The Caucasian Mountain system, which is 1100 km. in length, lies like a huge wall of rock between Europe and Asia. Most geographers consider the Caucasus as part of [36]the latter continent, which is correct in so far as these mountains show many characteristics of Asiatic mountain ranges. First of all they are hard to cross, much harder than the highest mountains of Europe, the Alps. Along a stretch of 700 km., the ridge of the Caucasus descends only twice to a level of 3000 m. On the other hand, the Caucasus is not wide—on the average only 150 km.—and at the point where the Grusinian army road crosses the range, barely 60 km. Then, the Caucasus, like many mountain ranges of Asia, stretches in a straight line from the peninsula of Taman to the peninsula of Apsheron, famous for its abundance of petroleum. The Caucasus is a plication-formed mountain range composed of folded crystalline and sedimentary rock of varying ages. Along huge ravines, the entire southern part of the range has sunk down, so that the highest crystalline central zone of the range declines directly and very steeply toward the south. The highest Caucasus peaks are old extinct volcanoes, set over the basic mountains; the Elbrus (5630 m.), at the source of the Kuban and the Kasbek (5040 m.), at the source of the Terek. Proof that the subterranean powers are still active are the numerous tectonic earthquakes of Transcaucasia. The main chain of the Caucasus possesses, besides the volcano peaks, many rocky granite peaks 4000–5000 m. in height, and, besides these, hundreds of lower peaks, all of which find their counterparts in the Alps. The present glaciation of the Caucasus is very considerable, while that of the glacial period was also very extensive and determined the present mountain forms of the Caucasus. Only the most beautiful ornament of the one-time glacial landscape is lacking in the Caucasus—the lakes, which are so abundant in the Alps. All the larger Caucasus rivers rise as milky glacial brooks in the main range. Then, by way of deep cross-valleys, [37]they break thru the lower ranges, which face the main ridge in several rows, and are composed of sedimentary rock formations of jurassic, cretaceous, and old-tertiary age. Their crests and peaks become constantly lower and more rounded toward the north. Beautiful mountain pastures and thick virgin forests, full of animals that may be hunted, cover the mountains.