The Formation of Fossils
Science: KS3, topic 2.5.10
Fossils
Fossils are the remains or traces of ancient life. Fossils are found in rocks and have been preserved by natural processes. There are 3 different ways of forming fossils:
Hardening soft materials
- The hardening of soft materials can produce casts or impressions, such as footprints.
- For example, clay hardens around an organism that is buried within it. This organism then decays, leaving behind a cast of itself.
Preservation when decay is not possible
- Where decomposers cannot act, preservation is possible.
- Decomposers cannot operate in glaciers (extreme, low temperatures) and peat bogs (extreme acidity).
Mineral replacement
- Hard parts of organisms are gradually replaced by minerals as they decay slowly, creating a rock-like substance.
- When the surrounding sediment turns to rock, the teeth-shaped mineral structure remains distinct (different).
Test yourself on The Formation of Fossils
Why can't decomposers act in peat bogs?
Why can't decomposers act on many glaciers?
Think about it: Why is the fossil record incomplete?
Scientists find a footprint-shaped hollow in solid rock, with no original foot material inside. What process most likely formed this fossil?
A child buries a plastic dinosaur toy in a garden. After one year, it is dug up looking the same as when it was buried. Why would scientists not count this toy as a fossil?