Exfoliating granite

The external delaminated layers of granite are gradually produced by the cyclic variations of temperature at the surface of the rock in a process also called spalling.

Frost and ice expansion in the joints during the winter accelerate the alteration process while the most unstable loose external layers are removed by gravity assisted by runoff water.

The surface layer, often a couple hundred feet thick, separates from the underlying granite along an expansion joint to form a shell.

[4] Concentric slabs/shells of rock begin to break loose, onion-like layers subparallel to the exterior called exfoliating, sheet jointing, or fractures.

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.

Exfoliating slabs of granite, on Half Dome in Yosemite National Park , USA
Exfoliating granite, at Enchanted Rock State Natural Area , Texas