The Altiplano-Puna volcanic complex is underpinned at about depth by a wide magmatic sill where rocks are partially molten, the Altiplano-Puna magmatic body. Its existence has been established with various techniques; it extends over an area of and has a volume of about with a thickness variously estimated to be between ; it has been referred to as the largest reservoir of magma in the continental crust of Earth. The Altiplano-Puna magmatic body is the source of magmas for many of the volcanoes in the Altiplano-Puna volcanic complex; in addition, about of brine are contained in the rocks underneath Uturuncu.