is unique in carrying extremely little nucleotide diversity." [bold in original]

Unless there is a tremendously unlikely coincidence, the cause of our lack of genetic diversity appears to be the eruption of the Toba supervolcano. It reduced the total membership of our species to a few thousand survivors, and every one of the 7 billion or so of us alive today are descendants of those hardy few. A Khoisan tribesman and you are almost certainly more genetically alike than two chimps from the zoo.

And it could happen again - the wonderfully named Armageddon Online has a survey of the main extant supervolcanoes. So yes, volcanic eruptions may wipe us out, just as some researchers think the tremendous vulcanism of the Deccan Traps in India 65 million years ago wiped out the dinosaurs - and not the comet that hit the Yucatan about the same time.

Either way, we have one more reason for terraforming Mars (or the Moon or even Venus - more on that in a future post), before it's too late.

Cheers!