Investigating slope failure and landscape evolution with red beans and rice!

Thomas Hickson

University of St. Thomas, St. Paul, MN

I use the full-blown lab activity in a 3 hour lab in a geomorphology course (a sophomore level course). I have also used the experiment as a demo in a large (100 person) introductory geology course by placing a video camera in front of the experiment and projecting it on a large screen.

To my knowledge, none. It is a great way to introduce and explore in-depth many ideas surrounding slope stability and landscape evolution. It is also a great lab to introduce data collection and analysis, as well as measurement. I do not assume that students know anything about slope stability when I start the lab or the activity in class.

This is a stand-alone lab exercise or an in-class demo. As a lab, it forms the central motivation for about 1.5 weeks of class material and in-class discussion.

1. Data collection, analysis, and synthesis.
2. Measurement.
3. Use of experiments in geology and geomorphology.
4. Control of rock type on slope failure and slope stability
5. Landscape evolution
6. Equilibrium (static vs. dynamic)
7. Time series analysis (basic)
8. Cumulative frequency plots

1. Data collection, reduction, analysis, and synthesis.
2. Hypothesis generation and testing.
3. Critical analysis of the literature.
4. Development of analog models.
5. Improving quantitative skills.

1. How to structure a good lab write-up.

This lab or in-class exercise is based on an actual experiment that appeared in the journal "Science" (Densmore et al., 1997) that used an analog model to simulate the role of bedrock landslides in long-term landscape evolution. Students essentially replicate this experiment by using an acrylic-walled slope failure box filled with either red beans or rice to simulate the landscape. A sliding door on one long side of the box simulates downcutting of the landscape by a river. Lowering the door leads to 'rock' avalanches; students weigh the material that fails and trace slope profiles on the sidewall of the box. As a result of this data collection process, they create a time series of slope failures and slope profiles that shows (a) that large landslides are interspersed with smaller landslides; (b) that oversteepened toes of slope may be an equilibrium landform; and (c) that the type of material that fails will in part govern the nature of the failures, slope profiles, and time series that they detect. Their task is to hypothesize about the behavior of the experiment before running it, then replicate the Densmore et al. (1997) experiment. They then analyze their data and submit a lab report that examines their results in light of the 'Science' article. The activity allows students to read the scientific literature, to collect and analyze real data, to investigate the nature of equilibrium, and to gain a gut feeling for the controls on slope failure.

Students submit a lab write-up that is graded based on a grading rubric. They must also submit the results of the experiment as a series of Excel plots/charts.

Densmore, A.L., Anderson, R.S., McAdoo, B.G., and Ellis, M.A., 1997, Hillslope Evolution by Bedrock Landslides, Science, Vol. 275, p. 369-372.