Gravitational convection
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Gravitational convection is a general term for buoyancy-induced convection in a gravity field, especially that not due directly to heat.
[edit] Examples
Gravitational heat convection is the same as free convection or natural convection. However, differential buoyancy forces which cause convection in gravity fields may result from sources of density variations in fluids other than those produced by heat, such as variable composition. For example, diffusion of a source of dry salt downward into wet soil assisted by the mechanism of the fact that saline is heavier than fresh water, is a type of gravitational convection [1] Variable salinity in water and variable water content in air masses, are frequent causes of convection in the oceans and atmosphere, which do not involve heat, or involve additional density factors other than density changes from thermal expansion (see thermohaline circulation). Similarly, variable composition within the Earth's interior which has not yet achieved maximal stability and minimal energy (in other words, with densest parts deepest) continues to cause a fraction of the convection of fluid rock and molten metal within the Earth's interior (see below).
