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Compressional orogens on the continents result from continent-continent collisions, collision and accretion of microcontinents like island arcs, and even excess friction along subduction zones. Collisions result in thickening of the crust - building of a mountain belt by thrust faulting and folding.
Continental collision zones are much more complicated than subduction zones. Continental crust is much less dense than the mantle and it won't subduct, so it piles up instead. Large scale thrust faulting is dominant in the central zone of convergence, but beyond the mountain belt there may be extensive regions of strike-slip faulting and even normal faulting (extension) as seen throughout central Asia north of the Tibetan Plateau. The India-Asia collision is particularly "mess." Southeast Asia is being squeezed out to the southeast by the collision of India with Asia. This has been dubbed "escape tectonics."
India and Asia have been colliding for at least 50 million years. The thickness of the crust in the still actively thrusting Himalayas is about 70 km. The maximum thickness of continental crust may be limited by flow in the ductile lower crust.
Old orogenic belts, like the Appalachians, will typically include a belt of folded and thrust faulted sedimentary strata, a belt of metamorphic rocks uplifted by the collision and also rocks that were originally metamorphosed in the core of the mountain belt that are later exposed by erosion. As the mountains are eroded, the eroded materials are deposited in a clastic wedge that is thickest and contains the coarsest sediments nearest to the eroding mountain front. The Siwalik redbeds in India is a clastic wedge forming along the margin of the Himalayas - The Himalayas are eroding as they continue to grow by active thrust faulting (and devastating earthquakes).
Foreland basins subside in front of approaching thrust sheets as a result of the load of stacked crust. The crust beneath the thrust load is depressed and the adjacent crust is depressed via flexure. The downward flexing of the crust also produces an outer bulge (like the bulge of ocean crust oceanward from a deep ocean trench).
Orogenic belts continue to be uplifted long after erosion has removed the original mountains. The mountains were originally supported by very deep roots. As the mountains are eroded the deep crustal roots undergo isostatic rebound.