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Class 11 Geography Chapter 7 Landforms and Their Evolution
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Landforms and Their Evolution
TEXTUAL QUESTION & ANSWER
(a) Multiple choice questions.
Q.1. In which of the following stages of landform development, downward cutting is dominated?
(i) Youth stage
(ii) Late mature Stage
(iii) Early mature Stage
(iv) Old Stage
Ans: (i) Youth stage
Q.2. A deep valley characterised by steep step like side slopes is known as-
(i) U-Shaped valley
(iii) Blind valley
Ans: (iv) Canyon
Q.3. In which one of the following regions the chemical weathering process is more dominant than the mechanical process?
(i) Humid region
(ii) Limestone region
(iii) Arid region
(iv) Glacier region
Ans: (ii) Limestone region
Q.4.Which one of the following sentences best defines the term ‘Lapies’?
(i) A small to medium sized shallow depression.
(ii) A landform whose opening is more or less circular at the top and funnel shaped towards bottom.
(iii) A landform formed due to dripping water from the surface.
(iv) An irregular surface with sharp pinnacles, grooves and ridges.
Ans: (iv) An irregular surface with sharp pinnacles, grooves and ridges.
Q.5. 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.
(ii) Glacial valley
(iii) Lateral Moraine
Ans: (i) Cirque
(b) Answer the following questions in about 30 words.
Q.1. What do incised meanders in rocks and meanders in plains alluvial indicate?
Ans: Incised meanders in rocks and meanders in plains of alluvial indicate the hardness and softness of the foundation but in the case of plain areas meanders are flowing over gentle slopes.
Q.2. Explain the evolution of valley sinks or uvulas.
Ans: A sinkhole is an opening more or less circular at the top and funnel-shaped towards the bottom with sizes varying in area from a few sq.m. to a hectare and with depth from less than half a meter to 30m or more. It formed due to the erosional works of the groundwater.
Again, when sinkholes and dolines join together because of slumping materials along their margins or due to roof collapse of caves a long narrow to wide trenches are developed which are termed as uvulas or valley sinks.
Q.3. Underground flow of water is more common than surface off in limestone areas. Why?
Ans: Underground flow of water is more common than surface run-off in-limestone areas because in the limestone areas rocks are more permeable, thinly bedded and highly jointed and cracked. Due to the nature of the underground rocks (limestone) the groundwater flows horizontally through the bedding planes, joints or through the materials themselves. So, in such areas we have not seen surface run- off.
Q.4. Glacial valleys show up many linear depositional forms. Give their locations and names.
Ans: The noted linear depositional forms of a glacial valley are as follows
(Fig): (a) Terminal moraine
(b) Lateral moraine
(c) Ground moraines
(d) Esker etc.
Q.5. How does wind perform its task in desert areas? Is it the only agent responsible for the erosional features in the deserts?
Ans: In desert areas winds move with great speed and the obstructions in their path create turbulence, some of which are very destructive. Generally wind perform their works in three different ways:
These are: (a) Deflation
(c) Impact or attrition.
Lifting and removal of dust and smaller particles from the surface of rocks is termed as deflection. In the transportation process, silt acts as effective tools to abrade the land surface which is called as abrasion. The third works i.e. impact is sheer force of momentum which occurs when sand is blown into or against a rock surface.
Winds is the dominant agent responsible for the formation of erosion as well as depositional features in the deserts but rain water also plays a minor role in this regard.
|Chapter 1||Geography As A Discipline|
|Chapter 2||The Origin and Evolution of the Earth|
|Chapter 3||Interior of the Earth|
|Chapter 4||Distribution of Oceans And Continents|
|Chapter 5||Minerals and Rocks|
|Chapter 6||Geomorphic Processes|
|Chapter 7||Landforms and Their Evolution|
|Chapter 8||Composition and Structure of Atmosphere|
|Chapter 9||Solar Radiation, Heat balance, and Temperature|
|Chapter 10||Atmospheric Circulation and Weather Systems|
|Chapter 11||Water in the Atmosphere|
|Chapter 12||World Climate and Climate Change|
|Chapter 13||Water (Oceans)|
|Chapter 14||Movements of Ocean Water|
|Chapter 15||Life on the Earth|
|Chapter 16||Biodiversity And Conservation|
|Chapter 17||Indian Location|
|Chapter 18||Structure and Physiography|
|Chapter 19||Drainage System|
|Chapter 21||Natural Vegetation|
|Chapter 23||Natural Hazards and Disasters|
(c) Answer the following questions in about 150 words:
Q.1. 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 humid regions which receive heavy rainfall water considered as the most important geomorphic agent in shaping the earth surface. Running water acts in two different ways over the earth’s surface.
(a) One is overland flow on the general land surface as a sheet.
(b) Secondary as a linear flow as streams and rivers in valleys.
With time, stream channels over steep gradients due to continued erosion, and as a consequence, lose their velocity, facilitating active deposition. Thus,. the river channels become gentler. When the stream beds turn gentler due to continued erosion, downward cutting becomes less dominant and lateral erosion of banks increases and as a consequence the hills and valleys are reduced to plains. And this way running water shaped the earth’s surface and developed many features over it.
Besides humid climatic areas it plays a dominating role in arid regions also. Although there is very little rainfall, suddenly torrential rain produced many features within a short period of time.
Q.2. 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 arid climates, it is because limestone is more permeable, very thinly bedded and highly jointed and cracked. So, when the surface water enters in such rocks the water moves horizontally through the limestone areas and produces various features such areas.
The most dominant and almost exclusive types of geomorphic process in limestone areas is the process of solution and deposition. As a result of solution and deposition of limestone a lot of landforms are developed. Among them the following are notable.( Fig)
Q.3. How do Glaciers accomplish the work of reducing high mountains into low hills and plains?
Ans: Glaciers are the most dominant geomorphic agent in the cold and polar areas of the earth’s surface. Erosion by Glaciers is tremendous because of friction caused by sheer weight of the ice. The material plucked from the land by glaciers get dragged through abration and plucking.
It is noted that Glaciers can cause significant damage to even unweathered rocks and also reduce high mountains into low hills and plains through abrasion and plucking.
The important features which are develop due to the various actions of glaciers are as follows with diagram (fig)
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