Convection currents

Movements in fluids or gases resulting in the equilibration of thermal differences.

Convection currents are formed by hot (and therefore light) material, which is dwelling up at certain places (the figure gives the convection current within the mantle of the earth as an example). At the upper border, the material is cooling down, moving sidewards, and finally sinking down due to its lower temperature (higher density). This continous movement is resulting in the transportation of heat from the bottom to the top. In the internal of the earth, rapid convection currents in the outer core are forming the magnetic field of the earth; slow convection currents in the mantle are causing the continental drift.