Orogeny refers to forces and events leading to a large structural deformation of the Earth's lithosphere (crust and uppermost mantle) due to the interaction between tectonic plates. Orogens or orogenic belts develop when a continental plate is crumpled and is pushed upwards to form mountain ranges, and involve a great range of geological processes collectively called orogenesis. The word "orogeny" comes from the Greek (oros for "mountain" plus genesis for "creation" or "origin"), and it is the primary mechanism by which mountains are built on continents.