For example, dinosaur tracks, trails and dung are all trace fossils. A body fossil is usually composed of the bones of an animal. Most body fossils are made when an animal dies and falls, or is washed into a stream, and is covered with mud. Sometime a fossil is the result of a volcanic eruption. Ash and mud from the volcano can cover animals and plants killing and preserving them at the same time.
Fossils come in all sizes.
The study of fossils is called Paleontology . The study of fossil plants is Paleobotany . Fossils exist all over the world. As hills erode, fossils become visible and a Paleontologist can find and remove them for study. Sometimes a small area only a few hundred feet across will be jammed with skeletal remains.