Why do glaciers carve U-shaped valleys, and how does a hanging valley form?

Glaciers are massive, slow-moving rivers of ice. They carve valleys as they move downhill due to gravity. While glaciers pass through mountains and valleys, they erode the land beneath them, shaping the landscape. The immense weight and pressure of the ice cause the rocks at the base of the glacier to fracture and be swept away. The process of erosion is called abrasion, and it carves the characteristic U-shaped valleys. In contrast to V-shaped valleys, which are formed by the erosive action of rivers, U-shaped valleys result from glacier movement. V-shaped valleys are often more pointed and narrow, while U-shaped valleys are broader and more rounded at the bottom. This difference is primarily due to the nature of these erosive forces: glaciers have the capacity to cover larger areas and erode the valley floor evenly, resulting in a more uniform bottom in a U-shaped valley.

Hanging valleys are formed when a smaller tributary glacier merges with a larger main glacier. As the larger glacier erodes the landscape more effectively due to its larger size and weight, it carves a deeper valley compared to the smaller tributary glacier. When the main glacier retreats, or melts, it leaves behind a U-shaped valley with a steep drop to the valley floor. The smaller tributary glacier has also carved a valley but at a higher elevation than the main valley. As a result, the joining point of the two glaciers (the tributary and the main one) forms a hanging valley. Hanging valleys are often characterized by waterfalls cascading down their steep walls as rivers or streams flow from the higher tributary valley to the lower main valley. In conclusion, glaciers carve U-shaped valleys as they erode the landscape through a process called abrasion, and hanging valleys form when smaller tributary glaciers join and have carved a higher, less deep valley compared to the main glacier.