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Three routes to a fossil
Fossils are preserved remains or traces of organisms from the past. They can form in several ways.
Preserved remains: conditions such as freezing or very little oxygen can prevent decay.
Mineral replacement: parts of a buried organism are gradually replaced by minerals.
Traces: footprints, burrows or root marks can be preserved in material that becomes rock.
The sequence here shows burial, mineral replacement and later exposure by erosion.
