Tablelands

Tablelands, or PLATEAUS, are extensive elevated regions with a plain-like or undulating surface. They may be bordered by steep declivities falling more or less suddenly from the level of the plateaus to the sea or the adjacent low grounds; or they may slope down imperceptibly and thus gradually merge with the lowlands. The tableland of the Spanish Peninsula is a good example of a plateau that rises abruptly from the sea. The 'Great Plain' lying east of the Rocky Mountains, on the other hand, is a plateau that sinks gradually from a height of 6000 feet down to the low prairie lands of the Missouri. Some high tablelands are surrounded by lofty mountains, such as those of Quito, Titicaca, and Uspallata in the Andes, and that of the Pamir in Asia; while others constitute elevated platforms upon which mountain-ranges stand. Two types of tableland are recognised: (a) plateaus of accumulation and (b) plateaus of denudation. The former are built up of horizontal or approximately horizontal strata, while the latter are composed of disturbed strata which have been planed down to one general level (see MOUNTAINS). The chief tablelands are in Europe, central Spain; in America, Oregon, the great salt plain of Utah, the north and centre of Brazil; in Africa, the interior of Barbary; while in Asia almost the whole of the south and centre of the continent consists of plateaus, which rise terrace above terrace till they culminate in that of Tibet. Of the Asiatic plateaus the principal are those of Asia Minor (3280 feet above sea-level), Armenia (7000), Persia or Iran (3000), Mysore (4000 to 5000), Deccan (1500 to 2000), Tibet (12,000 to 17,000), and Chinese Tartary (3000 to 4300).