Presentation on theme: "How to tell how old the layers of rock are."— Presentation transcript:
1 How to tell how old the layers of rock are. Dating Rock LayersHow to tell how old the layers of rock are.
2 What is Age? There are 2 kinds: Absolute Age – The number of years since the rock formed. (150 million years old, 10 thousand years old.)Relative Age – The age compared to the ages of other rocks. (older than this rock, younger than that rock.)
3 Age cont.Relative Age – Much easier to figure out. Can be deduced from clues on the Earth.Absolute Age – Much harder to figure out. Often impossible.
4 What are the ways to tell RELATIVE AGE. 1. Law of Superposition2. Extrusion & Intrusion3. Faults4. Unconformities
5 What is the Law of Superposition? In horizontal sedimentary rock layers, the oldest layer is at the bottom. Each higher layer is younger than the layers below it.
18 Summary Relative vs. Absolute Age Determining Relative Age: Law of Superposition – on top is youngerIntrusions – magma inside Earth.Extrusions – magma on top of Earth.Faults – breaks in the crustUnconformities – signs of erosion.