Printer Friendly

Glassy evidence of multiple crashes.

Measured by the geological clock, glass lasts but an instant. Because water eats away at glassy rocks, geologists rarely find any older than about 40 million years. Two research groups, however, report finding tiny glassy spherules dating back roughly 365 million years, apparently created during two distinct meteorite or comet impacts at that time.

In the June 12 SCIENCE, Kun Wang of the University of Alberta in Edmonton describes glassy microspherules found in China's Hunan province. Because of the spherules' shape and chemical composition, he proposes that they are "microtektites," formed when an impact hurls droplets of molten rock into the air, where they quickly cool into a glassy form.

In May, at a meeting of the American Geophysical Union in Montreal, researchers from the University of California, Davis, and the Royal Institute of Natural Sciences of Belgium described Belgian glassy microspherules slightly older than the Chinese ones. These also appear to be microtektites, they report.

The two sets of microspherules suggest that Earth suffered at least two crashes in the late Devonian period, a time of major extinctions. Geologists are now considering whether these impacts played a role in causing the extinctions.
COPYRIGHT 1992 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:geological research
Publication:Science News
Article Type:Brief Article
Date:Jul 4, 1992
Words:193
Previous Article:Sinking solution for carbon dioxide.
Next Article:Age no barrier to aggressive therapies.
Topics:


Related Articles
New signs of world upheaval at K-T.
Geomagnetic switch: not impact caused.
Cuba proposed site for K/T impact.
Tiny plants challenge greenhouse plan.
Ancient splash in the Atlantic.
Closing in on the killer.
What does a squashed crater look like?
Anti-impactors have their day in K-T court.
JET FIRE CAUGHT ON TAPE : FLIGHT 592 PILOTS RECEIVED WARNING.
CRASH PROBE RAISES FEARS : SOME SEE SIGNS OF TERRORISM; CLINTON COUNSELS CAUTION.

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters