Friday, 18 July 2014 07:22




Plateaux are elevated uplands with extensive level surfaces, and usually descend steeply to the surrounding lowland. They are sometimes referred to as tablelands. Like all highlands, plateaux are subjected to erosional processes. As a result, their original characteristics may be greatly altered.  According to their mode of formation and their physical appearances, plateaux may be grouped into the following types:

1. Tectonic plateaux: These are formed by earth movements which cause uplift. These are normally of a considerable size, and fairly uniform altitude. They include continental blocks like the Deccan Plateau in India. Some of the tectonic plateaux may be tilted like the Meseta of central Iberia, or faulted like the Harz of Germany.When plateaux are enclosed by Fold Mountains, they are known as intermontane plateaux. Examples are the Tibetan Plateau between the Himalayas and the Kunlun, and the Bolivian Plateau between two ranges of the Andes. Intermontane plateaux are some of the highest and the most extensive plateaux in the world.

2. Volcanic plateaux: Molten lava may issue from the earth’s crust and spread over its surface to form successive sheets of basaltic lava. These solidify to form a lava plateau. Some of the better known volcanic plateaux are the Antrim Plateau of Northern Ireland and the north-western part of the Deccan Plateau. The most remarkable plateau built by lava is the Columbia-Snake Plateau which covers an area almost twice as big as Malaysia. Each layer of the lava flow is over 100 feet thick and the entire depth of successive lava layers is estimated to be almost a mile.

3. Dissected plateaux: Through the continual process of weathering and erosion by running water, ice and winds, high and extensive plateaux are gradually worn down, and their surfaces made irregular. In the humid highlands, stream action and sometimes glaciation cut deep, narrow valleys in the plateaux, which are then described as dissected plateaux. An example is the Scottish Highlands. In drier countries, vertical corrosion by rivers and abrasion by wind will dissect the plateau into steep-sided tabular masses termed mesas and buttes, intersected by deep canyons. This is a common feature of arid and semi-arid areas, e.g. in the south-western U.S.A.Many of the world’s plateaux have rich mineral resources and have been actively mined. The African Plateau yields gold, diamonds, copper, manganese and chromium. In the Brazilian Plateau, there are huge resources of iron and manganese, particularly in the Minas Gerais area. The Deccan Plateau has deposits of manganese, coal and iron and the plateau of Western Australia is rich in gold and iron.