(professor)

Today, we're going to be talking about fossils. A basic definition of fossils is that they are the remains of plants and animals that have turned to stone, and today we're going to be talking about how animals become fossils.
The process begins when a living being dies. After an animal dies, its soft tissues break down. When the soft tissues have decomposed, only the hard parts of the body, such as the bones and teeth, remain.
Over a long period of time, um, the hard tissue becomes buried under layers of sediment. As more layers of sediment cover the hard tissue, it becomes buried more and more deeply.
When the bones are buried deep in the earth, they come into contact with groundwater, and a change begins to occur. Minerals from the groundwater seep into the bones and, over long periods of time, the minerals eventually replace the bones. This is the actual step when fossilization occurs, when minerals from the groundwater have replaced the actual hard tissue from the original body.
The buried fossilized remains, which are buried deep within the earth, may then make their way back to the surface. As the earth moves, the remains are pushed around ... if they get closer to the surface, where they can be seen, or get near enough to the surface, where they can be dug out.