The Suspect The Theory The Evidence The Proponents The Holes Asteroid impact A space rock strikes in the tropics, spews debris into the air and triggers lethal climate change Scientists found 250 million year old rocks from Antarctica and China said to contain meteorite fragments Researchers at the University of Rochester, Harvard, and UC Santa Barbara Scientists have yet to find the ultimate smoking gun, a crater Sudden methane explosion A massive cloud of methane gas abruptly bursts from the ocean, cataclysmic flooding and fires ensue Great Dying fossils show a sudden sharp rise in carbon-12 isotopes, best explained by a methane belch Chemical engineer Gregory Ryskin at Northwestern University The explosion requires an improbable 10,000 gigatons of methane Slow methane leak Volcanoes of frozen deposits leak methane over thousands of years, depleting oxygen The burrowing reptile Lystrosaurus, adapted for low-oxygen conditions, thrived during this period Researchers at the University of Oregon, the South African Museum, and the University of Washington The leak could not deplete enought oxygen to cause global death, critics say Hydrogen sulfide stink bomb Lethal levels of hydrogen sulfide, emitted by anaerobic bacteria, are expelled from the ocean into the air Proponents are searching for signs of sulfur bacteria in Japanese sediments dated to the extinction Scientists at Penn State, the University of Colorado, and the University of Tokyo There's no proof that the upper layers of ancient oceans were devoid of oxygen
Methane from cattle farts is meaningless, unless one is standing nearby. P, you. Decomposing organic matter in ocean sediments may actually be there, but the methane ices are from below, of abiogenic origin, and in huge quantities (50,000 years worth of natural gas at current rates of consumption).Methane Explosion Warmed The Prehistoric Earth, Possible AgainIn the last 200 years, atmospheric methane has more than doubled due to decomposing organic materials in wetlands and swamps and human aided emissions from gas pipelines, coal mining, increases in irrigation and livestock flatulence.
Greenbelt - Dec 10, 2001
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by Debbi McLean
NASA Goddard Space Flight Center
Multimedia Design Studio
However, there is another source of methane, formed from decomposing organic matter in ocean sediments, frozen in deposits under the seabed.
Global Warming Preserved "Mass Kill" Fossils, Study SaysGreg Retallack, geologist at the University of Oregon... says huge releases of carbon dioxide and methane starved the Earth of oxygen, causing mass extinctions over the last 500 million years. He adds that the resulting buildup of billions of dead prehistoric creatures may have acted as a carbon sink, reducing CO2 in the atmosphere and preventing the Earth from becoming as hot and lifeless as Venus... He bases his theory on a compilation of unusually well preserved fossils found around the world, including fish, crustaceans, insects, and other ancient life forms. The fossil record indicates about 40 episodes of exceptional preservation, he says -- episodes that coincide with periods of global warming, when the Earth was low in oxygen... In some mass extinctions, the scientist says, greenhouse gases "ramped up … to intolerable levels of more than ten times the modern level of atmospheric carbon dioxide." Volcanic activity and outbursts of undersea gases are the prime suspects for these periods of lethal pollution.
by James Owen
National Geographic News
October 18, 2005
Disraeli / Twain: "there are three kinds of lies: lies, damned lies, and statistics."
Table. Chances of dying from selected causes (USA) Cause of death Chances Motor vehicle accident 1 in 100 Homicide 1 in 300 Fire 1 in 800 Firearms accident 1 in 2,500 Electrocution 1 in 5,000 Asteroid/comet impact 1 in 20,000 Passenger aircraft crash 1 in 20,000 Flood 1 in 30,000 Tornado 1 in 60,000 Venomous bite or sting 1 in 100,000 Fireworks accident 1 in 1 million Food poisoning by botulism 1 in 3 million Drinking water with EPA limit of tricholoethylene 1 in 10 million (From C.R. Chapman & D. Morrison, 1994, Nature 367, 33-40.)
Four theoretical causes of the Permian extincion event.
To what extent could the first event have triggered one or more of the other three effects?