Divisions and Structure of Caucasus
Caucasus, one of the world's great mountain systems, is located in Armenia, Azerbaijan, the Republic of Georgia, and the Russian Federation. It occupies the isthmus between the Black Sea in the west and the Caspian Sea in the east. The Caucasus is considered by some geographers to be a natural boundary between Europe and Asia. The highest peak is the Elbrus, in the central part of the system, with an elevation of 18,481 feet (5,633 meters).
Divisions and Structure
Covering a territory of 170,000 square miles (440,000 sq km), including its piedmont, the Caucasus is a region of great natural diversity. The area can be considered as two mountain systems: the Greater and the Lesser Caucasus.
The main axis of the mountain system, the Greater Caucasus, extends about 700 miles (1,100 km) northwest-southeast from the Taman Peninsula, between the Black Sea and the Sea of Azov, to the Apsheron Peninsula on the Caspian Sea. The northern piedmont is an extensive region of lowlands and plateaus extending from the Greater Caucasus north to the Kuma-Manych river depression. This depression also runs northwest-southeast, parallel to the main mountain axis, between the lower reaches of the Don River and the Caspian Sea. The western part of the northern piedmont consists of the alluvial plains of the Kuban River and lesser streams draining into the Sea of Azov.
The central part of the piedmont is occupied by the Stavropol upland, a limestone and sandstone plateau rising to 2,730 feet (830 meters). To the southeast of the plateau, in the Beshtau region, is a cluster of laccoliths (dome-shaped hills) rising to 4,590 feet (1,400 meters). Some of the Russian Federation's best-known mineral springs (Pyatigorsk, Yessentuki, and Kislovodsk) are in these hills. The eastern part of the piedmont consists of a semiarid plain between the Terek and Kuma rivers and, farther south, the parallel Terek and Sundzha hill ranges, rising to 3,038 feet (926 meters). The anticlinal structure of these ranges is associated with the oil deposits of the Grozny area.
The Caucasus mountain system resulted from the Alpine mountain-making movement that took place in Europe in the Tertiary period. The northern slopes of the Greater Caucasus, in contrast to the steeper southern slopes, rise gently from the piedmont through a series of sloping plains and foothills to the main mountain ranges. The central ranges present a core of Precambrian and Paleozoic crystalline rocks amid Jurassic schists. The highest peaks are situated in the so-called watershed range and in the parallel lateral range, just to the north. In addition to the Elbrus, at the western end of the cluster of high peaks, are the Ushba (15,403 feet, or 4,695 meters); the Dykh-Tau (17,070 feet, or 5,200 meters); the Shkhara (16,594 feet, or 5,058 meters); and, on the east, the Kazbek (16,558 feet, or 5,047 meters).
The crustal upheaval that gave rise to the Caucasus was accompanied by volcanic activity. Both the Elbrus and the Kazbek are thought to be dead volcanoes. Mud volcanoes are still active at the Taman and the Apsheron ends of the Greater Caucasus ranges. Limestone plateaus and foothills frequently display karst forms.
South of the central ranges is a longitudinal depression made up of a series of river valleys that separate the Greater Caucasus from a mountain region sometimes called the Lesser Caucasus. The longitudinal depression begins in the northwest on the Black Sea in the Colchis swamps. The swamps are associated with the Greek legend of the Golden Fleece. Across the Surami Pass (3,113 feet, or 949 meters), the depression continues southeast along the valley of the Kura River, which opens onto the broad Kura-Aras plain on the Caspian Sea.
Unlike the Greater Caucasus, the Lesser Caucasus does not have a well-defined northwest-southeast alignment. It consists of a system of short fold mountains and the Armenian volcanic uplands that link with the neighboring mountainous regions of Turkey and Iran. The highest point within the Armenian part of the Lesser Caucasus is Mt. Aragats, an extinct volcano rising to 13,420 feet (4,090 meters). Mt. Ararat, a similar cone that is 16,916 feet (5,156 meters) high, is nearby, across the border in Turkey. A prominent feature in the Armenian uplands is Lake Sevan, the largest lake of the Caucasus region.