Plate tectonics on venus
An oft quoted surprising discovery about Venus is its lack of plate tectonics; this, however, comes from too specific and narrow an understanding of what plate tectonics actually is. When scientists first studied high-resolution images of Venus taken by NASA's Magellan spacecraft, they were looking for examples of spreading ridges, subduction zones and transform faults Ð the "hallmarks" of plate tectonics. The lack of these features led to the conclusion that Venus does not have plate tectonics. Yet neither are these features found on Earth's continents, because they are the hallmarks of a unique type of plate tectonics, found only on Earth's oceans.
It perhaps ought not to have been surprising to discover that Venus does not behave this way. With its surface temperature near to 750 K, its lithosphere is almost certainly buoyant, in contrast to Earth's oceanic lithosphere. The surface of Venus, far from looking like Earth's ocean floors, has much more in common with Earth's continents, with examples of rift zones, mountain belts, and strike-slip systems. The only similarities to Earth's oceans are the innumerable volcanoes of all varieties and the limited compositional evidence that points towards a basaltic crust.
That Venus, together with Earth's continents and, in a different sense, with Ganymede, displays evidence of plate-like behaviour that is different to Earth's oceans, points towards a more general model of plate tectonics. This general model must apply to positively as well as negatively buoyant lithospheres, to icy compositions as well as silicates and even to that most common, everyday example of convection-driven plate tectonics, the pan of boiling custard.
The mapping and interpretion of the regional tectonic features of Venus over the past ten years or so has led to a qualitative picture of buoyant plate tectonics. Coupled with a new understanding of Earth's earliest history, a coherent general model of plate tectonics is emerging.
This work is in collaboration with Dr George Tuckwell and Dr Stuart Egan at Keele University. Dr Huw Davies at Cardiff University will also be involved in planned future numerical modelling. My research was in part funded by PPARC ROPA grant no. PPA/R/R/1998/00011.
Associated Personnel
Publications
"Structure and Evolution of south-east Thetis Regio"(2002) R C Ghail. J. Geophys. Res., 107, E8, 4:1-7 [ PDF | description ]
"A 400-km-scale strike-slip zone near the boundary of Thetis Regio, Venus"(2003) G W Tuckwell, R C Ghail. Earth Planet. Sci. Lett., 211, 1-2, 45-55 [ PDF | description ]
