Determining Emplacement Conditions and Vent Locations for Channelized Lava Flows Southwest of Arsia Mons.

Abstract

The lava flow field southwest of Arsia Mons, Mars has complex volcanic geomorphology. Overlapping flows make observations of their total lengths and identification of their source vents impossible. Application of flow emplacement models, which rely upon physical parameters such as flow length, using only the exposed flow may produce inaccurate estimates of effusion rate, viscosity, and yield strength. We use an established terrestrial thermorheological model (PyFLOWGO), modified to Mars conditions, to estimate effusion rates, viscosities, yield strengths, and possible vent locations for five Mars flows. Our investigation found a range of effusion rates from 2,500 to 6,750m3s-1 (average of ∼4,960m3s-1). These results are an order of magnitude higher than terrestrial channelized basaltic flows. Corresponding modeled viscosities and yield strengths ranged from 9.4×103 to 6.6×105Pas (average of 5.5×104Pas) and 66 to 381Pa (average of 209Pa), respectively. A novel secondary application of PyFLOWGO that assumes upslope channel narrowing provided estimates of the entire channel length, which is on average four times longer than the exposed portions. Projecting these lengths upslope shows that four of the five flows may have a common vent location, which shares morphologic similarities to other Tharsis region vents. This modeling approach for partially-exposed lava flows makes it possible to not only determine eruptive parameters, but also to estimate total channel lengths and thereby identify possible source vents.