extensional structure of the back-arc Pannonian Basin. The last volcanic activity occurred at Ciomadul about 30,000 years ago. The mountains started to gain their current shape from the latest Miocene onward. The slopes of the Carphartian contain at some locations solifluction deposits. Iron, gold and silver were found in great quantities in the Western Carpathians. After the Roman emperor Trajan's conquest of Dacia, he brought back to Rome over 165 tons of gold and 330 tons of silver. Ecology The ecology of the Carpathians varies with altitude, ranging from lowland forests to alpine meadows. Foothill forests are primarily of broadleaf deciduous trees, including oak, hornbeam, and linden. European beech is characteristic of the montane forest zone. Higher-elevation subalpine forests are characterized by Norway spruce (Picea abies). Krummholz and alpine meadows occur above the treeline. Wildlife in the Carpathians includes brown bear (Ursus arctos), wolf (Canis lupus), Eurasian lynx (Lynx lynx), European wildcat (Felis silvestris), Tatra chamois (Rupicapra rupicapra tatrica), European bison (Bison bonasus), and golden eagle (Aquila chrysaetos). Divisions of the Carpathians The largest range is the Tatras in Slovakia and Poland. A major part of the western and northeastern Outer Eastern Carpathians in Poland, Ukraine, and Slovakia is traditionally called the Eastern Beskids. The geological border between the Western and Eastern Carpathians runs approximately along the line (south to north) between the towns of Michalovce, Bardejov, Nowy Sącz and Tarnów. In older systems the border runs more in the east, along the line (north to south) along the rivers San and Osława (Poland), the town of Snina (Slovakia) and river Tur'ia (Ukraine). Biologists shift the border even further to the east. The border between the eastern and southern Carpathians is formed by the Predeal Pass, south of Brașov and the Prahova Valley. In geopolitical terms, Carpathian Mountains are often grouped and labeled according to national or regional borders, but such division has turned out to be relative, since it was, and still is dependent on frequent historical, political and administrative changes of national or regional borders. According to modern geopolitical division, Carpathians can be grouped as: Serbian, Romanian, Ukrainian, Polish, Slovakian, Czech and Austrian. Within each nation, specific classifications of the Carpathians have been developing, often reflecting local traditions, and thus creating terminological diversity, that produces various challenges in the fields of comparative classification and international systematization. The section of the Carpathians within the borders of Romania is commonly