Submarine Mass Movements in The Passive Margin Offshore of Southwestern Taiwan

Submarine mass movement is one of the major forces which affect the morphology of continental margin. It is also one of the major mechanisms of sediment transport, and may cause geohazard. Therefore it is important to investigate the distribution, source, mechanisms and evolution model of submarine mass movement. The passive margin offshore of Southwestern Taiwan receives considerable quantities of terrigenous sediment that deposited on the continental shelf and slope. Due to the effect of strong submarine erosion, it could produce steep ridges and submarine canyons on the continental slope. From the multi-channel seismic reflection profile data, we can indentify bottom simulating reflector (BSR) which suggests that gas hydrate is widely distributed in this region. The dissociation of gas hydrate could result in filling of free gas in a layer, and change the steady state of strata. Those factors above are the major mechanisms which trigger submarine mass movement. Numerous submarine mass movements have been observed in the study area, and the distribution of the submarine mass movement has a tendency of depending on water depth and topography. The characteristics of submarine mass movement can transform from one type to another, according to changes of hydrodynamic parameters, and submarine mass movement may contribute to the migration of gas hydrate stability zone (GHSZ).