The young fold mountain system along India's northern border, formed by the collision of the Indian and Eurasian plates, and the world's highest mountain range.
- Formed by convergent collision; geologically young, structurally fold mountains, and still rising, which makes the region seismically active.
- Three parallel ranges from north to south: the Greater Himalayas (Himadri, highest, with Mount Everest and Kanchenjunga), the Lesser Himalayas (Himachal, with hill stations), and the Outer Himalayas (Shiwaliks, lowest).
- Source of major perennial rivers: the Indus, Ganga, and Brahmaputra systems, fed by snowmelt and the monsoon.
- Act as a climatic barrier, blocking cold Central Asian winds and forcing the monsoon to shed rain over India.
- Regional divisions (west to east): Punjab/Kashmir, Kumaon, Nepal, and Assam Himalayas; the Brahmaputra and Indus mark the eastern and western limits.
The three-range structure, the plate-collision origin, the climatic-barrier role, and the strategic high-altitude border (ITBP, SSB) are recurring physical-geography and security facts.
Himadri (Greater, highest) versus Himachal (Lesser) versus Shiwaliks (Outer, lowest); the Himalayas are young fold mountains, unlike the old Aravallis.
Young fold mountains from Indian-Eurasian collision; three ranges (Himadri, Himachal, Shiwaliks); source of major rivers and climatic barrier.