The Efficacy of Frost Weathering Processes in Alpine Rockwalls

Abstract

AbstractWeathering processes prepare and trigger rockfall, which is a key agent of alpine landscape evolution and a hazardous process. The relative importance of different weathering processes is hard to decipher; nevertheless, current knowledge assumes a dominant role of frost cracking in eroding alpine rockwalls. This study uses a laboratory approach to simulate volumetric expansion and ice segregation in four alpine rock samples, monitors crack deformation, and quantifies frost weathering efficacy. Our results show that short‐term volumetric expansion in cracks provides stresses up to 10 MPa over hours, while long‐term ice segregation causes stresses of 1 MPa over days. While volumetric expansion in fall can reach critical fracture levels, volumetric expansion in early summer and ice segregation rather approaches subcritical fracture propagation levels. We conclude that subcritical crack propagation is the dominant antecedent process of rockfall initiation, which can be amplified by rare critical cracking due to volumetric expansion.