Faults and submarine slides or slumps of Quaternary age are potential environmental hazards on the outer continental shelf (OCS) of the northern Gulf of Alaska. Most of the faults that approach or reach the seafloor cut strata that may be equivalent to the upper Yakataga Formation (Pliocene-Pleistocene). Along several faults the seafloor is offset from 5 to 20 m. A few faults appear to cut Holocene sediments, but none of these show offset at the seafloor.
Submarine slides or slumps have been found in two places in the OCS region: (1) seaward of the Malaspina Glacier and Icy Bay, an affected area of 1,770 km2 with a slope of less than one-half degree, and (2) across the entire span of the Copper River prodelta, an area of 1,730 km2, having a slope of about one-half degree. Seismic profiles across these slide areas show disrupted reflectors and irregular topography commonly associated with submarine slides or slumps. Potential slide or slump areas have been delineated in areas of thick sediment accumulation and relatively steep slopes. These areas include (1) Kayak Trough, (2) parts of Hinchinbrook Entrance and Sea Valley, (3) parts of the outer shelf and upper slope between Kayak Island and Yakutat Bay and (4) Bering Trough.
