Short Answer Questions
What is meant by a landform? Give two examples.
A landform is a natural feature on the surface of the earth. For example- mountains, plateaus.
Why are the fold mountains called so?
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.
Give two chief characteristics of the fold mountains.
Two chief characteristics of the fold mountains are-
- The fold mountain system has parallel ranges.
- A fold mountain region is also a region of sudden forces such as of volcanoes and earthquakes.
Give one example of each:
(a) Young fold mountain.
(b) Old fold mountain.
(a) Young fold mountain - The Himalayas
(b) Old fold mountain - The Aravallis
Give one example of residual mountain and an example of depositional plain.
An example of residual mountain - Nilgiri mountains
An example of depositional plain - Northern plains of India
Draw a well labelled diagram to show the formation of a residual mountain.
How is a rift valley formed? Give one example of a rift valley.
If there are two parallel faults, the valley floor may sink and a rift valley is formed. For example- African Rift Valley.
Give a brief definition of a plateau.
Plateau is defined as an area of high ground, 500 feet above the ground level.
What is an intermontane plateau? Give one example.
The plateaus surrounded by hills and mountains on all sides are called intermontane plateaus. For example- Tibetan plateau.
Give two points of importance of landforms.
The importance of landforms are-
- The mountain ranges of the world are the abode of snow and glaciers. They are thus the source of perennial rivers.
- Mountains, plateaus, plains and valleys are beautiful sculptures of nature on the surface of the earth. They add to the beauty of the earth.
Give a technical term for each of the following
A very steep hill rising to great heights above the land surrounding it.
Mountains lowered down as a result of being subjected to weathering.
Block mountains with flattened summits.
Plateaus surrounded by hills and mountains on all sides.
Plateaus formed by lava.
An extensive area of lowland with a level or gently undulating surface.
Plains formed at foothills of mountains as a result of river deposition.
Distinguish between each of the following
Fold Mountains and Block Mountains.
|Fold Mountains||Block Mountains|
|They are formed due to folding of the rocks.||Block mountains are formed due to faulting.|
|Fold Mountains are formed when two tectonic plates move towards each other leading to the folding of the layers of the Earth.||Block Mountains are formed when the two tectonic plates move away from each other causing cracks on the surface of the Earth.|
|They are characterized by large scale complex folds that have greater height but are comparatively narrow in width.||They are characterized by steep slopes and flat slopes.|
|For example- the Himalayas in India||For example- Black forest mountains in Europe.|
Intermontane plateaus and Volcanic plateaus.
|Intermontane plateaus||Volcanic plateaus|
|These are surrounded by hills and mountains on all the sides. They are formed along with fold mountains.||They are formed by numerous volcanic eruptions that slowly build up over time.|
|For example- the Tibetan plateau.||For example- the Peninsular plateau of India.|
Structural plains and Depositional plains.
|Structural plains||Depositional plains|
|These plains are formed due to uplift or subsidence of land.||These plains are formed by the deposition of materials which have been brought by various agents of transportation.|
|For example- the Great Plains of USA.||For example- Northern Plains of India.|
How are various landforms formed on the surface 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.
Describe the formation of mountains and their types.
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.
Give a reason for each of the following:
(i) Asthenosphere though underneath the crust is in a semi-molten state.
(ii) Exogenic forces are also called destructive forces.
(iii) Residual mountains are also called mountains of denudation.
(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.
Draw a well labelled diagram to show the formation of block mountain.
Describe the characteristics of two different types of plateaus.
The characteristics of Intermontane plateau are-
- These plateaus are surrounded by hills and mountains on all sides.
- They are formed along with fold mountains.
For example- the Tibetan plateau.
The characteristics of Volcanic plateaus are-
- They are formed by numerous volcanic eruptions that slowly build up over time, forming a plateau.
For example- the Peninsular Plateau of India.
Describe the characteristics of structural plains.
The characteristics of structural plains are-
- These plains are formed due to uplift or subsidence of land.
- Diastrophic forces may cause uplift of a portion of land beneath the ocean water or may cause submergence of coastal land under ocean water.
- 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.
Give a reason for each of the following:
(i) There are different types of plains.
(ii) Alluvial plains are regarded as the granaries of the world.
(iii) The landforms on the surface of the earth are symbols of the energy of the earth.
(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.
Explain the chief characteristics of depositional plains and their types.
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 dimes 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.