The geologic map of Mars (Tharsis) Mars geologic units Tharsis Montes Formation, member 2 UnitName Tharsis Montes Formation, member 3 Alba Patera Formation, lower member Tharsis Montes Formation, member 4 Alba Patera Formation, middle member Tharsis Montes Formation, member 5 Arcadia Formation, member 3 Tharsis Montes Formation, member 6 Ceraunius Fossae Formation Valles Marineris interior deposits, floor material Medusae Fossae Formation, middle member eolian deposits Medusae Fossae Formation, upper member highly-deformed terrain materials, basement complex Olympus Mons Formation, aureole member 1 highly-deformed terrain materials, older fractured material Olympus Mons Formation, aureole member 2 plateau sequence, hilly unit Olympus Mons Formation, aureole member 3 plateau sequence, subdued cratered unit Olympus Mons Formation, aureole member 4 slide material Olympus Mons Formation, plains member undivided material Olympus Mons Formation, shield member volcano, relative age unknown Syria Planum Formation, upper member younger fractured material Olympus Mons Tharsis Montes Formation, member 1 Ascraeus Mons Tharsis is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield Pavonis Mons volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons, which are collectively known as the Tharsis Montes. The tallest volcano on the planet, Olympus Mons, is often associated with the Tharsis region but is actually located off the western edge of the plateau. The Arsia Mons name Tharsis is the Greco-Latin transliteration of the biblical Tarshish, the land at the western extremity of the known world. NASA, JPL, USGS, DLL, UoA, ASU, CU, OSU, Brown University, Goddard, NASA, JPL, USGS, DLL, UoA, ASU, CU, OSU, Brown University, Goddard, AMES, PDS, AMES, PDS,.