Orogeny Orogen" resulted from these events and various others that are part of its peculiar orogenic cycle. In summary, an orogeny is an episode of deformation, metamorphism and magmatism at convergent plate margins, during which many geological processes play a role at convergent plate margins. Every orogeny has its own orogenic cycle, but composite orogenesis is common at convergent plate margins. Erosion represents a subsequent phase of the orogenic cycle. Erosion inevitably removes much of the mountains, exposing the core or "mountain roots" (metamorphic rocks brought to the surface from a depth of several kilometres). Isostatic movements may help such exhumation
Svecofennian orogeny rocks and the emplacement of the Jormua and Outokumpu ophiolites about 1950 million years ago. In the later stages of the Lapland-Savo orogeny an island arc, the Knaften arc, accreted to the Keitele-Karelia-Norrbotten collage. The stage to the Fennian orogeny was set by a collision between Keitele and Karelia about 1920–1910 million years ago which resulted in a reorganization of the local plate tectonics. As concequence the Bergslagen microcontinents collided with the Keitele–Karelia collage starting the Fennian orogeny. The until then linear Fennian orogen was "buckled" from 1870 million years ago onwards due to an orthogonal change in tectonic compressive