From a southeastern aerial view, this large, easily recognizable area extends and branches out over the entire state.
Upon examining the water division, it becomes apparent that it originates from the melting of the Yarpun glacier. This water then feeds into Lake Conococha. From there, the mountain range divides into two well-know branches, Cordillera Blanca and Cordillera Negra. Both, along with their respective sub-branches, follow an almost parallel route towards the northeast, finally meeting in the Corongo highlands (near snowcapped Pacta, 5,000 m.a.s.l. (16,400 ft.) ).
Before describing other sub-branches within the mountain range area, we should point out the geological characteristics of this large area are rather complex. They are related to the pressure processes caused by the friction between the tectonic Nazca and South American plates.
On the northeastern side of the state (Pallasca province), there is an igneous outcrop which was formed during the Pleistocene. The real base of said material is small when compared to the other two outcrops due to the fact that it served as a sort of barrier in the presence of later evens related to the formation of sedimentary-metamorphic materials. During the geological periods, Upper Jurassic, Lower Cretaceous, Medium to Upper Cretaceus and Lower Tertiary, there were marine transgressions which formed sedimentary deposits. These emerged progressively due to the incessant compressive creasing produced by the movement and collision of the Nazca and South American plates.
From the beginning of the Medium Cretaceous until the end of the Lower Tertiary periods, after withstanding the previously mentioned pressure, the west border in our mountain range area began to exhibit the most widespread outcrop of igneous rock that has ever taken place within our territory: coastal batholiths. During this outcrop process and in the beginning of the Lower Tertiary, processes related to volcanic activity in southern Peru began, and continued until certain stages in the Quaternary. The amount of ash produced must have been impressive, since it was cast several kilometers away and transported by the wind. It accumulated in the highest parts of these outcrops, which began to define the features of Cordillera Negra.
As a consequence of the increasingly strong compressive creasing, the sedimentary material in this location began to fragment, generating large faults. During the Upper Tertiary, the last type of igneous material known in our country began to appear along them. This high platonic mass (igneous granodiorite-type rock, abundant in quartz and pheldespate) forms the base of the current Cordillera Blanca. This is how the two main mountain ranges which identify the state and give it structure were formed.
Within the large mountain range area, the previously described geological materials have been so meteorized and eroded that we can clearly find two sub-branches there: Callejon de Huaylas and The Vertientes.
Callejon de Huaylas is found enclosed by the Cordillera Blanca and Cordillera Negra axes, and between them, the well-know Santa River valley.