1. Forces In The Earths Crust Crust: the thin outermost layer of the earth. Continental crust is relatively thick and mostly very old. Oceanic crust is relatively thin and is always geologically very young.

2. Forces In The Earths Crust

3. The continents we live on are parts of moving plates. Most of the action takes place where plates meet. Plates may collide, pull apart, or scrape past each other. Forces In The Earths Crust

4. The plates are technically called lithospheric plates. Forces In The Earths Crust

5. Lithospheric Plates: Move very slowly 10-20 cm per year Stress and strain produced by moving plates builds up in the Earth's rocky crust, resulting in tremendous forces. Forces In The Earths Crust

6. Types of Forces: Tension force- a force that tends to pull material apart Compression force- a force that tends to push material together Shear force- a force that tends to make two masses of material slide past each other Forces In The Earths Crust

7. Forces can cause the rocks in the the earths crust to: Fold Fracture (break) Slip along the fracture surfaces Forces In The Earths Crust

8. Fault: a fracture surface along which rock slips Forces In The Earths Crust

9. Basic Types of Faults Normal faults Reverse faults Strike-slip fault Forces In The Earths Crust

10. Normal Fault Formed by tension forces Rock above the fault plane slides down, relative to the rock below the fault plane Forces In The Earths Crust

11. Reverse Fault Formed by compression forces Rock above the fault plane slides upward, relative to the rock below the fault plane Forces In The Earths Crust

12. Strike-Slip Fault Formed by horizontal shear forces Rock on either side of the fault plane slides past each other horizontally Forces In The Earths Crust

13. Hanging Wall & Foot Wall Foot Wall: in this picture, the block farthest to the right (shaped like a foot) Hanging Wall: the block on the other side, resting or hanging on the footwall Forces In The Earths Crust

14. Fault Scarp: The fault has ruptured the Earth surface Fault-generated cliff is called a fault scarp Forces In The Earths Crust

15. Credits United States Geological Survey http://geology.wr.usgs.gov/docs/parks/deform/gfaults.html Earth Comm- 5 Unit Edition Activity #5 Structural Geology and Your Community