A Model of Iii Faults

U.S. Geological Survey

Activeness Source:

Background

One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects. An earthquake is a sudden movement of the World, caused by the abrupt release of strain that has accumulated over a long time. For hundreds of millions of years, the forces of plate tectonics have shaped the Earth as the huge plates that form the World'due south surface slowly move over, under and past each other. Sometimes the movement is gradual. At other times, the plates are locked together, unable to release the accumulating energy. When the accumulated energy grows stiff plenty, the plates break gratuitous. If the earthquake occurs in a populated area, it may crusade many deaths and injuries and all-encompassing belongings damage.

Today we are challenging the assumption that earthquakes must nowadays an uncontrollable and unforecastable hazard to life and property. Scientists have begun to gauge the locations and likelihoods of hereafter dissentious earthquakes. Sites of greatest hazard are being identified, and designing structures that will withstand the effects of earthquakes.

Materials

Objective

Students will discover fault movements on a model of the globe'due south surface.

Time Needed

ane or ii Class periods

Materials Needed (per group)

  • Physiographic map of the globe
  • Crayons or colored pencils
  • Scissors
  • Tape or glue
  • Metric ruler
  • Construction newspaper
  • Error Model Sail (included)

Instructions

  1. Have students work in pairs or small groups.
  2. Display the fault models in the classroom after the activity.
  3. An excellent globe physiographic map, showing the ocean floor, can be obtained from the National Geographic Society.

Application Stage

  1. Explain that faults are oftentimes (simply not always) found near plate boundaries and that each blazon of fault is frequently associated with specific types of plate movements. Yet, you lot can probably discover all types of error motility associated with each type of plate purlieus.
    • Normal faults are often associated with divergent (tensional) boundaries.
    • Thrust faults are often associated with convergent (compressional) boundaries.
    • Strike-slip faults are oft associated with transform (sliding) boundaries.
  2. Inquire the post-obit questions:
    • What kind of faults would y'all expect to notice in the Himalaya Mountains? Why?
    • What kind of faults would you look to find along the Mid-Atlantic Ridge? Why?
    • What kind of mistake is the San Andreas Fault? Is California probable to "fall off into the Pacific Body of water"? Why?
  3. Explain that non all faults are associated with plate boundaries. Explicate that in that location is a broad range of faults based on type, linear extension, displacement, age, electric current or historical activity and location on contintental or oceanic crust. Have students inquiry examples of not-plate purlieus faults.
  4. Explain to students that the stresses and strains in the earth's upper layers are induced by many causes: thermal expansion and contraction, gravitational forces, solid-globe tidal forces, specific volume changes because of mineral stage transitions, etc. Faulting is ane of the diverse manners of mechanical adjustment or release of such stress and strain.
  5. Accept students enquiry and written report on the types of faults found in your land.

Extension

  1. Have students Place the mistake movements in the contempo Loma Prieta, California earthquake.
  2. Have students research the fault histories and contempo theories apropos the Northridge, California Earthquake, the New Madrid, Missouri , and the Anchorage, Alaska fault zones.

Coloring Key

  • Stone Layer Ten - green
  • Rock Layer Y - yellow
  • Rock Layer Z - red
  • River - blueish
  • Road - black
  • Railroad tracks - dark-brown
  • Grass - green

Part 1

Exploration Phase

  1. Yous may wish to introduce this activity by asking students:
    • Can you proper name a famous fault?
    • What happens when giant fractures develop on the Earth and the pieces move relative to 1 another?
  2. Illustrate compressive world movements using a large sponge by squeezing from both sides, causing uplift. Using a piece of latex safety with a wide marker drawn on information technology, illustrate world tension, by pulling the ends of the latex to show stretching and thinning.
  3. Have students construct a error model using the Fault Model Sail. Instructions to students:
  4. Color the fault model that is included co-ordinate to the colour central provided.
    • Paste or glue the fault model onto a piece of construction paper.
    • Cut out the fault model and fold each side down to form a box with the drawn features on pinnacle.
    • Record or mucilage the corners together. This box is a iii dimensional model of the top layers of the Earth's crust.
    • The dashed lines on your model stand for a fault. Carefully cut along the dashed lines. You lot will end upwards with 2 pieces. Yous may wish to have your students record or glue a piece of construction paper on the side of the ii fault blocks along the error face. This will help with the demonstration.

    Note that an enlarged version of the mistake cake model can be fabricated for classroom demonstrations.

  5. Accept students develop a model of a normal fault.
    • Instructions to students: Locate points A and B on your model. Move point B and then that it is next to Signal A. Discover your model from the side (its cantankerous-section). Have students draw the normal fault as represented by the model they have just constructed.

Concept Development

  1. Ask the following questions:
    • Which way did point B move relative to bespeak A?
    • What happened to rock layers X, Y and Z?
    • Are the rock layers still continuous?
    • What probable happened to the river? the route? the railroad tracks?
    • Is this type of error acquired past tension, pinch or shearing?
  2. Explicate that this type of fault is known every bit a normal fault.
  3. Have students label their drawing "normal fault".
  4. Many normal faults are found in Nevada. This is because Nevada is located in a region called the Basin and Range Province where the lithosphere is stretching.

Part two

Exploration Phase

Take students develop a model of a thrust fault. Instructions to students:

Locate points C and D on your model. Move Indicate C next to point D. Observe the cross-department of your model.
Have students draw the thrust fault as represented by the model they have only synthetic.

Concept Evolution

  1. Ask the following questions:
    • Which way did point D move relative to bespeak C?
    • What happened to rock layers 10, Y and Z?
    • Are the stone layers nonetheless continuous?
    • What likely happened to the river? the road? the railroad tracks?
    • Is this type of mistake caused by tension, pinch or shearing?
  2. Explain that this type of fault is known as a thrust fault.
  3. Have students characterization their drawing "thrust fault".
  4. An instance of a thrust fault is the mistake in which the Northridge convulsion occurred. The thrusting movement raised the mountatins in the area past every bit much equally lxx cm.

Part 3

Exploration Phase

Have students develop a model of a strike-skid mistake. Instructions to students:

Locate points F and G on your model. Move the pieces of the model and then that point F is next to indicate K.
Have students describe an overhead view of the surface as information technology looks after motility along the error.

Concept Evolution

  1. Enquire the following questions:
    • If you lot were standing at point F and looking across the fault, which way did the block on the opposite side motion?
    • What happened to rock layers X, Y, and Z?
    • Are the rock layers all the same continuous?
    • What likely happened to the river? the road? the railroad tracks?
    • If the scale used in this model is 1 mm = two m, how many meters did the world motion when the strike-slip fault caused signal F to motion alongside signal G? (Notation that this scale would make an unlikely size for the railroad rail!) If there were a sudden horizontal shift of this magnitude it would exist about five times the shift that occurred in the 1906 San Andreas error equally a upshot of the San Francisco convulsion.
    • Is this blazon of fault caused by tension, compression or shearing?
  2. Explicate that this type of error is known equally a strike-sideslip fault.
  3. Have students label their drawing "strike-skid mistake".
  4. Explain to the students that a strike-slip fault can be described as having right or left-lateral movement. If yous look direct across the mistake, the direction that the opposite side moved defines whether the motion is left-lateral or right-lateral. The San Andreas fult in California is a right-lateral strike-skid error.

Model