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Volcanic Warming Eyed in 'Great Dying'
gollum123 writes "AP writes on an article in the journal Science where an ancient version of global warming may have been to blame for the greatest mass extinction in Earth's history. 'In an event known as the "Great Dying," some 250 million years ago, 90 percent of all marine life and nearly three-quarters of land-based plants and animals went extinct. Researchers think the answer is Massive volcanic flows in what is now Siberia, and believe the extinctions were caused by global warming and oxygen deprivation over long periods of time."
The dinosaurs died out 65 million years ago, you twit.
m ian.htm
We're talking about the Permian Extinction - which, by the way, no-one actually calls the "Great Dying".
I could tell y'all about it but it would be a duplication of effort. Do yourself a favor and read something:
http://www.bbc.co.uk/education/darwin/exfiles/per
http://en.wikipedia.org/wiki/Permian_extinction
The good and new comes from no quarter where it is looked for, and is always something different from what is expected.
To summarise, Nebraska is well known for its ash deposits - mined for cleaning products like Ajax - but no-one knew where it all came from.
Then in 1971, Mike Voorhies found a mass grave of prehistoric bones - sabre-toothed deer, zebra-like horses etc. - all killed by something big 12 million years ago. They were all buried under volcanic ash up to 3 metres deep.
One problem - no-one knew where all the ash came from.
Now Yellowstone was known to be pretty active, with its geysers, boiling mud-pools etc. but they couldn't find a caldera, ie. an actual volcano cone anywhere in the park.
But fortunately NASA were testing some high altitude photography techniques and decided to take some pictures of Yellowstone, thoughtfully dropping some copies off at the Visitor Centre. It was then that they realised that in fact Yellowstone is ONE BIG CALDERA - i.e. a 'superplume', 9000 square kilometres of crater left from some humungous explosion a long time back.
In Bill Bryson's words, "imagine a pile of TNT about the size of an English county and reaching 13 kilometres into the sky, to about the height of the highest cirrus clouds, and you have some idea of what visitors to Yellowstone are shuffling about on top of".
He goes on, "The Yellowstone eruption of two million years ago put out enough ash to bury New York State to a depth of 20 metres ..."
And then there's the last supervolcano eruption in Toba, in northern Sumatra, 74,000 years ago. Studies of ice cores in Greenland show that at least 6 years of 'volcanic winter' followed, and that humans probably were at the brink of extinction, with maybe only several thousand of us at any one time for thousands of years after (which maybe explains our relative lack of genetic diversity).
Yes, volcanoes are more than fire and magma - every now and then there're some *really* big ones.
here are ominous signs that the Earth's weather patterns have begun to change dramatically and that these changes may portend a drastic decline in food production- with serious political implications for just about every nation on Earth. The drop in food output could begin quite soon, perhaps only 10 years from now. The regions destined to feel its impact are the great wheat-producing lands of Canada and the U.S.S.R. in the North, along with a number of marginally self-sufficient tropical areas - parts of India, Pakistan, Bangladesh, Indochina and Indonesia - where the growing season is dependent upon the rains brought by the monsoon.
The evidence in support of these predictions has now begun to accumulate so massively that meteorologists are hard-pressed to keep up with it. In England, farmers have seen their growing season decline by about two weeks since 1950, with a resultant overall loss in grain production estimated at up to 100,000 tons annually. During the same time, the average temperature around the equator has risen by a fraction of a degree - a fraction that in some areas can mean drought and desolation. Last April, in the most devastating outbreak of tornadoes ever recorded, 148 twisters killed more than 300 people and caused half a billion dollars' worth of damage in 13 U.S. states.
To scientists, these seemingly disparate incidents represent the advance signs of fundamental changes in the world's weather. Meteorologists disagree about the cause and extent of the trend, as well as over its specific impact on local weather conditions. But they are almost unanimous in the view that the trend will reduce agricultural productivity for the rest of the century. If the climatic change is as profound as some of the pessimists fear, the resulting famines could be catastrophic. "A major climatic change would force economic and social adjustments on a worldwide scale," warns a recent report by the National Academy of Sciences, "because the global patterns of food production and population that have evolved are implicitly dependent on the climate of the present century."
A survey completed last year by Dr. Murray Mitchell of the National Oceanic and Atmospheric Administration reveals a drop of half a degree in average ground temperatures in the Northern Hemisphere between 1945 and 1968. According to George Kukla of Columbia University, satellite photos indicated a sudden, large increase in Northern Hemisphere snow cover in the winter of 1971-72. And a study released last month by two NOAA scientists notes that the amount of sunshine reaching the ground in the continental U.S. diminished by 1.3% between 1964 and 1972.
To the layman, the relatively small changes in temperature and sunshine can be highly misleading. Reid Bryson of the University of Wisconsin points out that the Earth's average temperature during the great Ice Ages was only about seven degrees lower than during its warmest eras - and that the present decline has taken the planet about a sixth of the way toward the Ice Age average. Others regard the cooling as a reversion to the "little ice age" conditions that brought bitter winters to much of Europe and northern America between 1600 and 1900 - years when the Thames used to freeze so solidly that Londoners roasted oxen on the ice and when iceboats sailed the Hudson River almost as far south as New York City.
Just what causes the onset of major and minor ice ages remains a mystery. "Our knowledge of the mechanisms of climatic change is at least as fragmentary as our data," concedes the National Academy of Sciences report. "Not only are the basic scientific questions largely unanswered, but in many cases we do not yet know enough to pose the key questions."
Meteorologists think that they can forecast the short-term results of the return to the norm of the last century. They begin by noting the slight drop in overall temperature that produces large numbers of pressure centers in the upper atmosphere. These break up the smooth flow of west