Grade-6 Social Science, Major Relief Features of the World
Major Relief Features of the World
1. Fill in the blanks with the appropriate words:
The highest mountain peak in the world is Mt. Everest.
Alluvial plains are made up of deposition of materials washed down from mountains and plateaus by rivers.
Earthquakes and volcanoes are a result of internal processes.
The Deccan plateau is rich in a variety of minerals.
Rift Valleys are also called garben.
2. Choose the correct answer:
A table and is also called a
Plain
Plateau (✔)
Mountain
Volcano
Block mountains are formed because of
Folding
Faulting/vertical upliftment (✔)
Lava deposit
Erosion
An anticline is a/an
Upfold (✔)
Fault
Garben
Vent
The Andes Mountains are in
Africa
South America
Australia
Europe
A block mountain is also called
Horst (✔)
Graben
Fault
Tableland
3. Match the column:
Ans-
4. Write true or false. Correct the false sentences in your notebook.
(a) Plains are up to 200 m above sea level. (True)
(b) A number of mountain ranges together form a mountain system. (False)
A number of mountain chains together form a mountain system.
(c) Mountainous areas are most suitable for human settlement. (False)
Plains are most suitable for human settlement.
(d) The Aravalli Mountains are young fold mountains. (False)
The Aravalli Mountains are old fold mountains.
(e) Mountains formed by the deposition of lava are called volcanic mountains. (True)
5. Answer the following questions in one or two sentences.
(a) What is a fold mountain?
Ans- Fold mountains are the mountains which are formed due to the compression i.e. pressure from both sides of horizontal layers of rocks.
(b) Distinguish between block mountains and volcanic mountains.
(c) What is a plateau?
Ans- Plateaus are elevated regions, lower than mountains, which have a steep side and a flat top. They are created by internal forces, volcanic eruptions or erosion. They are also called tablelands. E.g. Plateau of Tibet
(d) What is a plain?
Ans- A plainis a low-lying, flat land which is not more than 200m above sea level.
Most plains are formed by deposition of materials (silt, sand and clay) washed down by rivers from mountains and plateaus. E.g. Indo-Gangetic Plains, Nile Basin of Egypt and Mississippi Basin of North America
(e) What makes the plains fertile and habitable?
Ans- Deposition of alluvium (silt, sand and clay) washed down by rivers from mountains and plateaus makes the plains fertile.
Plains are habitable as they are appropriate for agriculture and also it is easy to develop roads, railways and canal systems for cheap transport on plains.
6. Answer the following questions in four or five sentences.
(a) Describe any two types of mountains.
Fold Mountains-
Mountains formed by compression (pressure from both sides) of horizontal layers of soft rocks are called fold mountains. The downfold of a fold mountain is called syncline or valley. The upfold of a fold mountain is called ridge or anticline.
Fold mountains which are 60 to 70 million years old are called ‘young fold mountains. Example- Himalaya
Fold mountains which are 200 to 300 million years old are called ‘old fold mountains. Example- Aravalis
Block Mountains-
Block mountains are formed due to tension (opposite of compression) that creates faults in the crust. The land between the cracks is uplifted by internal forces generated within the earth and this creates block mountains or horst. For example- Satpura and Vindhyachal ranges are block mountains.
(b) Explain the formation of a volcanic mountain with a suitable diagram.
Volcanic Mountains-
Internal earth movements push the molten material (lava) to the surface through vents (opening). This molten material gradually piles up and cools layer after layer and conical mountains called volcanic mountains. Example- Mt Fuji (Japan), Mt. Kilimanjaro (Tanzania, Africa)
7. Give one word for the following:
1- Subsided land between two block mountains- Rift valley/graben
2- A raised flat-topped tableland with steep sides- Plateau
3- These features can broadly be divided into mountains, plateaus and plains.- Relief features
4- All the relief features are formed as a consequence of these two forces- Internal and external forces.
5- Raised parts of the surface on either sides of a rift valley- Block mountains/Horsts
6- The only active volcano in India is located on this island in the Bay of Bengal - Barren Island
8. Define these terms:
Mountain- Mountains are the highest relief features formed by folding, faulting or volcanic action.
Plateau- A plateau is an elevated flat land, caused by volcanic or tectonic action, and erosion.
Plain- A plain is a low-lying region, formed by the deposition of fertile materials called alluvium.
Glacier - A large mass of moving ice that forms the source of rivers at high altitude
Fold mountains - Mountains formed by compression of horizontal layers of soft rocks
Volcanic mountains - Mountains formed by the deposition of molten material from inside the earth
9. Give Reason-
1- Aravalis lost their height with time.
Aravallis are old fold mountains (200-300 million years old). They have lost their height with time because they are worn down by wind, water and ice.
2- Narmada and Tapi Valleys are standing within the Vindhya and the Satpura Ranges.
Vindhya and Satpura ranges are block mountains which are formed due to uplift (by internal forces) for the land between cracks (faults).
When the area between these cracks is sunken down, it forms graben or rift valleys like Narmada and Tapi valleys.
3- Cotton and sugarcane is produced in the Deccan Plateau region.
Plateaus are formed by volcanic eruptions or erosions. These regions are rich in a variety of minerals. The Deccan plateau is formed by solidification of lava and it is rich in black soil which is excellent for growing cotton and sugarcane.
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