The Pamir Mountains, Tian Shan, Altai, Hindu Kush, and other mountain belts are all examples of mountain ranges formed in response to the collision of the Indian with the Eurasian plate. The collision of the Indian and Eurasian plates produced the Himalayas and is also responsible for crustal thickening north into Siberia. Heavy thrust faulting (of the Indian plate beneath the Eurasian plate) and folding are responsible for the suturing together of the two plates. The collision of the Indian and Eurasian plates is a good example of the extent to which orogenic uplift can reach. ![]() In this process, two continents are sutured together, and large mountain ranges are produced. ![]() Perhaps the most extreme form of orogenic uplift is a continental-continental crustal collision. Orogenic uplift is the result of tectonic-plate collisions and results in mountain ranges or a more modest uplift over a large region. For example, the lithosphere on the oceanward side of an oceanic trench at a subduction zone will curve upwards due to the elastic properties of the Earth's crust. Thus, when loaded, the lithosphere progressively reaches an isostatic equilibrium. The lithosphere rests on the asthenosphere, a viscous layer that in geological time scales behaves like a fluid. Lithospheric flexure is the process by which the lithosphere bends under the action of forces such as the weight of a growing orogeny or changes in ice thickness related to glaciation. The highest rates of working against gravity are required when the thickness of the crust (not the lithosphere) changes. If a change in surface height represents an isostatically compensated change in crustal thickness, the rate of change of potential energy per unit surface area is proportional to the rate of increase of average surface height. The dynamics of mountain ranges are governed by differences in the gravitational energy of entire columns of the lithosphere (see isostasy). Lateral density variations near the surface (such as the creation, cooling, and subduction of oceanic plates) also drive plate motion. A good example of this would be the large-scale circulation of the Earth's mantle. All tectonic processes are driven by gravitational force when density differences are present. The process of nappe stacking can only continue for so long, as gravity will eventually disallow further vertical growth (there is an upper limit to vertical mountain growth).ĭensity distribution of the crust and underlying mantle Īlthough the raised surfaces of mountain ranges mainly result from crustal thickening, there are other forces at play that are responsible for the tectonic activity. The preserved inverted metamorphic gradient indicates that nappes were actually stacked on top of each other so quickly that hot rocks did not have time to equilibrate before being thrust on top of cool rocks. Basically nappes (thrust sheets) from each plate collide and begin to stack one on top of the other evidence of this process can be seen in preserved ophiolitic nappes (preserved in the Himalayas) and in rocks with an inverted metamorphic gradient. The timing, magnitude, and rate of denudation can be estimated by geologists using pressure-temperature studies.Ĭrustal thickening has an upward component of motion and often occurs when continental crust is thrust onto continental crust. This process can redistribute large loads from an elevated region to a topographically lower area as well – thus promoting an isostatic response in the region of denudation (which can cause local bedrock uplift). ![]() Tectonic uplift results in denudation (processes that wear away the earth's surface) by raising buried rocks closer to the surface. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal thickening (such as mountain building events), changes in the density distribution of the crust and underlying mantle, and flexural support due to the bending of rigid lithosphere. Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. Geologic uplift of Earth's surface that is attributed to plate tectonics
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