NCERT Exercise
Que 1
Select the correct
answer from the four options given below :-
(i) In which of the
following stage of landform development , downward erosion is dominated?
(a) Youth Stage
(b) Early mature stage
(c) Late mature stage
(d) Old Stage
ANS.
(a) Youth Stage
(ii) A deep valley
characterized by steep step-like side slopes is known as
(a) U-Shaped valley
(b) Blind valley
(c) Gorge
(d) Canyon
ANS.
(d) Canyon
(iii) In which one of
the following regions the chemical weathering process is more dominant than the
mechanical weathering process?
(a) Humid Region
(b) Arid Region
(c) Limestone Region
(d) Glacier region
ANS.
(a) Humid Region
(iv) Which one of the
following statements best defines the term ‘Lapies’?
(a) A small to medium
sized shallow depression
(b) A landform whose
opening is more or less circular at the top and funnel shaped towards bottom
(c) A landform formed
due to dripping water from surface
(d) An Irregular
surface with sharp pinnacles, grooves and ridges
ANS.
(d) An Irregular surface with sharp pinnacles, grooves and ridges
(v) A Deep, long and
wide trough or basin with very steep concave high walls at its head as well as
in sides is known as:
(a) Cirque
(b) Lateral Moraine
(c) Glacial valley
(d) Esker
ANS.
(a) Cirque
Que 2
Answer the following
questions in about 30 words: -
(i) What do incised
meanders in rocks and meanders in plains of alluvium indicate?
ANS.
Erosion
in rocks and general erosion of alluvium in plains suggest that rivers flowing
on steep slopes flow more like a serpent with more horizontal erosion. The
origin of these wasps occurs in the early stages of river development.
(ii) Explain the evolution of valley sinks or uvalas.
ANS.
The
development of valley stomata or pubescence occurs when the gill stomata and
doline join together by falling roofs of caverns or by ejection of materials.
In this way long, narrow and wide trenches are formed. Which are called Valley
Sinks or Uvalas.
(iii) Underground flow of water is more common than surface
runoff in limestone areas. Why?
ANS.
Limestone
rocky regions have limestone or dolomite in which calcium carbonate
predominates. There, surface and ground water form many landforms by chemical
process - dissolution.
(iv) Glacial valleys show up many linear depositional forms.
Give their locations and names.
ANS.
In
the glacial valley, many landforms are formed by the deposition of clay, which
are called glaciers. Lateral glaciers are formed on the parallel sides of the
glacier. The two lateral glaciations together form the medial glaciation. A
sedimentary glacier is formed at the bottom of a glacier. In the last part of
the glacier, the end glacier is found.
(v) How does wind perform its task in desert areas? Is it the
only agent responsible for the erosional features in the deserts?
ANS.
Wind
acts as the most important erosive agent in the desert areas. Due to the lack
of vegetation and rainfall, the sand particles are loose, which is easily
carried by the fast moving wind. The landforms created by wind in desert areas
are called 'Aeolian Topography'.
In
the desert areas, sometimes heavy rainfall also occurs, due to which some
landforms are also formed from the internal water flow. For example - playa
(plain deposited by eroded water material between mountains in deserts).
Que 3
Answer the following
questions in about 150 words: -
(i) Running water is by far the most dominating geomorphic agent
in shaping the earth’s surface in humid as well as in arid climates. Explain.
ANS.
In wet regions, where there is a lot of rainfall, runoff water is the most
important geomorphic factor which is responsible for the degradation of the
surface.
Flowing
water has two elements: -
1.
Flow spread in the form of a layer on the surface.
2.
Linear flow that flows through valleys in the form of rivers and streams.
Most
of the erosive landforms created by run-off waters are related to the aggressive youthfulness of rivers flowing along the slope.
Over
a period of time, due to continuous erosion, the steep slopes are converted
into slow slopes and consequently the velocity of the rivers decreases, due to
which deposition starts. The steeper the slope of the flowing water, the
greater the deposition.
In
arid regions, however, wind is an important geomorphic factor. However,
sometimes there is torrential rain in such dry areas, which causes rapid soil
erosion in this vegetated region.
(ii) Limestone behaves differently in humid and arid climates.
Why? What is the dominant and almost exclusive geomorphic process in limestone
areas and what are its results?
ANS.
Limestone behaves differently in humid and dry climates. In humid climate,
surface water starts flowing horizontally and vertically through the joints and
crevices of permeable limestone rocks. Form many types of landforms through
dissolution and precipitation.
In
arid regions, there is a lack of rainfall and there is a lack of water and
water in large quantities does not enter the interior of the land. Therefore,
in arid regions, ground water has no special significance.
(iii) How do glaciers accomplish the work of reducing high
mountains into low hills and plains?
ANS.
Snow moving slowly downwards in the form of ice flows or valleys in the form of
a layer on the earth is called glacier.
Due
to the force of gravity, the glaciers, moving downhill at a very slow speed,
abrasive like sand and the edges and foothills of the rock formations are
highly eroded by friction and the high mountain areas get crushed by the
outwash plain.
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