Fossils are the remains of animals and plants from many centuries ago, when
animals and plants die, and soil and rocks from on top of them, some of the
animal carcasses many leave an indentation on one of the rocks, due to
the pressure build up over the years.
Fossils can form on rocks in one of three ways:
1 – When an animal dies the carcass which consists of bones, teeth, shells
etc, which don’t decay and they are eventually replaced by minerals which
eventually form a rock like substance. The surrounding areas will also turn
to rock, however the fossil will form a distinct shape within the rock.
2 – Sometimes fossils are formed when plants and animals are buried in soft
substances such as clay which will then form a cast around the organism
and therefore preserving the shape.
3 – Sometimes fossils are formed when the whole animal or plant is preserved
due to the environmental conditions, such as the lack of oxygen in tar pits, or
due to the temperature, for example in extreme cold where the animal may
get frozen in ice.