Fate of Dredge Disposal Material and Polluted Sediment, Offshore Honolulu, Hawaii

3D Color Perspective View Of The Southeast Oahu Margin

View is to the northeast. The insular shelf edge is dominated by a reef terrace (A) with numerous re-entrants. Seaward of Diamond Head is an extensive area of exposed rock and rubble (B), possibly the result of a landslide. Farther east is a volcanic ridge (C) built seaward in alignment with the Koko Head and Hanauma volcanic trend (C'). Diamond Head and Koko Head were formed very late in Oahu's history and the offshore ridge probably formed at that time, explaining why it is youthful in appearance and unburied by sediment. Numerous shallow channels (D) trend downslope from the reef escarpment. The channels are conduits for sediment transport off the insular shelf and out to the Mamala Bay seafloor. Transport in the form of sediment gravity flows likely occurred during lower sea levels. The scale across the bottom of the image is appx. 9 km. The vertical exaggeration is 5x.

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Michael E. Torresan

U.S. Geological Survey
345 Middlefield Road MS 999
Menlo Park, CA 94025