Landslide on Valles Marineris: morphology and flow dynamics
Ateliers des Fluides Géologiques
Salle non spécifiée
Résumé: Dynamics and deposition processes of Martian landslides at Valles Marineris were examined with numerical experiment and morphological analysis. We focused on the mobility and the surface pattern of the landslide deposits. The mobility given by the ratio of run-out length to drop height is a primitive parameter of the rheology of collapsed materials. Based on the mobility of Martian landslides that is generally very large, the contribution of the fluid phase such as water has been discussed for several decades. However, it is known that the mobility strongly depends on the debris volume. Martian landslides are 2~3 orders of magnitude larger than terrestrial ones, thus this effect is significant. Even though there are several explanations by geometrical configurations, the real effect of the volume on the mobility has not been clearly explained. In order to address this issue, we performed numerical experiments of granular materials which collapse and flow on a slope. As for the surface pattern, we focused on the longitudinal lineations which are frequently observed on the landslides at Valles Marineris but rarely found on terrestrial slope-failures. Since the lineations clearly indicate the flow pattern of debris, it should reflect the flow style and dynamics of collapsed materials. In order to get constraints for this pattern formation, we made morphological observations of the longitudinal lineations.