SCIENCE WATCH; Dinosaur Theory
Published: November 22, 1988
A geologist at the University of Rochester believes he has found support for the hypothesis that a meteorite struck India 66 million years ago, setting in motion the events that killed off the dinosaurs and many other species.
It is known that a great outpouring of lava covered a large part of India at that time and this has been cited by those who believe it was volcanic activity that caused the extinctions. They believe volcanic ash enveloped the globe, producing a lethal, semipermanent winter. The lava created a vast plateau whose remnants are known as the Deccan Traps.
Others have argued that a meteorite impact caused the extinctions, while some have proposed that both were responsible. A number of paleontologists prefer a more gradual effect, such as a climate change.
At a recent conference in Snowbird, Utah, it was suggested that the eruptions producing the Deccan Traps were touched off by an impact. A sudden cooling of the climate induced by smoke from both events could then have caused the extinctions. Others noted that India, at the time, was drifting over a volcanic ''hot spot'' that is now under Reunion Island.
Now the University of Rochester reports that Dr. Asish Basu, a professor of geology there, has found grains of quartz split by severe shock in a layer deposited under the Deccan Traps immediately before the eruptions began.
Grains of shocked quartz have been found in deposits of that age worldwide. They have been cited, by proponents, as strong evidence of the impact hypothesis. Dr. Basu believes that their occurrence directly below the Deccan deposits is evidence that the impact occurred nearby and initiated the eruptions.
Another candidate is a crater, 20 miles wide, found buried by sediment near Manson, Iowa. It, too, seems to have been a source of shocked quartz.