Chapter 1 – Exogenetic processes and Resultant Landforms | Class 10 School Geography Solution

Book Name	: School Geography
Subject	: Geography
Class	: 10 (Madhyamik)
Publisher	: Bengal Book Syndicate Pvt. Ltd
Chapter Name	: Exogenetic processes and Resultant Landforms

Identify the correct answers

Question 1

The geomorphic process that shapes and reshapes land externally is called :

1. Endogenic process
2. Exogenic process
3. Earthquake
4. Volcanism

Answer

(b) Exogenic process

Explanation:

The geomorphic process that shapes and reshapes land externally is called exogenic process. Exogenic processes are driven by external forces such as wind, water, ice, and gravity, and they work to wear down or reshape the Earth’s surface.

Question 2

The process by which water of rivers, lakes, and oceans turns into water vapour due to heat is called :

1. Precipitation
2. Saturation
3. Evaporation
4. Condensation.

Answer

(c) Evaporation

Explanation :

Evaporation is a process in which liquid water changes into water vapour, a gas, and enters the atmosphere.

Question 3

All the land drained by a river, its tributaries and distributaries is called :

1. River basin
2. Water divide
3. Hanging Valley
4. Outwash plain

Answer

(a) River basin

Explanation :

A river basin is the area of land that contributes surface runoff to a specific river system, including all of the land and waterways that drain into that river system.

Question 4

The isolated residual hill in the desert formed due to wind erosion is called :

1. Monadnock
2. Inselberg
3. Mesa & Butte
4. Gour

Answer

Inselberg

Explanation:

An inselberg is a hill, knob, or small mountain that rises abruptly from a flat or gently sloping surrounding plain, and is surrounded by lower, eroded terrain.

Question 5

The fragments of rocks shattered by frost action and brought down a valley by a glacier are called :

1. alluvium
2. salt pans
3. moraines
4. pyroclasts.

Answer

Moraine

Explanation:

A moraine is a landform composed of unconsolidated debris that has been brought down and deposited by a glacier.

Question 7

The largest reservoir of freshwater on earth is

1. river
2. glacial ice
3. oceans
4. groundwater

Answer

(b) Glacial Ice

Explanation :

Glaciers are large masses of ice that accumulate on land and can grow to thousands of meters in thickness. They store approximately 69% of the world’s freshwater, with the majority of this water contained in the ice sheets covering Antarctica and Greenland.

Question 8

The factor responsible for the melting of icecaps and the consequent rise of sea level is

1. change in the ocean floor
2. upliftment of land
3. global warming
4. subsidence of coastal areas

Answer

Global warming

Explanation:

The factor responsible for the melting of icecaps and the consequent rise of sea level is global warming.

If the sentence is true write T and if false write F against the following:

Question

1. The rivers move swiftly and create round holes by corrasion on the river bed called deflation hollows.
2. The knife-like sharp serrated ridge between two corries is called an Arete.
3. Most of the deserts in the world lie on the western parts of the continents where trade winds blow offshore.
4. One of the conditions of delta formation is that there should be large lakes in the river course.
5. Outwash plains present glacial-fluvial landforms.

Answer

1. False
2. True
3. False
   Most of the world’s deserts are located in the subtropics, which are typically located in the interior of continents, far from the cooling influence of maritime air masses.
4. False
   One of the conditions of delta formation is that the river should deposit its sediment load into a standing body of water, such as a lake or ocean, where the sediment can settle out and accumulate over time.
5. True

Fill in the blanks with appropriate words:

Question

1. ____ is the main work of a river in the upper course
2. The naturally formed raised banks of a river are called ____.
3. Sundarbans is located in the delta of the three rivers ____, ____.
4. ____ are low elongated hills formed by glacial deposition.
5. _____ or rock pedestal is produced by wind erosion.
6. The hard stony ribs of ridge and furrow topography formed due to wind erosion (on vertical bands of hard and soft rocks) are called ____.
7. ____ is the process by which a glacier steepens the back wall in the mountains.

Answer

1. Erosion is the main work of a river in the upper course.
2. The naturally formed raised banks of a river are called levees.
3. Sundarbans is located in the delta of the three rivers Ganges, Brahmaputra, and Meghna.
4. Drumlins are low elongated hills formed by glacial deposition.
5. A pedestal or rock pedestal is produced by wind erosion.
6. The hard stony ribs of ridge and furrow topography formed due to wind erosion (on vertical bands of hard and soft rocks) are called zeugen.
7. Plucking is the process by which a glacier steepens the back wall in the mountains.

Answer in word or words:

Question 1

What is the deep vertical crack which opens up at the head of the glacier called?

Answer

The deep vertical crack which opens up at the head of the glacier is called a Bergschrund.

Question 2

Name the typical crescent-shaped sand dunes in a desert.

Answer

The typical crescent-shaped sand dunes in a desert are called Barkhans dunes.

Question 3

What is the other word used to indicate the expansion of deserts?

Answer

Desertification is the other word used to indicate the expansion of deserts.

Question 4

What is the shape of a glacial valley?

Answer

The shape of a glacial valley is typically U-shaped.

Question 5

What do we call the winding channel of a river?

Answer

The winding channel of a river is called a meander.

Question

Match column A with column B:

Column A	Column B
(1) Inter flute	(a) sword
(2) Dry valleys in desert	(b) tributary glacier
(3) Mississippi river	(c) wadis
(4) ‘Seif’ in Arabic means	(d) higher land between two rivers
(5) Hanging valley	(e) Bird’s foot delta

Answer

(1) Inter flute – (d) higher land between two rivers

(2) Dry valleys in desert – (c) wadis

(3) Mississippi river – (e) Bird’s foot delta

(4) ‘Seif’ in Arabic means – (a) sword

(5) Hanging valley – (b) tributary glacier

Short answer type questions

Question 1

What is denudation ?

Answer

Denudation refers to the process of wearing down and removal of the Earth’s surface materials by natural agents such as water, wind, ice, and gravity. It involves erosion, weathering, and mass wasting, and leads to the formation of various landforms over a long period of time.

Question 2

How are waterfalls formed?

Answer

Waterfalls are formed when a river or stream flows over a layer of hard rock followed by a layer of softer rock. The softer rock gets eroded more easily, creating a vertical drop where the hard rock remains, resulting in the formation of a waterfall.

Question 3

Write two effects of global warming on the Sundarban Delta.

Answer

Two effects of global warming on the Sundarban delta are:

1. Rising sea levels: As a result of global warming, the polar ice caps are melting, causing sea levels to rise. This is having a significant impact on the Sundarbans delta, with saltwater intrusion causing damage to crops, vegetation, and wildlife habitats.
2. Increased frequency of natural disasters: Global warming is also contributing to an increase in the frequency and intensity of natural disasters such as cyclones and floods in the Sundarban delta. This is causing significant damage to infrastructure, homes, and livelihoods, and increasing the risk of disease outbreaks.

Question 4

What do you mean by snowing?

Answer

Snowing is a form of precipitation that occurs when water vapour in the atmosphere freezes into ice crystals and falls to the ground. It typically occurs in colder climates and can result in the accumulation of snow on the ground, which can impact transportation, recreation, and the environment.

Question 5

Write a few sentences explaining glacial-fluvial landforms.

Answer

Glacial-fluvial landforms are formed by the interaction of glaciers and rivers. Glaciers erode the landscape, creating landforms such as moraines, cirques, and U-shaped valleys, and depositing sediment in areas known as outwash plains. Rivers then transport and deposit this sediment, creating landforms such as deltas, alluvial fans, and terraces. Glacial-fluvial landforms are often found in areas that have experienced glaciation in the past and are characterized by a complex interplay of erosion and deposition by glacial and fluvial processes.

Question 6

Write any two measures taken to control the expansion of the desert.

Answer

1. Desertification Prevention: Implementing land-use planning and sustainable farming practices to protect against desertification, such as crop rotation and reduced grazing pressure.
2. Vegetation Restoration: Replanting native vegetation and using agroforestry to stabilize soil and combat desert expansion.

Answer the following questions:

Question 1

Compare the upper middle and lower courses of a river according to predominant action and features produced.

Answer

Comparison of the upper, middle, and lower courses of a river:

Course	Predominant Action	Features Produced
Upper Course	Vertical Erosion	V-shaped valleys, Interlocking spurs, Waterfalls, Rapids, Gorges, Potholes
Middle Course	Lateral Erosion	Floodplains, Meanders, Oxbow lakes, Levees
Lower Course	Deposition	Deltas, Estuaries, Floodplains, Meanders, Braided channels

 

Question 2

Describe the formation of any three features produced by glacial erosion.

Answer

Here are three features produced by glacial erosion and their formation:

1. Cirques: A cirque is a steep-walled hollow or basin found at the head of a glacial valley. It is formed when a glacier moves downslope and excavates the rock beneath it through plucking and abrasion. Over time, the glacier erodes the rock more deeply than the surrounding areas, resulting in a deep, bowl-shaped depression.
2. U-shaped valley: U-shaped valleys are formed when a glacier moves down a pre-existing V-shaped valley, which it then widens and deepens through the process of glacial erosion. The glacier removes the softer rock more easily than the harder rock, creating a U-shaped valley with steep, straight sides.
3. Fjords: A fjord is a long, narrow inlet with steep cliffs created by glacial erosion. Fjords are formed when a glacier moves down a U-shaped valley and extends beyond the coastline into the ocean. As the glacier retreats, seawater floods the valley, creating a fjord. The steep walls of the fjord are a result of the glacier’s erosion of the surrounding rock.

Question 3

Give reasons why some rivers have big deltas in their mouths.

Answer

Some rivers have big deltas in their mouths because of the following reasons:

1. The river carries a large amount of sediment, such as sand, silt, and clay, which is deposited at the mouth of the river when it meets the sea or a lake.
2. The river flows into a body of water with slow currents or no currents, such as a lake or an estuary. The sediments carried by the river settle down in such areas and cause the delta to form.
3. The river may have a high gradient or slope, which means it flows quickly and erodes the surrounding land more effectively, carrying a larger load of sediment to deposit at its mouth.

Question 4

Write the differences between barkhans and seif dunes.

Answer

Question 5

Why are bergschrunds and crevasses dangerous for the mountaineers?

Answer

Bergschrunds and crevasses are dangerous for mountaineers because:

1. Bergschrunds: They are deep gaps between a glacier and the mountain, posing a risk of climbers falling into them.
2. Crevasses: These are deep, hidden cracks in glaciers that can trap climbers, making rescue difficult and increasing the risk of injury or death.

Solve the puzzle from the clues given

Clues –

Across

(1) The process by which wind erodes.

(2) The triangular shaped land at the mouth of a river.

(3) A depression on the bed of a river produced by erosion.

(4) A natural raised bank of a river.

(5) The winding path of a river.

Down

(6) The serrated ridge between two corries.

(7) The process of corrasion active in the plains.

(8) The abundoned loop of a river in the middle course.

(9) A long sinuous ridge in the outwash plain (glacial deposition).

Answer

Across: (1) Deflation (2) Delta (3) Pothole (4) Levee (5) Meander

Down: (6) Arete (7) Abrasion (8) Ox-bow (9) Esker

Long answer or essay-type questions

Question 1

Describe the exogenetic processes active in producing landforms.

Answer

Exogenetic processes refer to the actions on the Earth’s surface that are due to external factors such as wind, water, ice, and gravity. These processes can create and shape various landforms over time.

1. Erosion is one of the most significant exogenetic processes that involves the breakdown and removal of rock and soil by wind, water, and ice. This action can create a range of landforms, such as valleys, canyons, and gorges. Water erosion can create features such as waterfalls, rapids, and potholes.
2. Transportation is the movement of eroded material by water, wind, or ice. The transportation process can involve rolling, sliding, and bouncing of rocks and sediments. Rivers transport material downstream, glaciers transport rocks and boulders, and wind transport sand and dust.
3. Deposition is the process of laying down eroded material in a new location. It is the final stage of the exogenetic process. Deposition can occur in the form of alluvial fans, deltas, sand dunes, and glacial moraines. The deposition of sediments can also create new landforms such as sandbars and barrier islands.

Question 2

Discuss the processes of erosion by a river and write about two landforms produced by river erosion with diagrams

Answer

The process of erosion by a river involves the wearing away of the earth’s surface by the force of moving water. The river’s water and sediment act as tools of erosion, which gradually cut through and remove soil, rock, and other materials from the riverbed and banks. The process of erosion by a river is classified into three types, including hydraulic action, abrasion, and attrition.

Two common landforms produced by river erosion are U-shaped valleys and hanging valleys.

• U-shaped valleys are formed in the upper course of a river where the erosive power of the river is at its highest. The river erodes downwards and sideways, cutting into the surrounding rock and widening the valley. The shape of the valley is gradually changed from a V-shape to a U-shape. This process is called glacial erosion and is often caused by the movement of glaciers. The result is a valley with steep sides and a flat bottom.
• Hanging valleys are formed when a smaller tributary valley meets the main valley. The tributary valley is typically eroded at a faster rate than the main valley due to differences in volume and velocity of water flow. As a result, the tributary valley is left “hanging” above the main valley. This creates a waterfall or steep drop-off from the higher valley to the lower valley.

Question 3

How do glaciers erode? Describe three erosional and two depositional features of a glacier. with suitable diagrams.

Answer

Glaciers erode the landscape in several ways. The three main types of glacial erosion are abrasion, plucking, and freeze-thaw weathering.

Glaciers are capable of eroding and shaping the landscape through a range of processes. Here are three erosional and two depositional features of a glacier:

Erosional features:

1. Cirques: Cirques are steep amphitheater-like depressions that form at the head of a glacier. They are formed through plucking and abrasion, as the glacier erodes the rock and scoops out the bedrock. Over time, the cirque may enlarge and deepen, forming a bowl-shaped valley known as a glacial trough.
2. Striations: Striations are parallel grooves or scratches on rocks that are caused by the abrasive action of glacial ice. As the glacier moves, it grinds rocks beneath it and carries the debris along, leaving behind parallel scratches or grooves.
3. Roche moutonnée: A roche moutonnée is a rock outcropping that has been sculpted by the movement of a glacier. One side of the rock may be smoothed and rounded, while the other side is jagged and angular.

Depositional features:

1. Moraines: Moraines are accumulations of rock and sediment that are carried by the glacier and deposited along its edges or at its terminus. There are different types of moraines, including lateral, medial, and terminal moraines, which all form at different points in the glacier’s journey.
2. Eskers: Eskers are long, winding ridges of gravel and sand that are deposited by meltwater streams flowing through a glacier. When the glacier melts, the sediment carried by the streams is deposited in a sinuous ridge, sometimes reaching tens of meters high.

Question 4

‘The action of the wind is most powerful in arid regions’ – Explain.

Answer

The action of the wind is most powerful in arid regions due to the absence or scarcity of vegetation, which is the main factor that helps to protect the land surface from wind erosion. Arid regions receive low precipitation and have sparse vegetation cover, resulting in loose and unconsolidated soil and rock particles that can be easily transported by the wind.

Furthermore, arid regions often experience large diurnal temperature fluctuations that cause thermal expansion and contraction of rocks and soil, leading to the formation of cracks and crevices. These cracks and crevices can be easily widened and deepened by the wind, resulting in the formation of various erosional features such as yardangs, mushroom rocks, and ventifacts.

Question 5

Write an account of the landforms produced by wind deposition with diagrams.

Answer

Wind deposition can produce various landforms, including sand dunes, loess deposits, and zeugen. Zeugen are elongated ridges or hills formed from the deposition of windblown sand and dust.

Zeugen typically form perpendicular to the prevailing wind direction and can range in size from a few meters to several kilometers long. They can be composed of sand, gravel, or other sediment, and may have a layered appearance.

One example of a zeugen formation is the Yardangs, found in the desert regions of the world, which are elongated ridges that are aligned with the direction of the prevailing wind. They are formed by the differential erosion of soft and hard rocks, with the harder rocks forming the ridges and the softer rocks being eroded away.

Question 6

What is desertification? – Explain with examples.

Answer

Desertification is a process by which fertile land becomes increasingly dry and barren, leading to the creation of deserts. This process is often caused by human activities such as deforestation, overgrazing, and improper irrigation practices, as well as climate change and natural disasters such as droughts.

Examples of desertification include the Sahel region of Africa, which has experienced widespread desertification due to overgrazing, deforestation, and drought. The Loess Plateau in China is another example, where deforestation and unsustainable farming practices have led to severe soil erosion and desertification. In Central Asia, the Aral Sea has shrunk dramatically due to over-irrigation and mismanagement of water resources, leading to the expansion of desertification in the region.

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