On the Tectonic and Morphologic Classification of Coasts

In terms of the gross first-order effects of plate tectonics, there appear to be three major classes of coasts and several subclasses, depending upon their position relative to the moving plates of the tectosphere: (1) collision coasts, that is, those on the collision edge of continents and island arcs; (2) trailing-edge coasts, that is, those on the trailing edge or noncollision side of a continent; and, (3) marginal sea coasts protected by island arcs. The trailing-edge coasts range in form from the tectonically new coasts facing beginning separation centers to the morphologically active coasts bordering the debris plains formed from the erosion products of the continents. The good coherence between certain morphologic and tectonic features of coasts was used as a guide in formulating a purely morphologic classification with tectonic implications. The morphologic classification is defined simply in terms of the width of the continental shelf and the relief of the adjacent land forms: (1) mountainous coasts; (2) narrow-shelf hilly, and plains coasts; and (3) wide-shelf hilly, and plains coasts.