Figuring Out Fossils Geologic Timescale The Geologic Time

Figuring Out Fossils

Geologic Timescale • The Geologic Time Scale divides the history of Earth into a series of time periods. • Scientists determine the ending of one period and the beginning of another by the presence or absence of certain fossils. • Review the Geologic Time Scale.

What is A Fossil? • A fossil is the mineralized remains of any organism that was once living. • Organisms with hard bodies, like shells or bones are more likely to be fossilized that organisms with soft bodies. • Aquatic organisms are also much more likely to become fossilized than land animals.

How do Fossils Form? • A living thing dies. • Its remains are buried under heavy dirt/rock. • The remains become replaced by minerals like calcium. • The fossil is uplifted and exposed.

The 5 Types of Fossils IMPRINT 1. 2. 3. 4. 5. Imprint – An impression left in rock. Mold – A hollow space left when an organism is buried and decomposes. Cast – Empty mold is filled in with different type of material. Petrified – The hard parts are replaced by minerals (shell turns to rock). Preserved Intact – Decay of the body is prevented and the organism’s body remains intact. MOLD CAST PETRIFIED INTACT

• Goniobasis • Alethopteris • Knightia • Tabulopyllum • Admetopsis • Mucrospirifer • Ammonite • Elrathi