Consider the following statements about the Evolution of the Himalayan Drainage system. 1. It evolved from the river Shivalik or the Indo-Brahma river that traversed the entire longitudinal extent of the Himalaya from Assam to Punjab and onwards to Sind. 2. Down-thrusting of the Malda gap, the area between the Rajmahal hills and the Meghalaya plateau, diverted the Ganga and the Brahmaputra system to flow towards the Bay of Bengal. Choose the CORRECT statements from above.

The correct answer is 3) Both 1 and 2 . Key Points Statement 1: The Himalayan drainage system evolved from the river Shivalik or the Indo-Brahma River, which traversed the entire longitudinal extent of the Himalaya from Assam to Punjab and onwards to Sind. The concept of the Indo-Brahma River explains that during the initial stages of the Himalayan uplift, a mighty river flowed parallel to the Himalayan range, draining water from the entire mountain chain. This river was later disrupted due to tectonic activity, including the upliftment of the Himalayas, which caused the river to disintegrate into several river systems like the Ganga, Brahmaputra, and Indus. Hence, this statement is correct. Statement 2: The down-thrusting of the Malda gap, the area between the Rajmahal hills and the Meghalaya plateau, diverted the Ganga and the Brahmaputra systems to flow towards the Bay of Bengal. The Malda gap is a tectonic depression that separates the Rajmahal hills to the west and the Meghalaya plateau to the east. This geological feature caused a diversion in the flow of river systems like the Ganga and Brahmaputra, which eventually started flowing towards the Bay of Bengal. It played a critical role in shaping the modern drainage pattern of eastern India. Hence, this statement is correct. Both statements 1 and 2 are correct. The evolution of the Himalayan drainage system is directly linked to the tectonic activities and changes in the geomorphology of the Himalayan region and its surroundings. Additional Information Formation of the Himalayas: The Himalayas were formed as a result of the collision between the Indian Plate and the Eurasian Plate approximately 50 million years ago. This tectonic activity caused significant changes in the drainage patterns of the region, leading to the formation of a complex river system. Drainage Patterns in the Himalayas: The Himalayan rivers display antecedent drainage patterns, meaning they existed before the upliftment of the Himalayas and maintained their course even as the mountains rose. Examples of antecedent rivers include the Indus, Ganga, and Brahmaputra. Role of Malda Gap: The Malda Gap, a tectonically active region, is a low-lying area that facilitates the flow of major rivers like the Ganga and Brahmaputra towards the Bay of Bengal. This gap has been instrumental in shaping the eastern drainage system of India. Indo-Brahma River Concept: During the Miocene epoch, a single mighty river system called the Indo-Brahma River flowed along the foothills of the Himalayas. This river later fragmented into the present-day river systems due to the upliftment of the Himalayas and other tectonic activities. Examples of Himalayan Rivers: Indus River: Originates in Tibet, flows through India and Pakistan, and drains into the Arabian Sea. Ganga River: Originates in the Gangotri Glacier, flows through northern India, and drains into the Bay of Bengal. Brahmaputra River: Originates in Tibet as the Yarlung Tsangpo, flows through India and Bangladesh, and drains into the Bay of Bengal. Important Points Factors Influencing Drainage Evolution: Plate tectonics and upliftment of the Himalayas. Climatic changes, leading to variations in precipitation and river flow. Geological features like the Malda Gap and associated fault lines. Significance of Himalayan Rivers: Provide water resources for agriculture, drinking, and hydropower generation. Support diverse ecosystems and sustain millions of people living in their basins. Play a critical role in sediment transport and deposition, shaping the floodplains and deltas.