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Mass extinction's cause: 'Sick Earth'
October 23, 2006USC earth scientists turn up clues to explain disappearance of 90 percent of ancient species
What really caused the largest mass extinction in Earth's history?
USC earth scientists will reveal new clues at the annual meeting of the Geological Society of America in Philadelphia Oct. 22-25.
The Permian-Triassic extinction, as it is called, is not the one that wiped out the dinosaurs. Nor does the cause appear to have been a meteorite strike, as in that famous event.
The most likely explanation for the disappearance of up to 90 percent of species 250 million years ago, said David Bottjer, is that "the earth got sick."
Bottjer, professor of earth sciences in the USC College of Letters, Arts and Sciences, leads a research group presenting several new pieces of the P-T extinction puzzle.
Matthew Clapham, a recent Ph.D. graduate of Bottjer's laboratory, has found that species diversity and environmental changes were "decoupled" long before the extinction. Conditions on the planet were deteriorating long before species began to die off, Bottjer said, casting doubt on the meteorite strike theory.
"People in the past used to think this big mass extinction was like a car hitting a wall," he said. Instead, Clapham's interpretation of the geological record shows "millions of years of environmental stress."
Pedro Marenco, a doctoral student in Bottjer's lab, has been testing a leading theory for the P-T extinction: that a warming of the earth and a slowdown in ocean circulation made it harder to replace the oxygen sucked out of the water by marine organisms. According to the theory, microbes would have saturated the water with hydrogen sulfide, a highly toxic chemical.
For a mass extinction "you really needed a good killer, and it [hydrogen sulfide] is really nasty stuff," Bottjer said.
Marenco has measured large changes in the concentration of sulfur isotopes that support the hydrogen sulfide theory.
University of Southern California
The Permian-Triassic extinction, as it is called, is not the one that wiped out the dinosaurs. Nor does the cause appear to have been a meteorite strike, as in that famous event.
The most likely explanation for the disappearance of up to 90 percent of species 250 million years ago, said David Bottjer, is that "the earth got sick."
Bottjer, professor of earth sciences in the USC College of Letters, Arts and Sciences, leads a research group presenting several new pieces of the P-T extinction puzzle.
Matthew Clapham, a recent Ph.D. graduate of Bottjer's laboratory, has found that species diversity and environmental changes were "decoupled" long before the extinction. Conditions on the planet were deteriorating long before species began to die off, Bottjer said, casting doubt on the meteorite strike theory.
"People in the past used to think this big mass extinction was like a car hitting a wall," he said. Instead, Clapham's interpretation of the geological record shows "millions of years of environmental stress."
Pedro Marenco, a doctoral student in Bottjer's lab, has been testing a leading theory for the P-T extinction: that a warming of the earth and a slowdown in ocean circulation made it harder to replace the oxygen sucked out of the water by marine organisms. According to the theory, microbes would have saturated the water with hydrogen sulfide, a highly toxic chemical.
For a mass extinction "you really needed a good killer, and it [hydrogen sulfide] is really nasty stuff," Bottjer said.
Marenco has measured large changes in the concentration of sulfur isotopes that support the hydrogen sulfide theory.
University of Southern California
Mass Extinction Current Events and Mass Extinction News RSSConservation targets too small to stop extinction
Conservation biologists are setting their minimum population size targets too low to prevent extinction.
The first neotropical rainforest was home of the Titanoboa
Smithsonian researchers working in Colombia's Cerrejón coal mine have unearthed the first megafossil evidence of a neotropical rainforest.
A new day dawned fast
In 1980, Luis Alvarez and his collaborators stunned the world with their discovery that an asteroid impact 65 million years ago probably killed off the dinosaurs and much of the the world's living organisms. But ever since, there has been an ongoing debate about how long it took for life to return to the devastated planet and for ecosystems to bounce back.
Surviving mass extinction by leading a double life
Drifting across the world's oceans are a group of unicellular marine microorganisms that are not only a crucial source of food for other marine life - but their fossils, which are found in abundance, provide scientists with an extraordinary record of climatic change and other major events in the history of the earth.
Ancient volcanic eruptions caused global mass extinction
A previously unknown giant volcanic eruption that led to global mass extinction 260million years ago has been uncovered by scientists at the University of Leeds.
Princeton geoscientist offers new evidence that meteorite did not wipe out dinosaurs
A Princeton University geoscientist who has stirred controversy with her studies challenging a popular theory that an asteroid wiped out the dinosaurs has compiled powerful new evidence asserting her position.
New blow for dinosaur-killing asteroid theory
The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a paper to be published in the Journal of the Geological Society on April 27, 2009.
New theory on largest known mass extinction in the history of the earth
Did volatile halogenated gases from giant salt lakes at the end of the Permian Age lead to a mass extinction of species?
Study unravels why certain fishes went extinct 65 million years ago
Large size and a fast bite spelled doom for bony fishes during the last mass extinction 65 million years ago, according to a new study to be published March 31, 2009, in the Proceedings of the National Academy of Sciences.
No joy in discoveries of new mammal species -- only a warning for humanity, Paul Ehrlich says
In the era of global warming, when many scientists say we are experiencing a human-caused mass extinction to rival the one that killed off the dinosaurs, one might think that the discovery of a host of new species would be cause for joy.
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