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We infer that the Alboran Basin, the first western Mediterranean Basin found after crossing Gibraltar, is an orogenic float underlained by a de´ collement system, a multi-layered ductile shear extending from 10 km to between 30 and 40 km below sea level. This float was formed as consequence of the collision of the African-Eurasian plates in the Oligocene-late Miocene. Synchronous with this compression the float experienced basin wide crustal thinning and subsidence about 25 m/year ago by subcrustal processes. Since latest Miocene the float has undergone compression due to the continuous convergence of Eurasia and Africa. The faults created as a result of this compression are dominated by a conjugate system of northeast trending left-lateral and northwest right-lateral strike-slip faults. This deformation is taking place under a simple shear mechanism. Associated with the northwest and northeast lateral faults are zones of compression trending west and east of north extending from the base of the basin's north upper slope to the Alboran Ridge. The initial morphology of the Alboran Ridge on the southern side of the Alboran Basin was due to the construction of a volcanic edifice at the northeast end of the ridge and igneous activity along northeast trending fractures southwest of the edifice. At the northeast end of the Alboran Ridge motion along a right-lateral fault cutting across the ridge led to sediment collapse and the creation of a prominent embayment on the ridge's northwest flank. Deformation is more subdued in the western than in the eastern part of the Alboran Basin, a tectonic style due either to differences in sediment rheology or that the accommodation of the convergence of Africa and Iberia is more diffused and attenuated in the west than in the east.

The continental margin from Nova Scotia to the Florida Keys exhibits a variety of physiographic forms. On the basis of surface morphology it can be divided into three zones. In the northern zone, the continental shelf extending from Nova Scotia to Nantucket Island, has broad basins separated by shallow flat-topped banks, undulating swells, and irregularly crested ridges; some of the basins reach depths greater than 200 meters. This type of shelf topography is characteristic of shelves off glaciated areas and terminates at or near the southern limit of Pleistocene glaciation. Seaward of the shelf most of the continental slope is deeply entrenched by submarine canyons. At the foot of the slope is a large sedimentary apron known as the continental rise. The central zone from Nantucket Island to Cape Lookout also consists of continental shelf, slope, and rise. Although smoother than in the northern zone, the surface of the shelf is disrupted by sand swells, channels, coral mounds, and terraces. Most of these features may be related to lower stands of sea level during the Pleistocene. The continental slope in this zone is as deeply entrenched by submarine canyons as the slope in the northern zone. The continental rise seaward of the continental slope is similar to that in the northern zone. The continental margin in the southern zone from Cape Lookout to the Florida Keys is more complicated than the areas farther north. The continental slope is relatively smooth and has gradients as high as 20°-five times steeper than the slope farther north. The area landward of the slope does not consist of a simple continental shelf as it does farther north but instead consists of a shelf, a marginal plateau (the Blake Plateau), a trough (the Straits of Florida), and the Bahama Banks. In this sector of the continental margin, the topographic position occupied by the continental rise farther north is occupied by the broad flat-bottomed Blake Basin and Blake Ridge. East of Nantucket Island, topographic differences are believed to be due to glacial erosion, which has deepened the normal shallow shelf; south of Cape Lookout, they are believed to be due to folding or faulting, erosion by the Gulf Stream, and calcareous accretion.