The southern region, with its plateau-like rocks (on the left of the image), is significantly higher than areas further north (on the right of the image), which mainly consist of smaller mesas and hills. These are interspersed with depressions that formed through erosion processes during the planet’s past. Water and ice transported the rocky material downslope into areas of lower elevation millions of years ago. The narrow valleys bear particularly clear traces of these flow processes, with line-like structures that show where material was transported by water or ice. The elevations in the adjacent northern lowlands are testament to the former level of the terrain and are thought to consist of more resistant material.