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Title:  Mountain Building
Level:  Middle
Time:  30 Minutes

Objective:

Visually demonstrate how rocks within the earth can be folded creating anticlines and synclines below the surface and mountains and valleys on the surface.

Materials:

1. 4 different colors of Plasticine of dough colored with food coloring (blue, green, red, yellow, black for coal).
2. 2 large books covered in plastic wrap.

Activity:

1. Prepare four different layers of Plasticine, about 15 cm x 8 cm x 1 cm each.
2. Stack the layers on the top of each other.
3. Stand the books up on opposite sides of the layers.
4. Have someone gently push on one of the books while you gently push on the other until the Plasticine folds.
5. Increase the pressure slowly until more folding occurs.
6. Draw a picture of what happened.

Discussion:

Sedimentary rocks are formed from deposits of mud, silt or sand at the bottom of the sea.  The rocks form in horizontal layers much like the layers of Plasticine you constructed.  Powerful forces in the Earth push on the rock layers.  After millions of years have gone by, the rock layers fold, much like the Plasticine did.

The arch of the Plasticine fold represents an anticline, which could be the top of a mountain.  The upside down arch of the fold, the trough, or syncline could represent a valley.  Later, rivers or glaciers erode the land surface to sculpt new valleys and hillsides.  Old mountains are the remnants of once larger uplifts and can contain both synclines and anticlines.  Old valleys are where the rocks were softer and easier to erode.

Adapted from EarthNet activities