Advanced steronet -finding rotation axes

Stephen Hurst, University of Illinois

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This page first made public: Jun 29, 2012

Summary

Using stereonets to find rotation axes of tilted planes. Paleomagnetic vectors used as indicators of rotations of dikes and planes.

Structural Visualizations, Regional Structural/Tectonic Activity, ...(more) | College Upper (15-16)

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Context

Audience

structural geology for majors, upper level

Skills and concepts that students must have mastered

simple use of stereonets, be able to project lines and planes, find great circles and measure angles.

How the activity is situated in the course

advanced extra credit exercise.

Goals

Content/concepts goals for this activity

Finding rotation axes and orignal orientation of planar features that have been deformed by one or more rotations. Visualizing the rotation in 3D and on a steronet.

Higher order thinking skills goals for this activity

3-D visualization, analysis of various kinds of field data.

Other skills goals for this activity

evaluating multiple results and choosing most likely

Description and Teaching Materials

Enclosed is a PDF with a description of a method to find arbitrary rotation axes given some orientation data - in this case a non-vertical dike with an initial and measured paleomagnetic direction associated with it.
A second Word doc is attached with some questions that might come up, trouble spots and possible example data to be used.

Method for finding rotation on a steronet (Acrobat (PDF) 9kB Jun29 12)
Data and Hints for steronet exercise (Microsoft Word 24kB Jun29 12)

Teaching Notes and Tips

A physical model consisting of a flat piece of wood (the plane or dike) with two dowels set into it (one perpendicular for the pole) and one at another angle is very helpful for visualizing the problem/solution. other suggestions in the Hints and data file.