Fossils are often said to take a million years to form. However, as of 2014 it has been proven that a fossil can take a shorter period of time to form. This period can be a thousand years or less. The earliest fossil discovered dates back to about 3.5 billion years; however, there are fossils that have been discovered to be only a few years old.
Fossils are the preserved marks or remains of plants or animals that lived in the geologic past. They are formed through a naturally occurring process known as fossilization. Fossils form from animal tracks or bones embedded on the earth’s crust. Fossils can be found on land and beneath water bodies, such as lakes and rivers.
There are different types of fossils, including mold fossils and cast fossils. However, the two main types are trace fossils and body fossils. Trace fossils consist of marks left behind by an organism, such as teeth marks or footprints, while it was alive. Body fossils consist of parts of an organism, such as bones, teeth or claws.
The fossilization process varies according to external conditions and tissue type. The various types of fossilization processes include permineralization, bioimmuration, adpression, replacement and recrystallization, cast and molds.