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.