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Salty Ancient Seawater Found Beneath Chesapeake Bay

GEOGRAPHY AWARENESS WEEK! SCIENCE

Scientists have discovered a pocket of ancient seawater that’s been trapped underground near the mouth of the Chesapeake Bay since the time of the dinosaurs—strong evidence that the Atlantic Ocean was once much saltier than today. (NPR)

Did someone say Chesapeake Bay water quality?!

Seawater from the Early Cretaceous North Atlantic Ocean—about 100 million years old—was discovered near Cape Charles, Virginia. Cape Charles is near the tip of the Delmarva Peninsula, beautifully visualized in this mosaic of five satellite images. Image courtesy NASA/USGS/Landsat 5
Seawater from the Early Cretaceous North Atlantic Ocean—about 100 million years old—was discovered near Cape Charles, Virginia. Cape Charles is near the tip of the Delmarva Peninsula, beautifully visualized in this mosaic of five satellite images.
Image courtesy NASA/USGS/Landsat 5

Discussion Ideas

  • The pockets of ancient Atlantic seawater found near Cape Charles, Virginia, are twice as salty as today’s ocean. Why?
    • From the NPR article: The Early Cretaceous Atlantic “had only been in existence [at the time of the meteor impact] for about 50 million years and it was isolated from the rest of the world’s oceans,” says Ward Sanford a USGS hydrologist who led the survey. “It had its own salinity and its salinity was changing at a different rate and by different amounts from the rest of the global oceans.”
  • Is this process happening anywhere on Earth today? Are there any isolated bodies of water that are significantly saltier than the ocean?
  • Look at our map of the Chesapeake Bay. It’s a part of the Atlantic Ocean, and yet scientists in the NPR article go out of their way to say that the water they discovered is from the ancient ocean, distinguishing it from the bay. What is the main reason these connected bodies of water would have such different chemistry? Why would the ocean be saltier than the bay?
    • Chesapeake Bay is an estuary, an area where freshwater rivers empty into the salty ocean. Many rivers empty into Chesapeake Bay—the Susquehanna, Potomac, Rappahannock, and James to name a few.
  • Like many bays, Chesapeake is brackish—a mixture of the freshwater and saltwater. Salinity in the Chesapeake is not uniform, however. Use our phenomenal mapping tool, FieldScope, to test the varying levels of “Salinity in the Estuary” and collect other data that impact water chemistry—proximity to agricultural or industrial runoff, turbidity and currents, temperature . . .

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