Cliffs and wave-cut platforms:
• High energy waves concentrate erosion at cliff base.
• Cliff undercut to form wave-cut notch.
• Undercut cliff collapses and retreats, leaving a gently-sloping forefront (wave-cut
platform).
• Wave cut platform extended by abrasion, corrosion and hydraulic action. When
exposed at low tide weathered by sub-aerial processes.
• Over time waves break further out to sea, wave energy dissipates, and erosion is
reduced.
Caves, blowholes, geos, arches, stacks and stumps:
• Orthogonals converge around headland as shallow water increases friction and
causes wave refraction.
• Geomorphic processes create caves via faults in the cliff face.
• Above a cliff vertical lines of weakness create a blowhole (a vertical shaft) through
the roof of the cave. At high tide water can be forced through this.
• The unsupported cliff top between the blowhole and the sea may collapse due to
weathering, forming a geo (a narrow, steep-sided inlet).
• Two caves either side of the headland can erode through to form an arch.
• Weathering and erosion lead to arch collapse, leaving a stack.
• Continued erosion of the stack forms a stump, only visible at low tide
E.g = Old Harry Rocks, Isle of Purbeck
