Wednesday, November 21, 2007

Fossils within fossils
Sometimes, a fossil animal is found with another fossil animal inside it. The larger animal may have been pregnant with young at the time it died, in which case the animal inside is an unborn baby animal. In other cases, the animal inside was eaten by the larger animal just before the larger animal died, and become fossilised with it.

Do dead animal always turn into fossils?
When animal die, the bone are usually chewed by other, scavenging animals, scattered by the rain and wind, or bleached broken down to dust by the Sun. For this reason, the bones of most animals that have ever lived, nomore than one in a million has survived as a fossil. Fossil form only when a dead animal is buried quickly by sediments, before there is a chance for the bones to be destroyed. When this happen, the bones are locked up in the sediment as it slowly turns to rock. The bones themselves also turn to rock in the process, but they keep their shape. Millions of years later, erosion strips away the layer of rock and exposes the fossil.

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