A wet, swampy and marshy region where rivers re-emerge
Explanation
The Northern Plains of India are divided into four distinct physiological belts based on the nature of relief and soil characteristics. From north to south, these belts are the Bhabar, Terai, Bhangar, and Khadar.
Option Analysis
- A dry, porous region where rivers disappear is incorrect: This describes the Bhabar belt. It is a narrow belt (8–10 km wide) running parallel to the slopes of the Shiwaliks. Rivers descending from the mountains deposit pebbles here. Due to the high porosity of the rock debris, streams disappear underground in this zone.
- A wet, swampy and marshy region where rivers re-emerge is correct: This describes the Terai belt. Situated south of the Bhabar, this is a wet, swampy, and marshy region where the streams that disappeared in the Bhabar belt re-emerge. This region was historically covered with thick forests and supported rich wildlife, though much of it has been cleared for agriculture.
- A region of old alluvium with calcareous deposits is incorrect: This describes the Bhangar belt. It is composed of old alluvium and lies above the flood plains of the rivers. The soil in this region often contains calcareous deposits locally known as 'Kankar'.
- A rocky region in the Peninsular plateau is incorrect: This generally describes the Peninsular Plateau, which is a tableland composed of old crystalline, igneous, and metamorphic rocks, distinct from the depositional features of the Northern Plains.
Key Takeaway
The Terai is the zone of re-emergence for underground streams south of the Bhabar belt, characterized by wet, marshy conditions and high biological diversity.