Accumulation Characteristics and Geological Hazard Effects of Gravity Flow on Northwestern Lower Continental Slope in the South China Sea

The northwestern lower continental slope margin in the South China Sea is the main fluid property conversion area of the debris flow and turbidity current, where accumulations of typical and special gravity flows are developed. In the upper strata of the research area, there are at least four stages of debris flow accumulations. Several 1-3 m high pressure ridges are developed on the seafloor surface and on the top of underlying accumulations. A large quantity of slide accumulations or extrusion deformation structures is developed on the slope and at the base of the slope. The slides accumulation surface can be clearly seen, and the accumulations are still moving downward slowly and extruding continuously, resulting in a series of geological hazard effects. The study shows that the sediments are mainly composed of silt and clayey silt on the northwestern lower continental slope in the South China Sea. The sediments are deposited at the foot of the slope where the energy of gravity flow begins to reduce rapidly. The cores and shallow seismic profiles of upper strata on the lower continental slope as described in this paper have proven that there are three different accumulation processes, and the geological hazard effects incurred are completely different so that we shall further enhance the research on the seafloor geological hazard effects.