There are three major landforms-

1. Mountain
2. Plateau 
3. Plains.

MOUNTAINS

1. An uplifted portion of the earth’s surface is called a hill or a mountain.
2. A mountain is differentiated from a hill, when its summit or top rises to more than 900 metres above the base, those with less than this elevation are called hills, in course of time the mountains are worn into hills.

Basics

Ridge

• Mountain ridges refer to mountains which originate as a result of local folding and faulting.
• Generally, the slope of one side of the ridge is steep in contrast to the moderate slope on the other side (in case of Himalayas, the southern slope is steeper compared to the northern slope).
• In some cases, a ridge may have a symmetrical slope on both sides.

Mountain range

• It refers to a series of ridges which originated in the same age and underwent the same processes.
• The most prominent or characteristic feature of mountain ranges is their long and narrow extension.
• Example: the Himalayas is a mountain range with Himadri ridge, Himachal ridge and Shiwalik ridge.

Mountain System

• A group of mountain ranges formed in a single period, similar in their form, structure and extension, is termed a mountain system.
• Examples are the Basin Range of Nevada (USA), the Rocky mountain system of North America and the Appalachian.

Mountain Chain

• It consists of mountain ranges which differ in size and period of formation.

Cordillera

• Cordillera is a community of mountains which includes ridges, ranges, mountain chains and mountain systems.
• The best example is the Western Cordillera in the western part of North America.

Types of mountains

1. On the basis of their origin or mode of formation, the mountains are classified as
   1. Structural or tectonic
   2. Residual or dissected
   3. Volcanic

 

1. On the basis of location
   1. Continental mountains
   2. Oceanic mountains

 

Continental mountains

1. Coastal mountains
2. Inland mountains

Coastal mountains

• the Rockies,
• the Appalachians,
• the Alpine mountain chains,
• the Western Ghats and
• the Eastern Ghats (India);

Inland mountains

• the Vosges and the Black Forest (Europe),
• the Kunlun, Tienshan, Altai mountains of Asia,
• the Urals of Russia, the Aravallis,
• the Himalayas, the Satpura, and the Maikal of India.

Oceanic mountains

Oceanic mountains are found on continental shelves and ocean floors.

If the height of the mountains is considered from the ocean floor, Mauna Kea (9140 m), would be the highest mountain. It is a dormant volcanic mountain in the Hawaii hotspot volcanic chain.

Original or Tectonic mountains

• Original or Tectonic mountains are the product of tectonic forces.
• The tectonic mountains may be categorized into
• fold mountains (the Himalayas, the Rockies, the Andes),
• block mountains (Vosges mountains in France, the Black Forest in Germany, Vindhya and Satpura in India)

Volcanic mountains

• Volcanic mountains are formed due to volcanic activity.
• Mount Aconcagua, Mount Kilimanjaro, Mount Mauna Kea and Mount Fujiyama are examples of such mountains.
• These are, in fact, volcanoes which are built up from material ejected from fissures in the earth’s crust.
• The materials include molten lava, volcanic bombs, cinders, ashes, dust and liquid mud.
• They fall around the vent in successive layers, building up a characteristic volcanic cone.
• Volcanic mountains are often called mountains of accumulation.
• They are common in the Circum-Pacific belt.
• volcanic mountains (Cascade Range in the USA, Mount Kenya, Mount Kilimanjaro, Mount Fujiyama).

Circum-erosional or Relict or Residual mountains

• Circum-erosional or Relict or Residual mountains (Aravallis in India, Urals in Russia) are the remnants of old fold mountains derived as a result of denudation (strip of covering).
• Residual mountains may also evolve from plateaus which have been dissected by rivers into hills and valleys.
• Examples of dissected plateaux, where the down-cutting streams have eroded the uplands into mountains of denudation, are the Highlands of Scotland, Scandinavia and the Deccan Plateau.

Major Mountain Ranges of the World, Highest Mountain Peaks

Longest Mountain Ranges

1. The Andes – 7,000 km
2. The Rockies – 4,830 km
3. The Great Dividing Range – 3,500 km
4. The Transantarctic Mountains – 3,500 km
5. The Ural Mountains – 2,500 km
6. The Atlas Mountains – 2,500 km
7. The Appalachian Mountains – 2,414 km
8. The Himalayas – 2,400 km
9. The Altai Mountains – 2,000 km (1,243 mi)
10. The Western Ghats – 1,600 km
11. The Alps – 1,200 km
12. Drakensberg – 1,125 km
13. The Aravalli Range – 800 km

The Andes

• The Andes is the longest continental mountain range in the world.
• The Andes is the world’s highest mountain range outside of Asia with an average height of 4000 m.
• The highest peak is Mount Aconcagua (6,962 m) (volcanic origin, but now it’s dormant).
• World’s highest volcanoes are in the Andes.
• Ojos del Salado (6,893 m) (active volcano) on the Chile-Argentina border is the highest volcano on earth.

The Rockies

• Rocky Mountain range forms a part of the American Cordillera

American Cordillera

• The American Cordillera is a chain of mountain ranges (cordilleras) that consists of an almost continuous sequence of mountain ranges that form the western backbone of the Americas and Antarctica.
• It is also the backbone of the volcanic arc that forms the eastern half of the Pacific Ring of Fire.

North Cordillera

• The ranges of the Cordillera from Mexico northwards are collectively called the North American Cordillera.
• They include the Alaska Range and the Brooks Range in Alaska, main belt of the Rocky Mountains along with the parallel Columbia Mountains, the Sierra Nevada, the Cascades, and various small Pacific coastal ranges.
• In Mexico, the Cordillera continues through the Sierra Madre Occidental and the Sierra Madre Oriental.

South Cordillera

• The Cordillera continues through the mountain ranges of Central America in Guatemala, Honduras, Nicaragua, Costa Rica, and Panama, and becomes the Andes Mountains of South America.
• The Andes with their parallel chains continue to the very tip of South America at Tierra del Fuego.
• The Cordillera continues along the Scotia Arc before reaching the mountains of the Antarctic Peninsula.

Cascade Range

• The Cascade Range or the Cascades is a major mountain range of western North America.
• The Cascades (Cascade volcanoes) are part of the Pacific Ocean’s Ring of Fire.
• They are made up of a band of thousands of very small, short-lived volcanoes.
• The Cascade Range has few strikingly large volcanoes, like Mount St. Helens.
• The volcanoes and earthquakes in the Cascades arise from a common source: subduction, where the dense Juan de Fuca oceanic plate plunges beneath the North American Plate.

The Great Dividing Range

• The Great Dividing Range, or the Eastern Highlands, is Australia’s most substantial mountain.
• It is also known as the Australian Alps and was formed due to rifting.

Transantarctic Mountains

Transantarctic Mountains

The Ural Mountains

• Mountain range that runs approximately from north to south through western Russia, from the coast of the Arctic Ocean to the Ural River and northwestern Kazakhstan.
• They are formed due to Continent-Continent collision of supercontinent Laurussia with the young and weak continent of Kazakhstania.
• Their eastern side is usually considered the natural boundary between Europe and Asia.
• Since the 18th century, the mountains have been a major mineral base of Russia.

Atlas Mountains

• Mountain range across the north-western stretch of Africa extending about 2,500 km (1,600 mi) through Algeria, Morocco and Tunisia.
• The highest peak is Toubkal (4,165 metres) in southwestern Morocco.
• These mountains were formed when Africa and Europe collided.

The Himalayas

• The Himalayan range is home to the planet’s highest peaks, including the highest, Mount Everest.
• Its western anchor, Nanga Parbat, lies just south of the northernmost bend of Indus river, its eastern anchor, Namcha Barwa, just west of the great bend of the Brahmaputra river (Tsangpo river).
• The range varies in width from 400 kilometres in the west to 150 kilometres in the east.

Geology

• The Himalaya are among the youngest mountain ranges on the planet and consist mostly of uplifted sedimentary and metamorphic rock.
• According to the modern theory of plate tectonics, their formation is a result of a continental collision or orogeny along the convergent boundary between the Indo-Australian Plate and the Eurasian Plate.
• The Arakan Yoma highlands in Myanmar and the Andaman and Nicobar Islands in the Bay of Bengal were also formed as a result of this collision.

Impact on climate

• The Himalayas are believed to play an important part in the formation of Central Asian deserts, such as the Taklamakan and Gobi.

The Alps

• The mountains were formed as the African and Eurasian tectonic plates collided.
• Extreme folding caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc (4,810 m) (French–Italian border).
• The Alpine region area contains about a hundred peaks higher than 4,000 m, known as the four-thousanders.

Highest mountain peaks

The highest known mountain on any planet in the Solar System is Olympus Mons on Mars (~26 km in elevation). It is also the highest active volcano in the Solar System.

Plateaus

• 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.

Plateau Formation

• 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

• 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.

Crustal shortening

• 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.

Others

• 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.

Plateau Types

• There are two kinds of plateaus: dissected plateaus and volcanic plateaus.

Dissected plateau

• 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.

Volcanic plateau

• 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.

Others

• 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

Tibetan Plateau

• 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).

Colorado 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

• 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.

Kimberley Plateau

• 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.

Katanga Plateau

• 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.

Mascarene Plateau

• Plateaus also form in the ocean, such as the Mascarene Plateau in the Indian Ocean.
• It extends between the Seychelles and Mauritius Islands.

Laurentian Plateau

• Lying in the eastern part of Canada, it is a part of Canadian Shield.
• Fine quality of iron-ore is found here.

Mexican Plateau

• 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.

Patagonian 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.

Massif Central

• This plateau lies in the central France.
• It is famous for Grapes cultivation.

Anatolian Plateau

• 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.

Others

• 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.

Plains

A Plain landform is a broad area of flat sweeping landmass that generally does not change much in elevation. It is relatively flat and does not change much in elevation within a common area. This type of landform is generally lower than the surrounding landmass and may be found along an inland or coast.

It exists on every continent and covers more than one-third of the world’s total land area. This type of landform is mostly suitable for settlement and agricultural purposes. In agriculture, plain landforms are more suitable for farming than plateaus or mountains.

Characteristics:

• It must be a land
• The land must be flat, broad or slightly rolling
• It must be low in elevation in comparison to the surrounding landmass.

Types of Plains

Although plains can be classified according to their surface relief and position, they are better classed according to their mode of formation. The following are the various types of plain landforms based on mode of formation:

1. Depositional plains
2. Erosional plains
3. Structural plains

 

Depositional Plains

This type of plain landform is formed from materials deposited by rivers, glaciers, waves and wind. The type of sediment which constitutes this plain landform has a significant impact on the fertility and economic relevance of the consequent plain formed by deposition.

Furthermore, depositional plains can be grouped into the following categories:

 

Alluvial Plains

A depositional plain which is created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions.

 

This type of depositional plain can be further classified as:

• Flood Plain: Usually adjacent to a lake, stream, river or wetland where occasional or periodic flooding occurs.
• Scroll Plain: A plain which has a very low gradient through which a river meanders
• Alluvial Plain: This type of depositional plain is formed over a long period of time by deposition of sediments by a river on flood plains or beds, which yields alluvial soil. This plain is characterized by a constant but small slope with little relief (local changes in elevation)

 

Examples of Alluvial plains include:

• The Po River plains in North Italy
• The Hwang Ho Plains of North China

 

Glacial Plains (formed from the movement of glaciers under the influence of gravity)

 

This type of depositional plain can be categorized as:

• Outwash plain: A glacial outwash plain formed at the terminus of a glacier by sediments deposited from melt-water. It consists of stratified gravel and sand.

 

• Till plains: A plain of glacial till that forms when a sheet of ice is detached from the main body of a glacier and melts in place, thereby depositing the sediments it carries. They are composed of unsorted materials of all sizes

 

Examples of Glacial plains:

• The plains of North-Western Eurasia
• Ladakh plains to the East of Shyok river and North of Chang Chenmo river

 

Abyssal Plains

Usually flat or gently sloping areas of the deep ocean basin

 

Planitia

Refers to plains found on extra-terrestrial bodies e.g. Planets and the Moon

 

Lava plain

A type of depositional plain formed by sheets of flowing lava

 

Lacustrine plain

This is a type of depositional plain that is formed at the bed of a lake

 

Erosional Plains

These are plain landforms that are produced from the action of various agents of denudation on an existing landform. These agents of denudation – River, running water, glacier and wind, wear out the rugged surface on an existing landform and smoothens them, giving rise to low undulating plain landforms. 

 

Two major types of plains result from this mode of formation of plain landforms:

• Peneplains (Almost plain): Which results from the action of the various agents of denudation mentioned above, exempting wind.

 

• Pediplains: Erosional plains formed from wind action

Examples of plains in this category include:

• Northern Canada plains
• Ice eroded plains of Western Africa

 

Structural Plains

They are undisturbed plain landforms on the Earth’s surface. They are structurally depressed areas which make up some of the most expanse natural lowlands on Earth. Usually, they are formed from horizontally bedded rocks relatively undisturbed by crust movements of the Earth. This type of plain landform is usually created by an uplifting diastrophic movement of a large landmass.

 

Examples of structural plain landforms are:

• The plains of the United States of America
• The central lowlands of Australia

Location of Plain Landforms

Plain landforms occur on the doorsteps of mountains as coastal plains (which rises from sea level until it runs into an elevated feature such as mountains or plateaus) and as lowlands along the bottoms of valleys. It also occurs as plateaus or uplands. A plain is usually enclosed on two sides when it is located in a valley or may be delineated by a partial or complete ring of hills by mountains or cliffs. A pass or gap connects various plains located within the same geological region.

 

Importance of Plain Landforms

• Plain landforms are of great importance in the agricultural sector. This is because, the sediments which makeup the various types of plain landforms contribute immensely to fertility, thereby facilitating excellent crop growth and grasslands which provide good grazing for livestock. Also, the approximate flatness of the various plain landforms facilitates mechanization of crop production.
• Population and settlements are usually concentrated on plains. This is because, towns are easily laid out on the approximately flat landform found on plains. The landform could be of great economic importance when traversed by rivers. Such plain landforms traversed by rivers make irrigation of farmlands on plains much easier than on any other land form used in agriculture.
• Plain landforms such as alluvial terraces attract good settlements and population concentration because of the advantage it offers over valley-bottom flood plains which is usually subject to annual or periodic and hill slopes which may be too steep and rocky to cultivate.
• Plain landforms are excellent for sporting activities as they provide a levelled ground for sports and other recreational activities.
• Plains provide good communication routes such as railways, roads, airports
• Plains are good sources of mineral resources such as Coal, Tin and Petroleum