Altai Mountains

Physiography

The Altai proper lie in the Altay republic of Asian Russia, in extreme eastern Kazakhstan, and in the northern tip of the Xinjiang region of China. A belt of northern foothills separates the Altai from the West Siberian Plain, while in the northeast the Altai border the Western (Zapadny) Sayan Mountains. From Nayramadlïn (Hüyten) Peak, with an elevation of 14,350 feet (4,374 metres), near the point where the borders of Russia, Mongolia, and China meet, the Mongolian Altai (Mongol Altayn Nuruu) extend to the southeast and then to the east. The western Mongolian Altai form part of the border between Mongolia and China. The Gobi Altai (Govĭ Altayn Nuruu) begin some 300 miles (500 km) southwest of Ulaanbaatar, the Mongolian capital, and dominate the country’s southern portions, towering over the Gobi expanses.

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Geology

The Altai were formed during the great orogenic (mountain-building) upthrusts occurring between 500 and 300 million years ago and were worn down, over geologic time, into a peneplain (a gently undulating plateau with generally accordant summit heights). Beginning in the Quaternary Period (within the past 2.6 million years), new upheavals thrust up magnificent peaks of considerable size. Earthquakes are still common in the region along a fault zone in the Earth’s crust; among the most recent quakes is the one that occurred near Lake Zaysan in 1990. Quaternary glaciation scoured the mountains, carving them into rugged shapes, and changed valleys from a V- to a U-shaped cross section; river erosion has also been intensive and has left its marks on the landscape.

As a result of these differential geologic forces, the highest ridges in the contemporary Altai—notably the Katun, North (Severo) Chu, and the South (Yuzhno) Chu—tower more than 13,000 feet (4,000 metres) in elevation, running latitudinally in the central and eastern portions of the sector of the system within the Altay republic. The Tabyn-Bogdo-Ola (Mongolian: Tavan Bogd Uul), the Mönh Hayrhan Uul, and other western ridges of the Mongolian Altai are somewhat lower. The highest peaks are much steeper and rockier than their Alpine equivalents, but the ranges and massifs of the middle Altai, to the north and west, have ridges of about 8,200 feet (2,500 metres), whose softer outlines betray their origins as ancient, smoothed surfaces. Valleys are nevertheless jagged and gorgelike. The ridges are separated by structural hollows (notably the Chu, Kuray, Uymon, and Kansk), which are filled with unconsolidated deposits forming steppe landscapes. Elevations range from 1,600 to 6,600 feet (500 to 2,000 metres) above sea level.

The extreme dislocations suffered by the Altai over the course of geologic time have occasioned a variety of rock types, many of them altered by magmatic and volcanic activity. There are large accumulations of geologically young, unconsolidated sediments in numerous intermontane depressions. The tectonic structures bear commercially exploitable deposits of iron, of such nonferrous and rare metals as mercury, gold, manganese, and tungsten, and of marble.

Climate

The regional climate is severely continental: because of the influence of the great Asiatic anticyclone, or high-pressure area, the winter is long and bitterly cold. January temperatures range from 7 °F (−14 °C) in the foothills to −26 °F (−32 °C) in the sheltered hollows of the east, while in the Chu steppes temperatures can plunge to a bitter −76 °F (−60 °C). There are occasional tracts of the permafrost (ground that has a temperature below freezing for two or more years) that coats great stretches of northern Siberia. July temperatures are warm and even hot—daytime highs often reach 75 °F (24 °C), sometimes up to 104 °F (40 °C) on the lower slopes—but summers are short and cool in most higher elevations. In the west, particularly at elevations between 5,000 and 6,500 feet (1,500 and 2,000 metres), precipitation is high: 20 to 40 inches (about 500 to 1,000 mm) and as much as 80 inches (2,000 mm) may fall throughout the year. The total decreases to one-third that amount farther east, and some areas have no snow at all. Glaciers coat the flanks of the highest peaks; some 1,500 in number, they cover an area of roughly 250 square miles (650 square km).

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Drainage

The Altai proper and the Mongolian Altai are crisscrossed by a network of turbulent, rapid rivers fed mainly by melted snow and summer rains, which occasion spring and summer floods. The Katun, Bukhtarma, and Biya—all tributaries of the Ob River—are among the biggest. Rivers of the Gobi Altai are shorter, shallower, and often frozen in winter and dry in summer. There are more than 3,500 lakes, most of structural or glacial origin. Those of the Gobi Altai are often bitterly salty.

Plant life

Four fairly distinct vegetation zones can be discerned in the Altai: mountain subdesert, mountain steppe, mountain forest, and the alpine regions. The first, found on lower slopes and in hollows of the Mongolian and Gobi Altai, reflects the high summer temperatures and low rainfall: the sparse life includes xerophytic (drought-tolerant) and halophytic (salt-tolerant) plants. The mountain steppe zone rises to about 2,000 feet (600 metres) in the north and to 6,600 feet (2,000 metres) in the south and east. Meadows and mixed-grass steppes are characterized by sod grasses, forb species, and steppe shrubs. The mountain forest zone is most characteristic of the Altai proper; it covers about seven-tenths of the territory, mostly in the low and medium mountain regions. Forests reach up to elevations of 6,600 feet (2,000 metres) but climb to about 8,000 feet (2,400 metres) on the drier slopes of the central and eastern Altai. Most prevalent are coniferous species—larches, firs, and pines (including the Siberian stone pine)—but there are also large areas covered by secondary birch and aspen forests. A forest belt is practically nonexistent in the Mongolian and Gobi Altai, but isolated clumps of coniferous trees grow in river valleys. Alpine vegetation—subalpine shrubs giving way to meadows widely used for summer pasture and then to mosses and bare rock and ice—is found only on the highest ridges.

Animal life

Animal life follows vegetation patterns. Various rodents populate the mountainous semideserts and steppes, while birdlife includes eagles, hawks, and kestrels. Most species are of Mongolian origin—e.g., marmot, jerboa (a jumping rodent), and antelope. Siberian mammals (bears, lynx, musk deer, and squirrels) and birds (hazel grouse and woodpeckers) frequent the moist coniferous forests. Alpine animal life includes the mountain goat, snow leopard, and mountain ram.