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In accordance with previous findings [1-3], we interpret Pityusa Patera as a volcanic caldera formed by subsidence (via collapse of a magma chamber) and therefore usually bound by normal faults (which we propose are now covered by the wrinkle-ridged plains). H. Bernhardt 1, D. A. Williams 1, C. Klimczak 2. 1 School of Earth and Space Exploration, Arizona State University, Tempe, USA (h.bernhardt@asu.edu); 2 Structural Geology and Geomechanics Group, Department of Geology, University of Georgia, Athens, USA. [Extracted from the article]

Venus has been thought to possess a globally continuous lithosphere, in contrast to the mosaic of mobile tectonic plates that characterizes Earth. However, the Venus surface has been extensively deformed, and convection of the underlying mantle, possibly acting in concert with a low-strength lower crust, has been suggested as a source of some surface horizontal strains. The extent of surface mobility on Venus driven by mantle convection, however, and the style and scale of its tectonic expression have been unclear. We report a globally distributed set of crustal blocks in the Venus lowlands that show evidence for having rotated and/or moved laterally relative to one another, akin to jostling pack ice. At least some of this deformation on Venus postdates the emplacement of the locally youngest plains materials. Lithospheric stresses calculated from interior viscous flow models consistent with long-wavelength gravity and topography are sufficient to drive brittle failure in the upper Venus crust in all areas where these blocks are present, confirming that interior convective motion can provide a mechanism for driving deformation at the surface. The limited but widespread lithospheric mobility of Venus, in marked contrast to the tectonic styles indicative of a static lithosphere on Mercury, the Moon, and Mars, may offer parallels to interior-surface coupling on the early Earth, when global heat flux was substantially higher, and the lithosphere generally thinner, than today., Competing Interests: The authors declare no competing interest.

On planets with little erosion, thrust faults produce broad, asymmetric, positive-relief, linear to arcuate ridges -often referred to as lobate scarps- that remain largely unaltered, such that their topographic expressions are a measure of the structural uplift caused by the displacement and associated country-rock deformation of the faults. Here we map and systematically assess the structural relief of 24 thrust faults across Mars to infer their growth behavior. Our mapping indicates that the majority of individual thrust faults have simple, linear map traces with lengths of up to ~450 km, but that some thrust faults form systems of up to 1400 km in length. For the most topographically pronounced landforms, the structural relief developed above the fault is as great as ~3400 m. We then relate topographic measurements to the displacement on the underlying fault planes to study the displacement variations along the fault length. We find a variety of displacement distribution shapes of the fault systems, which we attribute to differences in fault growth that include unrestricted and restricted growth, linkage, and/or fault interaction. Finally, we relate the maximum displacements ( D max ) determined for each of the faults to their respective fault length (L) to establish a maximum displacement-to-length relationship. The observed scaling characteristics and order-of-magnitude scatter of our D max /L data are not uncommon for fault populations on Earth and tie in well with the map patterns, tectonic geomorphology, and systematic along-strike displacement distributions to have grown in a basement-block faulting style found in intra-plate tectonic settings on Earth.