Sea cave
A hollow in a coastal rock face formed chiefly by wave action, often enlarged along joints or weaker rock.
Hydraulic action: Erosion caused when water is forced into cracks, compressing trapped air and exerting pressure on rock. Repeated wave pressure attacks cracks that can become a cave’s initial opening.
Sea cliff: A steep rock face at the coast, shaped by marine erosion, weathering, or land movement. A sea cave is an opening within this coastal landform.
Fingal's Cave: A sea cave on the uninhabited island of Staffa in Scotland, noted for its basalt columns and acoustics. Its columnar basalt illustrates how regular fractures shape a striking cave interior.
Sea arch: A coastal rock opening that passes through a headland, commonly formed when a sea cave erodes through it. An arch can develop when erosion links or breaks through a sea cave.
Abrasion (geology): Rock erosion caused by particles carried by water, wind, ice, or gravity scraping against surfaces. Wave-borne sand and stones grind cave walls and enlarge openings.
Headland: A piece of land projecting into a body of water, commonly formed where resistant rock meets the coast. Headlands often receive concentrated wave attack and contain sea caves.
Blue Grotto (Capri): A sea cave on Capri, Italy, known for intense blue light entering through an underwater opening. Its submerged entrance and light effects show how cave geometry shapes appearance.
Sea stack: An isolated pillar of coastal rock left offshore after erosion separates it from a headland. A stack may remain after a cave enlarges into an arch and the arch collapses.
Wave refraction: The bending of waves as parts of a wave front encounter different water depths or speeds. Refraction can focus wave energy on headlands where sea caves develop.
Coastal erosion: The wearing away and removal of material from coastlines by waves, currents, weather, and related processes. Sea-cave formation is one localized expression of coastal erosion.