The correct option is 1 only
Explanation
Glacial troughs, commonly referred to as U-shaped valleys, are prominent erosional landforms created by the movement of glaciers. They are typically formed when a glacier moves down a slope, modifying pre-existing V-shaped river valleys through extensive erosion.
Statement-wise Analysis:
- Statement 1 is Correct: Glacial troughs are characterized by a distinct U-shape, featuring steep, precipitous walls and a broad, flat floor. This morphology results from the glacier eroding both the sides (lateral erosion) and the bottom (vertical erosion) of the valley simultaneously.
- Statement 2 is Incorrect: These valleys are not always devoid of debris. Upon the retreat of the glacier, the valley floor is often littered with debris or till. Additionally, depositional features such as moraines may be present within the trough.
- Statement 3 is Incorrect: Glacial troughs are formed by glacial erosion (specifically abrasion and plucking), not by wind deposition. Landforms created by wind deposition include dunes and loess, which are geomorphologically distinct from glacial valleys.
Key Takeaway:
Glacial troughs are U-shaped erosional landforms with broad floors and steep sides, formed by the glacial modification of river valleys, and often contain depositional debris like moraines.