Earth Was Longtime Asteroid Punching Bag

Date: 2015-10-07; view: 438.

Dozens of asteroid impacts at least as bad as the dinosaur killer occurred long after such impacts were previously thought to have petered out (disappeared).

An asteroid ______________ is widely blamed for killing off the dinosaurs 65 million years ago. An asteroid 10 kilometers wide struck the Yucatan _______________ and left a giant crater. It also tossed up enough _______________ to catastrophically darken the sky and cool the Earth.

Now a study in the journal Nature indicates that such impacts _________ __________ __________ commonplace in Earth's history. As many as 70 asteroid impacts at least as severe as the one that did in the dinosaurs rocked the planet long after such impacts were thought to have petered out.

The _____________ is a hypothesized collection of asteroids called the E belt, only a small ________________ of which survives today. The E belt was closer to Earth than the main asteroid belt is now, and it was _______________ by the giant planets as they settled into their current orbits.

It had been thought that Earth's heavy ________________ by asteroids and comets died down about 3.7 billion years ago. But E belt asteroids would have rained down frequently for another two billion years after that, with the occasional dino killer coming in even later on. All those impacts would have had _______________ effects on life. Somehow, it all worked out for us—if not for the _________________.

—John Matson

Explain the meaning of the following words and phrases; use the script to provide the context:

to punch

impact

to be blamed for

peninsula

to toss up debris

be commonplace

severe

culprit

a remnant of

to be disrupted

bombardment

dino killer

Grammar Practice (2)