Landforms
Class 7 | Social Science — Geography | Unit 2
Class 7 Unit 2 Geography
In the earlier class, we have learnt that the surface of the earth is not the same everywhere. The earth has an infinite variety of landforms named mountains, plateaus, plains, valley etc., Some parts of the lithosphere may be rugged and some flat. These landforms are a result of two processes. They are i. The Endogenic Process ii. The Exogenic Process
Unit -2 Landforms
Learning Objectives
• To understand the landforms produced by running water
• To describe the landforms created by glacial action
• To learn about the landforms which are produced by wind action
• To gain knowledge about land forms formed by sea waves.
Introduction Landforms
(i) The Endogenic Process
The endogenic process (internal process) leads to the upliftment and sinking of the earth's surface at several places.
(ii) The Exogenic Process
The exogenic process (external process) is the continuous wearing down and rebuilding of the land surface.
The landscape is being continuously worn down by two processes – weathering and erosion. Weathering is the breaking and falling apart into small pieces of the rocks on the earth's surface. Erosion is the wearing down of the landscape by different agents like water, wind, ice and sea waves. The eroded material is carried away by water, wind, etc. and eventually deposited. This process of erosion and deposition create different landforms on the surface of the earth.
Gradation is the process of levelling of highlands through erosion and filling up of lowlands through deposition.
River
The water flowing from its source to river mouth, along a definite course is called a River. Rivers generally originate from a mountain or hill. The place of origin of the river is known as its Source. The place where it joins a lake or sea or an ocean is known as River mouth.
Land forms formed by River
The running water in the river erodes the mountainous track, which creates a steep-sided valley like the letter 'V' known as 'V' shaped valley.
Do You Know?
The world's highest waterfall is Angel Falls of Venezuela in South America. The other waterfalls are Niagara Falls located on the border between Canada and USA in North America and Victoria Falls on the borders of Zambia and Zimbabwe in Africa.
Falling of river water over a vertical step in the river bed is called waterfall. It is formed when the soft rocks are removed by erosion. E.g. Coutrallam falls across the river Chittar in Tamil Nadu.
Plunge pool is a hollow feature at the base of a waterfall which is formed by cavitation.
Alluvial fan is a deposition of sediment occurs at which the river enters a plain or the foot-hills.
Tributary: A stream or river that flows into and joins a main river.
Distributary: A stream that branches off and flows away from a main stream.
As the river enters the plain it twists and turns forming large bends known as Meanders. Eg. Meanders along the River Vellar near Sethiyathope in Cuddalore District, Tamil Nadu. Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loops come closer. In due course of time the meander loop cuts off from the river and forms a cut-off lake, also called an Ox-bow lake.
Do You Know?
The term 'Meander' has been named on the basis of Meander River of Asia Minor (Turkey), which flows through numerous curves and turns.
At times the river overflows its banks. This leads to the flooding of the neighbouring areas. As the river floods, it deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of a flat fertile floodplain. The raised banks are called levees.
As the river approaches the sea, the speed of the flowing water decreases and the river begins to break up into a number of streams called distributaries. The velocity of the river becomes so slow that it begins to deposit its load. The collection of sediments from all the mouths form Delta. Deltas are excellent productive lands. E.g. Cauvery delta, Ganges delta, Mississippi delta.
Find out the names of a few rivers of the world that form a delta with the help of the Atlas.
Glacier
A large body of ice moving slowly down a slope or valley due to gravity is called a glacier. Glaciers are grouped into Mountain or Valley Glaciers and Continental Glaciers.
Continental Glacier: The glacier covering vast areas of a continent with thick ice sheets. E.g. Antarctica, Greenland
Mountain or Valley Glacier is a stream of ice, flowing along a valley. It usually follows former river courses and are bounded by steep sides. E.g. The Himalayas and the Alps.
Glaciers, expose the solid rocks of earth by removing the loose materials found on it.
Cirque is a glacially eroded rock basin, with a steep side wall and steep head wall, surrounding an armchair-shaped depression. E.g. Corrie – Scotland (United Kingdom), Kar – Germany.
As the ice melts, they get filled up the cirque with water and become beautiful lakes in the mountains called as Tarn Lake. When two adjacent cirques erode towards each other, the previously rounded landscape is transformed into a narrow rocky, steep – sided ridges called Arete.
'U' Shaped Valley is found beneath the glaciers which is deepened and widened by the lateral and vertical erosion. The material carried by the glacier such as rocks - big and small, sand and silt get deposited. These deposits form glacial moraines.
When the wind blows, it lifts and transports sand from one place to another. When it stops blowing the sand falls and gets deposited in low hill – like structures. These are called sand dunes. The crescent shaped sand dunes are called Barchans.
Have you ever visited a desert? Try to collect some pictures of sand dunes. An active agent of erosion and deposition in the deserts is wind.
Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top. Wider top rocks in the shape of a mushroom, commonly called mushroom rocks. An isolated residual hill, standing like a pillar with rounded tops are called Inselbergs. E.g. Inselberg in the Kalahari Desert of South Africa.
When the grains of sand are very fine and light, the wind can carry it over very long distances. When such sand is deposited in large areas, it is called Loess. Large deposits of loess are found in China.
Do You Know?
Northern China loess deposits are brought from the Gobi Desert.
Sea waves
A part of the land adjoining or near the sea is called the Sea coast. The boundary of a coast, where land meets water is called the Coast line. The coastal areas are subject to change due to wave erosion and wave deposition.
Coastal Landforms
The erosion and deposition of the sea waves give rise to coastal landforms. Sea Cliffs are steep rock faces formed, when the sea waves dash against them. Sea waves continuously strike at the rocks. So Cracks develop. Over time they become larger and wider. Thus, hollow like caves are formed on the rocks. They are called Sea Caves.
As the cavities of sea caves become bigger and bigger only the roof of the caves remains, thus forming Sea Arches. Further, erosion breaks the roof and only walls are left. These wall like features are called Sea Stacks.
The sea waves deposit sediments of sand and gravel along the shores forming Beaches. Sand bar is an elongated deposition of sand or mud found in the sea, almost parallel to the coast.
Lagoon is a shallow stretch of water partially or completely separated from the sea. E.g. Chilika lake in Odisha, Pulicat lake in Tamil Nadu and Vembanad lake in Kerala are the famous lagoons in India.
Do You Know?
The longest beach in the world is the Miami beach in South Florida in U.S.A. The second longest beach in the world is the Marina beach in Chennai.
Summary
• The landscape is being continuously worn down by weathering and erosion.
• River, glacier, wind and sea waves are the major agents of exogenic forces.
• From its source to its mouth, the river is constantly reshaping the land and giving rise to different landforms.
• The river begins to break up into a number of streams called distributaries.
• Deltas are excellent productive lands.
• Glacier is large body of ice moving slowly down a slope due to gravity.
• Moraines are glacial deposits.
• Wind is the active agent of erosion and deposition in deserts.
• The sea waves deposit sediments of sand and gravel along the shores forming beaches.
Glossary
Gradation The process of leveling of highlands through erosion and filling up of lowland through deposition. சமநிலைப் படுத்துதல் Weathering Breaking and crumbling up of rocks on the earth's surface. வானிலைச் சிதைவு River mouth The place where the river joins a lake or an ocean. ஆற்று முகத்துவாரம் Tributary A stream or river that flow into and joins a main river. துணை ஆறு Meander Twists and turns forming large bends in the river. ஆற்று வளைவு Delta Large Fan shaped sediments formed by river deposition டெல்டா Cirque The arm chair shaped depression with steep sleep sided wall formed by glacial erosion. சர்க் Barchans The crescent shaped sand dunes. பிறைவடிவ மணற்குன்று Lagoon A shallow stretch of water partially separated from the sea. காயல்
Evaluation
Exercise I. Choose the correct answer
1. ____________ is a deposition of river sediments along the foot-hills.
a) Plunge pool b) Alluvial fan c) Flood plain d) Delta
2. Courtallam falls is located across the____________ river.
a) Cauvery b) Pennar c) Chittar d) Vaigai
3. The landform created by glacial deposition is
a) Cirque b) Arete c) Moraine d) Tarn lake
4. Large deposits of loess are found in
a) USA b) India c) China d) Brazil
5. Land forms which are not associate with wave erosion ____________
a) Cliffs b) Sea archs c) Stacks d) Beaches Exercise II. Fill in the blanks
1. The process of breaking and crumbling of rocks is .
2. The place where the river joins a lake or a sea is known as .
3. Inselbergs are found in the desert in South Africa.
4. A cirque is known as in Germany.
5. The longest beach in the world is .
Exercise III. Match the following
| 1. Breaking and crumbling of rocks | |
| 2. Abandoned meander loops | |
| 3. Large body of moving ice | |
| 4. Crescent shaped sand dunes | |
| 5. Vembanad lake | |
Options: Glacier, Barchans, Lagoon, Weathering, Oxbow lake
Exercise IV. Consider the following statement and tick (✓) the appropriate answer
1. Assertion (A): The deltas are formed near the mouth of the river.
Reason (R): The velocity of the river becomes slow when it approaches the sea.
a) Both A and R are correct b) A is correct and R is wrong c) A is wrong and R is correct d) Both A and R are wrong
2. Assertion (A): Sea arches in turn become Sea Stacks.
Reason (R): Sea Stacks are the results of wave deposition.
a) Both A and R are correct b) A is correct and R is wrong c) A is wrong and R is correct d) Both A and R are wrong Exercise V. Answer the following
1. Define erosion.
2. What is a plunge pool?
3. How are Ox – bow lakes formed?
4. Name the major landforms formed by glacial erosion.
5. Give a note on Mushroom rocks.
6. What is a lagoon? Give an example.
Exercise VI. Distinguish the following
1. Tributary and Distributary
2. 'V' shaped valley and 'U' shaped valley
3. Continental glacier and Mountain glacier
Exercise VII. Give Reason
1. The ends of the meander loops come closer and closer.
2. Flood plains are very fertile.
3. Sea caves are turn into stacks.
Exercise VIII. Answer in a paragraph
1. Explain different landforms produced by river erosion.
2. Describe the landforms associated with wind.
3. How are aretes formed?
Activity 1. Fill in the corresponding columns
Fill in the corresponding columns with reference to the landform features given below
[Barchan, 'V' Shaped valley, Cliff, Arete, Inselberg, Moraine, Alluvial fan, Lagoon]
| S.No | Natural Agents | Erosion | Deposition |
|---|
| 1 | River | | |
| 2 | Glacier | | |
| 3 | Wind | | |
| 4 | Sea wave | | |
Activity 2. Identify any one of the following features
Identify any one of the following features near your home town and write a note on them.
1. Hill 2. Waterfall 3. River (or) stream 4. Beach.
Reference Books
1. Savindra Singh (2015), Physical Geography, Pravalika Publications, Allahabad.
2. Rajeev Gupta (2012), Physical Geography, Sonali Publications, New Delhi.
3. A. Das Gupta, A.N. Kapoor, Physical Geography, S. Chand and Company Ltd, New Delhi.
4. Nater Singh Raina (2012), Contemporary Physical Geography, Concept Publishing Company Pvt. Ltd, New Delhi.
ICT CORNER
Landforms
Through this activity you will know about different types of land in the world
PROCEDURE:
Step – 1 Open the Browser and type the URL given below (or) Scan the QR Code.
Step - 2 Go to menu and select any types of land (Ex. Glacier)
Step - 3 Roll over the red dot on the map to the right to choose a glacier
Landforms URL:
http://www.harcourtschool.com/activity/types_of_land_2/index.html
Book-back Exercises — Questions & Answers
Answers generated strictly from the Samacheer Kalvi textbook content. Attempt each question first, then click "Show Answer" to check.
I. Choose the correct answer
1. ____________ is a deposition of river sediments along the foot-hills.
a) Plunge pool b) Alluvial fan c) Flood plain d) Delta
Answer: b) Alluvial fan
Explanation: Alluvial fan is a deposition of sediment occurs at which the river enters a plain or the foot-hills.
2. Courtallam falls is located across the____________ river.
a) Cauvery b) Pennar c) Chittar d) Vaigai
Answer: c) Chittar
Explanation: Coutrallam falls across the river Chittar in Tamil Nadu.
3. The landform created by glacial deposition is
a) Cirque b) Arete c) Moraine d) Tarn lake
Answer: c) Moraine
Explanation: The material carried by the glacier such as rocks - big and small, sand and silt get deposited. These deposits form glacial moraines.
4. Large deposits of loess are found in
a) USA b) India c) China d) Brazil
Answer: c) China
Explanation: Large deposits of loess are found in China.
5. Land forms which are not associate with wave erosion ____________
a) Cliffs b) Sea archs c) Stacks d) Beaches
Answer: d) Beaches
Explanation: Beaches are formed by wave deposition, not erosion. The sea waves deposit sediments of sand and gravel along the shores forming Beaches.
II. Fill in the blanks
1. The process of breaking and crumbling of rocks is ____________.
Answer: Weathering
2. The place where the river joins a lake or a sea is known as ____________.
Answer: River mouth
3. Inselbergs are found in the ____________ desert in South Africa.
Answer: Kalahari
4. A cirque is known as ____________ in Germany.
Answer: Kar
5. The longest beach in the world is ____________.
Answer: Miami beach in South Florida in U.S.A.
III. Match the following
1. Match the Following
| 1. Breaking and crumbling of rocks | - Glacier |
| 2. Abandoned meander loops | - Barchans |
| 3. Large body of moving ice | - Lagoon |
| 4. Crescent shaped sand dunes | - Weathering |
| 5. Vembanad lake | - Oxbow lake |
Answers: 1-Weathering, 2-Oxbow lake, 3-Glacier, 4-Barchans, 5-Lagoon
IV. Consider the following statement and tick (✓) the appropriate answer
1. Assertion (A): The deltas are formed near the mouth of the river.
Reason (R): The velocity of the river becomes slow when it approaches the sea.
a) Both A and R are correct b) A is correct and R is wrong c) A is wrong and R is correct d) Both A and R are wrong
Answer: a) Both A and R are correct
Explanation: As the river approaches the sea, the speed of the flowing water decreases and becomes so slow that it begins to deposit its load. The collection of sediments from all the mouths form Delta.
2. Assertion (A): Sea arches in turn become Sea Stacks.
Reason (R): Sea Stacks are the results of wave deposition.
a) Both A and R are correct b) A is correct and R is wrong c) A is wrong and R is correct d) Both A and R are wrong
Answer: b) A is correct and R is wrong
Explanation: Sea arches do become sea stacks through erosion, not deposition. Further erosion breaks the roof of sea arches and only walls are left. These wall-like features are called Sea Stacks.
V. Answer the following
1. Define erosion.
Answer: Erosion is the wearing down of the landscape by different agents like water, wind, ice and sea waves.
2. What is a plunge pool?
Answer: Plunge pool is a hollow feature at the base of a waterfall which is formed by cavitation.
3. How are Ox – bow lakes formed?
Answer: Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loops come closer. In due course of time the meander loop cuts off from the river and forms a cut-off lake, also called an Ox-bow lake.
4. Name the major landforms formed by glacial erosion.
Answer: The major landforms formed by glacial erosion are Cirque, Arete, U-shaped valley and Tarn lake.
5. Give a note on Mushroom rocks.
Answer: Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top. Wider top rocks in the shape of a mushroom, commonly called mushroom rocks.
6. What is a lagoon? Give an example.
Answer: Lagoon is a shallow stretch of water partially or completely separated from the sea. Examples include Chilika lake in Odisha, Pulicat lake in Tamil Nadu and Vembanad lake in Kerala.
VI. Distinguish the following
1. Tributary and Distributary
Answer: Tributary is a stream or river that flows into and joins a main river. Distributary is a stream that branches off and flows away from a main stream. The river begins to break up into a number of streams called distributaries as it approaches the sea.
2. 'V' shaped valley and 'U' shaped valley
Answer: 'V' shaped valley is created when the running water in the river erodes the mountainous track, forming a steep-sided valley like the letter 'V'. 'U' shaped valley is found beneath the glaciers which is deepened and widened by the lateral and vertical erosion of glaciers.
3. Continental glacier and Mountain glacier
Answer: Continental Glacier is the glacier covering vast areas of a continent with thick ice sheets, such as Antarctica and Greenland. Mountain or Valley Glacier is a stream of ice, flowing along a valley, usually following former river courses and bounded by steep sides, such as The Himalayas and the Alps.
VII. Give Reason
1. The ends of the meander loops come closer and closer.
Answer: Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loops come closer. This continuous process eventually leads to the formation of ox-bow lakes when the meander loop cuts off from the river.
2. Flood plains are very fertile.
Answer: When the river floods, it deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of a flat fertile floodplain, making them very fertile.
3. Sea caves are turn into stacks.
Answer: As the cavities of sea caves become bigger and bigger only the roof of the caves remains, thus forming Sea Arches. Further erosion breaks the roof and only walls are left. These wall-like features are called Sea Stacks.
VIII. Answer in a paragraph
1. Explain different landforms produced by river erosion.
Answer: The running water in the river erodes the mountainous track, creating a steep-sided valley like the letter 'V' known as 'V' shaped valley. Falling of river water over a vertical step in the river bed creates waterfalls, formed when soft rocks are removed by erosion. Plunge pool is a hollow feature at the base of a waterfall formed by cavitation. As the river enters the plain it twists and turns forming large bends known as Meanders. Due to continuous erosion and deposition along the sides of the meander, the ends come closer and eventually form cut-off lakes called Ox-bow lakes.
2. Describe the landforms associated with wind.
Answer: Wind is an active agent of erosion and deposition in deserts. Winds erode the lower section of rocks more than the upper part, creating mushroom rocks with narrower base and wider top. Isolated residual hills standing like pillars with rounded tops are called Inselbergs. When wind blows, it lifts and transports sand, and when it stops, the sand falls and gets deposited in low hill-like structures called sand dunes. The crescent-shaped sand dunes are called Barchans. When fine sand is deposited in large areas after being carried over long distances, it is called Loess.
3. How are aretes formed?
Answer: Cirque is a glacially eroded rock basin with steep side wall and steep head wall, surrounding an armchair-shaped depression. When two adjacent cirques erode towards each other, the previously rounded landscape is transformed into narrow rocky, steep-sided ridges called Arete. This process occurs through continuous glacial erosion from both sides of the mountain ridge.
📝 Summary
- Landforms are created by endogenic processes (internal upliftment and sinking) and exogenic processes (continuous weathering, erosion and deposition by agents like water, wind, ice and sea waves).
- Rivers originate from mountains or hills and create 'V' shaped valleys in mountainous areas through erosion, along with waterfalls when soft rocks are removed by erosion.
- As rivers enter plains, they form meanders (large bends) which can eventually cut off to create ox-bow lakes through continuous erosion and deposition processes.
- River mouths form deltas when the water flow becomes slow and deposits sediments, creating excellent productive lands like the Cauvery delta, Ganges delta, and Mississippi delta.
- Important river features include tributaries (streams joining main rivers), distributaries (streams branching away), alluvial fans (sediment deposits at foothills), and plunge pools (hollow features at waterfall bases).