Name _____________________________________
Date _________________
Period _________
Model-Making Lab
How Do You Stack Up?
According to the principle of superposition, in undisturbed sequences of sedimentary rock, the oldest layers are on
the bottom. Geologists use this principle to determine the relative age of the rocks in a small area. In this activity,
you will model what geologists do by drawing sections of different rock outcrops. Then, you will create a part of the
geologic column, showing the geologic history of the area that contains all of the outcrops.
Procedure: (Look at the geologic column example on Pg. 65 for help seeing how this works)
1. Carefully cut the outcrops out of the paper, and lay the individual outcrops on the long sheet of paper in
the order listed. Cut the outcrops along the unconformities (wavy lines) before moving on. Do not mix up
the outcrops!!
2. The shapes inside each layer represent different types of fossils. Find the layers that have the same rocks
and contain the same fossils. Move each outcrop up or down to line up similar rock layers next to each
other.
3. If unconformities (wavy lines) appear in any of the outcrops, there may be rock layers missing. You may
need to examine other sections to find out what fits between the layers above and below the
unconformities.
4. Eventually, you should have all the outcrops lined up with the proper rock layers. It will show rock layers
and fossils for all the known layers in the area. Combine your four outcrops into a complete geologic
column by drawing the entire thing in the geologic column space on the long paper.
5. Label the unconformity in each outcrop.
Analyze the Results:
1. How does a geologic column help to learn the history of the Earth?
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2. How many layers are in the complete geologic column that you drew?
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3. Which is the oldest layer in your column? Which rock layer is the youngest? How do you know? Describe
these layers in terms of rock type or the fossils they contain.
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4. Look at the unconformity (blank space) in outcrop 2. Which rock layers are partially or completely missing?
How do you know?
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