Volcanoes located within the densely cratered southern highlands have a very different morphology from either the Tharsis or Elysium volcanoes. Tyrrhena Patera has very little vertical relief (less than 2 km, or 1.2 mi), resulting in very shallow flank slopes. The flanks of the volcano are deeply eroded with many broad channels that radiate from the summit region. The low relief and easily erodible nature of the flank materials has been interpreted to indicate that the bulk of the volcano is composed of pyroclastic (ash) deposits. This interpretation implies that the style of eruption for the highland volcanoes like Tyrrhena Patera is significantly different from the repeated effusion of fluid lavas that built up the shield volcanoes.
22 S, 253 W; Viking Orbiter frame 87A14, high-pass spatially filtered version.