Physical Geography The Caucasus is a largely mountainous region sandwiched between the Caspian and Black seas. Running from the west-northwest to the east-southeast are two parallel mountain chains: the Greater (or Northern) Caucasus and the Lesser (or Southern) Caucasus. Between the two chains are two lowlands, funnel-shaped and opening toward the Black and Caspian and connecting at their narrowest point where the Mtkvari River cuts through a small mountain chain that connects the Greater and Lesser Caucasus ranges at the modern-day city of Tbilisi. North of the Greater Caucasus the terrain quickly widens, flattens and dries, becoming the Eurasian steppe. South of the Southern Caucasus there is no similar transformation. The Lesser Caucasus -- as the name implies -- are not nearly as steep or stark as the Greater Caucasus, and they soon merge with the rugged highlands of the Anatolian Plateau in the west and the Zagros Mountains in the south. The eastern of the two lowlands directly abuts the northwestern edge of the Elburz chain.
The western portion of the Northern Caucasus are considerably higher than the eastern portion, and the vertical difference helps wring considerably more water out of air currents. Consequently, the western lowland has a humid subtropical climate that typically receives more than 10 times the amount of annual precipitation as the eastern lowland. While this makes the western lowland more fertile, it also generates sufficient river activity to cut myriad deep valleys into the southern flanks of the western portions of the Greater Caucasus range. As a result, the western half of the interior region is peppered with a multitude of minority groups tucked away in the myriad valley fastnesses, while the eastern plain's ethnic makeup is more unitary. Despite the western funnel's abutting the Black Sea, it is also more limited in its contact with its immediate neighbors than the eastern funnel. The coastal plains in both directions are extremely narrow -- less than 2 kilometers (slightly more than 1 mile) between coast and mountain in most locations -- and the southern approach does not truly widen until the Turkish Straits.