Orogenic collapse

rdf:langString Orogenic collapse

rdf:langString In geology, orogenic collapse is the thinning and lateral spread of thickened crust. It is a broad term referring to processes which distribute material from regions of high gravitational potential energy to regions of low gravitational potential energy. Orogenic collapse can begin at any point during an orogeny due to overthickening of the crust. Post-orogenic collapse and post-orogenic extension refer to processes which take place once tectonic forces have been released, and represent a key phase of the Wilson Cycle, between continental collision and rifting. Orogens (also known as orogenic belts, or more simply mountain ranges) are sections of thickened crust which are built up as tectonic plates collide. The thickening of the crust marks the start of an orogeny, or "mountain building event." As the orogeny progresses, the orogen may start spreading apart and thinning. Collapse processes can begin either once the orogeny ends as the tectonic forces cease, or during the orogeny if the crust becomes unstable. There are two primary mechanisms at work in an orogenic collapse: excess gravitational potential energy and heat flow into the thickened crust. Overthickened crust can become brittle and begin collapsing and spreading under its own weight. The added weight from the thickened crust also causes it to sink deeper into the mantle, where additional heat can flow into the crust. The added heat softens the rock and makes it flow more easily, which can allow material in deeper sections to move up into thinner areas via buoyancy forces, reducing the total thickness. Orogens can also be destroyed by eduction and erosion, but these processes are not necessarily associated with orogenic collapse. It has been argued that extension during orogenic collapse is a more effective mechanism of lowering mountains than erosion.