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Northern Crater Shows Prehistoric Deep Impact
by Ned Rozell


April 7, 2004

To the rhinos and crocodiles of the far north, the day was like any other. They ate, swam and napped, unaware a celestial body was headed their way at 60,000 miles per hour. Suddenly, a wayward comet screamed into the atmosphere, struck Earth and created a bowl a mile deep and 15 miles in diameter. Haughton Crater was born.

This commotion happened 22 million years ago at a spot now known as Devon Island, located about 600 miles north of the Arctic Circle in Canada's Northwest Territories. Today, Haughton Crater provides geologists a unique chance to find out what happens when a massive object strikes the planet.

Buck Sharpton of the Lunar and Planetary Institute of Johnson Space Center in Texas has spent many hours crawling in and around Haughton Crater. Sharpton, who recently visited the University of Alaska in Fairbanks, has the challenging job of studying a cavity in Earth and extrapolating back to find what made the divot.

Haugton Crater is one of about 160 impact craters on Earth that range in size from 200 feet in diameter to 180 miles in diameter. On the large end of the spectrum is Chicxalub Crater in Mexico, which is dated to the time dinosaurs disappeared from Earth. Some scientists suspect the object that created the crater may have doomed the dinosaurs.

About 15 miles from lip to lip, Haughton Crater is much smaller than Chicxalub, but it is an excellent crater to study because so little of it has eroded in millions of years. During the last ice age, Haughton Crater was protected by an ice field that sealed the crater from wind and extreme weather. What remains allows scientists, such as Sharpton, the opportunity to work back to what happened at the moment of impact.

Haughton Crater is probably the mark of a smallish comet, Sharpton said. Because a comet is made largely of ice and gases, little evidence of the object that created the crater has been found. Instead, the crater itself has left clues to its creation. When the comet crashed into the ground, it was hot enough and packed enough punch to vaporize much of the rock (along with a few rhinos and crocodiles) at ground zero. Microseconds later, rocks farther from the impact were melted. Farther yet, other rock was crushed and launched skyward. Within seconds, rock beneath the point of impact rebounded to form a mountain range that still sits within the crater.

The hot core of the comet kept things active in the center of the crater, triggering small earthquakes for as long as a decade afterward. Though large rocks returned Earthward within minutes, dust particles may have remained in the sky for weeks. When the core of the crater cooled, plants once again invaded the site. Lakes formed in the bed of the crater, and it eventually began to resemble what it looks like today--a 15-mile blemish that would catch your eye if you flew over it in an aircraft. Musk oxen have replaced crocodiles as the animals best adapted to the barren country, and scientists and pilots are the only humans to be seen occasionally traversing the crater and its silver-gray mountains.

Why study something that happened 22 million years ago? Sharpton said by understanding the physics of the creation of Haughton Crater, scientists can understand more about how these impacts affect Earth. If the dinosaurs did indeed succumb to the effects of Chicxalub, there is reason to be concerned.

But one should not fret about a crashing comet or other heavenly body, Sharpton said. Though the effects could easily be devastating, the odds are astronomical. "To me, the thing we should worry about is if we're being good stewards of this planet," he said. "It doesn't matter if an asteroid hits us in 300 years if we're not going to make it that far."



This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell is a science writer at the institute.


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