TRANSYLVANIAN MOUNTAINS. This is an inclusive name for the mountainous region which abuts against the south eastern end of the Carpathian range south of the Jablonica pass. In the east they form a continuation of this range but across the rest of the tract the mountains are arranged in scattered groups, in broken connection with one another, the land between forming the Transylvanian basin. Formed in Tertiary times, they are part of the eastern arm of the Alpine fold-system which passes in a wide arc through the Carpathians, turns abruptly westward at Pietrite Fetei into the Transylvanian Alps, again turns almost as abruptly southward at Reteizat through the Szretinye mountains and across the Danube at Iron Gates to turn eastward into the Balkan mountains.
The eastern mountains, the Moldavian Carpathians, are divided parallel to their trend by the upper valleys of the Muresul and the Oltu, separating the outer (eastern) ranges which consist of highly folded Flysch (Cretaceous, Eocene and Oligocene) lying upon an (inner) crystalline massif of plutonic rocks, gneisses and schists with Carboniferous, Permian and Triassic rocks. The western of these two ranges, the Harghitei complex of Tertiary volcanic rocks (andesites, andesitic tuffs, etc.), forms the eastern boundary of the Transylvanian basin and through it break the rivers Oltu and Muresul. The Transylvanian basin seldom rises above 1,600 ft. in altitude and is covered by Miocene deposits. The southern boundary is formed by the Transylvanian Alps which consist almost entirely of a crystalline massif of gneiss, schist and granite with a very narrow and broken fringe of Flysch on its southern (outer) edge. This forms the most continuous range in the region and contains the highest peak (Negoiul, 8,32o ft.).
The mountains of the south-west and west, which do not form a continuous range but are isolated by wide valleys, have a more complex structure than the Transylvanian Alps, for around crystal line massifs, which beneath the covering rocks are probably con tinuous with that of the latter chain, are Triassic, Rhaetic, Juras sic and Cretaceous beds and to a less extent Carboniferous and Permian. Here are three main masses, the Szretinye moun
tains, the Transylvanian Ore-mountains and the Bihor mountains. Here, as well as in the Nagybanya district in the north, are Ter tiary volcanic rocks of andesitic composition associated with which are important gold and silver lodes. Some of the mines (e.g., Rosia-Montana [Verespatak]) have been worked since Roman times and the district still contains the most valuable gold deposits in Europe. These volcanic rocks are probably associated with north to south faulting which occurs in this region. The northern boundary is less well defined and comprises a low range in the west with the higher range, the Rodna Hegyseg, farther east.
There are evidences of past glaciation amongst the highest peaks which nowhere reach 9,00o ft., so that none of them are permanently snow-capped. Precipitation in the Transylvanian basin averages 24 in. and great extremes of temperature are experienced. This basin cannot be called a plateau for it does not possess extensive plains but is cut up by a network of valleys formed by mountain streams that drain into it from the peripheral ranges. The three main streams are the Great Samesul, which, draining the northern half of the basin, flows north-west to join the Theiss; the Muresul, which crossing from east to west enters the Hungarian plain along the southern scarp of the Transyl vanian Ore-mountains and also joins the Theiss ; and the Alt which breaks through the Transylvanian Alps by the Turnul-Ros pass to join the Danube. Other passes in this range, all of which are followed by railways, are the Bodza, Tomos, Vulcan and Tere gova, whilst those in the Moldavian Alps are the Prislopul, Rodna, Borgo, Tolgyes, Bekas, Gyimes and Oitoz passes, several of which are used by railways. (See RUMANIA.)