What exactly is an earthquake?

2. What exactly is an earthquake?

3. An earthquake is the shaking and trembling that results from the movement of rock beneath the Earth’s surface. • If friction between two blocks of rock is low, the rocks slide constantly without sticking. • If the friction is high, the blocks lock together. • When the amount of stress is greater than the amount of friction, the blocks unlock suddenly, setting off an earthquake! • The average length of an earthquake is from 30 to 60 seconds.

4. What is this stress that causes Earthquakes?(Can rocks get stressed out?) • Stress is the force that acts on rock to change its shape or volume. • Stress adds energy to the rock. The energy is stored in the rock until it changes shape or breaks. • The change in the shape or volume of the crust is called deformation.

5. What are the three types of deformation that stress can cause on rocks? • Tension • Compression • Shearing Tension Compression Shearing

6. Tension Stress • Stress that pulls on the crust, stretching rock. This stress causes the middle of the rock to thin out. • This stress is associated with which type of plate boundary? Divergent

7. Compression Stress • Stress that squeezes rock until it folds or breaks. • This stress is associated with which type of plate boundary? Convergent

8. A portion of the San Andres Fault is Compression Stress!

9. Shearing stress • Stress that pushes a mass of rocks in two opposite directions • This type of stress is associated with which type of plate boundary? transform

10. What are folds? • A fold is a bend in rock that happens from compression. This stress causes the middle of the rock to bulge.

12. What are the different kinds of folds? upward • A fold that bends in the middle is called an anticline. (think of an ANT hill!) • A fold that bends in the middle is called a syncline. (think of it as a sink-line!) Downward

14. More information about anticlines: • The tops of anticlines get weathered and eroded away to become mountains. • Weathered and eroded folds create chains of parallel mountains and hills. • Anticlines are where scientists search for oil deposits because impermeable rocks trap oil in the permeable rocks below it.

18. What is a fault? • When stress builds up in rocks, it fractures. This fracture in the Earth’s crust is known as a fault. (The Earth is cracking under so much stress!)

19. There are 3 Main Types of Faults • Normal fault • Reverse fault • Strike-slip fault

20. Normal Fault • Normal faults are caused by tension. • One block of rock lies above the fault, the footwall. • The other block, the hanging wall, lies below it.

22. Reverse Fault • Reverse faults are cause by compression. • In this fault, the hanging wall slides upward past the footwall. • Also known as a Thrust Fault

24. Strike-slip Fault • Shearing causes strike-slip faults. • The rocks on either side of the fault slide past each other in the opposite direction.

26. What are some other landforms created by faults? • When normal faults uplift a block of rock, a fault block mountain forms. The hanging walls from both normal faults, drop, they leave a block of mountains in the middle. • A plateau is a large area of flat land elevated high above sea level. If a fault pushes up a large flat block of rock, a plateau can form. • Over millions of years, fault movement can change a flat plain into a towering mountain range.