Mantle flow tectonics and the origin of Ishtar Terra, Venus

It is proposed that western Ishtar Terra formed due to compression and crustal thickening above a cylindrical mantle downwelling. A model for crustal deformation due to downwelling successfully reproduces many observed characteristics of western Ishtar. Although axisymmetric downwellings occur in numerical models of constant‐viscosity mantle convection, there is no evidence for their existence in Earth's mantle, where downwellings are sheet‐like. Either modes of downflow in Venus and Earth are fundamentally different, or differences in near‐surface conditions and material behavior selectively emphasize surface expressions of the different downwelling modes.