Chapter 7 Plate Tectonics 14 min. Plate Tectonics

Chap 7, Sec 4 (Deforming the Earth’s Crust) Objectives: 1. Review subduction. (yes, again!) Describe the three types of stress (force) that deform rocks. Explain the differences between the three major types of faults.

deformation – the change in the shape of rock in response to stress. New 7.4 Tech Terms: deformation – the change in the shape of rock in response to stress. stress – a force that acts on rock to change its shape or volume. In the example above, the spaghetti deformed in two different ways— by bending and by breaking. The same thing happens in rock layers. Rock layers bend when stress is placed on them. But when enough stress is placed on rocks, they can reach their elastic limit and break.                                    

Rock faults occur when 3 types of stress are applied: shearing –when rock is pushed in opposite directions tension - pulls on the crust, stretching rock so it becomes thinner in the middle compression – squeezes rock until it folds or breaks

3 types of faults: 3. normal fault – tension creates this fault at divergent boundaries, causing rock to pull apart (the footwall slides up and the hanging wall slides down). Occur along the Rio Grande rift valley.

Normal Fault

4. reverse fault – compression creates this fault at convergent boundaries, causing rock to compact (the footwall slides down and the hanging wall slides up). Occurs along the Appalachian Mountains.

Reverse Fault

5. strike-slip fault – shearing creates this fault at transform boundaries, which causes rock to slide past each other in opposite directions. Occurs along the San Andreas Fault in California.

Strike Slip Fault

Let’s Summarize! ( Flip over your Bell-Ringer sheet) Read and do everything but landforms. 208-209 musical review Landforms? 210-212 Mountains: 3 types Let’s label and color for review. Boundaries 20min