This long pit on the western flank of the Arsia Mons volcano shows a thick stack of volcanic layers.
This is probably a collapse pit that formed in a similar manner to how such pits form in Hawaii. Underlying large volcano complexes there is a large lava “plumbing system.” While active, these lava tubes can support the weight of overlying solidified lava layers. However, when volcanic activity slows down, and lava drains away, these lava tubes empty and often collapse.
Scientists can study the layers in the pit walls to learn things about the eruptions that built the volcano in this area.
Written by: Ross Beyer (1 April 2009)
This is a stereo pair with PSP_004412_1715 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_012310_1715
Image: NASA/JPL/University of Arizona