The caldera on Arsia Mons is considerably larger than the calderas on either Ascraeus Mons (slide #5) or Pavonis Mons (slide #7). However, the last major collapse event on Arsia Mons was followed by substantial outpouring of lava within the caldera. The caldera rim has been breached on the southwest side while the caldera floor lavas bury portions of the northeast rim. Aligned between these breaks in the caldera is a series of very subdued domes on the caldera floor (arrow), perhaps representing localized sources of the lava that flooded the caldera. The flanks of the shield have been deeply eroded near the locations of the breaks in the caldera rim and lava flows extend away from the volcanoes at these embayments. It is significant that the trend indicated by the subdued domes and the shield embayments is colinear with the three Tharsis Montes volcanoes, indicating that this trend is important for the entire Tharsis Montes region.
9 S, 120 W; Viking
Orbiter frame 62A36, shading corrected version.