Using a Rock Tumbler in Sedimentology Courses to Simulate Weathering and Erosional Processes
College of Liberal Arts and Sciences
Educators have suggested using rock tumblers in introductory geology classes at the college level and in K-12 earth science courses to simulate weathering of clasts, but we suggest experiments using a tumbler are also useful in sedimentology courses for geology majors. Experiments can be used to demonstrate loss of mass as a function of rock type or degree of lithification as well as to determine effects on grain shape. In addition to writing laboratory reports, groups can give presentations in class. By doing the experiments and presentations early in the semester, the instructor can refer back to the results when presenting a variety of topics including intra- versus extraformational origin of clasts, grain shape as a function of distance of transport, and the biased preservation of rock types in clastic rocks. We found that loss of mass and increase in roundness are predictable when the rocks being compared vary significantly in composition and texture (e.g., granite versus limestone); however, significant variation is observed when comparing different sandstones and carbonates due to variation in degree of lithification. Differences in weight loss between duplicate samples can range from almost zero to several percent depending on the homogeneity of the sample. Using carborundum rather than quartz sand for grit accelerates the tests. However, preliminary results indicate the amount of mass lost using the two grits may not be consistent for various rock types perhaps causing difficulty when equating distance of transport in the tumbler to a natural environment in which quartz sand dominates.
Geological Society of America Annual Meeting
Videtich, Patricia; Dalman, Erica; and Koeman, Elizabeth, "Using a Rock Tumbler in Sedimentology Courses to Simulate Weathering and Erosional Processes" (2010). Faculty Scholarly Dissemination Grants. 84.