Orogeny millions of years and build mountains from plains or from the seabed. The topographic height of orogenic mountains is related to the principle of isostasy, that is, a balance of the downward gravitational force upon an upthrust mountain range (composed of light, continental crust material) and the buoyant upward forces exerted by the dense underlying mantle. Frequently, rock formations that undergo orogeny are severely deformed and undergo metamorphism. Orogenic processes may push deeply buried rocks to the surface. Sea-bottom and near-shore material may cover some or all of the orogenic area. If the orogeny is due to two continents colliding,
Andean orogeny were inverted in the Miocene. After a period of quiescence the Agrio fold and thrust belt resumed limited activity in the Eocene and then again in the Late Miocene. In the south of Mendoza Province the Guañacos fold and thrust belt (36.5° S) appeared and grew in the Pliocene and Pleistocene consuming the western fringes of the Neuquén Basin. The early development of the Andean orogeny in southernmost South America affected also the Antarctic Peninsula. In southern Patagonia at the onset of the Andean orogeny in the Jurassic, extensional tectonics created the Rocas Verdes Basin, a back-arc basin whose southeastern