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How are fossils used in determining the age of the Earth?
Index
Good index fossils have?
wide geographic distribution and short geologic time range
Why might ancient lake and sea beds be rich sources of fossils?
water saves bones Because as the river erodes the soil beneath it and on the banks, the fossils that lie buried there are exposed and wash into the river; then the suspended soil settles onto the fossils in the river bed and covers them again.
What types of stones are most likely to contain fossils?
There are three basic types of rock; sedimentary, igneous and metamorphic. Igneous rocks are formed by volcanic action and don't contain fossils. Sedimentary rocks are formed, usually under water, by eroded material accumulating. Metamorphic rocks are formed when sedimentary rocks are changed by heating and/or pressure. From this, you can see that sedimentary rocks are the most likely to contain fossils, although metamorphic rocks also can contain fossils. Any sedimentary rock can contain fossils, but some make fossil hunting easier. Shales and mudstones are particularly good; chalk is pretty much entirely made of fossils - it's formed of skeletons of small organisms, but its difficult to see the individual fossils.
Why do you only have fossils of a fraction of the things that have existed on Earth?
There are very many reasons why some living things did not fossilise.natural processes will bio-degrade living things after their death.soft tissue does not usually fossilise.pre-historic predators and scavengers may have destroyed or scattered the potential fossil.modern predators or scavengers may have destroyed or scattered the potential fossil.geological changes may have obliterated fossils.
