LEARNING ABOUT GEOLOGIC MAPS IS A PIECE OF CAKE: USING ROLLED FONDANT IN AN INTRODUCTORY GEOLOGY LAB TO CREATE THE FOLDED MAP PATTERNS OF THE MARYLAND PIEDMONT

Among the most challenging skills to develop in introductory geology students is the ability to visualize three-dimensional geologic structures on a geologic map. To help students gain this proficiency, we created a laboratory activity that uses commercial rolled fondant as an analog for rock strata. Advantages of using fondant over modeling clay include: lower viscosity, making it easier to assemble multilayer stacks; color variety to match local geologic maps; and easier clean-up because it is water-soluble, biodegradable, and actually edible. As students create geologic structures and then erode them, they discover what the patterns on a geologic map reveal.

The complex refolded folds of the Maryland Piedmont are simplified into a series of domes cored by Baltimore Gneiss. Fondant colors are selected to match the three oldest units depicted on the Maryland geologic map: Baltimore Gneiss, Setters Formation (quartzite and schist members), and Cockeysville Marble. Each group is given a stack of rolled fondant and instructed to fold it into either a round or elongate dome, erode it to horizontal using a stiff index card, and draw the result as a map, cross-section, and then a block diagram. Students also discover the “Rule of V’s” by eroding stream valleys across their domes. Following the creation of their domes, students assemble them jigsaw-style and compare their resulting map pattern to the geologic map of Baltimore County. Students realize the real, more complicated, structural pattern when one of the domes must be refolded to match the map. A schematic regional cross-section is then drawn, followed by the illustration of a refolded nappe.

As the laboratory investigation concludes, learning outcomes are reinforced as students then examine sets of local rock samples and construct the local stratigraphy that correlates with the geologic map. Following this learning activity, students were able to correctly deduce dip directions and fold types on geologic maps at a markedly higher level of success than in previous years of teaching this topic. Summative assessment measures include interpreting the geology of a similar but more complex “dome” to the west of the area. Preliminary qualitative feedback is overwhelmingly positive, particularly among students self-identifying as visual and kinesthetic learners.