The Northern Plains are formed by the interplay of the three major river systems – the Indus, the Ganga, and the Brahmaputra – along with their tributaries. These rivers deposit vast amounts of fine silt and clay, known as alluvium, making the plains exceptionally fertile for agriculture. The Peninsular Plateau has fertile black soil in some areas but is generally known for mineral resources. The Himalayan Mountains are rugged and mountainous, while the Indian Desert is arid and sandy, neither primarily known for extensive alluvial fertility.