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Ch. 2.1 and 2.2 Lecture PPT

This lecture provides an overview of earthquakes, including the causes of shaking and trembling, different types of faults, and the characteristics of seismic waves. It also explains how earthquakes lead to mountain building and introduces terminology such as focus, epicenter, and magnitude.

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Ch. 2.1 and 2.2 Lecture PPT

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  1. Ch. 2.1 and 2.2 Lecture PPT

  2. Earthquakes • Earthquakes: • the shaking and trembling that results from the movement of rock beneath Earth’s surface • See simulation below: • Terashake

  3. Caused by STRESS • Stress: • a force that acts on rock to change its shape or volume

  4. 1. Shearing • pushes a mass of rock in twoopposite directions • Causes rock to break and slip apart or to change its shape • See simulation below: • http://scign.jpl.nasa.gov/learn/plate5.htm

  5. 2. Tension • Pulls on the crust • Stretching rock so that it becomes thinner in the middle • See simulation below: • http://scign.jpl.nasa.gov/learn/plate5.htm

  6. 3. Compression • Squeezes rocks until it folds or breaks • Compresses rock like a gianttrashcompacter • See simulation below: • http://scign.jpl.nasa.gov/learn/plate5.htm

  7. What is a Fault? • A break in Earth’s crust • Slabs of crust slippasteachother • Occurs along a plateboundary • Forces of plates: compress, pull, or shear the crust so it breaks

  8. Types of Faults • Normal- caused by tension • Reverse- caused by compression • Strike-slip-caused by shearing See simulation below: Fault Movements

  9. Mountain Building • From faulting • Two normal faults • From folding • Anticline - forms an arch • Syncline - forms a bowl • Plateau - large area of flat land • From vertical fault

  10. Earthquake Terminology • Focus • Point beneath Earth’s surface where rock that is under stress breaks, triggering an earthquake • Epicenter • Point on the surface directly above the focus

  11. Seismic Waves • P Waves • First waves to arrive • Compress and expand the ground like an accordion • Can travel through solids and liquids

  12. Seismic Waves • S Waves • Vibrate from side to side as well as up and down • Only move through solids, not liquids

  13. Seismic Waves • Surface waves • Move slower than P and S waves • They produce the most severe ground movements • Some roll like ocean waves • Others shake from side to side See simulation below: Wave Movements

  14. Detecting Seismic Waves • Seismograph • Records and measures the vibrations of seismic waves

  15. Measuring Earthquakes • Magnitude - measurement of earthquake strength based on seismic waves and movement along faults • Mercalli Scale - rate earthquakes according to their intensity • How affect people buildings, people and land surface • Richter Scale - rating of the size of seismic waves as measured by a particular type of seismograph • Moment Magnitude Scale - estimates the total energy released by an earthquake

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