University of Arizona News Services

July 15, 1997

Environmental damage caused by Meteor Crater impact

Fifty thousand years ago, a rock half the size of a football field in diameter struck the flat plain of the southern Colorado Plateau near what is now Winslow, Ariz. In an article published Monday, July 14, in the journal Meteoritics and Planetary Science, David A. Kring estimates that the blast from the meteorite impact sent a shock wave with 2,000 mile per hour winds that destroyed virtually every living thing in its path for at least 3 km.

In 1992, Kring, a research scientist at the Lunar and Planetary Laboratory at The University of Arizona in Tucson, and LPL colleague William V. Boynton, published evidence confirming that the 65 million-year-old Chicxulub Crater in Mexico's Yucatan Peninsula was produced by the impact of an asteroid or comet.

"One of the things we realized when we studied the extinction of dinosaurs, is that impact cratering affects the environment either of the local region where the impact occurred, or in the case of the Yucatan event, the entire world. So, what we're beginning to do is look at other impact events and assess what the environmental damages were," said Kring.

Meteor Crater may be the best preserved impact crater in the world. As such, it provides geologists with a ready-made field laboratory for studying impact sites. Among scientists, says Kring, Meteor Crater is as important geologically as the Grand Canyon.

At the time of the impact, northern Arizona was much different, with flowing streams and lush grasslands and forests. Using scaling relationships determined from nuclear explosions, Kring says that the meteorite that struck Arizona created a shock wave that radiated over the landscape, creating an air blast with hurricane force winds as far as 40 km (about 24 miles).

Vegetation would have been completely destroyed for up to 1,500 square km, and damaged over an additional 600 square km. Large animals as far away as 4 km would have been killed outright. Those as far as 24 km away might have sustained crippling injuries. Geologically, the force of the meteorite lifted the land around it, creating a visible rise in the plateau that hides the crater. Still, no extinctions were likely to have happened, and within several years, new plants and animals would have colonized the blast area within several years.

"We think the impact would have affected plants and animals as far away as Winslow, but probably the blast would not have reached Flagstaff (about 40 miles to the west).

Compared to Chicxulub, Meteor Crater is small potatoes. The object that struck the Yucatan was about 6 miles in diameter and had repercussions both life forms and weather around the world. A number of reputable scientists think it may have either wiped out the dinosaurs, or at least set in motion the conditions that led to their demise. Objects the size necessary to create Meteor Crater fall on Earth every 1,600 to 2,000 years, mostly falling into the oceans. Those striking land have a frequency of about every 6,000 years. Kring says this and future studies may help scientists understand the interactions between impact events and the surrounding vegetation and animal life.

"What we want to find is the threshold at which extinctions occur, both globally and locally" says Kring. "We know that Chicxulub had global ramifications. Somewhere between that event and the Meteor Crater event we probably crossed the threshold that drives extinctions."

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