Geneticists had puzzled for years about why those of us alive today appear to have all descended from the same 2,000 ancestors, meaning there is a remarkable lack of human DNA diversity in what is referred to as a ‘genetic bottleneck’ that occurred between 70,000 and 80,000 years ago. The mystery may have been solved when geneticists crossed paths with another scientific discipline and learned of a massive volcanic eruption on the island of Sumatra known as the YTT (Youngest Toba Tuff) occurring at about the same time. The YTT plunged the planet into a volcanic winter lasting six years and a super-winter lasting as much as a millenium.
Toba spat 2,800 cubic kilometres of volcanic ash into the sky, measuring 8, or ‘mega-colossal’, on the Volcanic Explosivity Index. To put it in context the 1815 eruption of Mount Tambora, also in Indonesia, which threw the entire northern hemisphere into a volcanic winter killing up to 200,000 people in Europe alone, clocked a six.
Ash and rock flew out of Toba at a staggering rate, coating an area from Arabia across the Indian subcontinent to the South China Sea in up to 6m of debris. Meanwhile a miasmal cloud of sulphur and other gases wrapped itself round the world, plumbing new levels of cold on a planet already in the vice-like grip of an Ice Age. Some experts estimate this super-winter lasted over a thousand years, citing a sudden climate change in Greenland, and estimate that the earth’s temperature dropped by between 3 and 5°C. Others put the figure nearer 1°C.
There is a lot of speculation that a geomagnetic shift in polarity or gravitational interference from passing planetary objects may trigger an eruption of America’s largest known supervolcano, Yellowstone National Park. The Yellowstone eruption is expected to be equivalent in ferocity to Toba, according to Professor Michael Rampino, spewing 2800 cubic kilometers of volcanic debris, and Yellowstone has been remarkably cyclical erupting approximately every 600,000 years. Whatever the cause, when Yellowstone blows it will be an extinction level event.
On the bright side, like Toba, it would have a very cooling effect on the climate. In 2006, weaponeer Lowell Wood suggested solving the global warming crisis by much the same means as Toba did, albeit in an artificial manner. In an article for Rolling Stone, (which no longer appears to be online, sadly), Wood, also known as Dr Evil, proposed a solution for polar bears.
What if you could do an end run around carbon-trading schemes and international treaties and political gridlock and actually solve the problem? And what if the cost to get started was not trillions of dollars but $100 million a year—less than the cost of a good-size wind farm?
Wood’s proposal was not technologically complex. It’s based on the idea, well-proven by atmospheric scientists, that volcano eruptions alter the climate for months by loading the skies with tiny particles that act as mini-reflectors, shading out sunlight and cooling the Earth. Why not apply the same principles to saving the Arctic? Getting the particles into the stratosphere wouldn’t be a problem—you could generate them easily enough by burning sulfur, then dumping the particles out of high-flying 747s, spraying them into the sky with long hoses or even shooting them up there with naval artillery. They’d be invisible to the naked eye, Wood argued, and harmless to the environment. Depending on the number of particles you injected, you could not only stabilize Greenland’s polar ice—you could actually grow it. Results would be quick: If you started spraying particles into the stratosphere tomorrow, you’d see changes in the ice within a few months. And if it worked over the Arctic, it would be simple enough to expand the program to encompass the rest of the planet. In effect, you could create a global thermostat, one that people could dial up or down to suit their needs (or the needs of polar bears).
Should the planet disgorge a lot of sulphur by way of a super volcanic eruption to cool itself off there is precedence it works. Short term global warming is implicated in two mass extinctions, one occurring 251 million years ago and more recently, the dinosaurs, a mere 65 million years ago. In both instances, volcanic activity combined with anoxic bacteria triggered catastrophic events.
Using carbon records and other measures, these researchers now believe that the extinctions were caused by an oxygen-depleted ocean spewing forth poisonous gas. The culprit? Global warming.
To put it simply, when an ocean becomes anoxic (low or no oxygen), a certain bacterial life becomes abundant in the water. These microbes are generally found in the depths of stagnant lakes and create sulfur as a byproduct. The reason oxygen gets reduced in the atmosphere and thus the ocean is increased carbon dioxide.These microbes are generally found in the depths of stagnant lakes and create sulfur as a byproduct. The reason oxygen gets reduced in the atmosphere and thus the ocean is increased carbon dioxide. It is assumed that large-scale volcanic activity raised carbon dioxide levels, reduced oxygen, and lead to intense global warming. Active, spewing volcanoes alone cannot account for the extinctions in the water and on land of the Great Dying 251 million years ago.
But the increased carbon dioxide, decreased oxygen, and global warming created a friendly environment for those sulfur-creating microbes. These deep-dwelling microbes spew out large amounts of hydrogen sulfide. If the ocean or sea has enough oxygen, the hydrogen sulfide and oxygen stay separated and remain stable. If the ocean is lacking in oxygen, eventually huge bubbles of toxic hydrogen sulfide gas will erupt into the atmosphere.
When an asteroid nine miles across collided with the earth forming the Chicxulub crater the collision and resultant explosion was so great that it aerosolized unusually high concentrations of elements like Iridium and Yttrium that would have burned the lungs of any breathing creature. However, there is now evidence the asteroid didn’t cause the die offs.
Gerta Keller of Princeton University and Thierry Addate of the University of Lausanne, in Switzerland have done some sleuthing.
The asteroid charged with killing the dinosaurs, after all, left more than the Chicxulub crater as its calling card. At the same 65-million-year depth, the geologic record reveals that a thin layer of iridium was deposited pretty much everywhere in the world. Iridium is an element that’s rare on Earth but common in asteroids, and a fine global dusting of the stuff is precisely what you’d expect to find if an asteroid struck the ground, vaporized on impact and eventually rained its remains back down. Below that iridium layer, the fossil record shows that a riot of species was thriving; above it, 65% of them went suddenly missing. (Read about China’s dinosaur fossils.)
But Keller and Addate worried that we were misreading both the geologic and fossil records. They conducted surveys at numerous sites in Mexico, including a spot called El Peñón, near the impact crater. They were especially interested in a 30-ft. layer of sediment just above the iridium layer. That sediment, they calculate, was laid down at a rate of about 0.8 in. to 1.2 in. per thousand years, meaning that all 30 feet took 300,000 years to settle into place.
Analyzing the fossils at this small site, they counted 52 distinct species just below the iridium layer. Then they counted the species above it. The result: the same 52. It wasn’t until they sampled 30 feet higher — and 300,000 years later — that they saw the die-offs.
“The mass extinction level can be seen above this interval,” Keller says. “Not a single species went extinct as a result of the Chicxulub impact.”
The debate about what killed off the dinosaurs will continue but one thing not in dispute is the planet was in a state of global warming at the time, followed by long periods of ice.
