COLLEGE STUDENTS DEVELOPMENT OF ROCK IDENTIFICATION SKILLS

The ability to correctly identify rocks in hand specimen using relevant evidence and correct geologic terminology is a common goal of undergraduate introductory geoscience courses. We conducted a longitudinal study over two semesters to investigate how students in an introductory geoscience course developed rock identification and map reading skills. For this study we followed a basic interpretive qualitative study methodology. Eleven students were interviewed at the beginning of their enrollment in the course (pre interview) followed by a post interview at the end of the first semester and a post-post interview at the end of the second semester. Student responses were analyzed using a modified version of constant comparative analysis.

We present preliminary finds of our interviews for student responses to a sandstone sample they were asked to describe, identify and provide evidence. In pre interviews, 10 students correctly identified the sample as sedimentary and 5 recognized it was sandstone. One student identified the sample as igneous. Students also used mostly relevant evidence for identification (e.g. presence of sand grains and/or layers); however, they did not identify all relevant evidence (e.g. grain size, composition). Some students provided irrelevant lines of evidence such as reporting ‘it looks like a sandstone’. In the post interviews all students identified the sample as sedimentary and sandstone and 5 students included grain size as a descriptor (i.e. identified the sample as medium grained sandstone). Most students used multiple lines of evidence including composition, texture and absence of igneous or metamorphic textures. In the post-post interviews students introduced term ‘lithic arenite’ when identifying the sample. Students continued to use multiple lines of evidence (textural and compositional), although they provided fewer lines of evidence as compared to their post-interviews.

The findings from this study show that over two semesters of instruction students develop an understanding of how to correctly identify sedimentary rock samples from initially using general terms to using more specific, technical rock terms. They also develop the ability to use both texture and composition of the sample as lines of evidence and reduce the use of irrelevant sample features.