Deciphering the Role of Solar Heating in Driving Rock Exfoliation: An Integrated Field and FEM Study

ABSTRACT: Surface-parallel exfoliation fracturing in rock domes shapes iconic landforms, contributes to rockfall hazards, and can provide insights into surface processes like weathering and solar heating. Recent studies have implicated solar heating in subcritical fracture propagation during exfoliation, yet the thermal-mechanical processes remain unclear. At Arabia Mountain, a biotite orthogneiss dome near Atlanta, Georgia, a spontaneous exfoliation event occurred in July 2023, uplifting a ~250 m2 area by ~30 cm. Instrumentation was deployed to record surface-parallel stresses, rock temperatures, and seismicity during summer 2024, capturing multiple real-time exfoliation events and dynamic fracture propagation, suggesting links between diurnal thermal cycles and subcritical crack growth. Using a phase field fracture model implemented in the Finite Element Method (FEM), we quantified thermal stress effects in the shallow subsurface under geostatic stress. Results indicate that stresses from summer temperature variations alone cannot explain the observed exfoliation fracturing without pre-existing micro-crack distributions or damage zones. This work highlights the importance of a likely complex interplay between surface thermal processes, topographic stress changes, and pre-existing tectonic stress fields in driving exfoliation. By integrating field observation and modeling, we provide new insights into the thermal-mechanical processes driving exfoliation, with implications for rock dome sensitivity to environmental changes.