Asia

I

Introduction

Asia, the largest of the Earth's seven continents. With outlying islands, it covers an estimated 44,936,000 sq km (17,350,000 sq mi), or about one-third of the world's total land area. Its peoples account for at least three-fifths of the world's population; in the early 1990s Asia had more than 3.4 billion inhabitants.

Lying almost entirely in the northern hemisphere, Asia is bounded on the north by the Arctic Ocean, on the east by the Bering Strait and the Pacific Ocean, on the south by the Indian Ocean, and on the south-west by the Red and Mediterranean seas. On the west, the conventional boundary between Europe and Asia is drawn at the Ural Mountains, continuing south along the Ural River to the Caspian Sea, then west along the Caucasus Mountains to the Black Sea. Many geographers prefer to regard the land mass formed by Europe and Asia as a single continent—Eurasia.

The continental mainland stretches from the southern end of the Malay Peninsula to Cape Chelyuskin in Siberia. Its westernmost point is Cape Baba in north-western Turkey, and its easternmost point is Cape Dezhnev in north-eastern Siberia. The continent's greatest width from east to west is about 8,500 km (5,300 mi). In Asia are found both the lowest and highest points on the Earth's surface, namely, the shore of the Dead Sea (395 m/1,296 ft below sea level) and Mount Everest (8,850 m/29,035 ft above sea level).

To the south-east of the mainland is an array of archipelagos and islands, extending east to Oceania. They include the islands of Indonesia and the Philippines, including Sumatra, Java, Celebes, Borneo, and New Guinea. To the north lie Taiwan, the islands of Japan, and Sakhalin. Sri Lanka and smaller island groups such as the Maldives, and the Andaman and Nicobar islands lie in the Indian Ocean.

Because of its vast size and diverse character, Asia is divided for convenience into five major regions. These are as follows: Asia of the former Soviet Union (see Central Asian USSR), including Siberia, western Central Asia, and the Caucasus; East Asia, including China, Tibet, Mongolia, North and South Korea, and Japan; South East Asia, including Myanmar, Thailand, Cambodia, Laos, Vietnam, Malaysia, Singapore, the Republic of Indonesia, Brunei, and the Philippines; South Asia, including India, Bangladesh, Pakistan, Sri Lanka, Nepal, and Bhutan; and south-west Asia, including Afghanistan and the countries of the region commonly called the Middle East—Iran, Iraq, Turkey, Syria, Lebanon, Israel, Jordan, Kuwait, and Saudi Arabia, and the other states of the Arabian Peninsula. The continent may also be divided into two cultural regions: that which is “Asian” in culture (East Asia, South East Asia, and South Asia) and that which is not (Asia of the former Soviet Union, and South-west Asia).

II

The Natural Environment

Unlike the other continents, the interior of Asia consists of mountains, plateaux, and intervening structural basins. The highland core, located somewhat south of the geometric centre of the continent, is composed of the Himalaya and associated ranges, and the Tibetan Plateau. Around this central core are four major plateau regions (Siberia, eastern China, southern India, and the Arabian Peninsula) and several great structural basins and river plains (see Arabia).

A

Geological History

According to the theory of plate tectonics, the Earth's surface crust consists of a number of huge continental plates and a number of equally large oceanic plates, most of which are in continuous motion. Of these, the largest is the Eurasian continental plate. Portions of this plate are composed of some of the most ancient rocks found on Earth, dating from the Precambrian (about 4.65 billion to 570 million years ago), which are found today in the Angara Shield of eastern Siberia, in much of the Arabian Peninsula, and in India south of the Indo-Gangetic plain.

During most of the Palaeozoic and Mesozoic eras (570 to 65 million years ago), a huge sea, known as Tethys, covered much of the interior of Eurasia and laid down thick deposits, which in time were converted into sedimentary and metamorphosed formations. Approximately 30 million years ago, the subcontinent of India, which had broken away from south-eastern Africa and drifted north-east, began to thrust under the Eurasian continental plate, creating an enormous “deep” that later filled with sediments to form the Indo-Gangetic plain. At the same time it generated tremendous pressure, causing the southern margin of the Eurasian continental plate to crumple into a series of great mountain ranges, of which the Himalaya is the most conspicuous.

Plate-tectonics theory also helps to explain the formation of the arcuate (arc-shaped) ranges, peninsulas, and archipelagos of Asia—as well as the volcanic activity and tectonic instability of East and south-eastern Asia. In East Asia the primary force results from the underthrusting of the westward-moving Pacific Ocean plate against the Eurasian continental plate. Japan, Taiwan, the Kuril Islands, the Ryukyu Islands, and the Philippines are products of these forces. In south-eastern Asia, the situation is complicated by the relative movements of the Pacific and Indian Ocean plates, and that movement helps explain the northern-southern trending highlands of mainland south-eastern Asia and the volcanic activity that characterizes most of the Indonesian archipelago.

B

Physiographic Regions

Asia's physiographic system focuses on the Pamir Knot, a towering plateau region known as the Roof of the World, located where the borders of India, China, Tajikistan, Pakistan, and Afghanistan converge; several peaks here exceed 6,100 m (20,000 ft). Spiralling out from the Pamirs to the west is the Hindu Kush and its extension across northern Iran, the Elburz Mountains. Beyond the latter are the Caucasus ranges, between the Caspian and the Black seas, and the Kuzey Anadolu Dağları (Northern Anatolian Mountains) along the Black Sea in Turkey. To the south-east are the Great Himalaya, paralleled by lesser but still great ranges to the north and south. Together these ranges form an imposing east-west arc, some 2,500 km (1,550 mi) in length, containing numerous peaks of heights well above 6,100 m (20,000 ft), including Mount Everest. Extending east and north-east of the Pamirs is the high Karakorum Range, which leads into the Kunlun Mountains, and a branch, the Altun Shan. This line of mountains continues east at lower elevations as the Nan Ling (Nan Shan), becoming the Qin Ling (Ch'in Ling) range of north China, which marks a major climatic divide between northern and southern China. Between the Himalayan system and the Karakorum-Kunlun ranges lies the Tibetan Plateau, which has average elevations of about 3,660 to 4,570 m (12,000 to 15,000 ft). Extending north-east from the Pamirs are the great Tian Mountains, also with peaks rising above 6,100 m (20,000 ft) but diminishing in height as it approaches the borders of Outer Mongolia. To the north-east, the Altai Mountains extend into the Republic of Mongolia. Beyond them are the Sayan, Yablonovyy, and Stanovoy ranges of eastern Siberia; the last two, however, are not part of the highland core.

Several major structural basins are found to the north of the central mountain core. Farthest north, located between the Tian Mountains and the Altai Mountains, lies the Junggar Pendi (or Dzungarian Basin) of China. To the south of this, between the Tian Mountains and the Karakorum and Kunlun, lies the vast Tarim Basin in which is found one of the largest middle-latitude deserts, the Takla Makan. Finally, embraced by the Kunlun and Altun Shan is the deep Qaidam (Tsaidam) Basin.

Soil types also vary enormously. Siberia is overlain by acidic forest soils characteristic of the tundra and taiga; permafrost is common, and drainage is usually poor. These soils merge into dark grassland, steppe, and desert soils across a vast band that extends from northern China to the Black Sea, and into south-west Asia. The dark steppe soils, among the most fertile in Asia, are found in north central China and south-western Siberia. In eastern and southern Asia, the most valuable soils for agriculture are the alluvial soils deposited in the lower valleys of the great rivers, especially the Indus and Ganges. These soils make up most of Asia's intensively used agricultural land. In low-latitude regions are found mature tropical soils, which are of generally low fertility. These mature soils grade, to the north, into soils with a higher humus content that are somewhat more fertile.