Effects of Experimental Freeze-Thaw and Wet-Dry Weathering Cycles on Fluvial Abrasion Rates

How do rocks break down as they work their way downstream? This study focuses on weathering and abrasion processes of volcanic mass wasting deposits in rivers of the Pacific Northwest. Implications include a more effective approach to modeling downstream fining as well as increased understanding of potential impacts of sediment pulses on flood risks. I combine methodologies from fluvial abrasion and rock weathering experiments to provide a foundation for further research into weathering mediated abrasion. I subject samples to 20 freeze-thaw (FT) and wet-dry (WD) cycles and compare each weathering process' effects on fluvial abrasion rates. Both weathering processes weaken the samples enough to increase abrasion rates; FT cycles are slightly more effective than WD cycles. Both weathering processes and the abrasion process all affect the samples that have lower Schmidt Rock Hammer Strengths (SHRS), lower densities, and contain clay minerals. The higher SHRS, higher density, and clay-absent rocks are more resistant to weathering, abrasion, and the combination of both processes. Further work should be done to validate the findings of this paper and expand the work to other lithologies and longer timescales of weathering and abrasion. This will be important in understanding the physical and mineralogical changes associated with these brief weathering durations.