Fossil

1. A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust.

Fossils are formed in a number of ways, but most are formed when a plant or animal dies and is buried in mud and silt. Soft tissues quickly decompose leaving the hard bones or shells behind. Over time the sediment builds up over the top and hardens into rock.

Fossils-What are they? How are they formed?