Deep-sea fans range from small fan-shaped depositional bodies with relatively simple internal structure to large variably shaped depositional bodies with complex internal structure. Their shape depends on several important factors: (1) the topography of the basin floor and shape of the basin in which they are deposited; (2) the number and distribution of submarine canyons or sea gullies transporting sediment to the ocean floor; (3) the strength and direction of bottom currents; (4) the effects of the Coriolis force; (5) the grain-size distribution of the sediment being fed to the fan; (6) the rate of sediment supply; (7) the presence of syndepositional tectonism either along basin-margin slopes or on the sea floor; and (8) the position of the shoreline and effects of sea- evel changes.

Fans in trenches can be extremely long and narrow, whereas those on flat ocean floors have more regular fan shapes. Fans fed by single submarine canyons are relatively simple, whereas those fed by sea gullies that extend outward from deltas are more complex. Bottom currents can redistribute fan deposits, and the Coriolis effect causes hooking of modern fan channels. Fans built primarily of sand from submarine canyons are highly channelized, whereas those containing a mixture of sediment sizes have well-developed non-channelized facies. The rate of sediment supply, strongly affected by sea-level changes and tectonism, provides overall constraints on the size and shape of fans.

Fans constructed along California-, Japan-, Andes-, and Atlantic-type margins have distinctive geometric, petrographic, and dispersal characteristics.

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