Relative vs. Absolute Ages of Fossils

1. Relative vs. Absolute Ages of Fossils

2. Relative Age vs. Absolute Age • Relative age – Age of rock compared to the ages of other rocks • Absolute age – The number of years since the rock formed

3. Law of Superposition • Oldest layer is at the bottom. • As you move higher in layers, the rock becomes younger

4. Clues Igneous Rocks • Extrusion – lava that hardens on the surface • Rock layers below are always older than extrusion • Intrusion – when lava pushes into layers of rocks • The intrusion is always younger than the rock layers around and beneath it

5. Extrusion vs Intrusion

6. Clues from Faults • Fault – a break in the Earth’s crust • The fault is always younger than the rock it cuts through

7. Gaps in Geological Record • Deposition will slowly builds layers upon layer of sedimentary rock • Some layers can erode away, exposing older rock surfaces beneath • This process of deposition and erosion happens again and again over time • Unconformity – a gap in the geological time (where rock layers have been lost because of erosion)

8. Unconformity

9. List the age of each letter in order of oldest to youngest

10. List the age of each letter in order of oldest to youngest

11. List the age of each fossil in order of oldest to youngest