Figure 15-16: Confirming an Extinction-Level Impact Site Measuring the gravitational force from slight variations in density (resulting from the impact) can reveal a buried crater. Concentric rings of the underground Chicxulub Crater (right inset) lie under a portion of the Yucatán Peninsula. This crater has been dated to 65 million years ago and is believed to be the site of the impact that led to the extinction of the dinosaurs. A piece of 65-million-year-old meteorite discovered in the middle of the Pacific Ocean in 1998 is believed to be a fragment of that meteorite. The fragment, about 0.3 cm (0.1 in.) long, was cut into two pieces for study (left inset).

(left inset: Frank T. Kyte, UCLA; right inset: Mark Pilkington/Geological Survey of Canada/Science Source; map: Peter W. Sloss, NOAA-NESDIS-NGDCD)