NATS 1540 Study Guide - Asteroid Family, Shocked Quartz, Global Cooling
Document Summary
Animal fossils only extend through the last 550 million years of the earth"s 4. 6 billion year history. 6 mass extinctions during the period of the past 600 million years. End cretaceous (impact of an extraterrestrial object) End-cretaceous extinction (65 million years ago) a large asteroid hit the yu- catan peninsula of mexico and wiped out the dinosaurs. In the late cretaceous dinosaurs dominated the land and diversified. Mammals only diversified and became dominant after the extinction of di- nosaurs. The extinction eliminated about 47% of marine life and 79% of plant life. Louis and walter alvarez linked the end-cretaceous mass extinction to an ex- traterrestrial impact, but they were criticized but most people had only thought about a slow and gradual extinction. The alvarez impact hypothesis was the discovery of high amounts of iridium at the kt boundaries around the world.
