An extensive (106 km2) lava flow field SW of Arsia Mons contains individual lobes that are 102--103 km long, are ~65 m thick, and display a surface ridging similar to the textures found on terrestrial andesite, dacite, and rhyolite flows, raising the question of whether large-volume evolved lava flows exist on Mars. The regularly spaced ridges on these Martian flows have wavelengths of ~100 ¿ 34 and amplitudes of ~27 ¿ 11 m. An andesitic lava flow field at Sabancaya volcano, Peru, is a morphologic analog, with flow thicknesses of ~60--170 m and surface ridges. One intensely studied flow lobe at Sabancaya has a ridge wavelength of ~67 ¿ 24 m and amplitude of ~5 ¿ 2 m. Despite morphologic similarities, comparing the calculated rheologic and emplacement parameters of the two lava flow fields reveals large differences. Calculated yield strengths for the Martian lavas are 103 Pa; those for lavas of Sabancaya, Peru, are 105 Pa. Effusion rates of 103--104 m3 s-1 calculated for the Martian flows are larger than those calculated for the Sabancaya lavas (1 m3 s-1). Calculations of emplacement times for the Martian and Sabancaya flows are 1--102 days and 1--103 days, respectively. Estimates of viscosity are 104--106 Pa s for southwestern Arsia Mons and 1010--1012 Pa s for Sabancaya. We therefore conclude that the flows southwest of Arsia Mons are most likely not the same composition as those at Sabancaya volcano, but rather are basaltic or basaltic andesite in composition.