Geologist interpret Earth’s history by studying sedimentary rocks

Relative Dating

Interpreting Earth’s History

1. Rock record gives evidence of geological event (earthquakes, volcanoes, erosion) and life forms of the past (dinosaurs)

2. Processes we find on Earth today also worked in the past

3. Earth is very old and changes over geologic time

Uniformitarianism

Physical Laws

Chemical Laws

Biological Laws

Steno’s LawsLaw of superposition (each layer is older than the

one above it)

Principle of Original Horizontality (layers of sediment are deposited in a horizontal position

Principle of Cross-Cutting Relationships (a fault cuts through rock or magma intrudes then the fault or intrusion is younger than the rock it cuts through)

Law of Superposition

Principle of Original Horizontality

Principle of Cross-Cutting Relationships