Q.A deep, long and wide trough or basin with very steep concave high walls at its head as well as in sides is known as:

A glacial valley, also known as a glacial trough, is a distinctive landform created by the erosional power of glaciers. As a glacier moves, it plucks away rock and abrades the valley floor and sides, widening and deepening the pre-existing river valleys.

The characteristic features of a glacial valley include:

• A deep, long, and wide trough or basin.
• Very steep, often concave, high walls along its sides and at its head.
• A U-shaped cross-section, which is a hallmark of glacial erosion, distinguishing it from the V-shaped profile of river valleys. …

Glaciers are powerful agents of erosion, capable of sculpting vast landscapes over long periods. As massive bodies of ice move across the land, they pluck away rock material and abrade the underlying surface, creating distinctive landforms. The question describes a specific type of erosional feature formed by glacial activity.

Let's break down the characteristics provided: "A deep, long and wide trough or basin with very steep concave high walls at its head as well as in sides."

• Deep, long and wide trough or basin: This suggests a significant depression in the landscape, extending over a considerable distance.
• Very steep concave high walls at its head: This points to a dramatic, bowl-shaped or amphitheatre-like feature at one end.
• As well as in sides: This indicates that the steep walls are not just at the head but also extend along the length of the feature.

Now, let's examine the given options:

• Cirque: A cirque (also known as a corrie or cwm) is an armchair-shaped, deep, steep-sided hollow or basin found at the head of a glacial valley. It has steep, often concave walls on three sides and an open side leading down into the valley. While it fits the "very steep concave high walls at its head" and "basin" part, it is typically not described as a "long and wide trough" that extends for a significant distance. A cirque is the starting point or head of a glacial valley.

• Glacial valley: A glacial valley, often called a U-shaped valley or trough, is formed when a glacier moves through a pre-existing river valley. The glacier widens, deepens, and straightens the valley, giving it a characteristic U-shaped cross-section with a broad, flat floor and very steep, often concave or nearly vertical sides. This perfectly matches the description of a "deep, long and wide trough" with "very steep concave high walls... in sides." The "concave high walls at its head" could refer to the cirque from which the glacial valley originates, or simply the dramatic, steep upper reaches of the valley walls near its source.

  Important

  Glacial valleys are distinguished by their characteristic U-shape, which results from the glacier's erosive power acting on both the floor and the sides of the valley. …