For all its geographical, cultural and political uniqueness, the definition of the Caucasus as a region is problematic. Geographers, geologists, political scientists, anthropologists and historians—all have disagreements between themselves and each other about such issues as what constitutes its borders, and what are the features of both its homogeneity and heterogeneity. Often, the use by representatives of one discipline of the conclusions and terminology from other disciplines in order to substantiate their positions complicates the problem even further. In any case, in general geographical terms the Caucasus is the territory between the Black, Azov and Caspian Seas, extending from the Kuma-Manych depression in the north to Georgia's and Armenia's borders with Turkey, and Azerbaijan's borders with Iran in the south. In physical-geological terms the Caucasus is predominantly a mountainous region which is shaped by the trajectories of the two mountain ranges, namely the Greater and Lesser Caucasus. The trajectory of the Greater Caucasus represents a diagonal stretching from the north-west to the southeast, while the trajectory of the Lesser Caucasus forms an ellipsoidal bow. At the Suram Passage the Lesser and Greater Caucasus practically merge. The Caucasus mountain range is divided lengthwise into the western Caucasus which stretches to Elbrus; the central Caucasus, which is between the Elbrus and Kazbek mountains; and the eastern Caucasus, which is to the east of the Kazbek.