Editing Convection (section)

===Gravitational or buoyant convection===
'''Gravitational convection''' is a type of natural convection induced by buoyancy variations resulting from material properties other than temperature.  Typically this is caused by a variable composition of the fluid.  If the varying property is a concentration gradient, it is known as '''solutal convection'''.<ref>{{cite journal|citeseerx=10.1.1.15.8288 |title=Pattern Formation in Solutal Convection: Vermiculated Rolls and Isolated Cells |journal=Physica A: Statistical Mechanics and Its Applications |volume=314 |issue=1 |pages=291 |bibcode=2002PhyA..314..291C |last1=Cartwright |first1=Julyan H. E. |author1-link = Julyan Cartwright |last2=Piro |first2=Oreste |last3=Villacampa |first3=Ana I. |year=2002 |doi=10.1016/S0378-4371(02)01080-4 }}</ref> For example, gravitational convection can be seen in the diffusion of a source of dry salt downward into wet soil due to the buoyancy of fresh water in saline.<ref>{{cite journal|last=Raats|first= P. A. C.  |year=1969 |title=Steady Gravitational Convection Induced by a Line Source of Salt in a Soil|journal = Soil Science Society of America Proceedings |volume = 33 |pages = 483–487 | doi=10.2136/sssaj1969.03615995003300040005x |issue=4|bibcode=1969SSASJ..33..483R}}</ref>

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 else involve additional compositional density factors other than the 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).

Gravitational convection, like natural thermal convection, also requires a [[g-force]] environment in order to occur.