Final answer:
Mountain streams and glaciers contribute to deep and narrow river valleys in Bhutan.
Explanation:
The river valleys in Bhutan are deep and narrow primarily due to two main reasons:
- The steep terrain of the Himalayan Mountains in Bhutan leads to fast-flowing mountain streams that cause significant erosion, carving deep channels over time.
- The presence of glaciers in the region further contributes to the deepening and narrowing of the valleys, as glaciers can carve U-shaped valleys by eroding predominantly at the base.
The dominant form of erosion in Bhutan is caused by mountain streams, which carve narrow, V-shaped valleys due to the rapid water flow and steep slopes.
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