Visualizing structural geometry from outcrop patterns

Charlie Onasch
Bowling Green State University
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Using Google Earth, students will investigate the relationship between the geometry of rock bodies and their outcrop patterns.

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This activity is used in an undergraduate structural geology class typically taken in the Junior year.

Skills and concepts that students must have mastered

Students must have some familiarity with Google Earth. Specifically, they must be comfortable with the controls to zoom, change viewing angle, rotate, and fly around images. They must also have some understanding of geologic maps and cross sections, and strike and dip.

How the activity is situated in the course

This activity was designed for use in an undergraduate structural geology course. Students were given a shortened version of it as part of their first lab to set the stage for one of the most important goals of the lab portion of the course: interpretation of geologic maps. They were given the full exercise about halfway through the course when the focus was on geologic maps and cross sections. Together, the two exercises were also used as a pre/post-test assessment.


Content/concepts goals for this activity

1. Students will be able to interpret the geometry of planar dipping layers from the outcrop pattern
2. Students will be able to recognize different rock units based on their characteristics as seen on satellite images
3. Students will be able to draw a geologic map and interpret structure based on the map pattern of different units

Higher order thinking skills goals for this activity

Students will be able to visualize the three-dimensional geometry of rock bodies from patterns on two-dimensional surfaces.

Other skills goals for this activity

Using tools available on the internet.

Description of the activity/assignment

Understanding the relationship between the outcrop pattern and the 3-D geometry of rock bodies is a challenge for students, especially those with low spatial ability. While memorization of learning aids, such as the "rule of V's" can help students interpret structure, it doesn't really help them understand the interaction between topography and rock bodies, and thereby be freed of having to rely on memory aids.

Google Earth offers the ability to view topography in 3D, and in areas of good exposure, the interaction between topography and rock bodies can be clearly visualized by manipulating the viewer's perspective. Through this user interaction, a much clearer understanding of how outcrop patterns related to rock structure can be gained.

Determining whether students have met the goals

The learning goals can be assessed by having the students use Google Earth to look at other mountain belts (e.g., Zagros region in Iran). Students should also be given paper geologic maps and asked to interpret the structure from the map patterns. The exercise described above can also be given at two times in the course as a pre- and post-test.

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