There are not nearly enough craters on Earth for the large number of asteroids that impact us every year. Over the past 250 million years, Earth should have been hit around 440 times by asteroids larger than a mile across. But scientists have found only 38 large impact craters from this period. Scientists now think that when many of them hit the Earth, they keep right on going and punch through the Earth's crust, triggering huge volcanic eruptions.
Dallas Abbott and Ann Isley studied the timing of these 38 impacts and found they line up with volcanic eruptions during the same period. Most volcanoes come from small amounts of the Earth's upper mantle boiling over, but these mantle-plume volcanoes happen when hot rock from deep within the Earth's mantle shoots straight up through the Earth's crust.
Adrian Jones and David Price used computer simulations to prove this theory. Their models suggest meteorites bigger than about 6 miles across can sometimes punch right through the Earth's crust, causing huge volcanic eruptions. "A large impact has the ability to cause instant melting where it hits, creating its own impact plume in the mantle and resulting in a massive surge of lava spilling out," Jones says.
The 6 mile-wide asteroid that hit Mexico 65 million years ago is blamed for wiping out the dinosaurs. But it could have been a much bigger asteroid that hit India and triggered huge volcanic activity.
"Many areas that exhibit extensive volcanism from the past?may in fact be sites of gigantic meteorite impacts," says Jones. The dinosaurs might have survived a meteorite impact alone, but the double jeopardy of a meteorite plus volcanoes was too much for them.
We'd have many more asteroid impacts (and volcanoes) if it wasn?t for the moon, which absorbs many of the blows. In 1956, amateur astronomer Leon H. Stuart said he had observed and photographed a flash a few years earlier on the moon, which could have been an asteroid impact. Bonnie Buratti and Lane Johnson have found a mile-wide crater at the location of the flash, from images taken by the Clementine spacecraft as it orbited the moon in 1994.
We should be thankful the moon is there to protect us?or we could have gone the direction of the dinosaurs. Did Nostradamus predict a major asteroid impact in the future? Read Nostradamus 2003-2025: A History of the Future and find out.
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