Faults & Stress Write everything in BLUE! Earthquakes Faults & Stress Write everything in BLUE!

What are Earthquakes? The shaking or trembling caused by the sudden release of energy beneath Earth’s surface. Usually associated with faulting or breaking of rocks Continuing adjustment of position results in what is known as aftershocks

What is stress? The force that acts on rock to change its shape 3 Types of stress Shearing Tension Compression

Shearing: stress that pushes rock in opposite directions Shearing: stress that pushes rock in opposite directions. Causes masses of rock to slip past each other.

Tension Stress that stretches rock so it becomes thin in the middle. Causes valleys

Compression Stress that squeezes rock until it folds or breaks. Causes hills

Questions What is the relationship between compression and a convergent boundary?

Questions What is the relationship between compression and a convergent boundary? Both compression and convergent boundary squeezes rocks together to form mountains or hills.

How is energy stored in Rocks? Rocks are put under stress so they become deformed or bend. Once the strength of the rock is exceeded rupture occurs and the rocks quickly rebound to an undeformed shape Energy is released in waves that radiate outward from the fault

A break in the Earth’s crust is called a Fault 3 types of faults

Strike-Slip Fault There is little up or down motion A strike-slip fault that forms the boundary between two plates is called a transform boundary. Shearing stress causes strike-slip faults

Strike-Slip Fault Example

Normal Fault The hanging wall slips downward below the footwall. The Normal Fault that forms the boundary between two plates is called a divergent boundary.

Normal Fault Example: Rio Grande Rift Valley

Reverse Fault The hanging wall slides up and over the footwall. The reverse fault that forms the boundary between two plates is called a convergent boundary.

Reverse Fault Example: Appalachian Mountains (East Coast)

Questions Explain the difference between a normal and reverse fault

Questions Explain the difference between a normal and reverse fault A reverse fault is formed at a convergent boundary and creates mountains. A normal fault is formed with divergent boundaries and forms valleys

Worst Earthquakes in the US New Madrid fault on the Mississippi River in 1811 8.1 Magnitude Epicenter in northern Arkansas 35% chance of another major earthquake in the next 50 years

New Madrid, MO