A weathering process where successive shells
of rock spall off the face of a mountain, like the skin of an
onion. The shells may be a few millimeters to several meters
thick. It is caused by sliding of rock sheets along joints that
form by differential stresses within a rock, typically generated
by chemical weathering or by cooling and uplift of the rock
mass from depth. For instance, weathering of feldspar to clay
causes an increase in volume. This volume increase is accommodated
through the generation of fractures parallel to the
surface, and the formation of some pop-up structures where
two slabs of rock pop up to form a triangular gap with a few
centimeters uplift off the surface. These pop-up structures
often break off, initiating the sliding of big slabs of rock off
the mountain. Exfoliation typically forms rounded, domeshaped
mountains known as exfoliation domes.
See also WEATHERING.
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