Counterpoint in Impact Debate

Science News, June 21, 1986 | Go to article overview

Counterpoint in Impact Debate


Counterpoint in impact debate

Scientists who believe that powerful volcanoes, rather than a gigantic asteroid impact, led to the extinction of the dinosaurs have a new argument for their side of the debate. It concerns the tiny pieces of shocked quartz and feldspar that have been considered evidence for the impact theory. These minerals are found in the layer of clay that was laid down all over the world 65 million years ago at the boundary of the Cretaceous and Tertiary periods, when the dinosaurs and about three-fourths of all animal species became extinct. The bits of quarts and feldspar contain microfractures that suggest they withstood a sudden and very intense shock--a greater shock than is created by most volcanoes. Therefore, impact theorists have said, they must have been created by an impact (SN:6/7/86, p.356).

But could the microfractures have been caused by exceptionally powerful volcanoes? That's a question nobody ever asked before, according to Charles B. …

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