- A plateau is a flat-topped table land.
- Plateaus occur in every continent and take up a third of the Earths land.
- They are one of the four major landforms, along with mountains, plains, and hills.
- Plateaus, like mountains may be young or old. The Deccan plateau in India is one of the oldest plateaus.
- Valleys form when river water cuts through the plateau. The Columbia Plateau, between the Cascade and Rocky mountains in the northwestern United States, is cut through by the Columbia River.
- Sometimes, a plateau is so eroded that it is broken up into smaller raised sections called Many outlier plateaus are composed of very old, dense rock formations. Iron ore and coal often are found in plateau outliers.
- Plateaus are very useful because they are rich in mineral deposits. As a result, many of the mining areas in the world are located in the plateau areas.
Model question on Plateaus
Plateaus are of great economic significance. Comment with reference to India And World.
- The plateaus are famous for minerals. The plateau of France [Massif Central], the Deccan plateau of India, Katanga plateau of Congo [Copper mines], Western Australian plateau [Kimberly Plateau – Diamond mines] and Brazilian plateau [Brazilian Highlands] are very good sources of minerals. Iron, copper, gold, diamonds, Manganese, coal, etc., are found in these plateaus.
- East African plateau is famous for gold and diamond mining.
- In India huge reserves of iron, coal and manganese are found in the Chotanagpur plateau.
- In the plateau areas, there may be several waterfalls as the river falls from a great height. In India, the Hundru Falls in the Chotanagpur plateau on the river Subarnarekha and the Jog Falls in Karnataka are examples of such waterfalls. These sites are ideal for hydro-electric power generation. Angel falls in Venezuela is also a waterfall that descends down a plateau.
[Plateaus are not very useful from the point of view of agriculture. The hard rocks on plateaus cannot form fertile soil but agricultural activities are promoted where lava soils have developed. It is difficult to dig wells and canals in plateaus. This hampers irrigation.]
- The lava plateaus like Deccan traps are rich in black soil that is fertile and good for cultivation. Example: Maharashtra has good cotton growing soils called regurs.
- Loess plateau in China has very fertile soils that are good for many kind of crops.
- Many plateaus have scenic spots and are of great attraction to tourists. (Grand Canyon, USA, many waterfalls)
- Tectonic plateaus are formed from processes that create mountain ranges – volcanism (Deccan Plateau), crustal shortening (thrusting of one block of crust over another, and folding occurs. Example: Tibet), and thermal expansion (Ethiopian Highlands).
- Thermal expansion of the lithosphere means the replacement of cold mantle lithosphere by hot asthenosphere).
- Those caused by thermal expansion of the lithosphere are usually associated with hot spots. The Yellowstone Plateau in the United States, the Massif Central in France, and the Ethiopian Plateau in Africa are prominent examples.
- When the lithosphere underlying a broad area is heated rapidly – e.g., by an upwelling of hot material in the underlying asthenosphere – the consequent warming and thermal expansion of the uppermost mantle causes an uplift of the overlying surface. The high plateaus of East Africa and Ethiopia were formed this way.
- The great heights of some plateaus, such as the Plateau of Tibet is due to crustal shortening.
- Crustal shortening, which thickens the crust as described above, has created high mountains along what are now the margins of such plateaus.
- Plateaus that were formed by crustal shortening and internal drainage lie within major mountain belts and generally in arid climates. They can be found in North Africa, Turkey, Iran, and Tibet, where the African, Arabian, and Indian continental masses have collided with the Eurasian continent.
Volcanic Flood Basalts – Traps
- Volcanism Types – Exhalative, Effusive, Explosive, Subaqueous
- Volcanic Landforms – Extrusive and Intrusive
- Volcanism – Andesitic, Basaltic-Geyser,Hot Water Spring
- A third type of plateau can form where extensive lava flows (called flood basalts or traps) and volcanic ash bury preexisting terrain, as exemplified by the Columbia Plateau in the northwestern United States, Deccan Traps of peninsular India, Laurentian plateau or The Canadian Shield and the Siberian Traps of Russia.
- Volcanic plateaus are commonly associated with eruptions that occurred during the Cenozoic or Mesozoic.
- Eruptions on the scale needed to produce volcanic plateaus are rare, and none seems to have taken place in recent time.
- The volcanism involved in such situations is commonly associated with hot spots. The lavas and ash are generally carried long distances from their sources, so that the topography is not dominated by volcanoes or volcanic centers.
- The thickness of the volcanic rock can be tens to even hundreds of metres, and the top surface of flood basalts is typically very flat but often with sharply incised canyons and valleys.
- The volcanic eruptions that produce lava plateaus tend to be associated with hot spots. For example, the basalts of the Deccan Traps, which cover the Deccan plateau in India, were erupted 60–65 million years ago when India lay in the Southern Hemisphere, probably over the same hot spot that presently underlies the volcanic island of Reunion.
- In North America the Columbia River basalts may have been ejected over the same hot spot that underlies the Yellowstone area today. Lava plateaus of the scale of those three are not common features on Earth.
- Some plateaus, like the Colorado Plateau, the Ordos Plateau in northern China, or the East African Highlands, do not seem to be related to hot spots or to vigorous upwelling in the asthenosphere but appear to be underlain by unusually hot material. The reason for localized heating beneath such areas is poorly understood, and thus an explanation for the distribution of plateaus of that type is not known.
- There are some plateaus whose origin is not known. Those of the Iberian Peninsula and north-central Mexico exhibit a topography that is largely high and relatively flat.
- There are two kinds of plateaus: dissected plateaus and volcanic plateaus.
- A dissected plateau forms as a result of upward movement in the Earth’s crust.
- The uplift is caused by the slow collision of tectonic plates. The Colorado Plateau, in the western United States, Tibetan plateau etc. are examples.
- A volcanic plateau is formed by numerous small volcanic eruptions that slowly build up over time, forming a plateau from the resulting lava flows.
- The Columbia Plateau in the northwestern United States of America and Deccan Traps are two such plateaus.
- Intermontane plateaus are the highest in the world, bordered by mountains. The Tibetan Plateau is one such plateau.
- Continental plateaus are bordered on all sides by the plains or seas, forming away from mountains.
Major plateaus of the World
- Highest and largest plateau in the world and hence called the ‘roof of the world’.
- Formed due to collision of the Indo-Australian and Eurasian tectonic plates.
- The plateau is sufficiently high enough to reverse the Hadley cell convection cycles and to drive the monsoons of India towards the south. [We will learn this in future posts]
- It covers most of the Autonomous Tibetan Region, Qinghai Province of Western China, and a part of Ladakh in Jammu and Kashmir.
- It is surrounded by mountains to the south by the Himalayan Range, to the northeast by the Kunlun Range, and to the west by the Karakoram Range.
Columbia – Snake Plateau
- River Columbia and its tributary Snake meet in this plateau.
- It is bordered by the Cascade Range and Rocky Mountains and divided by the Columbia River.
- This plateau has been formed as the result of volcanic eruptions with a consequent coating of basalt lava (Flood Basalt Plateau).
- It is lying to western part of U.S.A. It is the largest plateau in America.
- It is divided by the Colorado River and the Grand Canyon.
- This plateau is an example of intermontane plateau. Mesas and buttes are found here at many places [Arid Landforms].
- The plateau is known for the groundwater which is under positive pressure and causes the emergence of springs called Artesian wells.
- Deccan Plateau is a large plateau which forms most of the southern part of India.
- It is bordered by two mountain ranges, the Western Ghats and the Eastern Ghats.
- The plateau includes the Deccan Traps which is the largest volcanic feature on Earth.
- Made of multiple basalt layers or lava flows, the Deccan Traps covers 500,000 square kilometers in area.
- The Deccan Traps are known for containing some unique fossils.
- The Deccan is rich in minerals. Primary mineral ores found in this region are mica and iron ore in the Chotanagpur region, and diamonds, gold and other metals in the Golconda region.
- Lies in the northern part of Australia.
- This plateau is made of volcanic eruption.
- Many minerals like iron, gold, lead, zinc, silver and diamond are found here.
- Diamond is also found here.
- It is lying in Congo.
- It is famous for copper production.
- Other minerals like Cobalt, Uranium, Zinc, Silver, Gold and Tin are also mined here.
- Plateaus also form in the ocean, such as the Mascarene Plateau in the Indian Ocean.
- It extends between the Seychelles and Mauritius Islands.
- Lying in the eastern part of Canada, it is a part of Canadian Shield.
- Fine quality of iron-ore is found here.
- It is called as ‘Mineral Store’. Different types of metallic minerals like silver, copper etc. are obtained from here.
- World’s biggest silver mine Chihuahua is situated in the plateau.
- It is a Piedmont plateau (Arid Landforms) lying in southern part of Argentina.
- It is a rain shadow desert plateau.
- It is an important region for sheep rearing.
Altiplano Plateau or Bolivian Plateau
- It is an intermontane plateau which is located between two ranges of Andes Mountain.
- It is a major area of Tin reserves.
- This plateau lies in the central France.
- It is famous for Grapes cultivation.
- Also known as Asia Minor, most of Turkey lies on this plateau.
- It is an intermontane plateau lying between Pontiac and Taurus Mountain ranges.
- Tigris – Euphrates Rivers flow through this plateau.
- Precious wool producing Angora goats are found here.
- Spanish Plateau or Iberian Plateau: It is situated in the middle of Spain. It is a lava plateau. It is rich in minerals like Iron.
- Loess Plateau: It is in China. The soil here is made of fine particles brought by the wind. This fine loamy soil is extremely productive. Crops grown in this soil along the Yellow River give great yields.
- Potwar Plateau: It is situated in northern plateau (Punjab) region of Pakistan. Its average ‘Salt Range’ is located to the south-west of the plateau.
- Bavarian Plateau: Southern part of Germany.
- Ahaggar Plateau: A small plateau located in Algeria, Sahara.