What are “convection” and “diapirs”?
Convection is the transfer of heat by vertical circulation. In icy satellite interiors, ice can be heated through radiogenic or tidal heating, whereas the near-surface ice is generally very cold. The warm ice is less dense than the cold ice, so it warm ice tends to rise, and the denser cold ice tends to sink, if the viscosity (consistency) of the ice in question is not too stiff. Warmer and thicker ice layers are more likely to convect. Lava Lamps and miso soup provide nice illustrations of convection. Earth’s mantle convects, with warm rock masses moving upward through colder and denser ones. A rising or sinking blob of material, e.g. a rising blob of warm ice, is called a “diapir” when it pierces and moves through another material. Diapirism can also be triggered when a lighter material underlies a denser material of different composition. On Earth, salt commonly rises as diapirs through overlying denser sedimentary rocks, as in Iraq and Iran.
