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Secrets in Stone
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How do we find out about life on Earth long, long ago?
The secret lies in the fossils. These are the remains of the animals and plants that existed in past times and have become preserved in the rocks. Only a tiny fraction of the Earth's living things have become fossils. Even if their remains are buried before they rot, the sediment in which they are buried may be disturbed later and the remains destroyed. Then, if they do become fossils, land movements may destroy the surrounding rocks and the fossils with them. For us to discover them, they must become exposed at the surface. A vast amount of fossil material lies buried so deeply that we will never see it.
(A) ANIMAL DIES
Usually when an animal dies, its body is quickly eaten up by scavengers, or it rots away. The body has to be preserved quickly or it will be lost.
(B) BURIED UNDER SAND
If the animal falls into a river, its body may be covered up by sand before it decays.
(C) FOSSIL FORMATION
After millions of years the sand turns to sandstone, and the bones are replaced by minerals, fossilising them.
(D) FOSSIL FIND
If the sandstone bed is worn away, the fossil skeleton may be exposed at the surface.
(E) RECONSTRUCTION
Once excavated, the fossil bones can be reassembled into a complete skeleton - a reconstruction - and a model or painting of the living animal produced - a restoration.
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Previous:
Back
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Book:
Prehistoric Life
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Section:
Prehistoric
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Chapter:
Secrets in Stone
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