Notch (Coastal)

A coastal notch is a horizontal erosional indentation cut into the base of a sea cliff or rock coast at the level of greatest wave or dissolution attack, near mean tide level. On limestone coasts the notch is largely a solution and bioerosion feature, sharpest in the tidal mixing zone; on resistant clastic cliffs it is mechanical, cut by wave abrasion and quarrying. A deep notch undercuts the cliff and drives recession by collapse. Because the notch tracks the waterline, raised or drowned fossil notches are markers of relative sea-level change used in coastal tectonic and paleo-sea-level studies.