a b s t r a c tAlthough sediment waves cover many levees and canyon floors of submarine fan systems, their relation to the turbidity currents that formed them is still poorly understood. Over the recent years some large erosional sediment waves have been interpreted as cyclic steps. Cyclic steps are a series of slowly upslope migrating bedforms (steps), where each downward step (the lee side of the bedform) is manifested by a steeply dropping flow passing through a hydraulic jump before re-accelerating on the flat stoss side. Here, a general comparison is made between sediment waves and cyclic steps. First, the analogies between their geometries and internal structures are explored. Secondly, a basic numerical model is used to construct stability fields for the formation of cyclic steps. These stability fields are compared with large, existing datasets of both fine-and coarse-grained sediment waves. The numerical results enable an explanation of geometrical trends found over series of sediment waves in the upper part of the Monterey Canyon, on the middle Amazon Fan and on a leveed channel in the Makassar Strait in terms of changes in flow properties of the overriding turbidity current. Based on sedimentological arguments and numerical analysis it is concluded that cyclic steps form a potential alternative for the existing interpretations on the origin of upslope migrating sediment waves.

Natural, moderately loosely packed sands can only erode from the surface of the bed after an increase in pore volume. Because of this shear dilatancy, negative pore pressures are generated in the bed. In cases of low permeability, these negative pressures are released relatively slowly, which retards the maximum rate of erosion. This effect is incorporated in a new, analytically derived, pick‐up function that can explain the observation of gradual retrogressive failure of very steep subaqueous slopes, sometimes more than 5 m high, in fine non‐cohesive sands. This process, termed ‘breaching’ in the field of sediment dredging, may produce large failures in sand bars or river banks. The analytical function that describes the breaching process in fine sand is incorporated in a one‐dimensional, steady‐state numerical model of turbidity currents describing the spatial development of flow. This model is applied to simulate a large ‘flushing’ event in Scripps Submarine Canyon, Pacific coast of California. Breach retrogradation and the successive evolution in time of the resulting turbidity current in the canyon are predicted in a sequence of discrete steps. Predicted velocities are compared with values measured during a flushing event. Implications for the interpretation of deep‐water massive sands are discussed.

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Books review in this article: M. Stacey, The Sociology of Health and Healing: A Textbook M.B. McGuire (with the assistance of D. Kantor), Ritual Healing in Suburban America N. Gevitz (ed.). Other Healers: Unorthodox Medicine in America. R. Cooter (ed.). Studies in the History of Alternative Medicine. M. Lock and D. Gordon (eds.), Biomedicine Examined L. Wall, Hausa Medicine: Illness and Well‐Being in a West African Culture M. Oliver, G. Zarb, J. Silver, M. Moore and V. Salisbury, Walking into Darkness: The Experience of Spinal Cord Injury S. Ainlay, Day Brought Back My Night: Aging and New Vision Loss D.E. Beauchamp, The Health of the Republic: Epidemics, Medicine and Moralism as Challenges to Democracy L.K. Clarke and M. Potts (eds.) The AIDS Reader: Documentary History of a Modern Epidemic D. Crimp (ed.) AIDS: Cultural Analysis/Cultural Activism I. Robinson, Multiple Sclerosis. The Experience of Illness Series D. Kelleher, Diabetes: The Experience of Illness S. Spacapan and S. Oskamp (eds). The Social Psychology of Health: The Claremont Symposium on Applied Social Psychology E.E. Filsinger (ed.). Biosocial Perspectives on the Family J. Archer and K. Browne (eds.). Human Aggression: Naturalistic Approaches

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