Root zone
In geology, the root zone is that part of the earth's crust that is the base or the region of origin of a large rock body reaching to the surface . A distinction is made between mountain roots and ceiling roots .
Mountain root
The mountain root is a deeply subsurface thickening of the earth's crust under orogen . It displaces the material of the upper mantle and has a somewhat lower density than this. Therefore, it manifests itself in a gravity deficit , but on the other hand carries the overlying mountains in the sense of a swimming equilibrium ( isostasy ), so that even larger mountain regions are stabilized over long geological periods high above sea level .
Such thickening of the crust (from an average of 30 km to double) was postulated for the first time in 1885 by the English geodesist Airy . He calculated that the vertical deviations on the southern edge of the Himalayas are much smaller than the mass of the mountains themselves, and assumed a partial compensation for the severe disturbances caused by the mantle rocks displaced downwards. The first actual evidence of a mountain root was made in 1933 by the geophysicist Gutenberg in the Eastern Alps .
See also
Ceiling root
The nappe root is the area of origin of a tectonic nappe . Such large-scale thrusts in the course of fold mountains , which were first discovered and researched in the Alps , can originate from regions that are more than 100 km away from the current position of the rock cover. So z. B. the flysch on the northern edge of the Eastern Alps from a former deep sea area , which is located in the area of today's Mediterranean .