Answer:
I am pretty sure it is erosion.
Explanation:
um do you have a question to ask?
They have a characteristic U shape, with steep, straight sides and a flat or rounded bottom (by contrast, valleys carved by rivers tend to be V-shaped in cross-section). Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring.
Flat,high land surrounded by snow covered mountains. Hope this helps!