Olympus Mons levees along their margins (pictured). The cooler, outer margins of the flow solidify, leaving a central trough of molten, flowing lava. Partially collapsed lava tubes are visible as chains of pit craters, and broad lava fans formed by lava emerging from intact, subsurface tubes are also common. In places along the volcano's base, solidified lava flows can be seen spilling out into the surrounding plains, forming broad aprons, and burying the basal escarpment. Crater counts from high-resolution images taken by the Mars Express orbiter in 2004 indicate that lava flows on the northwestern flank of Olympus Mons range in age
Doom Mons Titanean "mountains" are little more than hills. However, some of these mountains rise to some several hundreds of meters high. Doom Mons is currently believed to be possibly the largest Titanean mountain range and with the eponymous peak one of the highest; the title of highest peak on Titan is thought to be held by the Mithrim Montes, which may have been formed by global contraction. Doom Mons is believed to be a twin-peak that rises above the relatively flat surrounding plain, and a probable massive cryovolcano. It has a 500–600 m deep indentation on its western side, containing a