The origin of the prominent capes and shoals along the southeastern coast has not been satisfactorily explained. Previously proposed mechanisms, including back-set eddies of the Florida Current (Gulf Stream), longshore-offshore drift, structural uplift, and variations in wave incidence, are improbable because of the concentration of wave energy on headlands. Wave refraction favors the retreat of headlands, and an alternate hypothesis for the origin of the capes and offshore shoals must be considered.
The concurrence of capes and rivers is too prevalent to be fortuitous. Cape Fear, North Carolina, and Cape Romain-Santee Point, South Carolina, coincide with the mouths of rivers; lesser capes at Tybee and Little St. Simons Islands correspond to the discharge areas of major Georgia rivers. Cape Lookout, North Carolina, is postulated to correspond to a shoal area seaward of the Pleistocene mouth of the Neuse River prior to capture by the Pamlico River. Development of the Cape Hatteras complex has been augmented by sediments from the Roanoke and Pamlico Rivers and from the Susquehanna River-Chesapeake Bay system.
These capes are not deltas under present conditions; however, at the beginning of a glacial stage, the river gradients were markedly increased by sea-level lowering and deltas developed. As the sea retreated, the deltas formed farther seaward on the continental shelf, resulting in the deposition of deltaic ridges of sediment perpendicular to the coast. During the subsequent submergence which accompanied glacial melting, the deltas became the loci of barrier islands and prominent capes. Submergence was accompanied by erosion and retreat of the barrier capes resulting in the present capes, shoals, and embayments.