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Ch. 2.1 and 2.2 Lecture PPT

Ch. 2.1 and 2.2 Lecture PPT. Earthquakes. Earthquakes : the shaking and trembling that results from the movement of rock beneath Earth’s surface See simulation below: Terashake. Caused by STRESS. Stress : a force that acts on rock to change its shape or volume. 1. Shearing.

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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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