Fossils help paleontologists understand the history of life on Earth. Paleontologists are biologists that study life that existed in previous geologic time periods, according to Enchanted Learning. Many organisms found in fossilized form, such as dinosaurs, are now extinct. Fossils are the only evidence we have that these life forms existed. Parents and teachers can teach kids fossil facts to show them how life on our planet has changed over time.
Of the millions of plants and animals that have existed on this planet, very few become fossils. Fossils are at least 10,000 years old, and may be as old as 500,000,000 years old. Except in rare cases where a plant or animal remains in an unaltered state of preservation, most fossils are heavy, stone-like copies of organisms that lived long ago, according to Enchanted Learning.
There are two types of fossils, according to Fossils-Facts-and-Finds.com. The first type includes the actual remains of a dead animal or plant that lived long ago or the impressions that the plant or animal left behind. The second type of fossil is called a trace fossil. An example of a trace fossil is a footprint that an animal left behind.
According to Fossils for Kids, fossils form when the organic material that made up the dead plant or animal is replaced with minerals. Fossils may be formed when the cell walls in an organism dissolve and are replaced with minerals, when the cell spaces are filled with minerals, or when the organic material becomes encased in mud and when plants and animals are trapped in the permafrost. These processes are known respectively as replacement, permineralization, internment and refrigeration, says Fossils for Kids. Fossils may also be formed when a plant or animal becomes trapped in asphalt, amber or through desiccation.
Fossils can be found in a variety of locations all over Earth. For example, says Fossils for Kids, fossils are found in deserts, mountaintops and underwater. Fossils are often found in sedimentary rock. Sedimentary rock is formed when layers of sediment made up of sand, rock and mud are compressed over a long period of time, says Enchanted Learning.