Mapping the slopes of expanding continental margins

The use of the modern mapping system, GLORIA, which provides imagery over a wide area, and Sea Beam, which provides swaths of detailed soundings, is considered. Sediments are transported down the continental slopes in canyons, as well as in gravity slides, with much of the material winding up in large fans. These sedimentary deposits subsequently are uplifted, expanding the continental margins seaward. One set of uplift structures with possible economic potential, which has been defined by Sea Beam in great detail, is a large field of diapirs in the Gulf of Mexico north of the Sigsbee Escarpment. Examples of uplift along the tectonically active north California and Oregon-Washington coasts also are discussed. It is concluded that the uplift of the tectonically active areas results from material pushing up from below, generally associated with Earth expansion