Magazine article Science News

Impact Crater May Lie beneath Lake Huron

Magazine article Science News

Impact Crater May Lie beneath Lake Huron

Article excerpt

Impact crater may lie beneath Lake Huron

With the help of magnetic sensors, scientists have detected a rimmed circular structure, 30 miles in diameter, more than a mile beneath the floor of Lake Huron. They believe the magnetic ring marks a buried crater -- potentially one of the largest known -- blasted by a meteorite at least 500 million years ago.

Four researchers with the Geological Survey of Canada unexpectedly discovered the circular pattern while examining new, high-resolution magnetic images of a southern Ontario region previously labeled as "essentially featureless." They noticed that the patterns of gravitational and magnetic forces emanating from the structure resembled those of verified impact craters. The Ottawa-based researchers, led by David A. Forsyth, temporarily named their discovery the Can-AM structure because it straddles the Canadian-U.S. border. They describe the find in the August GEOLOGY.

Scientists have taken particular interest in impact craters over the last decade, in light of new theories linking meteor and comet strikes with ancient climate disruptions and mass extinctions. These theories suggest that massive meteorites collinding with Earth have periodically clouded the atmosphere with dust, triggering climate changes, photosynthetic failures and subsequent mass extinctions, including the great dinosaur demise some 65 million years ago (SN: 5/19/90, p.311).

But so far, the impact data have been too scattered to prove any correlation between the collisions and the species extinctions, says Jay Melosh, a planetary scientist at the University of Arizona in Tucson. …

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