How can we use rock characteristics to interpret rock origin?

Tuesday 3:00pm-3:20pm Northrop Hall: 340
Teaching Demonstration Part of Tuesday B


Robyn Dahl, Western Washington University


I will share the worksheets that students complete during this activity, the rock specimens that student analyze, and links to the guided background research. For the demonstration, I will model an abbreviated version of the jigsaw.


Students employ the jigsaw method to characterize four rock types (A=sedimentary, B=metamorphic, C=igneous extrusive, and D=igneous intrusive), infer formation processes and determine how they are related via the rock cycle. In addition to learning content, this activity can be used to model the jigsaw method for pre-service teachers. Students start in four-person "home groups." Within home groups, each student is assigned to one specialty rock type (labeled only as A B C or D, with no extra information). Students split into "specialty groups," and are given a set of 10 specimens of their rock type. Students observe and describe each of the specimens, then the specialty group creates a consensus general description for their rock type. Students return to their home groups, share descriptions and speculate about how their observations might provide information on processes of formation. Students then put their descriptions aside and do guided background research on how rock characteristics (textures) relate to formation processes of sedimentary, intrusive igneous, extrusive igneous and metamorphic rocks, and the rock cycle. To complete the assignment, students use their descriptions and newly acquired content knowledge to infer formation processes for each of their specialty rock types, and hence classify rock types A-D.


At Western Washington University, this activity is used in the Science Education course Matter and Energy in Earth Systems, a course designed for pre-service elementary teachers, many of whom have not previous taken any geoscience courses. The course and this activity are designed to both teach content and model effective pedagogy. This activity would also be appropriate for use in introductory geology courses.

Why It Works

This activity uses a constructivist learning model that requires students to use their own observations to form their own classification system for rock types before learning the "official" classification system. It is also innovative because it splits intrusive and extrusive igneous rocks into two groups, which allows students to more effectively use observation to determine the range of formation processes for igneous rocks. Formative assessments ("check-ins," whiteboards and questions from instructors) ensure that specialty group knowledge is shared with all members of the home group. If the target audience includes teachers, this activity also effectively demonstrates the jigsaw method.