CH-18 MAJORE RELIEF FEATURES OF
THE WORLD
Answer the following questions in one or two sentences.
(a)What is Plateau?
Plateaus are elevated regions, lower than mountains, which have a flat top and steep sides.
(b)What is a fold mountain?
A fold mountain is a raised portion of the earth’s surface caused by the compression of the layers
of the earth from both sides. These generally have long parallel ranges, for example, the Rockies and
Andes.
(c) How are plains formed?
Plains are generally formed by the deposition of alluvium brought down by rivers and deposited in
low-lying areas.
(d) What makes the plains fertile and habitable?
Plains are fertile because of the alluvial soil and plenty of water for agriculture. This is also the
reason why a large number of people inhabit the plains.
(e) Distinguish between Block Mountains and Volcanic Mountains.
Block Mountains are formed due to faulting and uplifting. Volcanic mountains are generally formed
by the deposition of molten material that comes out from below the surface of the earth.
Answer the following questions in four or five sentences.
(a) Describe a fold mountain.




Fold Mountains are formed due to the compression (pressure from both sides) of horizontal
layers of rocks.
A simple fold mountain has ‘down folds’ or valleys called syncline and ‘up folds’ or ridges
called anticlines.
Fold mountains that were formed some 60-70 million years ago are called ‘young fold
mountains’, for example, the Himalayas. These are very high and covered with snow.
Fold Mountains that were formed 200-300 million years ago are call ‘old fold mountains’
such as the Aravallis.
(b) Explain the formation of a volcanic mountain with a suitable diagram.

Volcanic mountains are formed by deposition of molten material called lava from beneath the
crust.
 This happens due to internal earth movements which pushes the molten material to the surface
through openings or vents in the crust.
 The molten material gradually piles up and cools layer after layer over the years to form a
conical mountain. Mt Vesuvius (Italy) is a famous volcanic mountain.
(Refer to page157 of the textbook for the diagram.)
(c) Describe a rift valley.



A rift valley is formed due to tension that creates faults in the crust. The area between two
parallel faults or cracks sinks down forming a rift valley.
A rift valley is also called a graben. The largest rift valley in the world is the Great Rift Valley
in East Africa, which is about 6,000 km in length.
The Narmada Valley in India is a very good example of a rift valley.
(d) What is a plain?




A plain is a low-lying, flat land surface not more than 200 m above sea level.
Plains are generally formed by deposition of alluvium washed down from mountains and
plateaus by rivers.
The Indo-Gangetic Plain of India is world famous.
Plains generally have high population densities as agriculture is possible.
(e) How do mountains differ from plateaus?





A plateau is generally lower in height than a mountain.
A mountain has high pointed peaks and valleys whereas a plateau is generally flat.
This is why a plateau is also called a tableland.
Mountains are sparsely populated as they are not suitable for farming, and the climate is also
harsh while plateaus are generally well populated as cultivation is possible.
Plateaus also have rich reserves of minerals.