Fossils are the remains of animals and plants or the traces of their activity, preserved in rocks. A fossil may equally well be an enormous dinosaur skeleton and a tiny organism visible with a microscope. Most of fossils are hard parts of the ancient animals and plants, such as shells, bones, teeth and wood. Pierwotne substances, making up these parts, might be preserved in an unchanged composition or replaced by various minerals. Eggs, hindlegs and forelegs prints, as well as burrows of animals, may also undergo fossilization.

Fossils provide a lot of valuable information on the state of animal and plant life in the past, are a source of knowledge on the environment and the climate in the past periods. Many groups of fossils is the basis of dating of sedimental rocks, and, consequently, the basis of the geological time division. Upon the basis of fossils of the same group of organisms from different periods, it is possible to follow their development and changes over time; thus, fossils also provide evidence for the natural evolution of organisms.

How are fossils formed?

The process of transformation of a living organism into a fossil, called fossilization, may be millions years long. Right after the death of an organism, its decomposition begins. mussels, bones and teeth of animals and plants are more durable than soft parts, but they are often moved by animals, wind of flowing water.

The condition of forming a fossil is rapid covering the remains (most frequently in the sediments, brought by water), before they are utterly destroyed. Some fossils dissolve after some time, other change their chemical characteristics or they are deformed by high temperature and pressure. Only a few manages to undergo the whole process successfully, and thatˊs why they are so rare and precious.