The world's tallest mountains, as well as those exhibiting the greatest vertical relief over short distances, form the Himalaya range that developed in the continent-continent collision zone between India and Asia. The range extends for more than 1,800 miles (3,000 km) from the Karakorum near Kabul (Afghanistan), past Lhasa in Tibet, to Arunachal Pradesh in the remote Assam province of India. Ten of the world's 14 peaks that rise to more than 26,000 feet (8,000 m) are located in the Himalaya, including Mount Everest, 29,035 feet (8,850 m), Nanga Parbat, 26,650 feet (8,123 m), and Namche Barwa, 25,440 feet (7,754 m). The rivers that drain the Himalaya include some with the highest sediment outputs in the world, including the Indus, Ganges, and Brahmaputra. The Indo-Gangetic plain on the southern side of the Himalaya represents a foreland basin filled by sediments eroded from the mountains and deposited on Precambrian and Gondwanan rocks of peninsular India. The northern margin of the Himalaya is marked by the world's highest and largest uplifted plateau, the Tibetan Plateau.
The Himalaya is one of the youngest mountain ranges in the world but has a long and complicated history. This history is best understood in the context of five main structural and tectonic units within the ranges. The Subhimalaya includes the Neogene Siwa-lik molasse, bounded on the south by the Main Frontal Thrust, which places the siwalik molasse over the Indo-Gangetic plain. The Lower or subhimalaya is thrust over the subhimalaya along the Main Boundary Thrust and consists mainly of deformed thrust sheets derived from the northern margin of the Indian shield. The High Himalaya is a large area of crystalline basement rocks, thrust over the subhimalaya along the Main Central Thrust. Further north, the High Himalaya sedimentary series, or Tibetan Himalaya, consists of sedimentary rocks deposited on the crystalline basement of the High Himalaya. Finally, the Indus-Tsangpo suture represents the suture between the Himalaya and the Tibetan Plateau to the north.
sedimentary rocks in the Himalaya record events on the Indian subcontinent, including a thick Cam-brian-Ordovician through Late Carboniferous/Early Permian Gondwanan sequence, followed by rocks deposited during rifting and subsidence events on the margins of the Tethys and Neotethys oceans. The collision of India with Asia was in progress by the Early Eocene. This collision exposed the diverse rocks in the Himalaya, revealing a rich geologic history that extends back to the Precambrian, where shield rocks of the Aravalli Delhi cratons are intruded by 500 million-year-old granites. Subduction of Tethyan oceanic crust along the southern margin of Tibet formed an
Andean-style arc represented by the Transhimalaya batholith that extends west into the Kohistan island arc sequence, in a manner similar to the Alaskan range—Aleutians of western North America. The obduction of ophiolites and high-pressure (blueschist facies) metamorphism dated to have occurred around 100 million years ago is believed to be related to this subduction. Thrust stacks began stacking up on the Indian subcontinent, and by the Miocene, deep attempted intracrustal subduction of the Indian plate beneath Tibet along the Main Central Thrust formed high-grade metamorphism and generated a suite of granitic rocks in the Himalaya. After 15-10 million years ago, movements were transferred to the south to the Main Frontal Thrust, which is still active.
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