The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. Describe the mechanisms that enable glaciers to move and explain why they move. (B)

Before we dive into the mechanisms of glacier movement, let us briefly understand what glaciers are. Glaciers are large masses of ice formed by the accumulation and compaction of snow over a long period. They are found in high mountainous regions and polar areas, and they slowly flow and deform over time due to their weight and gravity.

There are two main mechanisms through which glaciers move: internal deformation and basal sliding. 1. Internal Deformation: This process occurs when the weight and pressure of the ice cause the glacier to deform and flow slowly. The ice crystals within the glacier rearrange themselves, resulting in the movement of the ice mass as a whole. 2. Basal Sliding: This process occurs when the glacier slides along its base, specifically over the bedrock or other underlying materials. The movement is facilitated by the presence of water, which acts as a lubricant between the ice and the bedrock. This water can be generated by the melting of the ice due to pressure or geothermal heat.

Several factors can influence the movement of glaciers, including: 1. Temperature: The temperature of the ice affects its deformation rate, with warmer ice deforming more easily than colder ice. In polar regions, where the ice is colder, glacier movement predominantly occurs through basal sliding. 2. Slope: The steeper the slope, the faster the glacier will flow due to the increased gravitational force acting on it. 3. Ice Thickness: Thicker ice has more mass, which leads to increased pressure and deformation, resulting in faster glacier movement. 4. Bedrock and Subglacial Material: The type of bedrock and subglacial materials can influence the basal sliding process. Smooth or soft underlying materials can facilitate sliding, while rough or hard bedrock can impede the glacier's movement.

Glaciers move primarily due to gravity and their own weight. The pressure generated by the weight of the overlying ice causes the ice to deform and flow, while gravity pulls the glacier downslope. Additionally, the presence of meltwater at the base of the glacier lubricates the contact between the ice and the bedrock, further enhancing the glacier's movement.