Folding and Faulting


Diastrophic processes - folding and faulting occur when pressure deep within the lithosphere cause the earth=s surface to buckle, bend and even split apart.


Folding - when the earth=s crust is pushed up from its sides

 - occurs at a very slow rate

 - Fold mountains occur where the crust is pushed up as plates collide which causes the crust to rise up in folds.

Examples: Andes, Himalayas, Juras in Switzerland, Appalachians


Types of Folds      1. Anticline- the peak or hill of folded rock layers

2. Syncline - the trough or valley of folded rock layers

3. Tight fold - a sharp-peaked anticline fold

4. Overfold - bending or warping of folding rock layers

5. Recumbent fold - a fold that is bent so much that it is no longer vertical.

6. Nappe - a fold that has overturned so much the rock layers have fractured.

Faulting - when tension and compression associated with plate movement is so great that      blocks of rock fracture or break apart.

- process can occur very rapidly

- this rapid movement causes the ground to shake and vibrate, resulting in      earthquakes.


Types of Faults    1. Normal - rocks move away from each other due to land moving apart.

2. Rift valley/graben -two normal faults occur parallel to each other and the land sinks between the two faults

3. Reverse Fault - opposite of normal; rocks are compressed such that one plate moves up while the other decends below it

4. Horst - land rises between parallel faults.

5. Tear fault/strike-slip - two plates slide laterally past each other.