Longitudinal valleys between lesser Himalaya and Shiwaliks
Explanation
The Himalayas consist of three parallel ranges: the Great Himalayas (Himadri), the Lesser Himalayas (Himachal), and the Outer Himalayas (Shiwaliks). The longitudinal valleys found between these ranges are significant physiographic features.Detailed Analysis:
- Duns are longitudinal valleys formed between the Lesser Himalayas and the Shiwaliks.
- These valleys are filled with sediment and gravel brought down by the Himalayan rivers. As the Shiwalik range rose, it obstructed the flow of rivers, leading to the accumulation of sediments in these depressions.
- Unlike deep gorges carved by erosion or high-altitude glacial lakes, Duns are structural valleys characterized by their flat floors and agricultural utility.
- Prominent examples include Dehra Dun, Kotli Dun, and Patli Dun. Dehra Dun is the largest and most well-known among them.
Key Takeaway: Duns are specific longitudinal valleys situated between the Lesser Himalayas and the Shiwalik range, distinct from other Himalayan features like passes, gorges, or glacial lakes.