Bulletin! Bulletin! Bulletin!
Huge cracks are opening in the earth, and
big rocks are falling out of the sky!
Details at eleven!
Al Sleet (George Carlin)
George Carlin's Hippie-Dippy Weatherman was too late by 65 million years. Dinousaurs never heard the grim details on evening news.
Geologist and paleontologists have long observed that dinosaurs seem to have vanished abruptly from the geologic record of Earth's life. Although some see evidence that dinosaurs faded gradually, most earth scientists have concluded that these "fearful lizards," most other large creatures, and many smaller organisms perished about 65 million years ago in global cataclysm. Marking the end of Cretaceous and Mesozoic time, this mass extinction may be called the Cretaceous Terminal Event.
What killed them? Based partly on analysis of a clay layer found worldwide at the Cretaceous-Tertiary boundary, Walter and Luis Alvarez hypothesized that a large extraterrestrial body -- a comet or asteroid about 10 km (6 miles) in diameter -- struck Earth, directly or indirectly killing most large life. Later researchers interpreted tektites (glass droplets) and stressed quartz in Cretaceous-Tertiary sediments as support for a large impact event. But where? In the early 1990's, geologists exploring for oil in Yucatan found subsurface traces of an impact crater about 100 miles in diameter; drill core samples dated the crater to 65 million years. Named for the Yucatan town of Chicxulub, this crater provides strong direct evidence for the Alvarezes' impact-extinction hypothesis.
Maybe it wasn't so simple. Some paleontologists believe that dinosaurs began to die out long before the end. Others, perhaps reluctant to invoke a special celestial cause, propose that massive volcanic eruptions in India's Deccan Traps may have caused this great extinction. Maybe so, but for now my money's on Chicxulub.
For further information on Chicxulub crater and the Cretaceous extinction, consult: