Anseris Mons Mons bedrock is actually pre-Noachian in age, perhaps dating back to over 4.1 billion years ago. The Anseris Mons massif has undergone a significant amount of erosion since it was uplifted. The flanks of the mountain have huge triangular re-entrants and associated spurs, which give the massif a broad, pyramidal shape. The re-entrants were likely produced through a variety of mass-wasting and periglacial/glacial processes. A large cirque-like re-entrant with channelized debris aprons or fans is present on the south side of the mountain. Anseris Mons Anseris Mons is an isolated massif (mountain) in the southern highlands of Mars, located at
Tharsis Montes is about across and stands above the ocean floor. The Tharsis Montes volcanoes lie near the equator, along the crest of a vast volcanic plateau called the Tharsis region or Tharsis bulge. The Tharsis region is thousands of kilometers across and averages nearly above the mean elevation of the planet. Olympus Mons, the tallest known mountain in the Solar System, is located about northwest of the Tharsis Montes, at the edge of the Tharsis region. The Tharsis Montes were discovered by the Mariner 9 spacecraft in 1971. They were among the few surface features visible as the spacecraft entered orbit