A Crater is Born
50,000 years ago, a giant fireball streaked across the North American sky. At its core was a meteorite – a chunk of nickel iron about 150 feet (50 meters) wide.
Millions of tons of limestone and sandstone were blasted out of the crater, covering the ground for a mile in every direction.
The meteorite weighed 300,000 tons and traveled at a speed of 26,000 miles per hour (12 kilometers per second). When it struck the earth in what is now northern Arizona, it exploded with the force of 2 ½ million tons of TNT, or about 150 times the force of the atomic bomb that destroyed Hiroshima.
Most of the meteorite was melted by the force of the impact, and spread across the landscape in a very fine, nearly atomized mist of molten metal. Millions of tons of limestone and sandstone were blasted out of the crater, covering the ground for a mile in every direction with a blanket of shattered, pulverized and partially melted rock mixed with fragments of meteoritic iron.
When the dust settled, what remained was a crater three-quarters of a mile (about 1 kilometer) wide and 750 feet deep. The impact occurred during the last ice age, a time when the Arizona landscape was cooler and wetter than it is today. The plain around it was covered with a forest, where mammoths, mastodons and giant ground sloths grazed. The force of the impact would have leveled the forest for miles around, hurling the mammoths across the plain and killing or severely injuring any animals unfortunate enough to be nearby.Over time, the landscape recovered.
A lake formed in the bottom of the crater, and sediments accumulated until the bowl was only 550 feet deep. Then, with the ending of the ice age, the climate changed and dried. The desert that we see today has helped to preserve the crater, by limiting the erosion that might otherwise have blurred or erased the traces of the ancient impact.