Caspian Sea the east often changed course to empty into the Caspian through a now-desiccated riverbed called the Uzboy River, as did the Syr Darya farther north. The Caspian also has several small islands; they are primarily located in the north and have a collective land area of roughly . Adjacent to the North Caspian is the Caspian Depression, a low-lying region below sea level. The Central Asian steppes stretch across the northeast coast, while the Caucasus mountains hug the western shore. The biomes to both the north and east are characterized by cold, continental deserts. Conversely, the climate to the southwest
Black Sea–Caspian Steppe of Islam led to the Arab-Khazar Wars (642-737) and in 737 Arabs briefly reached the lower Volga. The Pechenegs (c. 800 – 1100) moved from north of the Caspian into this area perhaps around 850. They pushed or were pushed westward and were eventually broken up in wars with the Byzantines. Behind them came the Cumans – Kipchaks (?-1241), two peoples that are hard to distinguish. Like the Pechenegs they continued west and fought the Rus’ and Byzantines. The appearance of the Kipchaks may mark the final establishment of Turkic languages north of the Black Sea. After the Mongols conquered