Cutting Edge > Courses > Geomorphology > Teaching Activities > Build a Delta!

Build a Delta!

Doug Clark
Western Washington University
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  • Scientific Accuracy
  • Alignment of Learning Goals, Activities, and Assessments
  • Pedagogic Effectiveness
  • Robustness (usability and dependability of all components)
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This page first made public: Jun 6, 2008


This is a 3-part lab that allows new geomorphology students to experience first-hand the scientific method by investigating the processes and results of river-delta formation.

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Geomorphology (Geology 310) is a 300-level, five-credit (quarter system), field-oriented course that emphasizes locally observable (and measurable) geomorphic processes: rivers, hillslopes, mass wasting, glaciers. Early geology majors make up the majority of the class, but we get 30-40% non-majors taking it as well.

Skills and concepts that students must have mastered

Although this a 300-level course, the prerequisites include only one course in Physical Geology and College Algebra. Many of the students are new geology majors taking their second geology course. We also get students from archaeology, computer science, and environmental science. The course is writing intensive, has two three-hour labs per week and includes four in-class field trips.

How the activity is situated in the course

This set of labs is taught early in the course (starting either the first or second week), and spans two weeks (three lab periods).


Content/concepts goals for this activity

1. Where and how do deltas form, and what are the processes that are involved?
2. How do bedload and suspended load affect delta formation?
3. How and why does grain size vary within and across a delta? How does river flow-velocity relate to grain size?
4. How to relate conceptual and physical models to a real-world example of a landform.
5. how to relate landform to stratigraphy in a delta specifically, but also in other landforms as well.

Higher order thinking skills goals for this activity

1. how to propose hypotheses, design a research strategy to collect data that will test those hypotheses, how to analyze quantitative data, and then synthesize the results.
2. how to assess the value (and limits) of physical models, analytic measurements, and field observations.
3. students develop an appreciation for rates of deposition and sediment transport through the use of time-lapse animation of a stream-table delta.

Other skills goals for this activity

1. students learn how to operate a laser particle size analyzer (and to assess the data in graphical form).
2. students create a short report that synthesizes their results from all three labs plus readings from McPhee's "Atchafalaya."

Description of the activity/assignment

Lab 1: the students begin by describing on a worksheet their own ideas of delta formation using concept sketches and written descriptions of the stages of formation, with only broad guidance from the instructor. They are also asked to describe the key features of their concept sketches, and to hypothesize how those features might develop (the processes). The students have all been exposed to deltas in Physical Geology, but likely only have rudimentary knowledge of them. Once they have completed the worksheet, the entire class moves to a lab with a stream table in it, preset to run a "model delta." The model has both a web cam and a time-lapse web cam set up over the table to record the development. The students help start the water flowing and the cameras recording, then watch as it develops over the next 2-3 days.

Lab 2: In the second lab, we use grain-size analysis of the stream-table delta as a means of testing some of their ideas from lab 1. The students as a class develop a strategy to sample the stream-table delta for grain size, using a laser grain-size analyzer. Each pair of students collect one sample, but are also asked to predict the changes in grain size distribution for samples elsewhere in the delta. The particle size analyzer rapidly provides results to the students near the end of lab.

Lab 3: the final lab is a field trip to a pair of gravel pits that expose the guts of two natural stranded deltas, including topset and foreset beds. The students are asked to assess the landforms on a topo map before arriving, and to describe the deposits at each site we visit. On the final writeup, the students need to synthesize all the elements of the three labs, along with input from our readings in the textbook (Easterbrook) and McPhee's "Control of Nature." 

Determining whether students have met the goals

Lab sheets for each lab are handed in, checked over by the instructor (with comments and a check, check +, or check -, depending on the quality), then handed back for the following class.
The final writeup is graded using a rubric.
The first midterm includes an essay question about delta formation, relating landform to sedimentology.

More information about assessment tools and techniques.

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Supporting references/URLs

Clark, D.H., and Linneman, S.R., 2005, Combining stream table experiments, high-tech particle analysis, and the web to help geomorphology students evaluate landform evolution, Journal of Geoscience Education, 53, p. 110-115.

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