Fossil

A fossil is the remains of an animal or plant that has been preserved in rock.When an animal died millions of years ago,its soft part rotted away quickly,but the bones and shell were scattered by scavenging animals.Some of the bone and shell were buried in mud and sand.Over the years,more and more mud piled on top,burying these remains deeply,and exerting tremendous pressure on them.Because of this pressure,the mud became rock,and the shape and structure of bones and shells became fossil.
sometimes,an entire animal was preserved. Sometimes,a fossil is just a film of carbon left by a decaying plant.Insects and other small animals,which were tapped in stick sap became fossil.Fossils were also formed when volcanoes erupted,covering vast area in red hot lava.The lava cooled and solidified into rock,preserving the animals and plants within.

Trace fossil

Footprint made by animals and humans and trails made by creature,that have been preserved in hardened mud are trace fossils.Other forms of trace fossils include eggs and droppings that have been preserved over millions of years.