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2.1 outline the conditions under which fossils may form
outline the conditions under which fossils may form
- For fossilisation to occur a dead organism has to be preserved and protected in some way. Examples of this type of protection would be if the organism is quickly covered by sediment, becomes trapped in amber or preserved in ice. The richest fossil beds are found in caves, in ancient lakes and the edge of the sea, in rivers and in volcanically active areas.
- Caves are found in limestone, sandstone and as lava tubes in volcanic rocks. Many organisms, including early humans and the predators of early humans, would go into a cave to eat their kill in relative safety. The bones are discarded and become fossilised by coatings of sediments. The caves at Sterkfontein are an example of a rich fossil bed containing the remains of early humans.
- Lakes and seas. Fine sediments produce fossils showing greater detail. These sediments need still conditions to be deposited. These still conditions are found in lakes and large seas. An example of this type of deposit containing the skeletons of early humans is found at Koobi Fora.
- Volcanic deposits. Most volcanic eruptions are violent events but in some instances volcanic ash is thrown up into the air by a volcano. This ash may cover and preserve fossils. A famous example of this is in Laetoli where fossilised hominid footprints have been discovered.
Fossilisation
Science and Nature, BBC.
Becoming a Fossil
(Video Resource) See Leaving a Trail of Evidence, Unit 3 Web Resources: What Is the Evidence for Evolution? PBS, Virginia, USA.