What Is Left Behind
Two major forms of coastal erosion contribute to the formation of a headland. The first and most obvious is known as Hydraulic Action, which is the force of water against the cliff face and the types of rock it consists of.
The second is known as Attrition, and just like it sounds, it means that as rocks crumble and fall, they hit other parts of the cliff breaking off pieces there too. The acids found in sea water can also contribute to corrosion of some types of rocks as well. In addition, all that sand and mineral particles in the water almost work like sand paper when waves pound into the rocks.
The mighty waves of the ocean will eat away at the less resistant rock and over time, and that is how bays are formed. Meanwhile, types of rock that are more resistant literally hold their ground and those stalwart headland formations are the result.
Their ability to stand firmly against the forces of erosion and an endless barrage of waves then enables them to become sheltering, protective sentinels to the bays and inlets found at their sides. Depending upon the factors regarding rock types, especially how resistant the hard rock is and the strength of prevailing winds effecting waves, a headland can be rather thin, as in only a few meters wide where it meets the sea. Alternatively, one can be many kilometers wide and anywhere in between those two extremes.