Phillip Resor

Wesleyan University

undergraduate core course in structural geology

Students should be familiar with fold description. They should be familiar with viscous flow and linear viscous materials.

This activity is done as a lab in my course prior to a field trip where the students measure wavelengths and layer thicknesses of pegmatite veins folded under amphibolite-facies conditions.

ductile deformation, viscous flow, buckle folding

Analog modeling, model evaluation

In order to better understand ductile deformation and the growth of folds students perform a series of experiments with readily available viscous analog materials. Students begin by exploring the concept of viscosity and viscous flow problems by using Stoke's Law to measure viscosity of corn syrup from the terminal velocity of a falling steel ball. The students then complete a second series of experiments folding a stiffer material (fruit leather) within a corn syrup matrix. By varying the thickness of the fruit leather layer they discover the linear relationship between layer thickness and dominant wavelength predicted by viscous fold theory.

Students submit a report that documents their experimental methods, results, and answers discussion questions. In my class this activity is tied directly to field observation of folds that likely formed by a similar mechanism.