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June 02, 2006
Interesting stuff
An apparent crater as big as Ohio has been found in Antarctica. Scientists think it was carved by a space rock that caused the greatest mass extinction on Earth, 250 million years ago.
The crater, buried beneath a half-mile of ice and discovered by some serious airborne and satellite sleuthing, is more than twice as big as the one involved in the demise of the dinosaurs.The crater's location, in the Wilkes Land region of East Antarctica, south of Australia, suggests it might have instigated the breakup of the so-called Gondwana supercontinent, which pushed Australia northward, the researchers said.
"This Wilkes Land impact is much bigger than the impact that killed the dinosaurs, and probably would have caused catastrophic damage at the time," said Ralph von Frese, a professor of geological sciences at Ohio State University.
From the scientific journal, Earth, in 1994:
Rampino believes that the Gondwanaland impact itself may have triggered the Siberian eruption. In the Permian, the Siberian Traps were almost at the antipode - the point on precisely the opposite side of the globe - of the impact site, Rampino says. It is his contention, supported by some theoretical modeling, that the interior of Earth transmits shock waves from an impact site to its antipode. If a plume of magma from the mantle happened to be poking up at the underside of the crust at this antipodal point in Siberia, Rampino says the shock from the meteor impact could have been enough to breach the crust here. This would have allowed the magma to rush up through the sedimentary rocks and cause lava to erupt onto the surface.
He also contends that the asteroid that did in the dinosaurs 65 million years ago probably sent shock waves racing to the antipode of the impact site near Chixchulub in the Yucatan. That area was the Deccan Traps, a thick layer of basalt that covers much of west-central India. The age of the Deccan Traps is in accordance with this idea: 65 million years. "In fact," Rampino says, "we have shown that the dates of other major flood basalts and mass extinctions correlate exactly."
Piecing these findings together, Rampino, who admits that this is a stretch, proposes a general scenario for mass extinctions: A large meteor strikes the Earth and sends shock waves to the antipodal point, triggering flood volcanism there; the debris from the impact crater, combined with the dust and other material ejected by the volcanic eruption, blocks enough sunlight to shut down photosynthesis and cool the globe.
"There are too many coincidences for there not to be a connection between impacts, basalt volcanism and mass extinction," Rampino asserts.
Posted by Mike at June 2, 2006 06:53 PM
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