Meteorite craters are holes in the surface of the earth caused by the impact of lumps of rock which come hurtling through space. The speed and force of the impact leaves a crater. Historically, asteroids, meteors and comets have bombarded our planet and a few of these have had a huge impact on climate, and been responsible for the extinction of huge numbers of plants and animals.

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There is a theory that the dinosaurs were wiped out by some such an impact event and a school of thought which says that the Moon was formed when a huge meteorite hit the earth and a chunk of rock flew off into space.

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Large scale meteor impacts are rare put they have happened historically and are always a possibility. Many science fiction films have been made with the impact of a huge meteor or comet as their central story. Astrogeologists have calculated that during the past six hundred million years the earth has been impacted by sixty objects with a width of five kilometres, or more.

There have been some relatively modern instances of impact events on the earth’s surface too. In 1490 in Shangxi Province, China, a storm in which lumps of rock fell on people was recorded. More that 10,000 people died and scientist attribute this to the break up of a large asteroid.

In Siberia, Russia, in 1908, it is thought that a comet exploded at a height of about 5 kilometres above the surface of the earth and the force from the impact felled a huge number of trees over an area of eight hundred and thirty square miles.

The other planets and moons in our solar system have the same problem but it is only on earth that the collision sites, or astroblemes, become weathered over time and cannot be seen properly. Some craters on the earth’s surface are still under scientific investigation because of this and debate continues as to whether some craters are formed by meteorites, or by long extinct volcanoes.

The Vredefort Ring which was thought to be the world’s largest meteorite crater at 186 miles wide (300 kilometres) was declared by scientists in 1963 to be volcanic in origin, but later recategorized as a giant meteorite crater.

The largest meteorite craters on earth are categorized and measured by the International Union of Geological Sciences Commission on Comparative Planetology.

At number 1 is the Vredefort crater in South Africa, followed by Sudbury, Ontario, Canada with a diameter of 155 miles (250 kilometres). Third is Chiculub, Yucatan, Mexico at 107 miles (170 kilometres).