Exfoliation geology is a type of rock weathering where the rock's layers peel off in whole sheets instead of grain by grain. Large-scale exfoliation occurs due to the mechanics of gravity on a curved surface, while small-scale exfoliation is due to chemical weathering.
In exfoliation, the rock layer that is peeled off is usually composed of coarse lava rock that is uniform and doesn't have fractures. It is placed under stress from the rock layers directly above it, and the pressure is relieved due to progressive erosion. Tension is created from this reduction in pressure at right angles to the rock's surface. This tension forms cracks that run along the rock's surface, and water fills these cracks to cause chemical erosion that separates the rock from the rest of the surface.