east of flagstaff, arizona, just off I-40, lies Meteor Crater, an impact crater roughly 4000 ft. in diameter and 570 feet deep. it was formed when a nickel-iron meteorite about 160 ft. in diameter made a direct hit in the region currently designated as the colorado plateau, roughly 50,000 years ago. at the time, local residents included giant ground sloths, north american camels and wooly mammoths.
there are many impact craters detectable on the earth's surface, but the arizona crater is the best-preserved and most accessible. as with all formations of this scale, mere photos don't give the view much of an idea of the sheer size of the crater. try clicking on this panoramic view to enlarge it for full effect.