Cbse class 6, Social Studies
Define Landform?
Natural Features of Earth’s Surface are flat in some places, elevated in some places. These are referred to as Landforms.
How are landforms Formed?
Landforms are the result of Internal and external forces
What is Internal force?
The forces that uplift areas of Earth’s crust/ The forces that cause Earth surface to sink form cracks/depression is called as Internal forces.
What is External Force?
The forces that wear down/rebuilt the landforms on Earth surface is called as External forces.
What are components responsible for Internal and External forces?
Two components responsible for Internal and external forces are Erosion and deposition.
What are factors affecting the erosion and deposition?
Erosion and deposition are carried out by running water, moving ice, winds, sea waves
What are the various landforms?
Based on height, Earth has variety of Landforms
Mountains, Plateaus and Plains
MOUNTAINS
What are Mountains?
- A hill is a landform that extends above surrounding area and smaller in height
- Mountains are higher and steeper than hill
- Mountains arise above the Terrain (ground level) in a limited area
State some characteristics of Mountain?
Mountains have
- Broad base
- Narrow Peaks
- Steep Slopes
- Deep valleys
What are the various types of Mountains? Give Examples for each?
Ex: For single isolated mountain top is Mt. Kilimanjaro in Africa
Mountains that are arranged in lines are called as Mountain ranges. Ex: Jura mountain range in Europe
A whole series of long narrow range of mountains that extend for hundreds or even thousands of mile is called as Mountain chain.
Ex: Himalayas in Asia
Andes in South America
Rockies in North America
What are the various types of Mountains?
There are three types of Mountains. They are
- Fold Mountains
- Block Mountains
- Volcanic Mountains
Fold Mountains
How are Fold Mountains formed?
- Fold mountains are formed by the compression of Earth’s Crust
- Fold mountains are formed by folding of rock layers into a wave like structure like anticlines, Synclines without breaking the rock layers
What are Anticlines and Synclines?
- Anticlines also called as Upfold/Troughs
- Synclines are also called as downfolds/ridges
List the difference between Young Fold and Old Fold Mountains?
| Young fold Mountains | Old fold Mountains |
| These are recently formed mountains | These are formed a long time ago |
| These are higher in height than old fold mountains | These are shorter in height than young fold mountains |
| Peaks are pointed | Peaks are rounded |
| Slopes are steep | Slopes are gentle |
| Ex: Rockies of North AmericaHimalayas in AsiaAtlas Mountains | Urals in RussiaAppala chains in North AmericaAravalli range |
Block Mountains
How are Block Mountains formed? List some characteristic features of Block mountains with examples?
- Block Mountains are formed by tensional forces that cause cracks/faults on the Earth’s crust
- These faults break the crust into blocks
- When blocks are raised, block mountains are formed
- Block mountains have flat topes and steep slopes
- Block mountains are also called as Horsts
- Ex: Block Mountain – Vindhyas and Satpuras
What is Rift Valley?
- When the section of crust rises, it forms Block mountains, When it subsides it form the rift valley
- Rift valley are also called as Grabens
- Rift Valley – River Narmada flows through resultant rift valley
Volcanic Mountains
How are Volcanic mountains formed? Give Some Ex. for volcanic mountain
- Volcanic mountains are formed by volcanic activity
- Materials from volcano cinder, ash, dust, liquid accumulate to form Volcanic mountain
Ex:
- Mouna Kae, Mauna Loa – Hawaii
- Mount Vesuvius – Italy
- Mount Fujiyama – Japan
- Mount Kilimanjaro – Tanzania
Importance of Mountains
- Mountains act as barriers from winds
- Mountains influence the climate by causing rainfall
- Glaciers , source of perennial rivers are found in mountains
- Ex: Gangotri glacier – River Ganga originates here and provide water for irrigation and generate hydroelectricity
- Mountain slopes with green pastures are ideal for rearing cattle
- Due to the dense vegetation of mountains, they are home for many birds and animals
- Large reserves of timber and medicines are found in these forest
- Mountainous region are terraced for cultivating crops such as tea, fruits, rice etc.
- Mountains are scenic beauty, ideal for tourist destination
Note:
World’s Youngest Mountain range – Alps in Europe
World’s Longest Mountain range – Andes in South America (7200 Km)
Plateaus
Define Plateaus, how are they formed and few characteristics of Plateaus with examples?
- Plateaus are highlands with a broad and flat surface
- Plateaus are referred to as Tablelands
- Plateaus rise abruptly above the surrounding plain
- Plateaus do not have pointed peaks
- The Tibetan Plateau is highest plateau in the World
- Deccan Plateau in India, Ethiopian Plateau in Africa are formed by the solidified volcanic area
- Bolivia Plateau in South America is located in between Andes
Importance of Plateaus:
- Plateaus are made up of old rocks having rich mineral deposits
- Mining is important occupation for people living in plateaus of Australia and Chhota Nagpur plateau of India
- Depending on the rainfall in plateaus, Farming is possible
- There may be waterfalls in some plateaus used to generate electricity
- Lava plateaus are rich in black soil, that is fertile and good for cultivation
- Plateaus are mostly tourist spots
Plains
Define Plains and how are they formed?
- Plains are flat low lying land
- Plains are formed by rivers flowing down mountains, they erode and transport a lot of materials which deposit over a long period of time to form plain
- Ex: Northern Plain of India
- Yangtze plain of China
List the various types of Plains formed?
- Plains are also formed by deposition of lava
- Ex: Hells’s half acre lava field in Idaho – U.S
- Sometimes River deepen valleys widen over a period and entire area is reduced to plain
- Ex: Nullarbor plain in Australia
Importance of Plain:
- Plains make up 1/3rd of World’s land and support 3/4th of human population
- Plains are fertile , climate suitable for agriculture
- Rivers flow slowly in plains used for agriculture, irrigation and navigation