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Post-Settlement Erosion and Deposition

Mary Savina
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This material was originally developed as part of the Carleton College Teaching Activity Collection
through its collaboration with the SERC Pedagogic Service.

Summary

In this example, a field laboratory in introductory geology becomes a test of a hypothesis: Does the model proposed by Stanley Trimble for Coon Creek, Wisconsin adequately describe the history of post-European-settlement erosion and deposition in a small drainage in southeast Minnesota?

Learning Goals

This exercise includes the following pedagogical strategies:
  • working in groups
  • collecting new data in the field
  • collecting and working with quantitative data
  • close reading of a professional article and associated commentary and debate
  • writing a lab report in the format of a scientific article

Context for Use

A version of this exercise can be constructed for any area of the country where agriculture, grazing and/or urbanization has altered the landscape. See references at the end of the .pdf file to resources for the Pacific Northwest and desert Southwest.

Look for the following characteristics in choosing a field site:

  • An area that can be covered on foot in a single lab period (less than one km2)
  • A stream valley that has been partially filled with sediment and later incised, so that sedimentary features of the fill are visible
  • Permission from all landowners for access

Teaching Materials

Students should bring to lab:
  • Metric ruler
  • Notebook and sharp hard pencil for taking notes
  • Field clothes (long pants, long sleeves, boots)

Instructors should provide:
  • 50 m tapes
  • Two meter sticks
  • Base maps of field area
Full lab handout in .doc form (Microsoft Word 41kB Sep6 06)

Teaching Notes and Tips

Teaching tips for this lab:
  • Many students will not read the Trimble paper carefully until after they return from the field. Thus, it is important to take time in the field to explain how their field measurements can be translated into volumes of material deposited and eroded.
  • You may want to divide the field site and have each small group of three students measure part of it. Each group's results could then be posted to the entire class.
  • Make a base map for the students from an air photo or topographic map. [Link to "How to find an air photo of your area?]

Assessment

From Geology 120 syllabus: "When reading written work, Mary looks for well-defined questions, good understanding of the subject, careful and complete observations of geologic processes, sound logic connecting the observations to the conclusions, clearly stated conclusions and complete discussion of the implications of the conclusions. All sources of information, including web sites, should be cited completely."
For this assignment specifically:
  • Does the paper have appropriate sections and subheadings?
  • Do each of the sections contain the appropriate content?
  • Are all three questions addressed in the discussion?
  • Are results reported accurately and clearly? Were enough measurements taken?
  • Does the paper show a reasonable level of understanding of the geological history and how humans may have influenced this history?
  • Can I tell from the paper that the students have read the Trimble article and its relatives?

References and Resources


References:
  1. Trimble, Stanley W., 1999, Decreased Rates of Alluvial Sediment Storage in the Coon Creek Basin, Wisconsin, 1975-93: Science, v. 285, p. 1244-1246.
  2. Glanz, James, 1999, Sharp Drop seen in Soil Erosion Rates: Science, v. 285, p.1187-1189

  3. (Both of the previous are in the August 20 1999 issue).
  4. Pimentel, David, Skidmore, Edward L., Trimble, Stanley W., 1999, Rates of Soil Erosion: Science, v. 286: p. 1477. (19 November issue)

  5. (This is a comment and response to Trimble's original article)
  6. Trimble, Stanley W. and Pierre Crosson, 2000, U. S. Soil Erosion Rates - Myth and Reality: Science, v. 289, p. 248-250. (14 July 2000 issue)
  7. M. A. Nearing, M. J. M. Romkens, L. D. Norton, D. E. Stott, F. E. Rhoton, J. M. Laflen, D. C. Flanagan, C. V. Alonso, R. L. Binger, S. M. Dabney, O. C. Doering, C. H. Huang, K. C. McGregor, A. Simon; Stanley W. Trimble, and Pierre Crosson, 2000, Measurements and Models of Soil Loss Rates: Science, v. 290, p. 1300-1301 (17 November issue)

  8. (This is a letter and response to the Trimble and Crosson article).

Subject

Geoscience:Geology:Sedimentary Geology:Techniques of Sedimentary Geology, Sediment Transport and Deposition

Resource Type

Activities:Field Activity:Field laboratories, Importation of field observations into the classroom

Special Interest

Field-Based Teaching and Learning

Grade Level

College Lower (13-14):Introductory Level

Ready for Use

Ready to Use, Meets Peer Review Standard:Anonymous Peer Review

Earth System Topics

Surface Processes:Soils, Solid Earth:Earth Materials:Rocks, Surface Processes:Weathering, Erosion, Mass Wasting

Topics

Human Dimensions/Resources, Earth surface

Theme

Teach the Earth:Teaching Environments:Intro Geoscience, Teach the Earth:Course Topics:Sedimentary Geology, Teach the Earth:Enhancing your Teaching:Teaching in the Field