Geological evolution of Venus: Rises, plains, plumes, and plateaus

Crustal plateaus and volcanic rises, major physiographic features on Venus, both formed over mantle plumes. Crustal plateaus were produced by large degrees of plume melting beneath thin lithosphere. The oldest tectonic features in crustal plateaus are ribbon-like troughs indicating early uplift and tensile stretching; their hallow depths suggest that surface temperature there was higher in the past. Widespread volcanic plains, derived from the broad upwellings of internally heated mantle convection, were continually erupted during the time of crustal plateau formation. Discrete volcanic rises, younger than crustal plateaus, formed over a thicker lithosphere, with less plume partial melting. The presence of only one transitional form indicates that the lithosphere thickened rapidly. Thermal and magmatic models show that the formation of these major features can be tied to an expected change in mantle convective style about 1 billion years ago.