[meteorite-list] Chesapeake Bay Impact Crater Studies Continue

[Ron Baalke]

http://www.dailytimesonline.com/news/stories/20040518/localnews/443242.html

Impact crater studies continue
By Ceri Larson Danes
Daily Times Online
May 18, 2004

CAPE CHARLES -- The Eastern Shore got slammed 35 million years ago, and 
today is getting drilled because of it. 

Installation of a 2,900-foot-deep monitoring well began here last week 
so scientists can more extensively study a 56-mile-wide impact crater 
that likely formed the Chesapeake Bay and caused extensively salty
groundwater in the state's southeastern area. 

The U.S. Geological Survey, in cooperation with the Virginia Department 
of Environmental Quality, recently began drilling the well at the 
county's Sustainable Technologies Industrial Park. In 1993, the survey 
and state geologists discovered the buried Chesapeake Bay impact crater, 
which was created by a comet or asteroid. The crater provided "the first 
plausible explanation" for the estuary. 

The asteroid was a mile or two in diameter and was traveling 134,000 mph 
when it hit shallow ocean waters. 

"This is the best studied, best preserved crater in the world," said 
David Powars, a survey geologist who has been studying the crater for 
nearly 20 years. 

Powars said it is the largest crater in the United States and the sixth 
largest in the world. 

He wants everyone on the Shore -- especially students -- to understand 
the local scientific treasure they have. 

Ongoing studies on the Shore include measurements of the local gravity 
and magnetic fields, and an electrical resistivity survey, which is 
intended to provide information on the distribution of saline 
groundwater from samples at moderately deep levels within the crater's 
center. 

Powars said they "forever" will be monitoring groundwater at the Cape 
Charles site and others on the Shore. 

Scott Bruce, a geologist with DEQ, said that "geology controls the 
occurrence, movement and quality of the groundwater" -- meaning the 
new monitoring well will be relevant for as long as there are people 
living on the Shore. 

Seismic surveys related to the crater will be taken later this year 
that produce images of the Earth's interiors and look much like a 
medical sonogram. 

The test area will span an 18-mile-long straight line from Cape 
Charles to Nassawadox where 30 small holes, about 80 feet deep, will 
be drilled for monitoring. 

As part of the process, explosives will be placed in the holes and 
detonated in the fall.