Salt tectonics

500px|thumb|rightSalt tectonics is concerned with the geometries and processes associated with the presence of significant thicknesses of evaporites containing rock salt within a stratigraphic sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength.

Passive salt structures

Structures may form during continued sedimentary loading, without any external tectonic influence, due to gravitational instability. Pure halite has a density of 2160 kg/m³. When initially deposited, sediments generally have a lower density of 2000 kg/m³, but with loading and compaction their density increases to 2500 kg/m³, which is greater than that of salt.McGeary. D and C. C. Plummer (1994) Physical Geology: Earth revealed, Wm . C. Brown Publishers, Dubuque, p.475-476 ISBN 0-697-12687-0 Once the overlying layers have become denser, the weak salt layer will tend to deform into a characteristic series of ridges and depressions, due to a form of Rayleigh–Taylor instability. Further sedimentation will be concentrated in the depressions and the salt will continue to move away from them into the ridges. At a late stage, diapirs tend to initiate at the junctions between ridges, their growth fed by movement of salt along the ridge system, continuing until the salt supply is exhausted. During the later stages of this process the top of the diapir remains at or near the surface, with further...
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