We see here a terrain with an incredible morphologic dichotomy: a relatively smooth region that transitions into sharp ridges. These ridges, aligned in the nearly same direction, are called yardangs. Yardangs are not unique to Mars. Many yardangs can be found on Earth, in very dry regions with strong prevailing winds.
Yardangs are formed when a surface that is composed of materials of differing strengths (i.e., of both harder and softer materials) is shaped by the abrasive action of sand and dust carried by the wind. In this case, and given the proximity of the Apollonaris Patera volcanic center, we think that these wind-carved deposits are comprised of volcanic ash and pyroclastics that erupted from Apollonaris when it was last active in the not-too-distant geologic past. [More at link]