World Physical Geography / Mountains — UPSC Mains Model Answer

The American Cordillera runs continuously along the western margin of the Americas, encompassing the Alaska Range, the Rockies, the Sierra Madre, and the Andes. This unbroken chain spans over 15,000 kilometres, making it the longest continental mountain system on the planet. It forms a near-continuous divide separating Pacific-draining rivers from Atlantic and Gulf-draining systems.

These mountains are young fold mountains formed primarily during the Mesozoic and Cenozoic eras through subduction of oceanic plates beneath the continental plates of North and South America. This ongoing tectonic activity explains the high seismicity and volcanism — the 'Ring of Fire' — along the Pacific coast. The Andes, in particular, result from the subduction of the Nazca Plate beneath the South American Plate.

The Cordillera acts as a major orographic barrier, causing heavy precipitation on windward western slopes and rain shadows on the leeward eastern side, producing contrasting ecosystems such as the Atacama Desert and the Amazon Basin. Glaciers in the Andes serve as critical freshwater reservoirs for millions of people in arid Andean nations.

The region is extraordinarily mineral-rich — copper, silver, gold, and lithium deposits underpin the economies of Chile, Peru, and Bolivia. Governance challenges include managing cross-border environmental impacts, indigenous land rights, and sustainable extraction, all of which require coordinated regional policy frameworks.