Mass extinctions are geologically rare and globally widespread.
You will be investigating possible causes for mass extinctions at the beginning and the end of the Mesozoic. Chicxulub Impact Crater Provides Clues to Earth's History by Virgil L. Sharpton from the Lunar and Planetary Institute, Houston, Texas that discusses how an extraterrestrial impact 65 million years ago changed the course of life on Earth. The crater it carved in the Earth's surface could now help scientists study past global change. The following pages discuss the pros and cons of impact crater theories. Speculated causes of the K-T boundary mass extinction.