About 35 million years ago, when dinosaurs were already extinct but the Appalachian Mountains were still covered in tropical rain forests, an asteroid more than a mile wide, moving at supersonic speed, crashed into the Atlantic Ocean off North America.
Traveling at about 70,000 miles per hour, the asteroid or comet dove 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 and vaporized. Millions of tons of debris and rocks were ejected into the atmosphere. The collision incinerated everything along the East Coast, triggered gigantic tsunamis, and destroyed 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, under more than a thousand feet beneath sand, silt, and clay. No one knew it was there until scientists discovered it in 1983.
Researchers are now extracting core samples from deep inside the crater. ?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,? says David Powars, a hydrologist at the U.S. Geological Survey.
The new findings offer greater insight into 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, despite the fact that earthquakes are uncommon in this region. Three rivers in the area have highly unusual 90-degree bends in them.
Utility companies in eastern Virginia are funding some of this work because it will help with the search for fresh ground water needed to supply growing populations in the region. Water from many of the wells in the region is salty or brackish.
The core samples show that the 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 and a width of 85 miles. This was a big hit,? says Powars.
The asteroid or comet that struck the area that later became the Chesapeake Bay may have been part of a 2 million-year-long comet shower that scientists think may have occurred between 36 and 34 million years ago. The heat from the impact would have incinerated every living thing within hundreds of miles. It could have helped cause the major extinction of life that occurred about 33 million years ago.
The early Oligocene extinction dramatically affected land mammals. Forest dwellers declined as their habitat became less abundant, while hoofed animals flourished as a result of increasing grasslands. A number of predators became extinct at this time, mainly because of changes in vegetation.
An even bigger crater in northern Siberia was created at about the same time. Scientists have also found traces of helium 3, an isotope associated with extraterrestrial objects, in sediment layers in Italy and other places dating to 35 million years ago.
The aftermath of the collision would have been prolonged darkness and acid rain caused by the fallout of rocks, dust, and particles that were blasted into the atmosphere, along with the residual effects of raging wildfires. These conditions would have caused a sudden cooling of the Earth, leading to the extinction that eventually occurred.
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