Unconformities are gaps in the geologic rock record, where strata of rock are missing due to erosion or non-deposition. They represent a break in the continuity of the rock record and reflect a period of time where no sediment was deposited or the existing sediments were removed by erosion.
There are three main types of unconformities:
Nonconformity: A nonconformity occurs when sedimentary rocks are deposited on top of igneous or metamorphic rocks.
Angular Unconformity: An angular unconformity occurs when younger sedimentary rocks are deposited at an angle on top of older sedimentary rocks that have been tilted or folded.
Disconformity: A disconformity occurs when a layer of parallel bedding is missing in the rock record, but the strata on either side are still parallel.
Unconformities are important to geologists because they provide information about changes in the environment, such as uplift, erosion, and changes in sea level, that occurred during the time represented by the gap in the rock record. They also provide clues about the relative ages of the rocks and help geologists determine the sequence of events that took place in the geologic past.