What happens when a rock from space thats more than a mile wide slams into the Earth at supersonic speed? Scientists from the U.S. Geological Survey (USGS) and its partners are learning as they analyze evidence they are recovering from cores drilled during the past two summers into the Chesapeake Bay impact crater and surrounding structures. USGS scientists David Powars, C. Wylie Poag, and J. Wright Horton, Jr. will present new evidence obtained from cores and seismic surveys, on the devastating effects this event had on the Earth 35 million years ago, during three separate sessions at the Annual Meeting of the Geological Society of America, scheduled for Nov. 4-8 in Boston, Massachusetts.
Its bigger and deeper than we imagined: This comet or asteroid shot through the Earths atmosphere, leaving a vacuum in its wake. Then it hit, splashing through several hundred feet of ocean and slicing through several thousand feet of coastal plain sediments, says Powars. It fractured the crystalline bedrock below to at least a depth of seven miles and a width of 85 miles. Billions of tons of ocean water were vaporized and millions of tons of debris were ejected into the atmosphere within minutes. Marine life was decimated, and a train of giant waves of seawater inundated the land, explains Powers, whose talk Structure and Composition of the Southwestern Margin of the Buried Chesapeake Bay Impact Structure, Virginia is scheduled for 4:45 pm Tues, Nov. 6, Hynes Convention Center Room 202.
Whats written in stone: USGS scientists are looking for clues left in the bedrock from this extraordinary event in the deep past, to deal with an ordinary modern-day issue: finding ground water suitable to support a rapidly-developing region. Studies are underway to understand the impact structure and its influence on ground water.
We are examining the composition, age, and structure of crystalline basement rocks beneath the Coastal Plain se
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Contact: Diane Noserale
dnoseral@usgs.gov
703-648-4333
United States Geological Survey
6-Nov-2001
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