Name three kinds of unconformities. How does each type form, and how might you distinguish them?

The three kinds of unconformities are angular unconformity, disconformity, and nonconformity. Angular unconformities form when sedimentary rock layers are deposited on top of tilted or folded rock layers, and can be distinguished by older, tilted layers underneath younger, flat-lying sedimentary layers. Disconformities occur when two parallel sedimentary rock layers are separated by an erosion surface or a soil layer, indicating a gap in time between the deposition of the two layers. Nonconformities form when sedimentary rock layers are deposited on top of igneous or metamorphic rocks, and can be distinguished by the contact between sedimentary rocks and the underlying igneous or metamorphic rocks.