National Geographic News
Map of Chesapeake Bay impact crater by Maggie Smith and Matthew Twombly, NG Staff. Source: USGS.

Christine Dell'Amore

National Geographic

Published November 20, 2013

Scientists drilling the United States' biggest crater have tapped into the oldest body of seawater ever found.

They weren't expecting to find the ancient water, estimated to be 100 to 145 million years old, while boring a hole 1.1 miles (1.8 kilometers) deep into the massive crater, located under the Chesapeake Bay.

The crater was formed about 35 million years ago when a large rock or chunk of ice slammed into what's now the mouth of the bay, off Cape Charles, Virginia, hollowing out a 56-mile-wide (90-kilometer-wide) hole in the floor of the North Atlantic Ocean.

"The water was in the sediment long before the impact occurred. The impact simply reshuffled the sediment in large blocks, which helped preserve it," said study leader Ward Sanford, a hydrologist with the U.S. Geological Survey.

The asteroid wallup also spawned gigantic tsunamis that possibly hit the Blue Ridge Mountains more than 100 miles (160 kilometers) away. (See "Asteroid Impacts: 10 Biggest Known Hits.")

The seawater trapped deep underground is now in an area roughly the size of a large lake—about 60 square miles (155 square kilometers) across.

Finding this unprecedented time capsule of Cretaceous seawater "was a little bit mind-blowing," Sanford said.

Sanford and his colleagues drilled into the crater in 2005 during a joint project with the International Continental Scientific Drilling Program, but it took several years to gather additional data that could determine the water's age.

How did they make the discovery?

To determine the origin of the newfound water, the team measured the ratio of two compounds—dissolved chloride and bromide—in the drilling samples, which revealed a clear "fingerprint" of ocean water, according to the study, published online November 13 in the journal Nature.

Pinpointing the age was a bit trickier. The scientists took samples of helium—a gas that accumulates over time in underground water—from nearby coastlines in the Chesapeake Bay. (Learn more about the Chesapeake.)

Then they sampled the helium in the ancient seawater, and discovered the concentration of the gas was about a hundred times higher than that of the other coastal samples.

By determining the rate at which helium accumulates, the team was able to figure out the rough age of the ancient water.

What does the discovery tell us?

The find appears to clear up the long-standing mystery of why previously collected samples of deep groundwater from the same region of the Chesapeake Bay are so salty.

Until now, scientists had various theories: Some proposed that buried salt in the rock slowly dissolved in the water. More recently, after the drilling under the crater in 2005, some suggested that the heat of the asteroid impact boiled much of the surrounding water and left it saltier than before.

But when the scientists finally determined the age of Sanford's sample of water in 2012, they realized both the new specimens and previous groundwater specimens are seawater from a small section of the North Atlantic Ocean that has been trapped in place since the asteroid hit 35 million years ago. And they believe the water was just as salty then.

As North America was separating from Europe and Africa, geological rifts developed that created separate salty basins, including in the North Atlantic, notes Peter Swart, a marine geologist at the University of Miami who wasn't involved in the new research.

Swart concurred with the recent study results concluding that the salty water under the crater has been that way for tens of millions of years, and did not become more salty over the millennia. (The majority of the ancient ocean wasn't so salty, he added by email, or marine life would not have been able to flourish.)

Why is it important?

"Analyses of ancient seawater are very important in [that] they provide insight into the evolution of life" and other ocean processes, Swart noted.

For example, understanding how acidic the ocean was in the past may help people figure out how to tackle modern ocean acidification, a phenomenon harmful to some ocean animals that's occurring due to global warming.

Study leader Sanford added the research also offers a window into how the ocean evolved: Before this study, no one knew for sure just how salty the North Atlantic was during the Cretaceous.

What's next?

Drilling into the Chesapeake Bay crater has ended for now, but Sanford suspects that more water of this age and composition is sequestered elsewhere deep off the Atlantic Coast, waiting to be found.

"If you had enough money and drilling [resources], you could probably learn a lot," he said.

Sanford was thrilled with his unexpected discovery, calling it "one of the highlights of my career."

Follow Christine Dell'Amore on Twitter and Google+.

49 comments
Sveet Vred
Sveet Vred

yeah yeah yeah. most "scientific"conclusions concerning events that happened 100 million years ago (supposedly) are nothing more than a guessing game. to state that "The asteroid wallup also spawned gigantic tsunamis that possibly hit the Blue Ridge Mountains more than 100 miles (160 kilometers) away" is HIGH speculation, to say the very least. but it is good fodder for a book.

Sveet Vred
Sveet Vred

yeah yeah yeah. most "scientific"conclusions concerning events that happened 100 million years ago (supposedly) are nothing more than a guessing game. to state that "The asteroid wallup also spawned gigantic tsunamis that possibly hit the Blue Ridge Mountains more than 100 miles (160 kilometers) away" is HIGH speculation, to say the very least. but it is good fodder for a book.

Thangellapally Brahma
Thangellapally Brahma

Excellent discovery.Interesting to know it.Such a huge pocket of oldest sea water plugged by Crater is amazing. Analysis of drilling samples is key factor 

Verg Matthews
Verg Matthews

We need a couple of hours of detailed programs on Nat Geo for further details....hope it will be aired soon!.....MATTS


Amit Chaturvedi
Amit Chaturvedi

Hilarious discovery.. waiting for its positive outcome...

Alma Leal Benavides
Alma Leal Benavides

It would be a treasure if it were nice fresh drinking water for humans

Abhishek Ghosh
Abhishek Ghosh

@Christine Dell'Amore, were any organic compounds found in the water ? The time period is too long for genetic material to survive but simple compounds like methane could still be present. There may be fossils embedded in the crater walls.

Habeeb Baloch
Habeeb Baloch

it is an amazing discovery tell us ancient environment of wolrd as well as about subsurfaces of earth for recoverinig hydrocarbon reservoirs.

Josh Lucion
Josh Lucion

Looks like the start of the Piranha 3d Movie to me..

I am sure this helped make the bay as any impact on the outer crush causes ripples and cracks where rivers later form.

Stewart Hurst
Stewart Hurst

 I wonder if it's possible that the asteroid impact contributed to the formation of the bay.  The bay almost seems to radiate from the crater.

Tyrone Hicks
Tyrone Hicks

i dont know yall sounds like the begining of a monster movie to me ..or the end of the bay from contamination...

Benedek Nagy
Benedek Nagy

couldn't they find any remains of plants or animals? couldn't the salty water preserved them? or is it too acidic? 

Nikolaos George Pargas
Nikolaos George Pargas

A commendable discovery, but some caution should be employed when its age is concerned. 

Ed Ward
Ed Ward

What a treasure house this would be to scientist !

Ann Greer
Ann Greer

What an amazing find, thank you for helping us learn more about our planet.

jaison Vincent
jaison Vincent

Its a new knowledge about water bodies on earth. I heard before that the water we are drinking is already billion years old, because the water resources in this earth is the part of water-cycle, happening regularly from the origin of water. So we are always using same water. Only difference in its combination and changes according to the surrounding of water body.

Nurul Ainni
Nurul Ainni

is there any big impact will happened towards the earth?

Maj VRayos
Maj VRayos

did they find any living crustaceans then?

Michael Van Laanen
Michael Van Laanen

So happy this was finally published.  Had a team of student filmmakers produce a short documentary about this subject as part of a pilot test for a children STEAM educational project I designed.  The girls did a fantastic job with their project, couldn't be happier for them.  

David Zavala Gutierrez
David Zavala Gutierrez

Ok, I've made myself a mistake. It is clear from the lecture of the above that a pool of saline water from the cretaceous time was sealed when a meteorite collided 35 my ago. ¡Sorry! Again, the lecture was clear enough, though I've to read from the source. ¡Greetings!

Thom Jones - Photographer
Thom Jones - Photographer

Amazing to find a Tithonian period time capsule - although i would expect any biological matter will have been destroyed...

David Zavala Gutierrez
David Zavala Gutierrez

Well, that's a big story, but, I'm afraid our friends have mistakenly put cretaceous seawater in a trap done by an asteroid that hit 35 my ago, in cenozoic times, currently about the eocene-oligocene transition, as indicated by: http://en.wikipedia.org/wiki/Cenozoichttp://science.nationalgeographic.com/science/prehistoric-world/cretaceous/ and https://class.coursera.org/dino101-001/lecture/63 Mh! Let's say it was a mistake, I hope it will be corrected, I'm very proud of been an entusiastic reader of NGM for years. Cheers!

charles potts
charles potts

Curious: were there any signs of life in the water?  If so, what?

Anu Kupaa
Anu Kupaa

wow, who knows what else we are going to find in the next coming years.

Kevin S.
Kevin S.

Wow! Thats awesome! Wonder what else we haven't recovered on our planet

song jia
song jia

mystery is under the ground.

Agnes Aszodi
Agnes Aszodi

Congratulations! Fingers crossed for more funds to continue the research.. could answer and open up so many questions!

Gustavo Gil
Gustavo Gil

Very interesting article. Do not miss it!

M. Waters
M. Waters

@Nurul Ainni Are you asking if the author of this article knows of anything due to impact the earth?  That is what you got out of reading this article?

Christine Dell'Amore
Christine Dell'Amore

@charles potts Good question Charles! I actually asked Ward Sanford this—he said it's possible there are microbes in the ancient seawater. You should email him to follow up if you're interested. 

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