Investigating controls on exfoliation fracture geometry across glaciated and non-glaciated granitic domes, Yosemite National Park, USA

Exfoliation fractures are a defining feature of Yosemite’s granitic landscapes, yet the relative roles of lithology, glacial history, inherited structural fabrics, and near-surface thermal processes in controlling their geometry remain incompletely constrained. To evaluate these controls, we collected detailed field measurements across a suite of granitic domes spanning glaciated (Pothole Dome, Puppy Dome, Lembert Dome, Turtleback Dome, Olmsted Point) and non-glaciated (Half Dome, Sentinel Dome, North Dome) settings. Field investigations included systematic measurements of exfoliation sheet thickness and length, fracture orientation data, photographic documentation, and GPS surveys to assess spatial distributions of exfoliation fractures on individual domes. These data are integrated with lidar-derived topographic measurements to provide surface context and support geometry-based analyses.

Preliminary results indicate that exfoliation sheet thickness varies between domes, with glaciated domes tending to display thicker sheets and broader thickness distributions than non-glaciated domes, although substantial overlap exists between groups. Non-glaciated domes commonly exhibit thinner sheets and more variable geometries, potentially due to longer near-surface exposure and progressive weathering accumulation. Across all sites, exfoliation sheet length shows weak to moderate scaling with thickness; however, prevalent scatter in the data suggests that sheet geometry may not be influenced by thickness alone, but also by pre-existing joint sets and cross-cutting structural features that may limit lateral fracture propagation. Spatial context from GPS transects demonstrates that measurements were collected across broad surface positions on individual domes, with transects capturing tens to nearly 300 m of relief, reducing sampling bias and supporting dome-scale interpretation. Prior monitoring studies and field observations of rockfalls and active surface cracking in Yosemite suggest diurnal and seasonal thermal fluctuations contribute to ongoing subcritical crack growth, implicating thermal stresses as an active modern process superimposed onto background stresses (e.g., inherited structural features, removal of overburden, and tectonic and topographic stress). By comparing exfoliation characteristics across contrasting geomorphic settings, this study better constrains how factors such as lithology, glaciation history, inherited structures, and thermal forcing interact to shape near-surface fracture development in granitic terrains, with implications for rockfall hazard assessment and climate-sensitive rock damage processes.