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Rock unconformity. An unconformity is a break between two rock types laid down at different times. This is an angular unconformity (or nonconformity), in which the rock layers are at different angles. Here, sedimentary rock (upper half) was formed by the deposition of successive layers of particles which became compressed. This occurred after the underlying igneous rock was folded. Photographed at Kilkenny Bay, England. (KEYSTONE/SCIENCE PHOTO LIBRARY/MARTIN BOND)