From a new paper by David Montgomery et al. on the formation of the outflow channels Mars, a rich metaphor from our own desert Southwest. Stare through the classically turgid scientific prose. This is poetry:
The Needles area of Canyonlands National Park, Utah, provides a terrestrial analog for the finer-scale extension parallel to the margins of some Valles Marineris chasmata. At The Needles, the Paradox Formation, a cyclic sequence of evaporites, black shale, and carbonates (Hite, 1968), consists of about two-thirds halite and just over 5% anhydrite (Schultz-Ela and Walsh, 2002). These evaporites form a detachment layer along which lateral spreading formed a stepped series of grabens in response to incision of the Colorado River. Erosion through the overlying sedimentary rock into the underlying salts during the past several million years (McGill and Stromquist, 1979) removed the downdip confinement for the salt deposits and lateral support of their overburden, which spread down a 1°–2° décollement toward the canyon, as simulated by finit-element modeling (Schultz-Ela and Walsh, 2002). Equivalent deformation on Mars could involve volcanic ash (cemented to some degree by salts) and lava flows above salts (or ice and salt-cemented deposits). Welded or cemented tuffs and lava flows would act mechanically much like lithified sedimentary rock when subject to viscous flow of an underlying layer.