Plateaux are elevated upland. They have extensive flat or level surface which usually descends sharply to the surrounding lowland. It has gentle slopes and is often referred to as table lands because of their flat or level surface. Plateaux are tabular in shape, steep-sided with rough and irregular surfaces.
They have narrow valleys and sometimes form hydrological centres. Mesas and buttes may be present. Most Plateaux are relics of ancient mountain ranges.
TYPES OF PLATEAUX
There are three types of plateau based on their mode of formation. These are:
- Tectonic Plateaux.
- Volcanic Plateaux.
- Dissected Plateaux.
- TECTONIC PLATEAUX
These plateaux are formed as a result of earth movement which causes the uplift of some areas and the depression of others. Uplifted areas of land or undulating land form tectonic plateaux and the depression area form basins.
Tectonic plateau are of two types:
- Table land: The uplifted areas of the level land slope down to surrounding lower land.
- Intermont: The uplifted areas of the level land slope up or are enclosed by Fold Mountains. Examples of a tectonic plateau are Deccan plateau (Indian). Some may be tilted e.g. Mesetal (Central Iberia), or faulted e.g. Harz of Germany. Examples of intermont plateaux are Tibetan plateau between Himalayas and Kunlun and Bolivian plateau between two ridges of the Andes.
- VOLCANIC OR LAVA PLATEAUX
These plateaux are formed when molten lava comes out the earth’s crust through a vent and spreads out in successive layers. The lava cools and solidifies to form volcanic or lava plateau. Examples include Antrim plateau of Northern Ireland and Columbia Snake plateau.
- DISSECTED PLATEAUX
These plateaux are formed due to weathering and agents of denudation such running water, wind, ice, etc. which wear down a large and extensive plateau into remnant structures of irregular surfaces called dissected plateau. Vertical erosion is the dominant action of some rivers that cross a plateau. These rivers carve out deep valleys which break up the plateau surface into many steep-sided pieces. They may also be formed as a result of uplift. Examples include Jos plateau (Nigeria), edges of Fouta Djallon plateau (Guinea) and Kumasi plateau (Ghana).
IMPORTANCE OF PLATEAUX
- Some plateaux are sources of valuable minerals like tin, gold, diamond, etc. which are useful to man e.g. Jos plateau in Nigeria, Kosciusko plateau South of Canberra in Australia.
- Since they are tableland, they greatly support human settlement. Example is the Jos Plateau.
- Plateaux also support the growth of pasture grasses and legumes which support the rearing of animals e.g. cattle, sheep and goat.
- Some plateaux are centres of tourist attraction.
- Most plateaux, due to their cold climate and fertility, promote some specialized farming which gives rise to the cultivation of specific crops.
- Some plateaux are the sources of many rivers.
DISADVANTAGES OF PLATEAUX
- Some plateaux are inaccessible as they are surrounded by escarpment and mountains which serve as obstacles to the construction of roads, railways and airports.
- Some plateaux are associated with erosion which tends to reduce or prevent serious farming activities.