50,000 years ago, a huge iron-nickel meteorite, hurtling at about 40,000 miles per hour, struck the rocky plain of Northern Arizona with an explosive force greater than 20 million tons of TNT. The meteorite, estimated to have been about 150 feet across and weighing several hundred thousand tons, in less than a few seconds, left a crater 700 feet deep and over 4000 feet across. Large blocks of limestone, some the size of small houses were heaved onto the rim. Flat-lying beds of rock in the crater walls were overturned in fractions of a second and uplifted permanently as much as 150 feet. Today the crater is 550 feet deep, and 2.4 miles in circumference. Twenty football games could be played simultaneously on its floor, while more than two million spectators observed from its sloping sides.
Daily guided are offered hourly from 9:15 a.m. until 2:15 p.m., and last about 1 hour, weather permitting.