Why hasn't the Earth been hit by anything devastating like an asteroid?

Question

So many planets have craters and everything and nothing that harmful has ever hit the Earth. Why is this?

Answer 1

your wrong.....earth every day is hit with thousands of asteroids, but the OZONE destroys the rocks b4 they impact the soil.....the moon has no ozone so they hit the ground without anything stopping it.

Answer 2

The answer lies in geology! Most of these answers are half right. Our atmosphere protects us from most small impacts, since the friction causes small meteors to burn up. This is in fact what "shooting stars" are.

There are a few large impact craters on the Earth, usually in older rocks such as found in Australia and Africa. So why aren't there more?

Most craters in the solar system are very old. When the solar system was young, there was a lot more material flying around and crashing into things. Most of the surface of the Earth is not that old. Earth undergoes a process known as "Plate Tectonics". The crust of the Earth can be likened to plates of solid rock floating on a liquid interior (it is more complicated than that, but a simple explanation is best). Over millions of years, these plates are pushed against each other and the crust is forced into the hot center and destroyed. At the same time, new crust is being made as upwelling magma reaches the surface and cools. Thus most of the rocks that make up the Earth's crust are a lot younger than the solar system. Most of the old impact craters have therefore been destroyed.

Only half of Mars is covered with craters, and it is theorised that the other half underwent plate tectonics at some point in its history.

I hope that helps!

Answer 3

I cannot really improve on Groverraj's answer, but I would like to correct a few of the other answers. Crater Lake is a volcanic crater, not an impact crater.

Berringer Crater in Arizona impacted very recently--a mere 50,000 years ago. It is not a big crater, only a mile across or so. Chicxulub (the Gulf of Mexico impact) that likely polished off the dinosaurs struck a thousand times as long ago--about 65 million years ago.

There have been numerous really big impacts on the earth. Erosion tends to obliterate traces of these. Subduction and orogeny (sea floor spreading subducted beneath plate margins and mountain building) and also continuous faults tend to wreak havoc on crater outlines as well.

Earth's atmosphere protects against small debris, but not really against anything large enough to make a crater visible from the moon (as the moon's craters are visible from earth). The moon lacks weathering and is not geologically active. The only thing to erase lunar craters is more cratering.

Answer 4

It has been, but it has been a while since anything really big hit -- about 65 million years. The planet got nailed but good just north of Yucatan, and by means not entirely understood wiped out the dinosaurs. Craters on the earth tend to disappear due to weathering, but the moon has no weather so it still has every crater that it has gotten since the day it was made.

Answer 5

"An Earth impact on April 13, 2029 can now be ruled out," wrote Don Yeomans, Steve Chesley, and Paul Chodas (NASA/Jet Propulsion Laboratory) in a statement issued Monday afternoon. The asteroid, which has an orbital period of 323 days, might strike Earth sometime in the distant future, but our home planet is safe for a long time to come — at least from this object.

Answer 6

Recently, we haven't but in geologic time we definitely have. Ever hear of the asteroid that killed the dinosaurs? Or Crater Lake?

The reason you don't see craters and such on Earth is because we have weather! Rain and wind erode the rocks. Also tectonic plate movements disrupt the craters. Lakes and glaciers also form in craters.

Answer 7

Meteoroids hit every day, but most are burnt up or so small by the time they get through the atmoshere that we wouldn't really notice or pass it of as bird crap or something. This may rock your world though. It has been confirmed that the Andromida Galaxy is on a collision course with the Milky Way Galaxy. No one knows when it will reach us, could be a hundred years or a hundred million, but it will happen and that will change life as we know it, big time.

Answer 8

It has .. all over. In Arizona, Gulf of Mexico and Siberia! Difference is that Earth has rain and water which transforms and fills these craters.

Answer 9

It happened here too. It was just a very long time ago. The Gulf of Mexico is one big crater. Our atmospere burns up most of the small meteors and we have air and water erosion to make the craters less recognizable.

Answer 10

The Earth is a fast healer, that's why traces of its wounds aren't so visible, they there are though.

I mean the big wound at the North Pole surely have healed, but you can still see traces of it.

Answer 11

I think an earth-shattering asteriod may be imminent, this is why I'm living each day to the absolute fullest.