Introduction
A wave-cut platform (also termed a shore platform, coastal bench, or wave-cut cliff) is a narrow, nearly level geomorphic surface produced by the erosive action of waves at the base of a sea cliff or along the shoreline of a bay, sea, or lake. It represents the abrasion and undercutting zone where persistent wave attack and associated coastal processes strip away rock to form a planar bench that extends seaward from the cliff base.
These platforms are most visible at low tide, when broad expanses of flat bedrock seaward of the cliff are exposed; their landward edge is commonly masked by beach sediments, so the underlying rock may only be apparent when tides fall or when storms strip the sand. Wave-cut platforms occur in both marine and lacustrine settings wherever sustained wave action lowers and flattens the shoreface. Classic field examples, such as the intertidal bench at Southerndown (South Wales, UK), illustrate the typical position of these benches at the cliff base and their intermittent exposure under varying tidal and storm conditions.
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Formation
Wave-cut platforms develop where persistent, high-energy wave attack concentrates erosion at the tidal zone at the base of sea cliffs, producing a flat, bench-like surface that is most evident at low tide. Mechanical and chemical processes—principally abrasion (rock fragments hurled against the cliff), hydraulic action (compressed water and air forced into fissures), and corrosion/solution—initiate undercutting and produce a localized hollow or wave-cut notch. Continued focused erosion may extend this void laterally and vertically into a sea cave within the same intertidal band. Progressive weakening of the cave roof from marine stresses combined with subaerial weathering (for example freeze–thaw, biological boring and root wedging) eventually precipitates roof collapse; such collapses are the principal mechanism by which the cliff face retreats landward. The collapsed debris is progressively reduced by attrition so that the former cave floor becomes a relatively level, bedrock-dominated platform, although coarser clasts and finer sediment can be winnowed offshore by wave transport rather than retained. At the platform margin, reworking and deposition of washed material may form a fringe or offshore beach whose size and form reflect the balance between sediment supply from erosion and the prevailing wave energy. Because the platform lies within the regularly submerged and exposed tidal zone and is continuously battered by waves, it is a physically hostile habitat occupied only by organisms adapted to strong hydrodynamic stress and saline spray. Geomorphologically, repeated cycles of notch formation, cave enlargement, roof collapse and platform extension produce episodic landward cliff retreat and gradual seaward widening of the intertidal bench; the rate and pattern of this evolution are controlled by rock lithology, jointing and bedding, the wave-energy regime, tidal range and dominant weathering processes.
Use of ancient examples
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Wave-cut shore platforms are planar benches produced by persistent wave abrasion at the contemporaneous lake or sea surface and may be preserved when relative water level falls or the land is raised. Platforms stranded landward of the modern shoreline therefore record higher palaeo–sea or lake levels; their elevation above present waterlines provides a direct measure of change in relative sea level since formation. In formerly glaciated regions such raised surfaces constitute clear evidence of isostatic adjustment: removal of the ice load produces crustal uplift that leaves former shorelines stranded and permits quantification of the timing and magnitude of post‑glacial rebound. Applying chronometric techniques (for example radiometric dating) to platform materials and analysing associated marine or lacustrine fossils yields ages and palaeoenvironmental information, so that platform elevation becomes a time‑stamped indicator of past water level. Combining elevation, fossil assemblage and age allows calculation of vertical land‑motion rates (uplift or subsidence) and helps separate global eustatic change from local tectonic or isostatic effects. In the United Kingdom and other previously glaciated areas, mapped heights and dated ages of raised platforms have been used to quantify ongoing isostatic rise since deglaciation. In tectonically active coasts, repeated coseismic uplift can produce a staircase of discrete shore platforms or terraces, each preserving the elevation and age of a former sea level and thereby recording the magnitude of individual seismic events. Integrating spatial distribution, high‑precision elevation surveys, fossil content and chronological data from such platforms produces robust palaeoshoreline reconstructions and provides essential constraints for models of past sea‑level change and coastal geodynamics.
Usage of the term “wave‑cut”
Several authors (Trenhaile; Sunamura; Massalink and Hughes) have argued that the label “wave‑cut platform” is misleading because it implies an exclusively wave‑driven origin. They therefore advocate replacing it with neutral terms such as “shore platform” or “rock platform” that do not presuppose the erosive agent. Conceptually, shore platforms are best understood as erosional surfaces analogous to river and lake platforms: the progressive removal of saprock and other weathered debris by waves and currents exposes a residual bedrock surface that commonly lies at or below the local water table, rather than being produced solely by direct wave abrasion. Empirical examples underscore this diversity of processes and contexts: Bleik, Norway, where a raised beach adjacent to a platform records interactions between coastal erosion and relative sea‑level change; Pleistocene shore platforms of Lake Bonneville (Utah), which demonstrate lacustrine formation and preservation of palaeo‑lake levels; St Bees Head (UK), illustrating temperate coastal exposure of bedrock by removal of weathered material; Tedbury Camp (southern England), where development into Jurassic strata highlights the control of lithology and age on platform morphology and preservation; Austinmer and Long Reef (New South Wales), typical southeastern Australian “rock platforms”; and Elet Island (Busuanga, Palawan), which shows a wave‑cut notch and partly submerged platform, illustrating how platform expression varies with relative sea level and submergence. On this basis, usage that emphasizes neutral, process‑independent terminology better accommodates lithologic, hydrodynamic and sea‑level controls on platform formation.