The Apuseni Mountains do not present an uninterrupted chain of mountains, but possess many low and easy
passes towards the
Crișana and the
Pannonian Plain. Going from south to north the principal groups are: the
Munții Metaliferi ("Ore Mountains") with the
basaltic masses of the
Detunata () near
Abrud; the
Bihor Mountains, with numerous
caverns, with the highest peak the
Bihorul (); to the east of this group are the
Muntele Mare (highest peak ), to the southwest of
Cluj-Napoca; the northernmost chain is the
Seș and Meseș Mountains. The
paleogeographic evolution of this mountainous area is closely linked to the evolution of the Western Carpathians and, in general, to the evolution of the entire Carpathian chain. The crystalline schists began to separate as early as the
Precambrian period, becoming much more clearly defined in the
Silurian period as a result of the
Caledonian orogeny and, especially, in the
Carboniferous period as a result of the
Hercynian movements that affected the entire Carpathian chain and the mountains of Central Europe as far as Northern Dobrogea. From the Carboniferous period to the end of the
Mesozoic era, the Carpathians were subjected to successive orogenic movements, volcanic and metamorphic processes with implications for natural deposits. The uplift of this area, as well as of the Carpathians, occurred in the Cretaceous period (Mesozoic) as a result of Alpine orogenesis, accompanied by subsidence movements, forming a series of depressions (Gurahonț, Brad), which functioned as lake areas where Carpathian rivers deposited sediments. After the Cretaceous period, the Apuseni Mountains underwent modeling processes, forming erosion platforms with lower altitudes than those in the
Southern Carpathians (Borăscu - 2000 m; Râu-Șes- 1200 m - 1600 m; Gornovița or Predealului- 1000 m), due to the less spectacular elevation of the Western Carpathians compared to the Southern Carpathians. During the Paleogene period, numerous marine transgressions and regressions took place in the depression basins, as well as the consolidation of the Carpathian
orogen. Volcanic activity in the second half of the
Neogene period formed the Metaliferi Mountains. The Apuseni Mountains reached their final elevation at the beginning of the Quaternary period. During this period, the waters receded from the depressions, forming the hydrographic network. Also during the Quaternary period, plant species began to differentiate according to altitude and the first humans appeared. They played an active role in shaping the geographical environment. == Climate ==