By weakening the crust in a localized area, a preferential region of strain can develop concentrating the flow of material. Ductile rocks deeper in the crust will be able to move towards the potential gradient, whereas brittle rocks near the surface will fracture when subject to increased strain. The transition between brittle deformation and ductile deformation is determined by the temperature which is generally controlled by depth as well as rheology. Weak hot minerals, below the ductile transition, with significant partial melt move into the area underlying the thinned crust as a result of the pressure gradient being decreased in the thin area. At a certain point, the pressure will decrease substantially moving from convergent basement rock into thinned crust. This causes rapid decompression at relatively stable and raised isotherms. Decompression melting occurs, which increases the proportion of partial melt within the material and causes rapid heat advection towards the surface. Continued convergent plate movement focuses the flow of material into the syntaxial areas with the localized weakness permitting upward escape as an accommodation mechanism. This process solves the fundamental problem of material being forced into a confined space by creating an outlet. The result of which creates a positive feedback with erosion focusing uplift which transports more weak rock vertically enhancing erosive capabilities. Areas of consistent elevation in river valleys and mountains with relief can be maintained by high exhumation rates of relatively young weak rocks. The ages of minerals in the area will be younger than the surrounding crust due to cooling occurring in an area with a steeper thermal gradient at shallower depths. Mature tectonic aneurysm systems, such as the Nanga Parbat, can have very high local reliefs of young rocks due to consistent erosion maintaining the elevation in the erosive area and vertical strain forcing material up along the proximal edges.