Chesapeake Bay Crater

The Chesapeake Bay crater was formed around 35 million years ago during the late Eocene Epoch. Because an ice age was ending, sea levels were unusually high. Richmond would have been on the sea shore at the time and tropical rainforests would have been everywhere you looked. A bolide (a very large impactor that can be either a comet or an asteroid) hit with fiery destruction. 3-5 kilometers in diameter, it swooped through the Earth’s atmosphere and blasted an enormous crater into the continental shelf. The crater is now approximately 200 km southeast of Washington, D.C., and is buried 300-500 meters beneath the southern part of Chesapeake Bay and the peninsulas of southeastern Virginia. The entire bolide event, from initial impact to the termination of breccia deposition, lasted only a few hours or days. The crater was then buried by additional sedimentary beds, which accumulated during the following 35 million years.

The Chesapeake Bay crater was only recently identified by C. Wylie Poag of the U.S. Geological Survey, who has assembled an international team to investigate its characteristics and consequences. Evidence of the crater comes from two sources: cores drilled by the USGS and the Virginia State Water Control Board, and marine seismic-reflection profiles collected by Texaco, Inc., the USGS, and the National Geographic Society. The cores sampled contain shocked quartz and melted grains, which confirm an impact. The crater is 85 km in diameter and 1.3 km deep. That makes it twice the size of Rhode Island and as deep as the Grand Canyon. It is three times larger than any other U.S. crater and is the sixth largest crater known on the planet.

According to Poag, “Within minutes, millions of tons of water, sediment, and shattered rock were cast high into the atmosphere for hundreds of miles along the East Coast.” An enormous seismic tsunami engulfed the land and possibly even overtopped the Blue Ridge Mountains. The sedimentary walls of the crater progressively slumped in, widened the crater, and formed a layer of huge blocks on the floor of the ring-like trough. The devastation along the East Coast would have taken centuries to overcome. The Chesapeake Bay crater is a great sign of what can happen as the results of a large impactor, and it was less than 10 km in diameter

The Chesapeake Bay crater is the largest in the United States and sixth largest in the world. It goes to show you what a small meteorite can do if it impacts the Earth. Think about what it would have been like if the area had been as heavily populated as it is now?

The USGS has a great article about the Chesapeake Bay crater and so does Wikipedia. Here on Universe Today there is a great article on the Chesapeake Bay impact and impact craters in general.

Reference:
USGS

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