Chesapeake Bay Crater Offers Clues to Ancient Cataclysm

Hillary Mayell
for National Geographic News
November 13, 2001

About 35 million years ago—the dinosaurs are dead, but the Appalachian Mountains are still covered in tropical rain forests—a rock from space that was more than a mile wide and moving at supersonic speed crashed into the Atlantic Ocean off North America.

Traveling at about 70,000 miles (113,000 kilometers) an hour, the asteroid or comet (bolide) splashed through several hundred feet of water and several thousand feet of mud and sediment.

Billions of tons of ocean water were propelled into the air as high as 30 miles (48 kilometers) and vaporized. Millions of tons of debris and rocks were ejected into the atmosphere. The incident incinerated everything along the East Coast, triggered gigantic tsunamis, and decimated marine life in the surrounding area.

For millions of years the crater lay buried in the southern part of the Chesapeake Bay and surrounding peninsulas, more than a thousand feet (300 meters) beneath sand, silt, and clay. Scientists discovered it in 1983 and have been studying it ever since.

For the past two summers, researchers have been extracting core samples from deep inside the crater. The core material is beginning to provide the answers to a lot of questions about the crater and its effects in the region.

"We're finding things that are giving us an idea of the heat and power at the time of impact—partially melted algae fossils, completely shattered rocks, lots of basin fragments, fractured and tilted seabeds," said David Powars, a hydrologist at the U.S. Geological Survey (USGS).

Powars and C. Wylie Poag, a USGS colleague, presented some of the results of their research earlier this month in Boston at the annual meeting of the Geological Society of America.

"It's pretty exciting," Powars said. "In every direction there's new data. Wylie and I are like two kids with candy."

Unusual Geologic Conditions

The new findings offer greater insight into geological and hydrological conditions of the Chesapeake area and eastern Virginia that have puzzled scientists for more than a century.

The land is sinking, erosion patterns are unusual, and earthquakes have occurred in this region not known for earthquakes. The groundwater in some areas of the region is salty, and three rivers in the area have abrupt—and highly unusual—90-degree turns.

One thing the core samples show, according to Powars, is that the roughly circular crater is much bigger and deeper than originally thought.

When it hit, the asteroid or comet "fractured the crystalline bedrock below to at least a depth of 7 miles (11 kilometers) and a width of 85 miles (137 kilometers). This was a big hit," he said.

Continued on Next Page >>


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