Alerryagi
The Alerryagi [a'lɛ:rjagi] on Arophania is the third-longest mountain range of Ilethes, and is the southern component of the Western Boundary Mountain System, continuing the course of the Iryagi on Marcasia, interposed by the Chisthian archipelago. The source of three most important rivers in Arithia, the range runs northwest-southeast down the continent, and continues into the Thorfu as the Tumides archipelago, which represent the submerged peaks of the range's southern tip.
The Alerryagi is just over 2,600km long on land, excluding the submerged peaks of the Chisthian and Tumides archipelagos. Due to the nature of its formation the range is considerably wide, measuring almost 1,800km at its widest point to cover the entire eastern third of Arophania, which entire mountainous region is known as the Eastern Seaboard. Besides the Tumides, the Sissemen archipelago is considered by some geologists as part of the Alerryagi (see article).
Geology
Like the Iryagi, the orogeny of the Alerryagi involved convergent tectonic plates, the Arophanian and, again, the Maellorian, in subduction and folding processes, but with one major difference. While the Iryagi were straightforwardly formed by crumpling and sedimentation of plate-boundary crust with minimal volcanic involvement, the crustal uplifting that made the Alerryagi involved considerably the formation first of oceanic volcanoes along a highly active Wadachi-Benioff zone, due to the basaltic composition of the underlying magma (in contrast, the magma under the Iryagi is largely felsic).
The subduction of the Maellorian, denser than the Arophanian due to its largely oceanic nature, had two simultaneous effects: first, the edge of the Arophanian plate crumpled and folded to rise above sea level as new mountains; second, increased volcanic activity on and under the Maellorian plate gave rise after repeated eruptions to an undersea lava plateau, which eventually surfaced, due to further tectonic lift, and became the modern Nimaean plain. The inland sea that existed around the Nimaean plain in the early stages of its formation disappeared to evaporation and percolation, remaining today only in the higher reaches of the Alerryagi as the Barrier Lakes.
Hallaryagi
- Main article: Hallaryagi
The Hallaryagi are a southwest-branching sub-range of the Alerryagi, stretching from approximately halfway down the latter towards the southern coast, near which it tapers off. It is believed that the Hallaryagi arose from a fracture in the Arophanian plate caused by the extreme stress originating from the plate boundary with the Maellorian plate.
