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Geologically, Asia consists of ancient Precambrian landmasses : the Arabian and Indian peninsulas in the south and the central Siberian plateau in the north : enclosing a central zone of folded ridges. In accordance with this underlying structure, Asia falls into the following major physiographic structures: the northern lowlands covering W central Asia and most of Siberia; the vast central highland zone of high plateaus, rising to c.15,000 ft (4,570 m) in Tibet in China and enclosed by some of the world's greatest mountain ranges (the Himalayas, the Karakorum, the Kunlun, the Tian Shan, and the Hindu Kush); the southern peninsular plateaus of India and Arabia, merging, respectively, into the Ganges and Tigris-Euphrates plains; and the lowlands of E Asia, especially in China, which are separated by mountain spurs of the central highland zone. Mt. Everest (29,035 ft/8,856 m), in Nepal, is the world's highest peak; the Dead Sea (1,312 ft/400 m below sea level) is the world's lowest point. Great peninsulas extend out from the mainland, dividing the oceans into seas and bays, many of them protected by Asia's numerous offshore islands. Asia's rivers, among the longest in the world, generally rise in the high plateaus and break through the great chains toward the peripheral lowlands. They include the Ob-Irtysh, the Yenisei-Argana, and Lena of Siberia; the Amur-Argun, Huang He, Chang (Yangtze), Xi, Mekong, Thanlwin, and Ayeyarwady of E and SE Asia; and the Ganges-Brahmaputra, Indus, and Tigris-Euphrates of S and SW Asia. Central Asia has vast areas of interior drainage, including the Amu Darya, Syr Darya, Ili, and Tarim rivers, which empty into inland lakes or disappear into desert sands. The Aral Sea, Lake Baykal, and Lake Balkash are among the world's largest lakes. Climatically, the continent ranges through all extremes, from torrid heat to arctic cold and from torrential rains (the product of monsoons) to extreme aridity (as in the Tarim Basin).
Asia can be divided into six regions, each possessing distinctive physical, cultural, economic, and political characteristics. Southwest Asia (Iran; Turkey, in Asia Minor; and the nations of the Fertile Crescent and the Arabian peninsula or Arabia), long a strategic crossroad, is characterized by an arid climate and irrigated agriculture, great petroleum reserves, and the predominance of Islam. South Asia (Afghanistan and the nations of the Indian subcontinent) is isolated from the rest of Asia by great mountain barriers. Southeast Asia (the nations of the southeastern peninsula and the Malay Archipelago) is characterized by monsoon climate, maritime orientation, the fusion of Indian and Chinese cultures, and a great diversity of ethnic groups, languages, religions, and politics. East Asia (China, Mongolia, Korea, and the islands of Taiwan and Japan) is located in the mid-latitudes on the Pacific Ocean, and is characterized by cultures strongly influenced by civilizations of the Huang He and Chang (Yangtze) river systems. It forms the most industrialized region of Asia. Russian Asia (in the northern third of the continent) consists of the vast region of Siberia and the Russian Far East. In the center of the continent is Central Asia, formed of a set of independent former republics of the Soviet Union. This region is characterized by desert conditions and irrigated agriculture, with ancient traditions of nomadic herding.
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