Mechanisms of slope failure in Valles Marineris, Mars

Abstract

The trough system of Valles Marineris, Mars contains numerous landslides in the large relief exposures (up to 8 km) of basaltic wall rock and soft interior layered deposits (ILDs). Eleven landslides, including eight circular failures, were mapped in the ILDs. Two wall rock landslide complexes and four ILD landslides were modelled using limit-equilibrium slope stability analysis to evaluate the mechanisms of slope failure. Wall rock landslide complexes in the Ophir and Hebes Chasmata required artesian fluid pressures of at least 41% of overburden pressure or ground accelerations of at least 0.19 Mars g for failure. Agreement between modelled and observed failure surface geometries and the difficulty of generating artesian pressures at a regional topographic high indicate that ground shaking from Marsquakes or impacts most likely triggered the modelled wall rock landslides. Triggering mechanisms, such as ground acceleration or fluid pressure, were also necessary for most other landslides in Valles Marineris wall rock. Given minimum rock mass strengths, ILD landslides in the Hebes and East Candor Chasmata did not require triggering mechanisms; thus, landslides in ILDs may be a result of gravitational, fluid, or seismic loading.

Interpretation and analysis of planetary structures

“…These median values are generally larger than previous estimates of w5 -18 for layered deposits elsewhere in Valles Marineris gathered from back-calculations of slope failures (Schultz, 2002), although a more detailed slope-stability analysis that incorporates dynamic seismic loading and groundwater confirms failure of layered deposits having friction angles of w18 (Neuffer and Schultz, 2006). The angles of friction for the faults discussed here, that are not related to slope instability, are consistent however with laboratory measurements of intact rock (e.g., Byerlee, 1978), as well as moderately weathered and fractured rock masses (e.g., Hoek and Brown, 1997).…”

Thin‐skinned deformation of sedimentary rocks in Valles Marineris, Mars

“…Mechanisms that can trigger submarine landslides include volcanic activity; seismic activity, either faulting or impact induced; and fluid overpressurization, which occurs when rapid deposition of low‐permeability sediments traps pore fluid that cannot escape as the sediment compacts [ Flemings et al , 2008; Lucente and Pini , 2008]. The same triggering mechanisms have been suggested to have caused the Amazonian landslides on Mars [ Quantin et al , 2004; Neuffer and Schultz , 2006; Soukhovitskaya and Manga , 2006] and could have provided a triggering mechanism for potential ancient landslides.…”

Evolution of major sedimentary mounds on Mars: Buildup via anticompensational stacking modulated by climate change

“…Gravity‐slide deposits, when interstratified with sedimentary rocks, point away from paleohighs on unconformity surfaces [ Sharp , ]. Landslides encircling Ceti, Coprates, and Juventae Mensae, Gale's mound, and possibly Melas Mensa, flowed away from mound crests and are overlain by sedimentary rocks, especially at locally high elevations [ Lucchitta , ; Neuffer and Schultz , ; Okubo , ] (Figures and ). (A moatward draining canyon at Gale's mound is also draped by sedimentary rocks; Figure ).…”