The End of Dinosaurs

The Impact Theory

Who first hypothesized the impact scenario?

In 1980, the American physicist Luis Alvarez (1911–1988) proposed that a large asteroid or comet hit Earth about 65 million years ago. His son, geologist Walter Alvarez (1940–), discovered a high concentration of iridium (an element associated with extraterrestrial impacts) at the Cretaceous-Tertiary (nicknamed “K/T”) boundary in Italy. Because of this find, and the realization that dinosaurs and many other species died out at the end of the Cretaceous, Luis and Walter Alvarez, along with colleagues Frank Asaro and Helen Michel, proposed that the extinctions at the K/T boundary were caused by the impact of a large space object. The iridium anomaly has since been found in over 50 K/T boundary sites around the world.


This is a web preview of the "The Handy Dinosaur Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App