Tectonics of Venus
Deformation of Venus's lithosphere by vertical motions, not lateral plate movement, producing highlands, rifts and Coronae without plate boundaries.
Plate tectonics: Theory that Earth's rigid outer shell is broken into moving plates whose interactions drive quakes, volcanism and mountains. The opposing model: lateral plate motion versus Venus's vertically driven, continuous deformation.
Coronae: Circular volcanic-tectonic features, up to 2,600 km across, formed by mantle plumes upwelling beneath the crust. The signature landform of vertical tectonics, absent on plate-covered Earth.
Mantle convection: Slow circulation of solid rock in a planet's interior driven by heat, deforming the surface from below. On Venus, convection loads the crust vertically instead of dragging plate-sized rafts.
Current volcanic activity on Venus: Evidence from orbital radar changes and missions suggests eruptions may be happening today. Active volcanism would show whether the lid is truly stagnant or quietly leaking.
Runaway greenhouse effect: A climate feedback where evaporation traps more heat until oceans boil away, as on Venus. Volcanic outgassing in a no-plate regime helped push Venus's atmosphere to this state.
Lithosphere: The rigid outer shell of a planet, comprising crust and upper mantle, that deforms and fractures under stress. Venus's hot, weak lithosphere resists breaking into plates; Earth's cold one succeeds.
Ishtar Terra: A highland continent the size of Australia containing Maxwell Montes, Venus's highest mountains at 11 km. Thick crust piled up by compression, with no subduction to absorb the shortening.
Mantle plumes: Buoyant upwellings of hot rock from deep mantle that domed, rifted and capped Venus's crust. Plumes raise highlands, spread Coronae and flood the surface with basalt.
VERITAS: A planned NASA orbiter to map Venus's surface topography, deformation and composition in high resolution. Will test whether the crust is deforming in plate-like ways today.
Volcanic outgassing: Release of carbon dioxide, sulfur dioxide and water vapor from eruptions into a planet's atmosphere. Without subduction to recycle carbon, outgassed CO2 accumulated unchecked.