Investigating slope failure and landscape evolution with red beans and rice!
University of St. Thomas, St. Paul, MN
Students investigate the behavior of a slope profile over geological timescales using a very simple experimental apparatus. The lab allows students to understand concepts of equilibrium, controls on slope profile, issues surrounding landslide hazard, and the application of experiments to real geological problems. The lab also precisely replicates an experiment that appeared in the journal 'Science' in 1997.
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.
Skills and concepts that students must have mastered:
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.
How the activity is situated in the course:
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.
National or State Education Standards addressed by this activity?:
Content/concepts goals for this activity:
- Data collection, analysis, and synthesis.
- Use of experiments in geology and geomorphology.
- Control of rock type on slope failure and slope stability
- Landscape evolution
- Equilibrium (static vs. dynamic)
- Time series analysis (basic)
- Cumulative frequency plots
Higher order thinking skills goals for this activity:
- Data collection, reduction, analysis, and synthesis.
- Hypothesis generation and testing.
- Critical analysis of the literature.
- Development of analog models.
- Improving quantitative skills.
Other skills goals for this activity:
- How to structure a good lab write-up.
Description of the activity/assignment
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.
Determining whether students have met the goals
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.
Download teaching materials and tips
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.
Controlled Vocabulary Terms
Subject: Environmental Science:Natural Hazards:Mass Wasting, Geoscience:Geology:Geomorphology
Resource Type: Activities:Lab Activity, Classroom Activity
Special Interest: Hazards, Large Classroom
Grade Level: High School (9-12), College Lower (13-14)
Learning Environment: Large Classes
Ready for Use: Ready to Use
Topics: Earth surface
Theme: Teach the Earth:Course Topics:Environmental Science, Teach the Earth:Incorporating Societal Issues:Hazards, Teach the Earth:Course Topics:Geomorphology