THE PET FUR TERNARY: USING ANALOGY TO INTRODUCE EARTH MATERIALS STUDENTS TO TERNARY DIAGRAMS

A well-constructed analogy can be a powerful method to aid students in learning unfamiliar phenomena, concepts, skills, or processes. Analogies work particularly well when the learning domain content is too small, too large, or too abstract to be immediately perceived – which includes much of the content in a typical earth materials, mineralogy, or petrology course. An analogy focuses student attention on salient features of a familiar (source) domain, and then draws parallels to the features of the unfamiliar (target) domain. The more features that the source and target share, the better the analogy works to aid knowledge transfer to the new domain. Instructors should also be careful in selecting source content that a wide range of their students will find familiar.

Ternary diagrams are one of the most ubiquitous data representations in the geosciences, yet introductory students often struggle to plot, read, and interpret data on ternary plots. In an introductory earth materials course for geoscience majors, I use a 15-20 minute, in-class exercise to introduce students to ternary diagrams. The fur colors of my pets (two brown, tan, and white guinea pigs and two orange, black, and white cats) serves as the source domain to introduce the target domain of multicomponent rock and mineral systems. After a brief introduction to reading ternary plots and an instructor-led exercise, students estimate the proportions of white, black, and brown ± tan ± orange fur in photographs of cats, dogs, horses, rabbits, and guinea pigs. Estimating and plotting the proportions of animal fur colors has multiple parallels to ternary plots used in mineralogy and petrology, in that some components (such as eye and nose colors) are ignored, or multiple similar components (such as brown ± tan ± orange fur) are combined. As I introduce ternary diagrams relevant to mineralogy and petrology throughout the course, I remind students of the pet fur exercise, thereby activating the familiar analogical source domain to help them transfer knowledge to the unfamiliar mineral and rock domains.