This document discusses various mechanisms by which mountains are formed, including plate tectonic processes at convergent plate boundaries like subduction and continental collisions. Mountain building occurs through orogenesis, which involves folding, faulting, metamorphism and igneous activity. Major mountain belts formed through subduction include the Andes and island arcs, while collisions produced the Himalayas and Appalachians. Fault-block mountains result from extension and some areas like the Basin and Range exhibit evidence of mantle upwelling. The concept of isostasy explains how the crust adjusts to changes in mass.