When sea-level fell, the land was exposed to erosion creating an unconformity. When the sea level was high marine strata formed. The strata in the Grand Canyon represent alternating marine transgressions and regressions where sea level rose and fell over millions of years. A nonconformity occurs when sedimentary rock is deposited on top of igneous and metamorphic rocks as is the case with the contact between the strata and basement rocks at the bottom of the Grand Canyon. There are three types of unconformities, nonconformity, disconformity, and angular unconformity. The pinching Temple Butte is the easiest to see the erosion, but even between the Muav and Redwall, there is an unconformity. \): All three of these formations have a disconformity at the two contacts between them.
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