A prominent collapse feature (box 1) can be seen in Mars' Phoenicis Lacus. It is a long pit with a depth of about 3 kilometres below the surrounding terrain. In the central fault zone, there are blocks (box 2), showing that significant tectonic deformation has taken place in this region. A crater can be seen (box 3). This impact structure was elongated during the spreading of the region and evolved from a circular to an ellipsoidal form.