Fossilisation
There are three type of fossils; Originals, moulds and casts. When an
organism or some of its parts are covered by sediment like sand or mud the
sediments protect and preserve the organic parts. The preserved organic part
is an original fossil. Eventually the sediments harden into sedimentary rock.
Often the organic part rots away thus leaving a cavity in the rock material.
This cavity is called a mould; detailed imprints of a fossil can be seen in the
rock. Sometimes this cavity is filled with material which eventually hardens
into rock. The new material forms a cast of the original organism.
1. The diagrams above show the process of a fish skeleton becoming fossilised.
Put them in correct order from 1-5.
2. Identify what the three necessary conditions are for fossilisation.
3. What covers a dead organism when its becoming a fossil?
4. What covers a dead organism on land?
5. What covers a dead organism in water?
6. What do vultures eat?
7. How long does it take for a fossil to form.
8. How would falling into a swamp of lake help an organisms become a fossil
9. What is another term for decay?
10. What could decay the hard parts of an organism
11. What does the dead organism need protection from?
12. Why is finding a fossil an exciting event?
13. What are examples of soft parts of an organism
14. What other hard parts are there of an organism apart from bones and shell?
15. Why should lack of oxygen prevent decay?
16. Why should low temperatures prevent decay?
17. Apart from dead organism what else could become a fossil?
18. What type of rock contain fossils?
19. What cause erosion?
20. Why would scientists look for fossils in a particular area?
21. Why is it rare the whole skeletons are found?
Fossils Internet Activity.
Use:
abc.net.au/beasts/fossilfun/
1. Play burying bodies. Comment on each of the following areas for their
ability to form good fossils, state why or why not the area is/isn’t good for
fossil formation.
Lava flow:
Base of crumbling cliff:
Ocean Floor:
Open exposed area:
Muddy Estuary: