Slope instability near the shelf break, Western Gulf of Alaska*

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Abstract
The uppermost continental slope in the western Gulf of Alaska, from southern Albatross Bank to Portlock Bank, includes two broad areas where large submarine landslides occur and one intervening area where they are absent. In the areas containing large slides, seismic reflection records show evidence for active nearsurface folding and consequent slope steepening, which is apparently the ultimate control on this sliding. Evidence is lacking for similar active steepening in the area containing no large slides, where slope gradients are relatively gentle. Relatively small, shallow slides, fundamentally different from the larger ones, occur in all three areas on slopes that are not necessarily actively steepening. These slides are probably stratigraphically controlled, with failure occurring along weak subsurface strata. Strong earthquakes and the related accelerations are probably responsible for the actual triggering of many of the large and small slides. As long as the tectonic setting remains as it is today, future large‐scale sliding should remain confined to the two broad areas in which it now exists. Relatively small‐scale and shallow sliding might occur in any of the three areas.