ASIA, the name of one of the great continents of the earth's surface, embracing the north-east portion of the great land mass constituting the Old World, of which Europe forms the north west and Africa the south-west region.
Much doubt attaches to the origin of the name. The early Greek geographers divided their known world into two portions only, Europe and Asia, in which last Libya (the Greek name for Africa) was included. Herodotus ranks Libya as one of the chief divisions of the world, separating it from Asia, but is unable to explain the origin of the name. It is probable that it has an Assyrian or Hebrew root and was used first of all with a specific or restricted local application, a more extended signification having eventually been given it, though it continued in use among the Greeks to denote the country around Ephesus.
Asia, the great land-mass of the Old World, stretches from well within the Arctic Circle to 13° N. of the Equator in south Arabia, 6° in Ceylon and within a degree and a half at the tip of the Malay peninsula.
On the west the continent reaches the shores of the Mediter ranean—Cape Baba in 26° E. being the outpost. The boundary passes thence in one direction through the east Mediterranean and down the Red sea to the south point of Arabia, and in the other direction through the Black sea to the Caucasus, the lower Volga and the Ural mountains to the Arctic ocean. Asia's eastern outpost is East cape at the entrance to Bering strait 190° east. The boundary from this point to the Malay peninsula follows the coast of the North Pacific and the China sea. Asia viewed as a whole (on the globe) forms a great isosceles spherical triangle, having its north-eastern apex at East cape in Bering strait ; its two equal sides, in length about a quadrant of the sphere, or 6,500m., extending on the west to the south point of Arabia, and on the east to the extremity of the Malay peninsula; and the base between these points occupying about 6o° of the great circle, or 4,500m., and being deeply indented by the Arabian sea and the Bay of Bengal on either side of the Indian peninsula. A great circle, drawn through East cape and the south point of Arabia, passes nearly along the coast line of the Arctic ocean, over the Ural mountains, through the western part of the Caspian and, with the exception of Asia Minor and the north-west half of Arabia, indicates, with fair accuracy, the north-west boundary of Asia. In like manner a great circle through East cape and the extremity of the Malay peninsula passes nearly over the coasts of Manchuria, China and Cochin-China.
The series of highlands from Lake Baikal south-westwards to the Hindu Kush and the Elburz have on their northern and western sides the great Euro-Asiatic lowland that reaches from the Carpathians to the Yenisei and, in the form of the Angara plateau of moderate height, beyond it to the Lena river and the Verkhoyansk mountains where it abuts upon the Pacific coastal region, widely characterized by land forms arranged in steps, the edges of which are raised. South-east of the highlands from Baikal to Hindu Kush, and west of the Pacific coast region are the basins of inland drainage of the high plateaux of east central Asia, for the most part more than 3,000f t. above sea level. To its south again is the mountain land of Tibet with even valley floors near or above the 12,000ft. level in many places. The above four regions constitute what zoological geographers all agree to call the Asiatic portion of the Palaearctic region. Asia south of the line from the Armenian mountain knot and the Elburz moun tains to the Himalaya we may divide into four chief regions. The first is south-west Asia with the Euphrates lowland between the Arabian block and the mountains; the next is the series of basins between mountain curves complicated by fragments of old blocks and forming the countries of Persia, Afghanistan and Baluchis tan ; the third is India with the old block of the Deccan separated from the Himalaya by the Indo-gangetic lowland ; in the fourth, the Indo-Malayan region, the great mountain f olds bend sud denly southward between the old block of the Deccan on the south-west and old blocks in south-east China, Cambodia and Borneo on the east. These f olds are continued as determinants of the land-forms of the East Indian archipelago.
The Euro-Asiatic lowland rarely rises beyond i,5ooft. over sea-level and huge expanses are below the 600ft. contour. The drainage, especially in the Ob basin, is thus slow and imperfect and when snows melt in the south, but ice holds fast farther north, there are wont to be widespread floods. The Arctic ocean receives drainage of a larger Asiatic area (4,367,000sq.m.) than the Pacific (Asiatic drainage area 3,641,000sq.m.) or the Indian ocean (Asiatic drainage area 2,873,000sq.m.) and by far the greater part of the drainage to the Arctic is via the Ob, Yenisei and Lena and lesser rivers, which serve the Euro-Asiatic lowland and rise on its eastern and south-eastern mountain borders. The Ob basin is one of the world's most extensive areas of pure lowland. The Yenisei, fed from Lake Baikal and the Sayan mountains, is also the collector of the drainage of the western edge of the Angara plateau. The Lena drains the east of that plateau, and the arc of highland (Verkhoyansk, etc.) which bounds our region on the east. The Lena's length is estimated at 3,000m., the Yenisei is 2,7oom. and the Ob 2,400m. South of the rather higher zone of Semipalatinsk (one area above the 3,000f t. con tour) the lowland is continued as the world's most remarkable internal drainage area, containing Lake Balkash and the Aral and Caspian seas, each and all now without outlet. To this part of the lowland the name of Turkistan is often applied. The general soil of the northern part of the Euro-Asiatic lowland is alluvial or glacial mud with some more stony areas on the Angara plateau, but in several parts at the foot of the mountains and elsewhere, and very notably south of the Oxus in Afghan Tur kistan, there are huge accumulations of loess (q.v.).
To the north of the northern steppe the soil remains so cold that pine forest is the natural vegetation (this is called the Taiga) with riverside meadows, so that men have migrated, probably under pressure, in this direction along the rivers, using them for fish, as food from flocks and herds diminished. On the tundra, north of the pine forest in Asia, man has found the reindeer and with it has penetrated westward to Lapland. The Ural mountains (maximum height 5 , 53 7 f t., average probably well below 3,000ft., passes in some cases i,400ft. above sea level) form an incomplete boundary towards Europe, but to the west of them the greater amount of summer rain permits a much larger extent of oak forest, which can be cleared for cultivation, than occurs on the Asiatic side. In the south part of the Urals are important mineral resources.
This country is on the whole fairly well watered and has a good deal of pasture, and some of its better valleys have been the homes of groups dependent largely upon the horse. It contrasts strik ingly with the great plateau-waste of Gobi, at a lower altitude but still almost everywhere more than 3,000f t. over sea level. Here are great undulating stretches with areas of grass here and there, and remains of ancient drainage sometimes indicated by salt swamps. Oases of relative fertility occur, but the rigours of winter make them very different from the intensively de veloped fertile spots of the warmer Sahara.
To the west, the Gobi plateau descends westward to the north ern steppe-lowland of Turkistan by the historic Dzungarian gate, bounded on the south by the Tien Shan range, a sharp-featured, ridged range of great length and height (Khan Tengri 23,600f t.) , contrasting very markedly with the older mountains north-east of the Dzungarian gate. Between the Tien Shan and the Altyn Tagh, the northernmost of the Tibetan mountain arcs, lies the Tarim basin with the Yarkand Darla and Tarim rivers draining into a northerly depression, and with the lake-swamp of Lob Nor occupying an easterly depression. Feeders of the Yarkand Darla come down from the pass between the Tien Shan and the Pamir, the pass which has the famed market town of Kashgar at the entry to the Tarim basin. This basin has been studied in much detail by Stein, who finds many indications of desiccation of what seems to have been an area of much importance. The eastern end of the great Gobi plateau is marked by the Khingan mountains, one of the steps from the high Asiatic interior down to the coasts and deeps of the Pacific ; and the north-east of the plateau is drained by the Amur which goes round the north end of the Khingan mountains. Huge amounts of loess near and beyond the eastern border of this region, in Kansu, and the Wei-ho and associated valleys, have played a great part in the development of Chinese civilization, and have furnished ways into China from the desert, to bar which was built the famous wall, so that in a sense the wall of China may be considered the boundary of our region.
In the north the mountain arcs form a complex transition zone between the Pacific coastlands and the Euro-Asiatic low lands. In the latitude of Japan a very interesting step-structure is noticeable. East of Japan are the deepest hollows of the ocean, west of Japan the sea has considerable, but by no means comparable, depth, then the edge of Korea and the Sikhota Alin rise sharply. Beyond them again are the shallow waters of the Yellow sea, the lowland of Manchuria and of the middle and lower Amur. Beyond this again is the step up to the high plateaux, marked by the Khingan mountains. South of this interesting zone of step-forms, the physiography is complicated by inter action of fold mountains and old blocks in China. The great river basins here are those of the Hwang-ho (2,400m.) and the Yangtse-kiang (3,000m. or more), cut deeply into the highlands and ending in a large alluvial area which is the great agricultural region of north China, and offers the most striking contrast to the deeply dissected plateau country of the old block of south China. Whereas the alluvium of north China has become thronged with cultivators using the soil most intensively, south China is relatively less thickly peopled, and retains remnants of pre-Chinese peoples. The social and economic contrasts based on physiographical differences, and on the varying ranges of influences of the immigrant cultures from the loess of the north-west, form the fundamental difficulty of the problem of political organization in modern China.
Formosa is essentially a continental island on the Tropic of Cancer with an axial ridge that reaches 12,939ft. near the centre. It has ancient elements and immigrant Chinese, and now also some Japanese in its population. In the Philippines and beyond we have the continuation of the festoon of mountain curves that girdles the Pacific, but in this section it is complicated by its inter-relations with the fold mountains of Indo-Malaya.
South of the Armenian mountain knot is the ancient block, of Arabia, with the "fertile crescent" of the Mesopotamian low land and Syria separating the two. Relief is complicated by the fact of the great rift system (see AFRICA) which has contributed to give west Arabia a high edge with much lava. Palestine is the country between the Mediterranean and the north part of the rift system, i.e., the Jordan valley and the Dead sea. Mesopo tamia and the shallow Persian gulf form one depression between the Arabian block and the Persian mountain arcs. Here land and water have had varied relations, and there seems every reason to think that in early historic times (c. 4000-2000 B.C.), at least, the gulf shores were much farther north than they now are, as Ur of the Chaldees was a port; changes are due largely to silting. The contrast between the southern steppe (i.e., the bor ders of the Arabian desert, with its proximity to the "fertile crescent," a great cradle of civilization), and the northern steppe of the Euro-Asiatic lowland is of the utmost interest in connec tion with the interpretation of history. In the fertile crescent, as nowhere else in the ancient world, wandering, trading patri archal herdsmen came into contact with settled cultivators living in agglomerations near the waterside, and organization taking both into account in various ways grew up.
Persia, Baluchistan, Afghanistan.—East-north-east of the Mesopotamian lowland and the Persian gulf, the Armenian moun tain knot branches, forming the Elburz mountains (Mt. Dema vend, 18,600f t.) of the south coast of the Caspian eastwards, and the Zagros mountains stretching south-eastwards as the boundary between Mesopotamia, in the physical sense, and the Persian highland, though politically Persia includes the Karun basin and reaches down to the Euphrates just below Basra. Farther south the mountains turn into a west-to-east di rection and proceed towards the Indian border in lines behind the Baluchistan coast, whereafter they turn north as they front the Indus lowland. Analogously, from the Pamir's south-west ern region the great Hindu Kush extends south-westwards, with branch mountain lines fanning out in Afghanistan, the eastern most fronting the Indus lowland while the northernmost are con tinued with only a slight break right to the Elburz. The Afghan and Baluch highlands of the border of the Indus basin come into relation with one another, but the famous Bolan pass (Quetta Kandahar) is near their junction. There is thus in Persia, Afghanistan and Baluchistan a collection of mountain arcs not compressed closely as in Tibet but set round about basins, in which old blocks play their part. The basins are mostly without outlet and include the Salt desert of north Persia, the Lut desert of east Persia, the basin of Seistan and the Helmand (Registan) in south Afghanistan, the basins of Jaz Murian Hamun and Hamun-i-Mashkel in south-east Persia and south Baluchistan. These and other similar smaller basins usually have salt lakes or swamps in their desert floors. The mountain sides in many parts are far more fertile.