Influences Driving and Limiting the Efficacy of Ice Segregation in Alpine Rocks

Abstract

Rockwall erosion by rockfall is largely controlled by frost weathering in high alpine environments. As alpine rock types are characterized by crack-dominated porosity and high rock strength, frost cracking observations from low strength and grain supported pore-space rocks cannot be transferred. Here, we conducted laboratory experiments on Wetterstein limestone samples with different initial crack density and saturation to test their influence on frost cracking efficacy. We exposed rocks to real-rockwall freezing conditions and monitored acoustic emissions as a proxy for cracking. To differentiate triggers of observed cracking, we modeled ice pressure and thermal stresses. Our results show initial full saturation is not a singular prerequisite for frost cracking. We also observe higher cracking rates in less-fractured rock. Finally, we find that the temperature threshold for frost cracking in alpine rocks falls below −7°C. Thus, colder, north-exposed rock faces in the Alps likely experience more frost cracking than southern-facing counterparts.