Angle of Repose
In this activity students measure the maximum slope at which grains are stable (angle of repose). They explore how different properties of the sediment influence slope stability and lead to different slope failures (mass movements). The results are then used to examine the nature, frequency, timing, and causes of landsliding events in Seattle.
Students make piles from a variety of sediments and measure (either with a protractor or using basic trigonometry) the angle. They examine sediments with different sizes as well as different angularities. They also add water to the piles to evaluate its impact.
- measure the angle of repose
- determine how grain size, angularity, and water content impact the angle of repose
- relate angle of repose to mass wasting types and causes
- apply knowledge gained during the experiments to patterns of mass wasting in the Seattle area.
Context for Use
This activity can be done in an hour to two hours in an introductory class.
Description and Teaching Materials
Teaching Notes and Tips
Students need to be warned to take their measurements with care and precision. If they are little off, they could have difficulty answering the questions well. Also, students tend to make small piles which increases error. (This is a terrific place to discuss error and propagation of error).This activity requires some additional materials:
- rounded gravel
- angular gravel
- coarse gravel
- protractors and rulers
- trays to contain the experiments
The gravel can be easily purchased at a pet shop - aquarium gravel works wonderfully. Most hardware or home improvement stores sell sand and gravel as well.