Geologic map of the Phaethontis Quadrangle of Mars

The Phaethontis quadrangle of Mars is dominated by densely cratered uplands and plateaus which form some of the oldest surfaces on the planet. Extensive low-lying areas within the cratered terrains, including the floors of large craters, are covered to different degrees by plains-forming material. The youngest plains units surround Tharsis Montes to the north. Various erosional processes, including eolian scour and possibly scarp retreat through volatile-release sapping and mass wasting, have modified martian terrains in the northwestern part of the quadrangle, producing several distinctive physiographic features: knob and mesa terrains, plains with small knobs, and plateaus dissected by furrows, steep-walled gorges, and pits.