Moro Rock is a dome-shaped granite monolith. Common in the Sierra Nevada, these domes form by exfoliation, the spalling or casting off in scales, plates, or sheets of rock layers on otherwise unjointed granite. Outward expansion of the granite results in exfoliations. Expansion results from load relief; when the overburden that once capped the granite has eroded away, the source of compression is removed and the granite slowly expands. Fractures that form during exfoliation tend to cut corners. This ultimately results in rounded dome-like forms.