Alleghanian orogeny Alleghanian orogeny The Alleghanian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957. The Alleghanian orogeny occurred approximately 325 million to 260 million years ago over at least five deformation events in the Carboniferous to Permian period. The orogeny was caused by Africa colliding with North America. At the time, these continents did not exist in their current forms: North America was part of the Euramerica super-continent, while Africa was part of Gondwana. This collision formed
Svecofennian orogeny of the Transscandinavian Igneous Belt has. The Svecofennian orogeny involved the accretion of numerous island arcs in such manner that the pre-existing craton grew with this new material from what is today northeast to the southwest. The accretion of the island arcs was also related to two other processes that occurred in the same period; the formation of magma that then cooled to form igneous rocks and the metamorphism of rocks. The Svecofennian orogeny developed as a succession of four orogenies which by chronological order are: the Lapland-Savo orogeny, the Fennian orogeny, the Svecobaltic orogeny and the Nordic orogeny. In