Fossils Clues to Earths Past What is a

Fossils: Clues to Earth’s Past

What is a Fossil? A fossil is any naturally preserved evidence of life. Fossils come in many sizes and shapes. Some fossils are the remains of the entire organism. Other fossils provide a glimpse of only part of the original life form.

How Do Fossils Form? A fossil takes a long time to form. Most fossils form in the following sequence of steps. 1. After an organism dies, scavengers and bacteria eat away the soft parts of the dead animal or plant. 2. Fine particles of sediment – mud sand, or dust – cover the remains. This protects the bones and other hard parts from decaying any more.

3. More layers of sediment settle on the previous layers. The newer layers press down on the lower layers, eventually turning the layers into sedimentary rock. The hard body parts change into fossils in these layers 4. Over millions of years, Earth’s crust shifts, changing the location of the layers and the fossils they contain. Geologic forces such as mountain building push the fossil close to Earth’s surface. Rain and wind may remove the top part of the rock, exposing the fossil.

What Are Some Typical Fossils? There are many different kinds of fossils. Here are pictures of just some of them. coral gastropod fish trilobite brachiopod insect in amber crinoid stem lepidodendron