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Three submersible dives in DSRV Alvin were made on the continental rise seaward of Atlantic City, New Jersey: two in Wilmington Canyon and one in South Wilmington Canyon. The dives, made on features observed in midrange sidescan sonar records reveal a sharp contrast in physiography between the two canyons and provide an insight to the sedimentologic processes associated with canyon development.

On the upper rise, Wilmington Canyon is characterized by a well-developed meander pattern with alternating steep and gently sloping side walls. The steep channel walls correlate with the outside (concave) part of a meander bend and are segmented by numerous steep-walled, steplike depressions. Therefore, undercutting at the base of the channel wall, accompanied by localized slumping, is inferred. These depressions are missing on the gently sloping channel walls. Unconsolidated sediment, in excess of 1.3 m thick, is present in the channel axis but is generally missing in the depressions on the channel wall. The high quartz sand content (30%) in the channel sediments and the paucity of unconsolidated sediment in the depressions indicate recent activity.

In South Wilmington Canyon various deformed and displaced(?) sediments support a previous suggestion of large-scale slumping. These features include upturned clay horizons at the base of the wall, stratigraphically overlain by disaggregated gravels, a loosely bound gravel conglomerate, and oxidized sandstone horizons. A tubular object 1 m long, tentatively interpreted as a tree root cast, was recovered from the sandstone. A meander pattern was not found in South Wilmington Canyon.

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