This paper describes the behaviour of soft soils created by the rapid deposition of a sediment slurry and the mechanisms by which pore fluid escapes from the consolidating bed. Such rapid deposition occurs as a result of dumping dredge spoils at sea or in the case of disposing of mine tailings in settling ponds. Soft soils may experience a variety of natural deformations during consolidation. Consolidation-related structures are commonly observed in settling column experiments, geotechnical centrifuge tests and in the field. This paper deals with the specific class of soft-sediment intrusive and extrusive dewatering structures called respectively pillars and boils (or sediment volcanoes) that form spontaneously through self-weight consolidation. Dewatering structures were formed during self-weight consolidation centrifuge experiments of a naturally-occurring marine sediment under the influence of high “g” conditions. A description of the phenomenon is given, describing the geometry and nature of the dewatering structures observed, and highlights some of the soil physical properties and depositional conditions which appear to control the formation of the structures. This phenomenon is believed to have relevance to dredge spoil and mine tailing disposal, and to the safe handling and disposal of polluted high water content soil like wastes.