The longitudinal valleys also called Duns/Doons are found in :

Key Points

• The longitudinal valleys, also called Duns or Doons, are located between the Shiwalik Hills and the Lesser Himalayas.
• These valleys are formed due to tectonic activity and are characterized by flat-bottomed, elongated landforms.
• Examples of such valleys include the Dehradun Valley, Kotli Dun, and Patli Dun.
• The Shiwalik Hills, also known as the Outer Himalayas, are the youngest mountain range of the Himalayas and are composed of unconsolidated sediments.

Additional Information

• Shiwalik Hills:
  • The Shiwalik Hills are the southernmost range of the Himalayas and extend across northern India, Nepal, and Bhutan.
  • They are composed of sedimentary rocks like sandstone and conglomerates, which were deposited by rivers flowing from the higher ranges.
  • These hills are prone to erosion due to their unconsolidated nature.
  • The altitude of the Shiwalik Hills varies from 600 to 1,500 meters.
• Duns/Doons:
  • Duns are flat-bottomed longitudinal valleys situated between the Shiwalik Hills and the Lesser Himalayas.
  • They are formed due to the folding of the Himalayas, which creates depressions that are later filled with alluvium brought by rivers.
  • These valleys are fertile and are often used for agriculture.
  • Dehradun, one of the most famous duns, is located in the state of Uttarakhand in India.
• Lesser Himalayas:
  • The Lesser Himalayas, also known as the Himachal Range, lie to the north of the Shiwalik Hills.
  • This range consists of metamorphic rocks and is older and more stable compared to the Shiwalik Hills.
  • The altitude of the Lesser Himalayas ranges from 3,500 to 4,500 meters.
• Greater Himalayas:
  • The Greater Himalayas, also called the Himadri, are the northernmost and highest range of the Himalayas.
  • They contain some of the world's highest peaks, including Mount Everest and Kanchenjunga.
  • The altitude of this range exceeds 6,000 meters in many places.
• Trans-Himalayas:
  • The Trans-Himalayas are located to the north of the Greater Himalayas and include ranges such as the Karakoram, Ladakh, Zanskar, and Kailash.
  • This region is characterized by high-altitude plateaus and cold deserts.