What is the term for the indent at the base of a cliff formed by undercutting?

The term for the indent at the base of a cliff formed by undercutting is known as a wave-cut notch. This feature develops as waves continuously attack the base of the cliff, creating a recess. Over time, erosion due to wave action removes material, leading to the formation of this notch. As the notch deepens, it can contribute to the stability of the cliff above, as eventually the unsupported rock may collapse, leading to further retreat of the cliff line.

In the context of coastal processes, a wave-cut notch plays a significant role in the development of coastal landforms and the overall reshaping of the coastline. It is distinct from other coastal features, such as a beach, which is an accumulation of sediment, or a coastal sand dune, which comprises sand deposited by wind. A spit, on the other hand, refers to a depositional landform extending from the mainland into the water, created by the accumulation of sediment due to longshore drift. Each of these terms represents different processes and features related to coastal geography.