THE VIRGINIAN-PILOT
Copyright (c) 1995, Landmark Communications, Inc.
DATE: Thursday, September 14, 1995 TAG: 9509140349
SECTION: LOCAL PAGE: B1 EDITION: FINAL
SOURCE: BY JAMES SCHULTZ, STAFF WRITER
LENGTH: Medium: 69 lines
Roughly 20 tons of heavenly junk falls through, and burns up in, the upper reaches of the atmosphere each day. But 35 million years ago, a meteorite the size of a small mountain made it all the way to Earth. That cosmic collision gave birth to the Chesapeake Bay, scientists meeting in Washington this week confirmed.
Proof of the Bay's extraterrestrial origin came courtesy of new seismic mapping data supplied by Texaco and Exxon, as well as government drilling of core samples on Virginia's Eastern Shore and on the Peninsula.
Further investigations by scientists at the U.S. Naval Academy also indicate high concentrations of the extremely rare metallic element iridium, found in large quantity only in natural space debris.
The fault lines, fractured boulders and jumbled sediments found by researchers attest to the force of the blast which, if it occurred today, might destroy the area from Virginia Beach and Norfolk up through Richmond and Washington.
``I had people telling me I was crazy,'' said David S. Powars, a U.S. Geological Survey research geologist who first proposed in 1993 that the Bay could have been formed from a meteoric impact. ``This explains a whole lot of the Bay's geology: how and why the rivers drain the way they do.''
Powars said information provided by the oil companies, interested in identifying possible petroleum deposits, was especially helpful in affirming his notions. Detailed underwater maps of ancient sediments and bedrock, produced by sending out concentrated sound waves that penetrated through the accumulated layers, revealed a series of fault lines that snaked throughout present-day bedrock.
Core samples, obtained by both the U.S. Geological Survey and the state Department of Environmental Quality, produced ``shocked'' quartz, rock fractured by the force of explosive pressure. The evidence of iridium was further proof.
``You've got all this phenomena agreeing,'' said Gerald H. Johnson, professor of geology at the College of William and Mary. ``There's nothing else, no volcanic eruption, nothing. This is the only thing that fits.''
The meteorite slammed into the shallow sea that covered most of what is now eastern Virginia, near present-day Cape Charles. The collision sent enormous tidal waves, perhaps as high as 1,600 feet, racing to tear at the prehistoric coastline, located west of what is now Richmond, in the foothills of the Appalachians.
A blanket of silt, sediment and fractured boulders was thrown up and away from the immediate crater, draping over thousands of square miles around the crater's edge. Any life within the central, elliptical blast zone - about 23 miles long and 15 miles wide - would have been vaporized immediately.
Another celestial visitor, 10 times the size of the Bay-forming meteorite, is thought to have contributed to the demise of dinosaurs 65 million years ago.
That rocky object hit near the present-day Yucatan Peninsula in Mexico with an estimated force of 100 million tons of TNT. An explosion of that magnitude could have started a global firestorm, sending ash and soot high into the stratosphere, blocking sunlight and lowering planetary temperatures. ILLUSTRATION: COSMIC COLLISION GAVE BIRTH TO CHESAPEAKE BAY
Text and research by JAMES SCHULTZ, graphic by ROBERT D.
VOROS/Staff
SOURCES: David S. Powars, U.S. Geological Survey; Gerald H. Johnson,
College of William and Mary; The Washington Post
[For a copy of the graphic, see microfilm for this date.]
by CNB