Online guide to the continental Cretaceous-Tertiary boundary in the Raton basin, Colorado and New Mexico

Sixty-five million years ago when dinosaurs were roaming about on floodplains and lakeshores in the western interior of the United States, an asteroid about 6 miles in diameter struck the Earth at a place now called Chicxulub on the northern tip of the Yucatan Peninsula in Mexico. The impact explosion created a crater more than 100 miles across and 20 miles deep that later filled and has since been buried beneath younger sediments nearly a mile thick. It blasted thousands of cubic miles of pulverized rock and water vapor into and above the atmosphere dispersing debris around the globe, blocking out the sunlight, and causing months of darkness, cold, and poisonous rain. When the skies finally cleared above a devastated Earth, not only the dinosaurs, but also about 75 percent of all other living animals and plant species were extinct and the Dinosaur Era was over.

Illustration from Alvarez (1997); courtesy of Walter Alvarez.

U.S. Department of the Interior, U.S. Geological Survey
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Last modified Wed 15-Mar-2006 14:40:31 MST
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