Sikhote-Alin

a mountain system in the southeastern USSR, between the Sea of Japan and the valleys of the Ussuri and lower Amur rivers, in Khabarovsk and Primor’e krais, RSFSR. The system extends 1,200 km along the Sea of Japan, with a width of 200–250 km; the average elevation is 800–1,000 m, with a maximum of 2,077 m (Mount Tordoki-Iani). The system consists of a series of ranges, massifs, and plateaus separated by the deep valleys of numerous rivers.

Most of the system is composed of Triassic, Jurassic, and Cretaceous argillaceous schists and sandstones. The Sikhote-Alin’ Anticlinorium extends along the axis, and its nucleus contains outcrops of Paleozoic, primarily Permian, deposits cut by numerous intrusions. This anticlinorium is separated from the Vostochnyi Synclinorium by a deep fault—the Central Si-khote-Alin’ Joint; there are basic and ultrabasic intrusions along the joint. The synclinorium is composed of Jurassic and Cretaceous deposits, overlain in the maritime section by Meso-cenozoic andesites and basalts. Deposits of coal and lignite are found in the tectonic depressions, for example, the Uglegor-skaia Depression. Different kinds of mineralization (gold and complex ores are present) are associated with the intrusions.

The northern section of the Sikhote-Alin’ is a high plateau, which falls steeply to the sea and is composed primarily of basalts; individual small basalt plateaus are also found in the southern section. The central section consists of the highest ranges to be found in the northeastern trend, composed of granites, less often of volcanogenic and metamorphic rocks. In the west, narrow tectonic depressions separate the front ranges (900–1,300 m in elevation), including the Sinii, Vostochnyi Si-nii, and Kholodnyi ranges.

The shoreline of the region along the Tatar Strait and the Sea of Japan (except for the banks of Petr Velikii Bay) is weakly indented, but it is complicated by ingression bays along the river valleys, including Sovetskaia Gavan’ and Vladimir and Ol’ga bays.

The area has a temperate monsoonal climate. The winters are very severe, with little snow. The average January temperature in the west ranges from – 22° to — 26°C, and in the littoral section of the east from — 10° to – 12°C. The summers are warm; in the south they are hot and rainy. The average July temperature on the western slopes ranges up to 21 °C, and on the eastern slopes up to 19°C. Annual precipitation ranges up to 1,000 mm in the central section; in the west it is 600–800 mm.

The rivers of the Amur River basin—the Ussuri, Bol’shaia Ussurka, Bikin, and Khor rivers—rise on the western slopes of the Sikhote-Alin’; the shorter, more typically mountain rivers, including the Samarga, Kopii, and Tumnin rivers, rise on the eastern slopes. The rivers are characterized by extremely low water in winter and heavy flooding in summer.

The landforms of the Sikhote-Alin’ vary considerably from north to south because of the system’s extensive length. The differences are very pronounced between the landforms of the eastern littoral section and those of the western slopes and foothills. In winter the warming influence of the Sea of Japan is felt. In the southern and central sections the slopes are covered with coniferous and broadleaf forests of cedar, Khingan fir (Abies nephrolepis), elm, maple, linden, and ash up to an elevation of 500 m. Phellodendron and thickets of wild grape and Schizandra are found on the valley floors. The steep slopes have thickets of oak and hazel growing on brown forest soils. Coniferous forests of Yeddo spruce and Khingan fir predominate in the north. The upper topographical zone consists of mountain tundra, with boggy, mildly peaty gley soils with detritus.

The forests are inhabited by Eurasian brown bear, American black bear, wild boar, Manchurian red deer, goral, tiger (in the Ussuri River valley), and a large number of birds. Shrenk’s snake and snakes of the genus Ancistrodon are typical of the indigenous reptiles. To the north the fauna is sparser and consists primarily of game animals. The Sikhote-Alin’ Preserve is located in the system.