TEACHING CLUES AND CUES
Remind students that
arrows placed on fault
diagrams show the
relative direction of the
motion.
You may want to cover
the copy at the bottom of
the master (Figure 2,
p. 85) while you ask
B. Lesson Development
1. Project the first transparency made from Master 2.3f, Ditch Creek.
Tell students that the diagrams they see show the effect of faulting in
successive earthquakes. As you point to each of the figures, 1 through
5, read the accompanying text aloud to the class.
2. Divide the class into working groups of three to five students each.
Distribute paper for covering desks, clay, knives, rollers (if available),
and one copy of Master 2.3g, Ditch Creek Template, to each group.
Give these directions:
a. Make three layers of clay, one white, one yellow, and one red,
patting or rolling the clay to a thickness of about 1 cm (1/3 in.) and
trimming it to fit within the confines of Area 1 on the grid. Place the
white layer on the Area 1 part of the grid and remove the others. Make
a pencil-thick string of blue clay and lay it along the line marked on
the grid as Stream Line, running the length of the first layer. With the
knife, cut along the E-F fault line marked on the grid, which is
perpendicular to the stream. Now offset the C-D section of the model,
moving it to the position marked 1857 on the grid. This offset
represents the movement along the fault of 1857.
b. Now place the yellow layer on top of the white layer and the offset
stream. Be sure to place this second layer within the grid marks. Make
another pencil-thick stream out of blue clay and place it on the same
stream line indicated on the grid. Cut the layers again along the same
fault line as in the previous step. Offset the C-D section to the position
marked 1906.
c. Repeat this one more time with the red clay layer and one additional
blue streamline.
C. Conclusion
Build a class discussion around these questions:
students to describe what they think
has happened to produce the new
picture.
Q
How is the principle of superposition applied in this activity?
Q
How is the principle of crosscutting relationships applied in this
activity?
Q
How is the principle of uniformitarianism applied in this activity?
Q
Would you build your home in 1994 or later near this fault?
ADA P T A T I ON S AND E X T E N S I ON S
Provide a small-scale map of a seismic area and ask students to locate
other streams along fault lines and identify offset stream channels. For
example, on a map of the Grand Canyon, locate Bright Angel Canyon
and point out the place where it meets the Colorado River. Ask: What
caused the Bright Angel Creek to cut a canyon where it did? (The
Bright Angel fault caused a weak place in the rock for the water to
erode.)
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F E M A
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