Red Beans and Rice: Slope failure experimental modeling

Thomas Hickson

University of St. Thomas

Summary

Students replicate a slope failure experiment published in Science (Densmore et al., 1997) using a simple, acrylic slope failure box in an effort to forge a link between autocyclic processes, long-term landscape evolution, and slope morphology. This exercise also conveys important concepts about landscape stability.

Context

Audience

I use the full-blown assignment in my sophomore level geomorphology course. I have a scaled-down version that I use in a large, introductory geology course.

Skills and concepts that students must have mastered

Essentially none. I use this exercise to MOTIVATE a lot of skill mastery and concepts in future class sessions (autocyclicity, equilibrium, dynamic equilibrium, slope failure dynamics, etc.)

How the activity is situated in the course

This exercise can be a stand-alone exercise, but it is very useful for illustrating very broad concepts in geomorphology and landscape evolution, so I tend to bring it in early. It also forges a link between experimentation, physical process, and actual landscape elements.

Goals

Content/concepts goals for this activity

Modeling slope failure; collecting, analyzing, and interpreting experimental data; dimensional reasoning; replication of scientific results and the scientific method; explain the role of substrate in the nature of slope failure processes

Higher order thinking skills goals for this activity

Observation and interpretation of data; hypothesis formulation; critical evaluation of the literature; the use of physical models to understand geomorphic processes

Other skills goals for this activity

Excel plotting

Description of the activity/assignment

In this activity, students replicate the slope failure experiment presented by Densmore et al. (1997) in the journal Science. They use a 2D slope failure box filled with either red beans or rice, armed with a sliding gate that simulates river incision, and they create slope failures. They collect and measure the weight of failed material and generate a slope-length normalized time series of failures for the two materials. Students are asked to predict the outcome of the experiment in advance and then to test this prediction. Students also measure slope profiles through time and are asked to speculate on the real-world applicability of this experiment. Finally, they read the original article (Densmore et al., 1997) and they critically evaluate their results in light of the article's content.