ABSTRACT: Tectonic Processes on Venus: Comparisons and Contrasts with the Earth

SOLOMON, SEAN C., Massachusetts Institute of Technology, Cambridge, MA

Radar imaging and altimetry data from the Magellan mission have revealed a diversity of deformational features at a variety of spatial scales on the Venus surface. The plains of Venus record a superposition of distinct episodes of deformation, typically manifested in areally distributed strain of modest magnitude and coherent over hundreds of kilometers. Ridge belts and mountain belts represent successive degrees of lithospheric shortening and crustal thickening. As on Earth, mountain belts show widespread evidence for lateral extension and collapse both during and following orogeny. Large-scale extensional structures include the quasi-circular coronae and broad rises with linear rift zones, both sites of significant volcanic flux. Few large-offset strike-slip faults have been observe , but limited local horizontal shear is accommodated across many zones of crustal shortening. Several large-scale tectonic features have topographic slopes in excess of 20 degrees over a 10 km scale; because of the tendency for such slopes to relax by ductile flow in the lower crust, such regions are likely to be tectonically active. In general, Venus is tectonically unlike Earth's oceanic regions, with their large rigid plates and deformation confined to narrow plate boundaries, but actively deforming continental regions provide a closer analog. The styles and distribution of tectonic deformation on Venus may be consequences of three differences from Earth: the absence of a hydrological cycle and significant erosion, strong coupling of mantle convection to the upper mantle portion of th lithosphere, and a high surface temperature and thus a significantly shallower onset of ductile behavior in the crust.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)