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How many Earthquakes Occur each year??

How many Earthquakes Occur each year??. More than 1 million !!!. What are Earthquakes?. Vibrations of the earth’s crust caused by a sudden release of energy. What causes EQ’s? . Build up of stress along the boundaries of tectonic plates. Stress.

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How many Earthquakes Occur each year??

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  1. How many Earthquakes Occur each year?? More than 1 million !!!

  2. What are Earthquakes? Vibrations of the earth’s crust caused by a sudden release of energy

  3. What causes EQ’s? Build up of stress along the boundaries of tectonic plates

  4. Stress Stress = the total force acting on crustal rocks per unit of area 3 Kinds of stress • Compression – decrease volume • Tension – pulls apart • Shear – twist Example : sponge

  5. Strain How rocks respond to stress is called strain Strain= deformation of a material expressed in rocks by folding (bending) or faulting (breaking)

  6. Elastic Rebound Theory Describes the process between stress & strain

  7. Elastic Rebound Theory • 2 sides along a fault are locked by friction • Energy in the form of stress is stored in rock • When stress exceeds frictional lock, movement occurs • Energy is released in form of waves • Rocks rebound to original shape

  8. Elastic Rebound Theory Demo:

  9. Wood blocks, sandpaper, and rubber bands, can model the slow storage and rapid release of elastic energy

  10. In Class • Read text p 528 – 530 • Define stress & strain

  11. ANY QUESTIONS?

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