A wave-cut platform is a flat, gently sloping rock surface found along coastlines, extending from the base of a steep cliff out towards the sea. These geological formations are sculpted by the action of ocean waves and are typically exposed during low tide. They are a distinctive feature of coastal erosion.
How Wave-Cut Platforms Form
The formation of a wave-cut platform begins with waves impacting the base of a sea cliff. This process is concentrated in the intertidal zone, the area between high and low tide marks. Several types of wave erosion contribute to this formation, including hydraulic action, abrasion, attrition, and solution.
Hydraulic action occurs as the force of waves crashes against the cliff face, compressing air within cracks and crevices, which weakens the rock over time. Abrasion involves the grinding and scraping of the cliff by sand, pebbles, and other rock fragments carried by the waves. These materials also collide with each other, breaking down into smaller pieces through attrition. Additionally, some rocks can be dissolved by chemicals in seawater, a process known as solution or corrosion.
Continuous erosion at the cliff’s base forms a wave-cut notch, an undercut indentation in the rock. As this notch deepens, the unsupported rock above it eventually collapses due to gravity. This cycle of undercutting and collapse causes the cliff face to gradually retreat inland. The relatively flat, eroded surface left behind is the developing wave-cut platform.
Identifying Key Features
Wave-cut platforms have a flat to gently sloping surface, typically inclining seaward at angles of 3 to 5 degrees. While often appearing smooth due to constant abrasion by moving sediment, sections of the platform can also be rugged, with deep cracks and variations in texture depending on the rock type and specific erosional patterns. These platforms are most visible when the tide is low, as they are submerged during high tide.
The platform’s landward side meets the retreating cliff face at a distinct junction. Scattered across the platform, especially in depressions and hollows, are rock pools. These pools retain seawater as the tide recedes, creating temporary habitats for various marine organisms. The presence of barnacles and seaweed can also be observed clinging to the rock surface.
Geological Significance
Wave-cut platforms serve as indicators of geological processes and past environmental conditions. They provide evidence of long-term coastal erosion and the dynamic evolution of coastlines. The rate at which these platforms form and cliffs retreat can provide insights into the intensity of wave energy and the resistance of the local rock types.
Wave-cut platforms can also act as markers of ancient sea levels. When tectonic uplift or drops in global sea levels occur, previously formed wave-cut platforms can be raised above the present-day high tide mark, becoming marine terraces. Studying these raised platforms allows geologists to reconstruct past sea-level changes and understand the history of land elevation or subsidence in a region. They offer a tangible record of how coastal landscapes respond to geological forces over extended periods.