[1] Arsia Mons is a shield volcano with a relatively low slope and a massive caldera at its summit.

Arsia Mons has 30 times the volume of Mauna Loa in Hawaii, the largest volcano on the Earth.

The rift area to the southwest has been imaged in significant detail by the European Space Agency probe Mars Express.

It has been proposed that these are the result of plate tectonics, which on Earth makes chains of "hot spot" volcanoes.

[16] A repeated weather phenomenon occurs each year near the start of southern winter over Arsia Mons.

On the leeward slope, water ice condenses, forming a cloud which can extend westward for more than 1000 km.

The autumn of 2018 saw a particularly pronounced version of this orographic cloud, as the planet-wide dust storm finally subsided.

[22][23][24] They have been informally dubbed Dena, Chloë, Wendy, Annie, Abbey, Nikki, and Jeanne and resemble "skylights" formed by the collapse of lava tube ceilings.

[25] A more recent photograph of one of the features shows sunlight illuminating a side wall, suggesting that it may simply be a vertical pit rather than an entrance to a larger underground space.