Alpine–Himalayan belt

The Alpine–Himalayan belt (also called the Alpide belt or Tethyan orogenic belt) is the second most seismically active zone on Earth after the Circum-Pacific "Ring of Fire," accounting for roughly 17 percent of the world's largest earthquakes. It originated during the Cenozoic era, principally the Tertiary period, when the closure of the ancient Tethys Sea brought the northward-drifting Gondwana fragments — the African, Arabian, and Indian plates — into collision with the Eurasian plate. The resulting compression folded the marine sediments deposited in the Tethyan geosyncline into the great young fold mountains, a process explained by plate tectonics and continental drift as theorised by Alfred Wegener (1912) and later refined by the seafloor-spreading hypothesis of Harry Hess (1962).

The belt runs as an almost unbroken east–west arc. From the west it comprises the Atlas of the Maghreb, the Sierra Nevada (Baetic) ranges of Iberia, the Pyrenees, the Alps, the Apennines, the Carpathians, the Dinaric Alps, and the Balkans, then continues through the Pontic and Taurus ranges of Anatolia, the Caucasus, the Elburz and Zagros of Iran, the Hindu Kush, Pamir and Karakoram knot, and culminates in the Himalayas — the loftiest segment, including Mount Everest (8,849 m) and Kangchenjunga. Eastward it bends through the Arakan Yoma of Myanmar and curves into the island arcs of the Indonesian archipelago, where it meets the Pacific belt near the Banda Sea. These ranges share defining features: high relief, sharp folding and thrust faulting, frequent shallow- and intermediate-focus earthquakes, the presence of marine fossils at altitude, and isostatic uplift that continues today as the Indian plate pushes north at about 5 cm per year.

Named instances illustrate the belt's continuing tectonic vigour. The 2005 Kashmir earthquake (Mw 7.6), the 2015 Gorkha (Nepal) earthquake (Mw 7.8), the 1999 İzmit earthquake in Turkey, and the catastrophic February 2023 Türkiye–Syria earthquakes (Mw 7.8 and 7.5 on the East Anatolian Fault) all lie along this collision zone. The Himalayan sector in particular remains a zone of high seismic risk, with seismologists warning of a long-overdue "great earthquake" in the central Himalayan seismic gap. As of 2026 the belt continues active orogeny, and its rivers — the Indus, Ganga and Brahmaputra — are antecedent streams that predate and cut across the rising ranges.

For the UPSC examination, the Alpine–Himalayan belt is core Physical Geography tested in the General Studies Paper I (Prelims) and in the Geography optional. Typical question angles include: distinguishing young fold mountains from old block and relict mountains; correlating the belt with the global distribution of earthquakes and volcanoes; explaining its origin via the Tethys Sea and plate convergence; and identifying constituent ranges in map-based or statement-matching questions. Candidates should be able to contrast it with the Circum-Pacific belt and link Himalayan orogeny to the broader Indian monsoon and drainage systems.