Skip to comments.Drilling Finds Crater Beneath Va. Bay
Posted on 06/01/2004 4:21:15 PM PDT by Rebelbase
CAPE CHARLES, Va. - Geologists drilling half a mile below Virginia's Eastern Shore say they have uncovered more signs of a space rock's impact 35 million years ago.
For more than two weeks, scientists drilled around the clock alongside a parking lot across the harbor from Cape Charles. They stopped at 2,700 feet.
From the depths came jumbled, mixed bits of crystalline and melted rock that can be dated, as well as marine deposits, brine and other evidence of an ancient comet or asteroid that slammed into once-shallow waters near the Delmarva Peninsula.
Cape Charles is considered Ground Zero for the resulting 56-mile-wide depression below what's now the Chesapeake Bay. The drilling project marks the first time the geologists explored the inner portion of the inverted-sombrero-shaped crater.
"We expected to see some pretty strange rocks because of the extreme pressure and temperatures that occurred" approximately 35 million years ago, said geologist Greg Gohn, who led the $180,000 project for the U.S. Geological Survey (news - web sites).
Over the past decade, USGS (news - web sites) and Virginia scientists have investigated indications that a 2-mile-wide brilliant ball traveling tens of thousands of miles per hour crashed off the Virginia coast, burrowing thousands of feet and depressing and fracturing the bedrock.
Billions of tons of ocean water vaporized. Millions of tons of debris spewed 30 miles high before collapsing back into the excavation. A train of giant waves inundated the land. The waves then dragged debris as they washed back into the crater, preserving it beneath a blanket of rock and sediment.
It probably took just a few minutes to create the largest crater in the United States and sixth-largest known on the planet, according to computer simulations.
The catastrophe squeezed freshwater from many of the aquifers of southeastern Virginia and filled others with briny water. Its legacy is well-known to residents who try to drill for drinkable groundwater and encounter the saltwater "wedge," pockets of brine nestled in an arc from the lower Eastern Shore to the Hampton Roads-Newport News area.
Geological research off the coast of New Jersey and in Virginia, begun in 1983, led to the crater's discovery a decade later. Drilling and further study of seismic data narrowed the location in the Chesapeake Bay.
"We're getting evidence about how hot this thing (was) and what was the energy," said USGS hydrologist David Powars, one of those credited with the crater's discovery.
More clues to the space rock's identity will come from cores taken in the drill's final 280 feet.
A $1.2 million proposal to dig 7,000 feet not far from Cape Charles is before the International Continental Scientific Drilling Program, which would then assist the USGS with funding.
It has been known for a long time, but this confirmation is rather interesting.
Thanks for the post. I love science!
Do you think Bill Clinton knows about the "jumbled, mixed bits of crystalline and melted rock that can be dated"?
I'm waiting for Ted Kennedy to blame the asteroid impact on neo-conservatives and Halliburton...
There are also huge natural gas deposits under the Continental shelf offshore from Atlantic City NJ to Fla.
Congress stopped exploration prior to drilling back in 1983. I know because I was one of the many drillers who had to be certified with the USGS for surface and sub-sea well control techniques prior to the industry being allowed to develop this field. Needless to say, I remember hearing a small blurb shortly thereafter stating Congress had placed the area "off limits" to offshore drilling. Guess it was the NIMBY syndrome. Let 'em produce it out West and pipe it to us. Then NE congressmen can gripe about the high cost. As I recall it was a who's who of Eastern liberals who killed this important clean energy source. Anyone else recall this event or know of any records of the vote? I wonder. Hmmm. Kerry again?
I wonder if this eventhad anything to do with the Carolina Bays.
The Chesapeake Bay Bolide: Modern Consequences of an Ancient Cataclysm - U.S. Geological Survey - Coastal and Marine Geology - Woods Hole Field Center
During the late Eocene, the formerly quiescent geological regime of the Virginia Coastal Plain was dramatically transformed when a bolide struck in the vicinity of the Delmarva Peninsula, and produced the following principal consequences:
- The bolide carved a roughly circular crater twice the size of the state of Rhode Island (~6400 km2), and nearly as deep as the Grand Canyon (1.3 km deep).
- The excavation truncated all existing ground water aquifers in the impact area by gouging ~4300 km3 of rock from the upper lithosphere, including Proterozoic and Paleozoic crystalline basement rocks and Middle Jurassic to upper Eocene sedimentary rocks.
- A structural and topographic low formed over the crater.
- The impact crater may have predetermined the present-day location of Chesapeake Bay.
- A porous breccia lens, 600-1200 m thick, replaced local aquifers, resulting in ground water ~1.5 times saltier than normal sea water.
- Long-term differential compaction and subsidence of the breccia lens spawned extensive fault systems in the area, which are potential hazards for local population centers in the Chesapeake Bay area.
I love this stuff...
Thanks. Nice maps.
And a third of the waters were made bitter...
First I heard of this discovery, also, although I was living in Virginia at the time and for years afterward.
But actually, quite interesting. Thanks!
Does anyone know if they have an estimate for how far inland the waves came?
fault...hahaha (geologist humor)
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.