Final answer:
A crescent-shaped scarp often appears above a rock glacier is true. Rock glaciers can cause such formations through their downward flow, and other erosive processes can contribute as well.
Step-by-step explanation:
The statement that a crescent-shaped scarp on a high slope often appears above a rock glacier is True. Rock glaciers are formations that occur when rocks and sediments mix with ice, often found beneath a layer of debris in mountainous regions. As these rock glaciers flow downward, akin to the movement of a traditional glacier, they can indeed create a crescent-shaped scarp above them. This is due to the movement and deformation of material within the rock glacier affecting the overlying land and possibly leading to a visible scarp formation. Furthermore, erosion by water and ice on the mountains created by upthrusting of the crust, can sculpt the rock into sharp peaks and serrated edges, which can also contribute to the formation of scarps.