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Earthquakes

Earthquakes. Stress in the Crust. An earthquake is the shaking and trembling from rocks moving beneath Earth’s surface. The rocks move due to forces that cause stress in the crust. Types of Stress. There are three different kinds of stress Shearing Tension Compression

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Earthquakes

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  1. Earthquakes

  2. Stress in the Crust • An earthquake is the shaking and trembling from rocks moving beneath Earth’s surface. • The rocks move due to forces that cause stress in the crust

  3. Types of Stress • There are three different kinds of stress • Shearing • Tension • Compression • Stress changes the shape and volume of rocks.

  4. Shearing • Shearing is when pieces or rocks are pushed in opposite directions. • This happens at a transform boundary.

  5. Tension • Tension is when the rock is stretched in opposite direction. • This happens at a divergent boundary.

  6. Compression • Compression is when a rock is squeezed until it folds or break. • This happens at a convergent boundary.

  7. Deformation • All of these stresses cause deformation, which changes the volume and shape of Earth

  8. Kinds of Faults • Eventually, with enough stress, rocks break to create a fault. • Faults occur on plate boundaries where plates are compressed, pulled, or sheared so much the crust breaks.

  9. Kinds of Faults • There are 3 kinds of faults • Strike-Slip Faults • Normal Faults • Reverse Faults

  10. Strike-Slip Faults • Shearing creates a strike-slip fault. • The rocks slide past each other sideways. • Strike-slip faults create a transform boundary.

  11. Strike-Slip Fault

  12. Normal Faults • In normal faults, the fault is at an angle. • One part of the rock is ABOVE the fault, the other part is BELOW

  13. Normal Faults • Hanging wall is the half ABOVE the fault • Footwall is the half that lies BELOW the fault

  14. Normal Fault • Tension forces create normal faults. • The hanging wall slips down. • Normal faults happen at divergent boundaries.

  15. Reverse Fault • Compression creates a reverse fault. • It is like a normal fault, but the plates move in opposite directions. • The hanging wall slides up over the footwall.

  16. Reverse Fault

  17. Friction Along Faults • If friction is low along a fault, the rocks slide smoothly. • If friction is high along a fault, the rocks jam and then jerk free, creating large earthquakes.

  18. Mountain Building • Movement along faults can create mountains or valleys. • Two normal faults can leave land lying between them. Fault-block mountains

  19. Mountain Building • Rocks under compression can fold without breaking. • Video

  20. Anticlines and Synclines • When the crust folds, it creates upward hills and downward hills. • The upward hills are called anticlines. • A downward hill is called a syncline.

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