Bays form where weak rocks, such as sands and clays, are eroded, leaving bands of stronger rocks, such as chalk, limestone, or granite, forming a headland, or peninsula. Headlands and bays are formed when there are parallel sections of softer and harder rock perpendicular to the coast. The sea erodes the softer rock faster than the harder rock, forming a bay. The harder rock that is left protruding into the sea is the headland. 