Final answer:
A rock glacier isn't immobile due to rock cover but moves slow due to ice beneath. Rocks insulate ice, allowing survival in warmer climates. Movement is dictated by internal ice deformation and gravity on landscape slope.
Step-by-step explanation:
A rock glacier is a type of glacier that has a heavy covering of rocks and debris, but contrary to the original student's statement, it is not necessarily immobile. Instead, rock glaciers are often characterized by their slow, creeping motion, driven by the ice within and beneath the rock cover. They are a significant feature in periglacial environments, areas near the margins of icy regions.
The presence of the rock debris on top can actually insulate the ice beneath, allowing the glacier to survive in climates warmer than would be possible for a typical ice glacier. The motion of a rock glacier occurs due to the deformation of this internal ice, and to gravity acting on the slope of the landscape.
Learn more about Rock Glacier