Mr. Fawlty: Simulating Geological Faults

  • Mr. Fawlty: Simulating Geological Faults
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    Title: Simulating Geological Faults

    Hits the standard: HS-ESS1-5 Evaluate evidence of the past and current movements of continental and oceanic crust and the theory of plate tectonics to explain the ages of crustal rocks.

    Lesson Brief: The surface of the earth is composed of tectonic plates that slowly move over a molten core. The movement of these plates leads to earthquakes, mountain building events, and band of rock of increasing age as you move away from bathymetric ridges where divergent plate movement causes new rock to be formed. This geological sandbox can be used to simulate faulting in a tectonic plate that can lead to mountain building and earthquakes.

    Background: The movement of tectonic plates causes earthquakes and builds mountains. The upper layers are relatively brittle compared to the lower, hotter, layers. Within the upper layers however, layers of different types of rock vary in how they respond as well. In places where plates are subject to extension forces or tension, faults may develop that interrupt the bands of similar-aged rocks. At the surface, these faults can lead to parallel bands of mountains, as in the ranges east of the Sierra Nevada.

    Example of “geology sandbox” in use:

    1. Print out the Geology Fault Simulator and assemble it (Figure 1). This will require 2 sheets of 3/16” acrylic plastic to act as the clear sides. Dimensions of these clear sides are 7-1/4 inches by 4-3/4 inches. Round the corners for safety. For added realism, bolt a doubled-up Ace bandage to the bottom between the body and moving plate to mimic the ductile mantle layer (Figure 2). If the bandage is used, bolts through carefully drilled holes; screws will split the model.
    2. Fill the fault simulator with alternating layers of different dry materials such as sand, flour, cocoa, and corn meal. Coarser material such as coarse sand is more ductile and is well-suited to the bottom layer, and for acting as a heavy layer at the top. Fine materials will be more cohesive and initiate fault lines. Experiment with different alternating layers.
    3. Tape an acetate sheet to one side of the simulator. Slowly use the screw to pull the plate back to cause tension in the layers. As the faults begin to develop, use a marker to draw the location of the fault on the sheet. Alternately, photograph the simulator and add the fault lines digitally in a program such as Powerpoint. Do this at several points during the experiment


    1. Did faults develop in the layers? How well did this model what happens in actual rock layers under tension? What are the important features of a good model?
    2. Did ridges develop in the surface? How does this simulation differ from the movements of actual tectonic plates? How is it similar?

    Figure 1: Assembly of the 3-D printed parts of the Geological Fault Simulator.
    Figure 2: Installation of acrylic plastic sides. The optional Ace bandage to mimic a ductile mantle layer has been bolted in. It is folded to create a double layer and cut to length.


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