Headlands and bays are formed when the sea's waves push hard and soft rock into the landscape, which eventually erodes it. These structures usually form in areas where weak rock rests in front of stronger rock. While some remain stable, others can lead to landslides.
Headlands and bays form in areas where rocks such as sand and clay are eroded, leaving stronger rocks behind. In order for the erosion to result in a headland, it must be surrounded by water on three sides. In contrast, a bay is surrounded by land on three sides. These formations happen over time as waves crash into the land and gradually erode the soft rock. Depending on the wave refraction, other structures, such as caves, arches and stacks, may form at the same time.
When beaches and cliffs form in this way, they have different degrees of stability. While beaches in a state of static equilibrium do not experience loss of sedimentation, those that are unstable are usually man-made and eroding because of dammed rivers and breakwater. During the erosion process, cliffs with a high proportion of weak rock experience landslides. The sea usually washes the by-products of the landslides away, and they are more likely to occur during stormy periods.