In the dumpsite area, the irregularity of the sea bottom,
characterized by surficial boulders, hills, hillocks,
depressions, and faulted sedimentary strata, is similar to
submarine landslide deposits off Hawaii (Lipman and others,
1988), parts of submarine debris flows (Prior and others, 1984),
and to deposits created by subaerial debris avalanches (Siebert,
1984; Francis and Wells, 1988). This area shows a complex
geologic history of localized events requiring closely-spaced
profiles and images to outline the separate units. The
perspective view of the Sea Beam bathymetry data shows the
trough along the base of the slope (A) and the lobate, mounded
deposits to seaward of it on the uppermost rise (compare the
seabeam bathymetric map). The origin of the slope-base trough is
not well understood. Similar slope-base morphology is found
along the northeast U.S. continental slope (Dennis O'Leary,
personal commun., 1989). In places it appears to be formed by a
reverse slope behind blocky landslide deposits which sli