When Is Mud Dangerous?
ES1204  Factors Affecting Mudflows

The angle of a hillside or cliff is one factor that controls whether mud will start to slide. The board in these photographs represents a model hillside. Each line on the protractor cards represents 15°.

2. What conclusion can you draw from the two images?

Mud on slide plane tilted at 30°
Zach Smith, TERC
Mud on slide plane at 40°

The mud on the 30° plane didn't slide, but it still has the potential to move downhill. Besides changing the angle of the slide plane, what could you do that might make the mud slide down?

3. List at least two ways you could make the mud slide off the 30° slide plane without changing the plane's angle.

4. What conditions in nature would be represented by the answers you gave for question 3?

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