Fudge Factors in Lessons on Crystallization, Rheology and Morphology of Basalt Lava Flows

Abstract

Fudge is an excellent analog for basaltic lava and making or tasting fudge leads to memorable lessons on the importance of crystals in controlling the morphology of basaltic lava flows. In particular, students learn why ‘a’a flows have rough broken surfaces, while pahoehoe flows are smooth or folded. Furthermore, fudge provides an interesting analog in lessons on the factors that control crystal nucleation and growth as well as how crystals affect magma rheology. Although the full process of making fudge from scratch is too long for a lecture demonstration, fudge can be incorporated into lessons on basalt flows by way of taste-tests, photographs or simplified experiments with pre-made fudge and syrup. Advanced students can run experiments during a laboratory period and examine the crystal textures under a microscope, or do their own experiments in small groups outside of the classroom. Evaluation with written quizzes shows that fudge demonstrations can be an effective aid for teaching the complex concepts of crystal nucleation and growth and their effects on basalt lava flows.