Most of the southern region of Arizona lies inside the Basin and Range Geologic Province. Most of the province of Arizona spreads from the southeast of Oregon in the southern region through Nevada in this area. The range topography and basin gives the appearance as if the earth is pulling apart. In order to compensate for this stretching, breaking up of the rocks along the faults takes place. Insome places the blocks rise while in other nearing areas they drop. The blocks which rise form the ranges of fault block while those which drop form the valleys of the basins. It is for the same reason the term “basin and range” is used.
The climax of the Basin and Range topography of southern Arizona is in the region of Sky Islands which is located in southeastern corner of the state. In this region there are several mountain ranges which rise more than 6000 feet above the surrounding basin. The mountain ranges of Mt. Graham located in Pinaleno Mountains are nearly 8000 feet. The geology of the region of Sky Islands is very complex and cannot be easily categorized. It is because this region comprises of great variety of rocks and geologic features.
Metamorphic, sedimentary and igneous rocks are found in various areas of the island. The mountain ranges of Pinaleno, Santa Catalina and Rincon are considered to the hub of complex metamorphic rocks by the Geologists.These Mountains comprise of cores of metamorphic and igneous rocks some of which are highly deformed. The inside study of these mountains revealed the faulty uplifting and erosion of the overlying rocks which is exposing their core.
The region of Sky Islands in southeastern Arizona is most biologically diverse in the North America. It is the place where both the tropical and the temperate zones meet and two major deserts of the region also meet here. It is for the same reason that the number of species of mammals, reptiles, birds, ants and bees are found here are more as compared to any place in the country.
The richness of this mountainous island in ecology and the inhabitants living here is equal to the ecology found throughout Cochise country. Thus, the island is diversely rich in both flora and fauna which has to be protected from the natural hazards.