Stratigraphy, Fossils and Geologic Time Evidence of Change Stratigraphy, Fossils and Geologic Time

Stratigraphy Study of rock layers Principle of Original Horizontality – As the earth ages, layers of sediments are deposited horizontal to the earths surface due to gravity

Stratigraphy Principle of Superposition- The bottom layers were deposited first, making them older than the top layers

Fossils A fossil is the remains (bones) or impressions of ancient organisms

Fossil Facts 1. Fossils are not bones… all of the materials that made the bones have been replaced with other minerals 2. Fossils represent the remains of once living organisms 3. Most fossils are the remains of extinct species 4. Marine organisms are more likely to become fossilized than land animals due to environmental conditions needed to form a fossil