What features are characteristic of a U-shaped glacial valley?

A U-shaped glacial valley is characterised by steep, straight sides and a flat or rounded bottom.

A U-shaped glacial valley, also known as a trough valley, is a distinctive geographical feature formed by the erosive action of glaciers. The valley gets its name from its characteristic U-shape, which is markedly different from the V-shape typically formed by river erosion. This shape is a result of the glacier's unique erosive pattern. Unlike rivers, which erode more at the bottom and less at the sides, glaciers erode the valley sides and bottom equally, leading to steep, straight sides and a flat or rounded bottom.

The steep sides of a U-shaped valley are often near-vertical, a result of the glacier's lateral erosion. This is in contrast to the gentle slopes of a river valley. The valley floor, on the other hand, is usually wide and flat, a result of the glacier's basal erosion. This flat floor is often filled with water, forming a ribbon lake or a fjord if it reaches the sea.

Another characteristic feature of a U-shaped glacial valley is the presence of hanging valleys. These are smaller valleys that join the main valley at a higher elevation. They are formed when smaller glaciers, flowing into the main glacier, are unable to erode their valleys as deeply as the larger glacier. When the glaciers retreat, these hanging valleys are left as tributaries to the main valley.

Truncated spurs are another feature often associated with U-shaped valleys. These are the remnants of former river valleys that have been cut off by the advancing glacier. The glacier's powerful erosive force shears off the ends of these spurs, leaving behind steep, cliff-like faces.

In summary, a U-shaped glacial valley is characterised by its steep, straight sides and flat or rounded bottom, formed by the equal erosion of the valley sides and bottom by a glacier. Other characteristic features include hanging valleys and truncated spurs.