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Innovative Approaches to Teaching Sedimentary Geology, Geomorphology, and Paleontology
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Cutting Edge > Sedimentary Geology > Sedimentology, Geomorphology, and Paleontology 2014 > Teaching Activities > Exploring hypsometry in glacial and fluvial environments

Exploring hypsometry in glacial and fluvial environments

Karen Gran, University of Minnesota-Duluth
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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

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  • Pedagogic Effectiveness
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This page first made public: Jun 12, 2014

Summary

This laboratory exercise explores the topographic signature of fluvial and glacial landscapes in different tectonic environments. Students develop a list of mountain ranges around the world to explore, then extract topographic data from 90-meter SRTM DEMs, and develop a series of hypsometric curves for each range. Each student works on a single range, but as a class we build up a database of 10-15 ranges around the world. The hypsometric curves are compared with each other and with published curves to look for signals of fluvial incision vs. glacial erosion in the landscapes.

Context

Audience

I use this lab in an upper-level geology course in tectonic geomorphology, although it is also suitable to use in a geomorphology class. 90% of the students are either upper-level undergraduate geology majors or M.S.-level graduate students.

Skills and concepts that students must have mastered

Students have done one lab in ArcGIS prior to this lab. We have discussed fluvial and glacial erosion in mountain landscapes; interactions between tectonics, climate, and erosion; the glacial buzzsaw concept; and basics of hypsometric curves. We read and discussed papers by Montgomery et al. (2001) and Egholm et al. (2009).

I expect students to be able to use Excel for simple calculations and plots.

How the activity is situated in the course

This lab is the second GIS-based lab in the course, falling in week 4 or 5. It is a stand-alone lab, although I assume students will use some of the GIS skills they picked up in lab 1.

Goals

Content/concepts goals for this activity

Topographic signatures of glacial vs. fluvial landscapes
Hypsometry

Higher order thinking skills goals for this activity

Data extraction in GIS
Data manipulation in Excel
Comparison of different datasets over a range of parameters
Comparing published findings with exploration of new areas

Other skills goals for this activity

Data synthesis and report writing
How to create cumulative distribution curves

Description and Teaching Materials

Prior to this lab we cover basic processes in fluvial and glacial erosion in mountainous environments, including the concept of a glacial buzzsaw limiting peak elevations. We read the Montgomery et al. (2001) paper that compares the north, central, and southern Andes as well as the Egholm et al. (2009) paper which investigates the glacial buzzsaw signal world-wide. Students have thus seen hypsometric data in two different modes of presentation along with the authors' interpretations of the data.

During the class session right before lab, we go over the mechanics of how to create a classic hypsometric curve (normalized, cumulative plot) as well as alternatives to this (non-cumulative, binned data). We brainstorm a series of mountain ranges around the world that fall under a range of climatic conditions (fluvial to glacial) and tectonic environments. Students each pick one mountain range to analyze in lab.

Prior to lab, I download 6 SRTM tiles in each mountain range and merge the DEMs into a single file. (Over time, I have built up datasets for most ranges students pick, so this is not onerous). You could have students do this themselves in lab, but then you risk problems like having the SRTM data servers down during lab.

In lab, each student extracts data from their DEMs and brings them into Excel. There, they create the different hypsometric curves. They are also responsible for estimating their local modern and LGM snowlines based on global curves. I collate all the data and post them for everyone to have access. Students are then asked to write up a report comparing 4-5 different locations.

Student handout (Microsoft Word 2007 (.docx) 21kB Jun11 14)

Teaching Notes and Tips

I have included dates in the handout attached here, so you can see the general timeline we use for data collection and analysis, posting to the class website, and for report writing.

This lab currently only covers elevation distributions, but I have also had students look at slope distributions and relief distributions, too. That is one potential extension of this. I have found it is a little harder for students to compare those datasets in a meaningful way.

Assessment

Students are assessed both on their technical skills (data extraction, analyses, and plotting) and on their ability to synthesize data from different environments (as seen in their reports).

References and Resources

Egholm, D.L., Nielson, S.B., Pedersen, V.K., and Lesemann, J.-E., 2009, Glacial effects limiting mountain height. Nature, v. 460, DOI:10.1038/nature08263.

Montgomery, D.R., Balco, G., and Willett, S.D., 2001, Climate, tectonics, and morphology of the Andes. Geology, v. 29, n. 7, pp. 579-582.

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