National Geographic News
While searching for oil beneath the North Sea, British geologists located what they think is a crater caused by the impact of a meteor or comet that crashed into Earth more than 60 million years ago.
Named the Silverpit crater after a nearby seafloor channel, the site130 kilometers (80 miles) east of the English coastcould give scientists a better look at what happens when an object from space crashes into Earth.
The crater, consisting of a central crater surrounded by ten concentric rings of escarpments, is 20 kilometers (12 miles) wide. It lies under 40 meters (130 feet) of water and a layer of sediment that in places is as thick as 1,500 meters (4,920 feet).
The team that reported on the discovery in the August 1 issue of Nature said the Silverpit crater is remarkably well preserved in comparison with other known craters on Earth that have been eroded by wind and rain, which should make it especially interesting to those who study meteor impacts.
"Most craters found on Earth are highly eroded, poorly preserved, and only found on land," the United Kingdom-based authors, Simon A. Stewart of British Petroleum in Aberdeen and Phillip J. Allen of Production Geoscience Limited in Banchory, said in their journal article.
The Silverpit crater, they added, resembles craters seen by astronomers on the Moon and Europa, a moon of Jupiter. Such craters are not subject to the eroding effects of wind and rain.
Stewart said that the undersea crater discovery was "an accident." While Allen was examining seismic data in search of gas fields, Stewart explained, "he noticed out of the corner of his eye some anomalous features" in the shallower layers of the seafloor.
Allen then mapped the unusual area and hung the map in the hope that someone else might know what the features represented. Stewart said he suspected the crater might have been formed by the impact of a meteor or asteroid.
Stewart and Allen ruled out a volcanic origin because there were no magnetic anomalies in the crater. They also eliminated salt intrusions from lower layers of rock, because the underlying Triassic and Permian strata were undisturbed.
The crater is formed in Cretaceous chalk and Jurassic shale, covered by an undisturbed layer of Tertiary sediment. This means the crater was formed between 60 and 65 million years ago, near the end of the age of the dinosaurs.
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