Natural disasters II: Asteroid.

Asteroids are solid objects which spread all over the Solar System. There are millions of asteroids. Their size varies a lot, from the smaller ones (like small stones) to the bigger ones (kilometres and kilometres of metal, rock and ice)

Asteroids would be a boring matter if they were not dangerous. But they are.The impact of an asteroid in our planet could imply terrifying consequences, depending on its size:

1.- Small asteroids: local destruction (like a bomb)
2.- Medium size asteroids: they can wipe out a city and its surrounding area.
3.- Big asteroids. they can devastate a large region, resulting in global climatic changes.
4.- Very big asteroids: they can destroy our civilization, causing a global disaster.

For this reason astronomers are constantly monitoring the asteroids which are close to Earth, trying to predict trajectories and possible collisions. They have created a scale for grading asteroids thinking in their danger. It is the "Torino scale", where asteroids are classifyied from 0 to 10, being 0 no risk and 10 global destruction.