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Earthquakes: Causes and Effects

Learn about earthquakes, the shaking of the Earth's crust due to energy release from plate movements. Understand fault lines, epicenters, and wave types to grasp the science behind these natural disasters. Watch a video for visual aid.

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Earthquakes: Causes and Effects

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  1. Earthquakes

  2. Earthquakes • Earthquake: the shaking of the Earth’s crust caused by a release of energy. • Common cause: movement of the Earth’s plates

  3. Elastic-Rebound Theory – DO NOT WRITE • As the Earth’s plates move past one another, friction causes the plates to get “stuck”.· Stress and pressure builds up and causes the plate to become deformed (bend) as it continues to try and move (the plates are elastic-they can change shape).· Eventually, the pressure is great enough to overcome the friction and the plates slip past one another.· The plate movement is the earthquake. The greater the plate movement, the larger the earthquake.· The plates are in a new location, but they go back to their original shape (rebound). **Think of pushing on the ends of a wooden ruler. As you push, the ruler will bend. When you release the pressure on the ends, the ruler snaps back to its original shape.

  4. Earthquake Definitions • Fault: break in the lithosphere along which movement has occurred • Focus: the point at which the first movement occurs • Epicenter: the point on Earth’s surface directly above the focus

  5. More information • Friction prevents plate movement most of the time. • Boundary Type vs. Earthquake Depth: a. divergent boundaries: within 30 kilometers of the surface b. transform boundaries: occur at shallow depths c. subduction boundaries: occur as deep as 700 km

  6. Waves • Body wave: travels from the focus of an earthquake through Earth • P-wave: a body wave that squeezes and stretches rock materials - AKA: compression wave or a primary wave - P-waves can travel through any material- solid, liquid or gas

  7. S-wave: a body wave that causes particles of rock to move at right angles -AKA shear waves or as secondary waves -can travel through only solids, not liquid or gas

  8. Illustration • P and S waves

  9. Surface Waves • Surface wave: a wave that travels along Earth’s surface- caused by body waves. • Can cause considerable damage

  10. Finishing up • P-waves and S-waves move faster when material is rigid and more dense • S waves travel at a little less than half the speed of P waves • Surface waves travel the slowest when compared to P and S waves

  11. Video • https://www.youtube.com/watch?v=e7ho6z32yyo

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