The general shape of the continental margin is usually determined by the shape of the coastline from which it extends. If it extends from a plane, then the margin will be broad and level. If it extends from a mountainous coast, then it will be steep and rocky. Steep cliffs that may have been formed by wave action when the level of the sea was lower may now be submerged and form part of the margin.

The present shape of a continental margin may also be due to other influences. Movement of the Earth's crust may have given it a "folded" appearance where the sea floor cracked and was pushed underneath the margin. Huge boulders and rocks may indicate that a glacier once moved across the region. The presence of a river may mean a larger quantity of sediment where it enters...