Study of gravity and magnetic fields in the Yucatan Peninsula, Mexico has helped to locate a large crater caused by the impact of a comet or meteorite at the end of the Cretaceous Period about 65 million years ago. Some scientists postulate that the effect of this extraterrestrial object colliding with the Earth is responsible for the extermination of many life forms on Earth, including the dinosaurs. Although today the crater does not have an obvious topographic expression (because of the Earth's active weathering and erosional processes), the gravity and magnetic data allow us to "see" through a kilometer of younger sedimentary rocks to image a buried, 200-km wide crater that was excavated by an extraterrestrial body that may have killed off the dinosaurs.
Hildebrand and others, 1991, Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatan Peninsula, Mexico, Geology, v. 19, p. 867-871.
Glen, W., July-August 1990, What killed the dinosaurs?, American Scientist, v. 78, p. 354-70.
Alvarez, W., and Asaro, F., October 1990, An extraterrestrial impact, Scientific American, v. 263, p. 78-84.
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