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Global catastrophe

Part of Arthur Ross Hall of Meteorites.

D.2.4.2. Global catastrophe

Exhibition Text

FREQUENCY: 100 MILLION OR MORE YEARS

Asteroids large enough to cause widespread extinctions collide with Earth very rarely. These asteroids measure more than 10 kilometers (six miles) across. Because they're so large, astronomers think they've spotted all of the ones that could cross Earth's orbit during the next two centuries.

All of Earth's most devastating impacts happened many millions or even billions of years ago. Researchers have found about a dozen of the colossal craters that resulted-one impact 35 million years ago gouged open the mouth of Maryland's Chesapeake Bay. But the best-known impact happened 65 million years ago.

Did an impact do in the dinosaurs?

A thin layer of grayish clay marks the geologic boundary between the period wh