By contrast, orogenic belts may include mountain belts or the eroded remnants of mountain belts. Orogenic belts are typically long, arcuate bands of crystalline rocks in terranes or blocks of deformed rocks separated by dipping thrust faults.
Mountain belts typically comprise multiple layers of sedimentary and volcanic rocks. These accumulations, which can be several kilometers in thickness, were mostly originally deposited in a marine environment. The clastic components of the sedimentary rocks are derived from weathing and transport (erosion) of the continental crust of nearby terrestrial landmasses. These sediments are deposited and lithified to form shales, limestones, and sandstones at the continental shelves, slopes, and rise.
At convergent boundaries, rising magma forms volcanic island arcs and plutonic emplacements. Island arcs typically form in line with the interplate junction, perpendicular to the direction of crustal movement.
Mountains arise through several mechanisms:
The general model proposes that mountain building involves three stages:
Tectonic convergence can be arc-continent, ocean-continent, or continent-continent:
Tectonic convergence folds and elevates the sedimentary strata from the original ocean basin, and creates faulting when the compressional forces exceed the ability of rocks to deform. The high compressional forces typically cause reverse and overthrust faulting.