Chesapeake Bay Impact Crater

Ancient Seawater Found Under The Chesapeake Bay

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USGS scientists have determined that high-salinity groundwater found more than 1,000 meters (0.6 mi.) deep under the Chesapeake Bay is actually remnant water from the Early Cretaceous North Atlantic Sea and is probably 100-145 million years old.  This is the oldest sizeable body of seawater to be identified worldwide.

Twice as salty as modern seawater, the ancient seawater was preserved like a prehistoric fly in amber, partly by the aid of the impact of a massive crater or meteorite that struck the area about 35 million years ago, creating Chesapeake Bay.  About 35 million years ago a huge rock or chunk of ice traveling through space blasted a 56-mile-wide hole in the shallow ocean floor near what is now the mouth of the Chesapeake Bay.  The force of the impact ejected enormous amounts of debris into the atmosphere and spawned a train of gigantic tsunamis that probably reached as far as the Blue Ridge Mountains, more than 110 miles away.

The impact of the comet or meteorite would have deformed and broken up the existing arrangement of aquifers (water-bearing rocks) and confining units (layers of rock that restrict the flow of groundwater).  Virginia’s “inland saltwater wedge” is a well-known phenomenon that is thought to be related to the impact crater.  The outer rim of the crater appears to coincide with the boundary separating salty and fresh groundwater.

http://www.chesapeakebay.net/blog/post/ancient_seawater_found_under_chesapeake_bay

http://www.usgs.gov/newsroom/article.asp?ID=3725#.UoPGqHDkvv0

 

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