Activity: Folds and Faults

Hawai'i Space Grant College, Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, 1996

Folds and Faults

Purpose

To learn why and how rock layers are folded and faulted and to learn how to represent the structures in maps and cross sections.

Key Words

stratigraphy

structure

anticline

fault

strike-slip movement

offset

map view

cross section

Materials

cardboard

playdough or clay in 4 different colors

rolling pin

cheese slicer

plastic knife

drawing paper

pencils

colored pencils

Procedure

1.: Place the cardboard down on your work table.
2.: Collect four balls of playdough, one of each color.
3.: Flatten each ball into a layer about 10 cm to 15 cm along the sides and 1 cm thick.
4.: Stack the four layers neatly into a block on the cardboard.
5.: Where is the oldest layer, the layer placed first?
6.: Where is the youngest layer, the layer placed last?
7.: Push on the playdough block from two opposite sides. What happens?
8.: Use the cheese slicer to shave off some of the playdough from the top. Shave off enough to see different colors revealed on the new top surface.
9.: Looking straight down, draw a colored picture of the surface of the playdough. Label this drawing: MAP VIEW #1.
10.: What clues does the surface give you about the inside structure of the playdough block?
11.: Draw a colored picture of what you think the playdough structure looks like underneath the surface. Label this drawing: MY INTERPRETATION OF THE INTERIOR.
12.: Now let's find out what's inside. Using the plastic knife, make a vertical cut through the playdough carefully so as not to squash the structure.
13.: What does this cut represent?

14.: Look at one of the cut faces of the playdough. Draw a colored picture of this side view. Label this drawing: CROSS SECTION.
15.: Does your interpretaiton (from #11 above) agree with your cross section? Why or why not?
16.: Now slide each half of the playdough block along the cardboard in opposite directions. The two halves should still be touching but be offset about 5 cm. You have just created strike-slip fault movement!
17.: Again, looking straight down, draw a colored picture of the surface of the playdough. Label this drawing: MAP VIEW #2.
18.: Describe the differences between your two map views.
19.: Which of your drawings give you the most information? Why?
20.: Compare your structures and maps with your classmates' work. Did different fault orientations result in better cross sections? Why?

Go to Folds and Faults Teacher pages.

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