This is a profile view of the rim of a young maar volcano on the Ethiopia/Kenya border. The Mega volcanic field includes a number of maars that cut through ancient crystalline rock. Photo by Chuck Wood, 1972.
This view looks into the floor of the maar shown above. The dark ridge below the rim is the edge of the crystalline basement rocks. Like many maars, this one has collapsed so that its floor is lower than the surrounding plain. If this area did not have a desert climate, the maar would probably contain a lake.