A giant meteorite struck the Earth
65 million years ago, wreaking global devastation. Over a
very brief period, an estimated 70 percent of all species
died out. While the explosion itself was enormous, the biologic
disaster probably resulted from a cascading sequence of events:
wildfires, decreased sunlight, acid rain, and, eventually,
mass starvation. The extinction of so many species, which
marks the boundary between the Cretaceous and Tertiary geologic
periods, changed the course of evolution.
The lowest density rocks (indicated in blue), which fill
the center of the crater, are made of materials that were
frag-mented and melted by the impact.