This is a featured article. Click here for more information. Mitchell collision estimating guide pdf an impact can release the equivalent energy of several million nuclear weapons detonating simultaneously.
Pg boundary clay represented debris from an asteroid impact. Pg extinction was caused by the asteroid. Yet the devastation caused by the extinction also provided evolutionary opportunities. The turnover in this group is clearly marked at the species level. Recent studies indicate that there were no major shifts in dinoflagellates through the boundary layer.
It does not represent all marine species, just those that are readily fossilized. Pg extinction event was severe, global, rapid, and selective. In terms of severity, the event eliminated a vast number of species. The event appears to have affected all continents at the same time. Cenozoic anywhere in the world.
Similarly, fossil pollen shows devastation of the plant communities in areas as far apart as New Mexico, Alaska, China, and New Zealand. This plant extinction caused a major reshuffling of the dominant plant groups. Similar, but more complex patterns have been found in the oceans. Modern crocodilians can live as scavengers, can survive for months without food, and their young are small, grow slowly, and feed largely on invertebrates and dead organisms or fragments of organisms for their first few years. These characteristics have been linked to crocodilian survival at the end of the Cretaceous.