Dyanna Czeck

University of Wisconsin- Milwaukee

undergraduate required structural geology course for majors

Students must be familiar with the following terms and concepts: rheology, force, stress, strain, elastic, plastic, competence, deformation experiments, yield strength, ultimate strength, and rupture.

This activity is one of many lab exercises students complete throughout the semester. It is followed by an in-class activity where the students use analogue materials to explore rheologic models such as Elastic, Newtonian, and Plastic.

The students should gain an intuitive sense for the role of the following in determining the rheology of a deforming rock: lithology, stress, temperature, confining pressure, preexisting weakness, strain rate, and accumulated strain. They will also closely examine the important results of some deformation experiments and learn where natural deformation may help us learn more about rheology.

analysis of data, synthesis of ideas.

critical reading of data presented in graph format, working in groups.

A short laboratory exercise, conducted by students, is used to illustrate the multiple factors that contribute to rocks' varied responses to deformation. Analogue materials (play-doh, notebook springs, butter, silly putty, plastic bags, etc.) are used to illustrate many of the controlling factors such as lithology, stress, temperature, confining pressure, strain rate, preexisting weaknesses, and accumulated strain. The analogue experiments are presented in conjunction with parallel data from deformation experiments and field studies. The tandem presentation of analogue experiment and real data requires the students to obtain a natural "feel" for rheologic parameters and more exhaustively analyze the important conclusions obtained from field and deformation experiment data.

I help students with the exercises as needed. The students submit their written responses to the exercise for credit. The students use their understanding of rheology in future assignments.

Davis, G. H., and Reynolds, S. J. 1996. Structural Geology of Rocks and Regions, 2nd edition. New York: John Wiley & Sons, p. 132-137.

Donath, F. A., 1970. Some information squeezed out of rock. American Scientist 58, 54-72.

Griggs, D. T., Turner, F. J., and Heard, H. C., 1960. Deformation of rocks at 500° to 800° C, in Griggs, D. T., and Handin, J. (eds.), Rock deformation: Geological Society of America Memoir 79, 39-104.

Heard, H. C., 1963. Effect of large changes in strain rate in the experimental deformation of Yule marble. Journal of Geology 71, 162-195.