Exfoliating granite

Exfoliating granite is granite that is exfoliating.

Homogeneous granitic plutons are created in high-pressure environments and slowly solidify beneath the earth’s crust. Vertical compression of overburden releases through erosion, or removal of overlying rocks resulting in unloading. Other contributors of unloading are tectonic uplift, glacier retreat, and mass wasting. The pressure is relieved when the granite is exposed at the surface, allowing it to expand towards the atmosphere.

On the surface, if the granite is not jointed, or if it has few joints, then the exposed surface usually expands faster than the underlying granite. The surface layer, often a couple hundred of feet thick, separates from the underlying granite along an expansion joint to form a shell. As this continues, several concentric shells may form to depths of 100 feet (30 m) feet or more. Concentric slabs/shells of rock begin to break loose, onion-like layers subparallel to the exterior called exfoliating, sheet jointing, or fractures. As the granite expands the outer, most shells become susceptible to weathering by water pressure, freeze/thaw cycles, and functioning vegetation is a process called physical weathering.  The sheets of granite are large enough to shave off sharp edges on the granite’s surface creating a dome shape. The overall activity creates exfoliation domes.

Exfoliating rock can trigger rockfall. Rock Falls in Yosemite National Park are common and pose threats to visitors. United States Geological Survey (USGS) conducted a study over a three-year period monitoring granite cracks within the park’s Valley. Data collected by Park Geologist Greg Stock, and USGS civil engineer Brian Collins using deformation and temperature gauges. They concluded that there is an outward expansion with the change in thermal temperature up to an inch. With prolonged movement, the cracks expand over time and create exfoliation. 

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Wikipedia