Relative- Age Dating

A. Relative-Age Dating 1. when you give the age of a rock or fossil compared to another rock or fossil. Example: Rock A is OLDER than Rock B. An actual age in years is not determined.

B. Law of Superposition 1. When sedimentary rock layers are deposited, younger layers are on top of older deposits.

C. Law of Original Horizontality: 1. Sedimentary rock layers are deposited horizontally. If they are tilted, folded, or broken, it happened later.

D .Lateral Continuity 1. sediments are deposited in large continuous sheets 2. a river might cut through, but the order of the layers does not change

E .Law of Cross-Cutting Relationships: 1. If an igneous intrusion or a fault cuts through existing rocks, the intrusion/fault is YOUNGER than the rock it cuts through

F. Correlation 1. Rock layers in different places and be correlated or matched up by matching up the rocks and fossils in the layers.

G. Unconformity 1. When rock has been eroded, so you have a missing section of time in the rock record.

H. Index Fossils 1. Represent species that existed on Earth for a short time, were abundant, and inhabited many locations. Trilobite: Index fossil for the Paleozoic Era Age: 590-250 mya

You will draw and label each one You will draw and label each one. You will include a definition for each one. 1 2 3 4 5. INCLUSION 6. Relative Dating Definition: Relative Dating Definition: