Presentation on theme: "Earth’s Story 6.1 & 6.2. 1788 James Hutton Theory of the Earth Uniformitarianism."— Presentation transcript:
Earth’s Story 6.1 & 6.2
1788 James Hutton Theory of the Earth Uniformitarianism
Present is the key to the past
Main concepts of uniformitarianism: Geologic processes we see now were active in the past. The physical, chemical & biological laws that operate today have operated throughout Earth’s history. (Earth Science, Tarbuck…) Earth’s physical features were formed by these same processes over long periods of time.
1830s Charles Lyell Reintroduced uniformitarianism Now widely accepted by scientists
Catastrophes Occasionally occur Example: 65 mya asteroid hit Earth Dinosaur extinction
Homework Read pages
Paleontology Study of past life paleobotanists
6.2 Relative Dating: Which Came First?
Law of Superposition Younger rocks lie above older rocks ce/terc/content/investigations/es2903/es2903 page03.cfm ce/terc/content/investigations/es2903/es2903 page03.cfm
Principle of Original Horizontality Sediments are deposited horizontally. So…if we see beds of sedimentary rock that are folded or tilted, they were deformed after deposition. ce/terc/content/investigations/es2903/es2903 page04.cfm ce/terc/content/investigations/es2903/es2903 page04.cfm
Law of Cross-cutting Relationships An igneous intrusion is younger than the layers which it cuts. ce/terc/content/investigations/es2903/es2903 page08.cfm ce/terc/content/investigations/es2903/es2903 page08.cfm
Law of Cross-cutting relationships If a fault or intrusive rock cuts through other rocks, then it is younger.
Law of lava flows A lava flow is younger than the layers which it covers.
What Can Cause Disturbances? Folding Faulting Intrusion Erosion
Inclusions When one rock has pieces of another included in it The rock containing the inclusions is younger.
What Do We See? Unconformity Break in geologic record Erosion Lack of deposition Can represent long or short time period