Forces in Earth’s Crust

Stress A force that acts on an area of rock to change its shape or volume.

There are 3 types of stress Tension stretches rocks Compression pushes rock together Shearing pushes the rock in two opposite directions

Questions What type of landforms results from tension? What type of landform results from compression?

Faults When enough stress builds up in rock, the rock breaks, creating a fault. Most faults occur along plate boundaries

There are 3 kinds of faults Normal Faults - Tension in crust pulls rock apart. Reverse Faults - Compression pushes rock together Strike-Slip Faults – Shearing causes rocks to slip past each other

Mrs. Brown’s Fault Movie http://youtu.be/hfir5KQpu6c

Hanging Wall – The block of rock that is above the fault plane Footwall – The block of rock that is below the fault plane.

In a normal fault, the hanging wall slips down relative to the footwall

In a reverse fault, the hanging wall moves up relative to the footwall

San Andreas fault is a strike-slip fault with little up or down motion

The forces of plate movement can change a flat plain into anticlines, synclines, folded mountains, fault-block mountains, and plateau.

Fault Block Mountain When two normal faults cut through a block of rock, a fault block mountain forms.

Q: Where in California are there fault-block mountains? A: The Sierra Nevada and Mojave Desert regions.

Plateau A large area of flat land elevated high above sea level without much folding or faulting.