145-Million-Year-Old Seawater Discovered In The Chesapeake Bay Impact Crater
About 35 million years ago, a space object two-miles wide fell from the sky and landed in what is now the Chesapeake Bay. It rocked the earth and left a 56-mile-wide hole in the ground, which was slowly covered over with hundreds of feet of sand and rock.
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No one knew it was there until 1999. In the years since the discovery, scientists have explored the area looking for geological and astronomical clues. This month, researchers from the U.S. Geological Survey reported a discovery they weren't expecting: ancient seawater, perhaps as old as 145 million years, trapped under the impact crater.
"This study gives us confidence that we are working directly with seawater that dates far back in earth's history," said Jerad Bales, acting USGS Associate Director for Water, in a statement. The USGS called the water the "oldest sizeable body of seawater to be identified worldwide."
The team of scientists say the water has been preserved in place about a half-mile underground since probably between 100 and 145 million years ago, around the time crocodiles and birds were evolving. Their research, which appears in the current issue of the journal Nature, shows that the seawater is much saltier than the water in our oceans today.
Over the last 14 years, scientists have been driling around the Chesapeake Bay to explore the impact, which sits below Virginia's tip of the Delmarva Peninsula. An impact like that (the like of which probably killed the dinosaurs several million years later) would have pushed a massive wave rippling across the ocean, sent debris raining down for miles around and ruptured all kinds of existing underground water formations.
Scientists exploring the area wanted to learn more about what fell (an icy comet or a rocky asteroid?) and how it has affected the bay area. This U.S. Geological Survey crew, led by Ward E. Sanford, was trying to find out what the impact meant for the earth's crust, he told The Washington Post.
Though these researchers weren't expecting to find underground seawater, they knew it had been discovered in the area. And they knew it would be very salty — about twice as salty as modern seawater. There were various theories about why that was. Osmosis was one. Evaporation, caused by the extreme heat generated by the asteroid-or-comet's impact with the atmosphere and crust, was another.
This disovery may have solved the riddle once and for all. The water, they say, is from the North Atlantic Ocean at a time when that body of water was much, much saltier.
"Up to this point," Bales said, "no one thought that this was North Atlantic Ocean water that had essentially been in place for about 100 million years."
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