The structure is a combination of rock type and strata orientation. The type of rock will greatly determine the features produced. Hard granite rocks produce gently rounded cliffs, such as those produced at 'Refuge Cove' on Wilsons Promontory, Victoria. Soft rocks such as sandstone and limestone result in the angular cliffs and varied features of Port Campbell National Park. The strata orientation is the way in which the sedimentary layers are aligned.
Erosion usually takes place along the lines of weakness that are found between each layer.
In the first example above the lines are aligned at an angle running down. The resulting cliff face is more resistant to erosion as the waves are working against the lines of weakness. In the second example the lines are aligned at an angle running up. The resulting cliff face is easily eroded as the waves are able to attack the lines of weakness. The cliff is easily undermined forming caves and arches.