USING STICK FIGURE DRAWINGS AND PERLITE HILLS TO EXPLORE THE CAUSES AND EFFECTS OF MASS WASTING

The definition of mass wasting is quite simple: the downslope movement of rocks, soil, or regolith under the influence of gravity. The process of mass wasting, however, is more complex involving factors such as: slope angle, bed orientation, and moisture content. Students can learn about the process of mass wasting and explore conditions that lead to slope failure through simple hands-on experiments using just a few basic, reusable supplies. This in-class activity consists of three parts: 1) Defining types of mass wasting; 2) Exploring the causes of slope failure; and 3) Applying students’ knowledge. First, students are asked to draw stick figures representing persons sliding, slumping, falling, and caught in a flow. As mass wasting is defined and classified by movement type, students connect the movements of the people in their drawings to the mass movement of earth materials. Next, to explore the causes of slope failure, students construct perlite hills, manipulate the angle of repose, and observe how the changes affect slope stability. Students further explore slope stability by determining the effects of removing the toe of a landslide and by comparing the stability between dry, moistened, and oversaturated perlite hillslopes. In the final portion of the activity, students apply their new knowledge of mass wasting by identifying areas in illustrations and photos that may be landslide prone or have already experienced slope failures. To evaluate landslide potential, students consider hillslope angle, composition, and orientation of bedding. To identify past slope failures, students identify the effects of mass wasting: the formation of scarps, hummocky texture, toes, and changes in vegetation and orientation of trees or man-made structures. By the end of the class period, students have an understanding of the causes and effects of mass wasting, and also of the tools used to identify areas of past and potential slope failures.