Slicing Channels

Tom Hickson, University of St. Thomas, and Ilyse Resnick, Temple University
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Students examine 3D channel-shaped objects and 2D slices through those objects. The purpose is to get them thinking about how the 3D geometry of a channel is reduced to a random 2D slice through the channel in a typical outcrop, so that they can recognize channel deposits.

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Learning Goals

After successfully completing this exercise, students will be able to recognize channel deposits in outcrop and visualize the 3D shapes of channels that could produce the 2D cross-sectional shapes we see in outcrops.

Context for Use

This pair of exercises is designed to get students thinking about the possible geometries of channel deposits in outcrop, and what the geometry of that 2D exposure tells us about the 3D morphology of the stream deposit.

Description and Teaching Materials

Slices through channel-shaped objects (Microsoft Word 2007 (.docx) 12.3MB May19 15)
Slices through geological channels (Microsoft Word 2007 (.docx) 4.6MB May19 15)

Teaching Notes and Tips

When students have completed the second exercise, I lead a discussion on the final question (What are the features in outcrops that you look for to recognize channels?). I make sure that answers include concave up, lateral pinching, and truncation of lower layers.

This exercise was developed as part of a set of exercises to support 3D visualization skills. These exercises had an intended order. Instructors can pick and choose the exercises, but the order we intended was as follows:

  1. Introduction to 3D sketching
  2. Sketching block diagrams
  3. Sketching 3D Ripples and Dunes
  4. Slicing cylinders
  5. Slicing channels
  6. Slicing fruit
  7. Slicing rocks
  8. Slicing fossils


I take a quick look at students' answers to see how well they are able to complete the exercise.

References and Resources

Using Gesture to Support Spatial Thinking highlights the value of gesture in communicating spatial information. It consists of two short exercises, and can be used in preparation for any other exercise in which students will be asked to use gesture to communicate spatial information.