THE URAL AND CAUCASUS MOUNTAINS.

The Ural Mountains are a mountain range that runs from North to South through Western Russia, from the coast of the Arctic Ocean to the Ural River originating in the Southern Urals and flowing through Russia and  North Western Kazakh-Stan and ending at the Caspian Sea. The Ural River (2,428km / 1,509mi) is the 3rd longest River in Europe after the Volga and the Danube and considered together with the mountain range, the Northern boundary between the continents of Europe and Asia. Its highest peak is Mount Narod-Naya, approximately 1,895m / 6,217 ft in elevation.
The Caucasus Mountains are a mountain system in the combined continental land-mass of Europe and Asia. They include the Greater Caucasus which extends from the Caucasian Natural Reserve on the North Eastern shore of the Black Sea to Mount Elbrus, then aligned West- North West to East-South East and reaching nearly to Baku on the Caspian Sea; and the Lesser Caucasus, which runs parallel to the greater range, at a distance averaging about 100 km / 62mi South. the highest peak in the Caucasus range is Mount El-Brus in the Greater Caucasus, which rises to a height of 5,642 m / 18,510 ft above the sea level.
The Caucasus Mountains formed largely as the result of a tectonic plate collision between the Arabian plate moving Northwards with respect to the Eurasian plate. As the Tethys Sea was closed (India, Pakistan, Indonesia, and the Indian Ocean now cover the area) and the Arabian plate collided with the Iranian plate and was pushed against it and with the clockwise movement of the Eurasian plate towards the Iranian plate and their final collision, the Iranian plate was pressed against the Eurasian plate. As this happened, the entire rocks that had been deposited in this basin from the Jurassic to the Miocene eras were folded to form the Greater Caucasus mountains. The entire region is regularly subjected to strong earthquakes from this activity. While the Greater Caucasus have a mainly folded sedimentary structure, the Lesser Caucasus are largely of volcanic origin.
The concepts of Europe and Asia as distinct continents date back to antiquity and their borders are geological arbitrary, with the Ural and Caucasus ranges being the main delimiters between the two.
Physiographically, Eurasia is a single continent and is connected to Africa at the Suez Canal, and sometimes is combined with Africa as the super continent Afro-Eurasia.
Eurasia has been the host of many civilizations, including those based in Mesopotamia, the Indus Valley and China. In the mid-1st millennium BC a continuous belt of civilizations stretched through the Eurasian subtropical zone from the Atlantic to the Pacific. This belt became the mainstream of world history for over two millennia.