The word fossil comes from the Latin and means 'to dig'. Fossils give scientists important clues about the age of the earth. They act as signposts which reveal how and when the rock they are buried in were formed . Tracing the history of rock formations can be a complex process because the burial, folding, faulting and erosion of the earth's crust often produces a complex jumble of different types and ages of formations.
Fossils are therefore very useful scientific tools for dating beds of rock.
The flesh and other soft parts usually decay quickly and are rarely found as fossils. To form a fossil, the organism must be buried in a protective coating such as mud, sand or silt to prevent the hard parts from being destroyed by scavengers and weather. Aquatic plants and animals, especially marine ones, have the best chance of fossilisation. Land living plants and animals have very little chance of being preserved unless they are washed into lakes, swamps, rivers or peat bogs because the land surface usually erodes away over time. A single organism can be preserved as a variety of fossil types depending on the different types of sediments in which it is buried.