7th Grade Ch. 2 Sec. 2 Earthquakes & Seismic Waves
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7th Grade Ch. 2 Sec. 2 Earthquakes & Seismic Waves






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7th Grade Ch. 2 Sec. 2 Earthquakes & Seismic Waves 7th Grade Ch. 2 Sec. 2 Earthquakes & Seismic Waves Presentation Transcript

  • Ch. 2 Sec. 2 Earthquakes & Seismic Waves
    • shaking & trembling that results from movement of rock beneath Earth’s surface
    TLC-Make a quake
  • Focus -area beneath Earth’s surface where rock under stress breaks Epicenter -point on surface directly above focus
  • seismic waves
    • vibrations that travel thru Earth carrying energy released during earthquake
    • carry energy from earthquake away from focus  Earth’s interior  across surface
  • types of seismic waves P waves S waves surface waves
  • P waves
    • P rimary waves
    • 1 st to arrive
    • move thru. solids & liquids
    • compress & expand like accordion
  • S waves
    • S econdary waves
    • 2nd to arrive
    • vibrate from side to side & up & down
    • cannot move thru. liquids
  • surface waves
    • move slower than P & S waves
    • produce the most severe ground movements
  • 3 types of seismic waves
  • 3 ways of measuring earthquakes Mercalli scale Richter scale moment magnitude scale rates earthquakes according to level of damage rated using seismographs estimates total energy released by earthquake rates earthquakes of all sizes (near & far) good for small, nearby earthquakes describes how earthquakes affect people, bldg. & land
  • The Mercalli scale was developed to rate earthquakes according to the amount of damage at a given place.
  • Mercalli Scale Earthquake Intensity Earthquake Effects I-III People notice vibrations like those from a passing truck. Unstable objects disturbed. IV-VI Dishes and windows rattle. Books knocked off shelves. Slight damage. People run outdoors. VII-IX Moderate to heavy damage. Buildings jolted off foundations or destroyed. X-XII Great destruction. Cracks appear in ground and landslides occur. Waves seen on ground surface.
  • magnitude
    • # geologists assign to earthquake based on earthquake’s size
    • how much energy released
    • instrument that records & measures ground movements of seismic waves
  • seismograph
    • use seismic waves
    • measure difference between arrival times of P & S waves using data from 3 seismographs
    • draw 3 circles from different seismographs
    • point where they intersect= epicenter
  • A Vocabulary Review Activity
  • Directions:
    • One student stands with their back to this presentation.
    • Another student gives the student clues to the vocabulary word onscreen as a clock keeps time.
    • The student tries to guess the word before the buzzer.
  • Ready to play?
  • earthquake The is…
  • magnitude The is…
  • Richter scale The is…
  • epicenter The is…
  • seismograph The is…
  • Mercalli scale The is…
  • P waves The is…
  • S waves The is…
  • Surface waves The is…
  • focus The is…
  • In your drawing, be sure to include:
    • A drawing of your building
    • List of materials
    Walls- styrofoam Roof- graham crackers