Gravitational convection

Gravitational convection is a general term for buoyancy-induced convection in a gravity field, especially that not due directly to heat.

Gravitational heat convection is the same as free convection or natural convection

Natural convection

Natural convection is a mechanism, or type of heat transport in which the fluid motion is not generated by any external source but only by density differences in the fluid occurring due to temperature gradients. In natural convection, fluid surrounding a heat source receives heat, becomes less...

. 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.

Gravitational convection is a general term for buoyancy-induced convection in a gravity field, especially that not due directly to heat.

Examples

Gravitational heat convection is the same as free convection or natural convection

Natural convection

Natural convection is a mechanism, or type of heat transport in which the fluid motion is not generated by any external source but only by density differences in the fluid occurring due to temperature gradients. In natural convection, fluid surrounding a heat source receives heat, becomes less...

. 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 Variable salinity

Salinity

Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

 in water and variable water content in air asses, 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

Thermohaline circulation

The term thermohaline circulation refers to the part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes....

).the hot air cools and drops while the cool air heats and rises 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).