There are several types of unconformities, each representing a different type of break in the geologic record:

* Angular unconformity: Tilted or folded sedimentary rocks are overlain by younger, flat-lying sedimentary rocks.

* Disconformity: Parallel layers of sedimentary rock are separated by a period of erosion or non-deposition.

* Nonconformity: Sedimentary rocks lie directly on top of igneous or metamorphic rocks.

Unconformities are important because they indicate periods of time when there was no deposition or when existing rocks were eroded. They can provide valuable information about the geologic history of an area.