PETROGRAPHIC PROBLEM-SOLVING ASSIGNMENTS: AN AUTHENTIC ASSESSMENT STRATEGY FOR UNDERGRADUATE PETROLOGY COURSES

An authentic assessment strategy was developed that actively engages students in the study of rocks and minerals within the context of an Earth Science degree at a four-year liberal arts university. The inquiry-based pedagogy consists of a series of two-week mini-projects, called petrographic problem-solving (PPS) assignments, in which students use thin sections as a geologic data source for conducting scientific investigations. The central idea behind PPS assignments is for students to make observations, identify a scientific question, propose a working hypothesis, collect data to test the hypothesis, and defend their results in written reports and oral presentations. Computer-based technologies, including digital cameras interfaced with microscopes and data-processing software, are used to acquire photomicrographs, collect data, and analyze results. For each assignment, deliverables consist of a two-page paper and presentation. In the presentation sessions, modeled after professional meetings, class members are encouraged to question their student colleagues.

PPS assignments serve as an authentic assessment strategy in two upper-division Earth Science courses. Students are introduced to PPS assignments in a prerequisite Microscopy course. In the subsequent Petrology course, three assignments are conducted, and a summative take-home PPS exercise is completed as part of the final exam. PPS assignments are directly aligned with course content in Petrology and are designed to augment traditional assessment strategies. To determine whether the learning goals of PPS assignments have been met, student work is evaluated in terms of application of scientific methodology, problem solving, and communication skills. Analysis of assessment data collected over a six-year period shows that student performance improved over the course of each term by 4.5% on average (n=53), demonstrating increased proficiency in conducting authentic investigations, solving geologic problems, and communicating results. As a key component of the mineralogy-petrology curriculum in a broad-based undergraduate degree program, PPS assignments engage students in the study of Earth materials, involve them in the scientific process, and promote active learning with an emphasis on analysis, synthesis, and evaluation.