Landforms of the Earth

Orogenic movements

Epeirogenic movements

Diastrophic forces

Exogenic forces

A: Anticline B: Syncline

Ridges

Young fold mountains

A is true but R is false.

Explanation — The external forces or Exogenic forces are described as Destructive Forces because they cause widespread destruction through weathering and erosion of existing landforms.
Diastrophic Forces (originating deep inside the earth) are responsible for producing reliefs such as mountains, plateaus, plains, lakes and big faults.

Both A and R are true and R is the correct explanation of A.

Explanation — Residual mountains are also called mountains of denudation. This is because denudation and erosion by natural agents such as winds, water, snow, etc., cause the mountains to be lowered. However, some resistant areas may remain and form residual mountains.

Old fold mountains

Relict mountains

All of the above

Both A and R are true but R does not explain A.

Explanation — The forces of faulting, also known as epeirogenic forces, lead to the formation of Block mountains. Due to tensional force, cracks or faults may occur on the earth's crust. If two parallel faults occur, the land in between subsides to form a rift valley. If a block rises, it forms a horst or block mountain.

Subsidence, deposition

Depositional plain

existence of sand dunes and hallows.

Polder

Structural plains

Marine Deposition Plains : Western Coastal Plains (India)

All of the above.

Intermontane Plateaus

Both A and R are true and R is the correct explanation of A.

Explanation — The fact that they were submerged under water is responsible for the existence of many lakes in the vast lowland.

A landform is a natural feature on the surface of the earth. For example- mountains, plateaus.

Fold mountains are the result of large scale earth movements caused by stresses in the earth’s crust. Such stresses may be caused by weight of the overlying rocks, movements in the mantle, the expansion or contraction of some part of the earth, etc. These stresses subject the rocks to compressive forces, producing wrinkling or folding along the lines of weakness. Hence, these mountains are called fold mountains.

Two chief characteristics of the fold mountains are-

1. The fold mountain system has parallel ranges.
2. A fold mountain region is also a region of sudden forces such as of volcanoes and earthquakes.

(a) Young fold mountain - The Himalayas
(b) Old fold mountain - The Aravallis

An example of residual mountain - Nilgiri mountains
An example of depositional plain - Northern plains of India

The Great Plains of the USA were formed due to uplift of land submerged under water. The fact that they were submerged under water is responsible for the existence of many lakes in the vast lowland. The Great Plains of the USA are examples of Structural plains.

If there are two parallel faults, the valley floor may sink and a rift valley is formed. For example- African Rift Valley.

Plateau is defined as an area of high ground, 500 feet above the ground level. Plateaus have steep slope on one side. The upper part is generally flat and is called tableland.

The plateaus surrounded by hills and mountains on all sides are called intermontane plateaus. For example- Tibetan plateau.

The importance of landforms are-

1. The mountain ranges of the world are the abode of snow and glaciers. They are thus the source of perennial rivers.
2. Mountains, plateaus, plains and valleys are beautiful sculptures of nature on the surface of the earth. They add to the beauty of the earth.

Landforms are formed on the surface of the earth due to the following natural processes-

1. Plate Tectonics — The tectonic plates push, collide and slide past each other due to which sedimentary rocks are compressed. This causes folding of the rocks and forms fold mountains.

2. Uplift and Submergence — A set of forces operates inside the earth's centre to the surface and is characterized by large scale uplift and subsidence of land area. These forces result in the formation of block mountains, basins, rift valleys, plateaus, plains, lakes and big faults.

3. Exogenic Forces — These forces cause widespread destruction through weathering and erosion of existing landforms and form new landforms through both erosion and deposition.

A mountain is a very steep land or hill rising to great heights above the land surrounding it. Mountains are classified into three types based on the forces that have formed them.

1. Fold mountains — Fold mountains are the result of large-scale earth movements caused by stresses in the earth’s crust. Such stresses may be caused by weight of the overlying rocks, movements in the mantle, the expansion or contraction of some part of the earth, etc. These stresses subject the rocks to compressive forces, producing wrinkling or folding along the lines of weakness. For example- the Himalayas in India.

2. Residual Mountains — Mountains which are subjected to weathering and erosion for a longtime, are lowered down and called residual or relict mountains. Denudation and erosion by natural agents like winds, water, snow etc., cause the mountains to be lowered but some resistant areas may remain and form residual mountains. They may also be formed on plateaus that are dissected by rivers. For example- Nilgiri in India.

3. Block Mountains — It is an uplifted land mass situated between two adjacent faults. The central block is upthrown or land on the outer-sides of the faults is downthrown so that the central mass appears like a highland. Its surface is like a plateau, but it has steep edges. For example- Vosges in Europe.

(i) The internal heat of the earth doesn't travel to the surface because rocks are bad conductors of heat. The internal heat of the earth melts the rocks and keeps the asthenosphere in a semi-molten state.

(ii) Exogenic forces are also called destructive forces because they cause widespread destruction through weathering and erosion of existing landforms.

(iii) Residual mountains are also called mountains of denudation as they are formed due to denudation and erosion by natural agents such as winds, water, snow etc.

The characteristics of Intermontane plateau are-

1. These plateaus are surrounded by hills and mountains on all sides.
2. They are formed along with fold mountains.
   For example- the Tibetan plateau.

The characteristics of Volcanic plateaus are-

1. They are formed by numerous volcanic eruptions that slowly build up over time, forming a plateau.
   For example- the Peninsular Plateau of India.

The characteristics of structural plains are-

1. These plains are formed due to uplift or subsidence of land.
2. Diastrophic forces may cause uplift of a portion of land beneath the ocean water or may cause submergence of coastal land under ocean water.
3. For example- The Great Plains of USA were formed due to the uplift of land submerged under water while the Coromandal plains in India are a result of mild submergence followed by sedimentation.

(i) There are different types of plain based on the way they are formed. While some have been formed due to depositional activities of rivers and winds, some are formed due to the upliftment and submergence of lands.

(ii) Alluvial plains are regarded as the granaries of the world because they are formed by the deposition of rivers. So, the soil in these plains is very fertile and supports agriculture.

(iii) The landforms on the surface of the earth are symbols of the energy of the earth as they are basically a result of enormous heat generated inside the earth and climate factors operating on the surface of the earth.

Depositional plains are formed by the deposition of materials which have been brought by various agents of transportation. Depositional plains are of three types-

1. River Deposition — The most widespread of these are alluvial plains like the Northern Plains of India; the flood plains like the Mississippi Plains in the USA, deltaic plains in Egypt and India.

2. Wind Deposition — Most such plains are sandy deserts like the Sahara in Africa and the Thar desert in India. They have irregular and undulating surface made by existence of sand dunes and hallows. Loess plains in China are formed from deserts.

3. Marine Deposition — These plains are found in coastal regions. Examples are the east coast of India, the estuarine banks in the Netherlands, coast of Germany and Denmark.

My state is in Northern India. It is home to a variety of landforms that have been shaped by both natural and human processes. These include the vast alluvial plain of the Indo-Gangetic region, the Himalayan foothills, and the valleys, deltas, and floodplains formed by major rivers such as the Ganges, Yamuna, and Ghaghara.

These landforms have been shaped by erosion, sedimentation, and tectonic activity over millions of years, while human activities such as deforestation, agriculture, and urbanization have caused changes to the landscape over time.

If the energy released through tectonic activity, earthquakes, and volcanoes were trapped inside the Earth, it could lead to a buildup of pressure and result in catastrophic consequences.

For example, if the pressure were to build up within a volcano, it could potentially cause a violent eruption, releasing huge amounts of ash, lava, and toxic gases into the surrounding environment, which could lead to widespread destruction of property and loss of life. The 1815 eruption of Mount Tambora in Indonesia was caused by a buildup of pressure within the volcano, resulting in one of the largest volcanic eruptions in recorded history, with devastating consequences for the region.

Similarly, if the pressure were to build up along a tectonic plate boundary, it could lead to a massive earthquake, causing severe damage to buildings, infrastructure, and other vital structures, resulting in significant loss of life and property damage.

Volcanic activity releases gases such as carbon dioxide, sulphur dioxide, and water vapour into the atmosphere, which can have a significant impact on global climate. If this energy is not released, it can lead to changes in the Earth's climate and ecosystem, affecting agriculture, wildlife, and human populations.