Combining Stream Table Experiments, High-tech Particle Analysis, and the Web to Help Geomorphology Students Evaluate Landform Evolution

Journal of Geoscience Education, Jan 2005 by Clark, Douglas H, Linneman, Scott R

At the stream table, we have stationed computers linked to two digital Web cameras (web-cams; Figure 1). One web-cam is used to download overhead pictures of the delta every 10 seconds to the class Web site (WWU Delta-Cam Web page; http://www.ac.wwu.edu/ ~dhclark/webcam.htm), and the other records time-lapse imagery of the delta forming by taking a picture every 3-4 minutes. The first web-cam allows the students to check the progressive development of the delta remotely over the next two days (until the following lab), and to compare it to their predictions of landform development from Lab 1. It also provides an incentive for the students to get registered on and familiar with the course Web site (which is used extensively throughout the term). The time-lapse photography from the second web-cam provides one of the most useful visual aids in understanding delta development, but is not revealed to the students until near the end of the second lab. Between the first and second labs, students are encouraged to check the Delta-Cam Web page repeatedly, and to consider ways to test some or their hypotheses of delta growth (e.g., grain size variation, external morphology, and internal structure) from Lab 1.

Lab 2 - Analyzing a Delta - The second lab focuses on analyzing delta formation, sediment character, and structure. Students are shown the final form of the delta (which has been drained) via a projection of the web-cam link. On the basis of this image, and with guidance from the instructor, the class as a whole develops a strategy for sampling the delta to test the hypotheses generated during the first lab. The students are also introduced to the concept of grain-size analysis in studying geomorphic landforms. Specifically, they are reminded ow grain-size and grain-size distribution relates to the energy and processes of deposition. After being shown a graph of the grain-size distribution of the original (unsorted) dunite sediment (Figure 3), the students are asked to predict how (or if) grain-size will vary across the delta. This is done qualitatively, with the students sketching grain-size distribution curves for different locations on the delta (from apex to distal bottomset sites) on a graph that shows the original sediment's grain size distribution. They are also asked to hypothesize why grain-size variations might occur. An important goal of this exercise is to get the students to relate surface processes to landform development and sedimentary structures.

At this point, students are shown the time-lapse MPEG video of delta growth. Students (and other faculty, for that matter) find this aspect fascinating because most have never seen a geologic landform develop; it is one of the best reasons to use a stream-table delta model rather than a real delta to teach geomorphic concepts. The MPEG video also gives students clues as to how and why deltas develop their characteristic shape, as channels shift through time to maintain me symmetrical form. Slumping along the foreset face of the delta is apparent as well. Close-up time-lapse photography can also be used to show bedload transport along the surface of the delta, and deposition at the edge, details of slumping on the foreset face, and turbidity currents traveling to the bottomset sites.