Transcript Earthquakes
Too Much Stress in your Life?!?! • Earthquake- is the shaking and trembling that results from the movement of rock beneath Earth’s surface. The movements of Earth’s plates creates powerful forces that squeeze or pull the rock in the crust. • Stress- a force that acts on rock to change its shape or volume. – The forces that cause Earthquakes. – Energy is stored in the rock until the rock either breaks or changes shape. Too Much Stress in your Life?!?! • 3 kinds of stress in the crust – Shearing – Tension – Compression • These forces cause the rocks to become brittle and snap or to bend slowly. Kinds of Stress • Shearing – Stress that pushes a mass of rock in two opposite directions. – Causes rock to break and slip apart or change its shape. • Tension – Pull on the crust, stretching rock so that it becomes thinner in the middle. • Compression – Squeezes rock until it folds or breaks. Deformation • Any change in the volume or shape of Earth’s crust. • Most changes occur so slowly that you cannot observe them directly. Kinds of Faults • Fault- a break in the Earth’s crust where slabs of crust slip past each other. – This happens when enough stress has built up. – Does not have to be at a plate boundary, but many are • 1) Strike-Slip Faults • 2) Normal Faults • 3) Reverse Faults • Rocks on either side of the fault slip past each other sideways with little up or down motion. • http://www.pbs.org/wnet/savageearth/animat ions/fault-strikeslip.html Normal Faults • One block lies below the fault and the other lies above the fault. http://www.pbs.org/wnet/savageearth/animations/fault-normal.html Reverse Fault • Same idea as a normal fault but the blocks move in the opposite direction. Mountain Building • Formed from faults: – When normal faults uplift a block of rock. • Formed by folding: – Bends in rock that form when compression shortens and thickens part of Earth’s crust. • Like when you skid on a rug and it gets wrinkled. – Himalayas are an example. Plateaus • A plateau is a large area of flat land elevated high above sea level. • Some plateaus form when vertical faults push up a large, flat block of rock.