The Pacific is a leading-edge coast, which is the side of a continent moving towards an oceanic subduction zone. Unlike the Atlantic and Gulf coasts, the Pacific coast has an extremely narrow continental shelf and no coastal plain. Much of its shores are composed of coarse sediments that travel from the mountain ranges, which are relatively close to the coast. As a result, sediments do not undergo extensive weathering while traveling to the coast and are coarser than those found on many Atlantic coast beaches.
Along the coast of the Pacific Northwest, pocket beaches of coarse sediment are found between rocky headlands and sea cliffs. The Columbia River is the region's major riverine source of sediment.
Much of the California coast contains high sea cliffs and few river valleys, and in southern California highly erodible bluffs and raised terraces characterize the coast. This region is prone to erosion because houses are located directly on cliffs of unconsolidated material.
Because of the narrow continental shelf, the Pacific coast loses significant amounts of sediment to submarine canyons as it reaches the coast. Erosion is therefore a problem along Pacific beaches, and maintaining sediment in this region is a challenge.