Relative Age of Rocks

1
Relative Age of Rocks

• Chapter 9
• Section 2
• Pgs. 250 - 255

2
Principle of Superposition

• Oldest rocks on the bottom and become younger
  going towards the top
• Sediments form horizontal beds and creates layers
• Formation of mountains can cause layers to go
  upside down

3
Relative Age

• Something is its age in comparison to the ages of
  other things
• Determine age by examining their places in a
  sequence
• Fossils can also help determine age of rocks

4
Unconformities

• Incomplete rock layers missing or gaps in rock
  sequence
• Angular layers are tilted upward by forces,
  erosion occurs, new layers formed on top
• Disconformity gap in layers or when no new
  deposits form a new layer
• Nonconformity metamorphic or igneous rocks are
  uplifted and eroded

5
Questions

• What is the Principle of Superposition?
• When a mountain forms what happens to the rock
  layer?
• What is relative age?
• How do scientists determine the age of rocks?
• What are the three types of unconformities?