Lesson.6 Lithosphere – II Exogenetic Processes
Lesson.6 Lithosphere – II Exogenetic Processes
I. Choose the correct answer
1. The disintegration or decomposition of rocks is generally called as
- Weathering
- Erosion
- Transportation
- Deposition
Ans: a) Weathering
2. The process of the levelling up of land by means of natural agents.
- Aggradation
- Degradation
- Gradation
- none
Ans: c) Gradation
3. …………… is seen in the lower course of the river.
- Rapids
- Alluvial fan
- Delta
- Gorges
Ans: c) Delta
4. Karst topography is formed due to the action of ……………
- Glacier
- Wind
- Sea waves
- Ground water
Ans: d)
5. Which one of the following is not a depositional feature of a glacier?
- cirque
- Moraine
- Drumlins
- Eskers
Ans: a) cirque
6. Deposits of fine silt blown by wind is called as ……………
- Loess
- Barchans
- Hamada
- Ripples
Ans: a) Loess
7. Stacks are formed by ……………
- Wave erosion
- River erosion
- Glacial erosion
- Wind deposition
Ans : a) Wave erosion
8. …………… erosion is responsible for the formation of cirque.
- wind
- glacial
- river
- underground water
Ans : b) glacial
9. Which one of the following is a second order land form?
- Asia
- Deccan Plateau
- Kulu Valley
- Marina Beach
Ans: b) Deccan Plateau
II. Match the following
| 1. Distributaries | glacial action |
| 2. Mushroom rock | action of sea wave |
| 3. Eskers | Lower course of river |
| 4. Stalactites | Aeolian process |
| 5. Cliff | karst topography |
| Ans: 1 – C, 2 – D, 3 – A, 4 – E, 5 – B | |
III. Answer the following Questions Briefly:
1. Define weathering.
- Weathering is the breaking disintegration and decomposition of materials of the Earth’s crust by their exposure to atmosphere.
- Weathering is affected and controlled by the factors such as temperature, rock structure, land slope and vegetation.
2. What do you mean by biological weathering?
- Weathering is the disintegration and decomposition of materials of the Earth’s crust by their exposure to atmosphere.
- Biological weathering occurs due to the penetration and expansion of plant roots, earthworms, burrowing animals (rabbits, rats, etc.,) and some human activities.
3. Mention the three courses of a river with any two land forms associated to each course.
The three courses of a river with any two land forms associated to each course are
| Courses of a river | Land forms |
| 1. Upper course | V Shaped Valleys and Waterfalls |
| 2. Middle course | Alluvial fans and Ox-bow lakes |
| 3. Lower course | Delta and Estuary |
4. What are ox-bow lakes?
- The rivers loaded with debris flows slowly and forms sweeping loops and bends. It is referred to as meanders.
- Meanders in due course of time become almost a complete circle with narrow necks. This in turn gets abandoned and forms a lake.
- This is called as Ox-bow Lake.
5. How does a cave differ from a sea arch?
- Caves are hollows that are formed by the dissolution of limestone rocks when carbon di oxide in air turns into carbonic acid after its reaction with water.
- But, two caves approach one another from either side of a headland and unite, they form an Arch.
6. List out any four karst topographical areas found in India.
Karst topographical areas found in India are-
- Guptadham caves in Western Bihar.
- Tapkeshwar temple in Uttarakhand.
- Pandav caves at Pachamri in Madhya Pradesh and
- Borra caves of Visakhapatnam in Andhra Pradesh.
7. What do you mean by a hanging valley?
- A valley is a low area between hills or mountains often with a river running through it.
- There valleys are eroded by tributary glacier and that hangs over the main valley.
8. Define: a) Moraine b) Drumlin c) Esker.
Moraine :
Landforms formed by the glacial deposits of valley or continental glaciers are termed as Moraines.
Drumlin :
The deposits of glacial moraines that resemble giant inverted teaspoons or half cut eggs are known as Drumlins.
Esker :
Long narrow ridges composed of boulders gravel and sand deposited by steams of melting water which run parallel to a glacier are called eskers.
9. Mention the various features formed by wind erosion.
- The air that blows horizontally at or near the Earth’s surface is called wind.
- The erosional, transportational and despositional action of wind is predominant in arid regions.
- Some of the erosional landforms of wind are Mushroom rocks, Inselbergs and Yardangs.
10. What are wave cut platforms?
- Flat surface found at the foot of sea cliffs are called as Wave cut platforms.
- Wave cut platform is also referred as beach, shelf, terrace and plain
IV. Distinguish between
1. Physical and chemical weathering.
| Physical Weathering | Chemical Weathering |
| 1. It is the breakdown of rocks without changing their chemical composition through the action of physical forces | Disintegration and decomposition of rocks due to chemical reactions is called Chemical weathering |
| 2. Heat and cool weather are the agents of physical weathering | The agents of chemical weathering are oxygen, carbon-dioxide and hydrogen. |
2. Delta and Estuary
| Delta | Estuary |
| 1. A triangular shaped low lying area formed by the river at its mouth is called delta | Estuary is formed where the rivers meets the sea |
| 2. Cauvery Delta in Tamil Nadu is an Example | River Narmada and Tapti are examples of Estuary |
3. Stalactite and stalagmite.
| Stalactite | stalagmite |
| 1. The water containing dissolved calcite gradually drips from the ceiling of the caves. Water evaporates and the remaining calcite hangs from the ceiling and form Stalactite | Here, when the calcite deposits rises upward like a pillar stalagmites are formed. |
| 2. Stalactites are formed in the ceiling of the caves | Stalagmites are formed on the floor of the caves. |
4. Longitudinal and Transverse sand dunes.
| Longitudinal Secondary waves | Transverse sand dunes |
| 1. Hard rocks like igneous rocks are more resistant to wind action. Such isolated residual hills rising abruptly from their surroundings are termed as inselbergs. | The rocks in arid regions have hard and soft layers arranged vertically. When wind blows over these rocks, the soft layers get eroded leaving irregular crests. These are called Yardings. |
| 2. Uluru or Ayers Rock, Australia is an example of Inselberg. | Example – Yardang located at Medow, Texas in the USA. |
5. Inselbergs and yardangs
| Inselbergs | yardangs |
| 1. Certain hard rock like igneous rocks are more resistant to wind action. | In arid regions, certain rocks have hard and soft layers arranged vertically. |
| 2. Such isolated residual hills rising abrupt by from their surroundings are truned inselbergs. | When winds blow over these rocks, the soft layers get eroded leaving irregular cerests. They are called Yardangs. |
6. Continental glaciers and Valley glaciers.
| Physical Weathering | Chemical Weathering |
| 1. Thick sheets of ice that covers vast areas of a continent is called Continental glacier | The glacier which takes its origin from a show covered mountain range is known as a Valley glacier |
| 2. These glaciers cover large swaths of land. | These glaciers are confined to mountains and don’t exceed the length of 100 km. |
| 3. These are far thicker and usually moves very little. | These glaciers are viewed as ‘rivers of ice’ far thinner. They move very fast. |
7. Spit and bar.
| Spit | bar |
| 1. A spit is a ridge or embankment of sediment, attached to the land on one end and terminating in open water on the other end. | A bar is an elongated deposit of sand, shingle or mud found in the sea, almost parallel to the shoreline |
| 2. Spit are common at the mouth of estuaries | Bar is found parallel to the shoreline |
V. Answer in Paragraph:
1. Write a note on weathering. Classify and explain.
Weathering is the disintegration and decomposition of materials of the earth’s crust by their
exposure to atmosphere. They are three types of weathering: Physical weathering, Chemical weathering and Biological weathering.
Physical weathering:
- It is the breakdown of rocks without changing their chemical composition, through the action of physical forces.
- The constant freezing and thawing of rocks during the night and day leads to the expansion and contraction of rocks.
- Exfoliation, block disintegration, granular disintegration, etc, are the different types of weathering.
Chemical weathering:
- Disintegration and decomposition of rocks due to chemical reactions is called Chemical weathering.
- The agents of Chemical weathering are Oxygen, Carbon-dioxide and Hydrogen.
- The Chemical weathering takes place through the process of oxidation, carbonation, solution and hydration.
Biological weathering:
- Biological weathering occurs due to the penetration and expansion of plant roots, earth worms, burrowing animals and some human activities.
2. Explain the erosional landforms formed by underground water.
The erosional landforms formed by underground water are
Terra Rossa:
- Deposition of red soil on the surface of the Earth is due to the dissolution of limestone content in rocks.
- The redness of the soil is due to the presence of iron oxide.
Lappies:
- When the joints of limestone rocks are corrugated (ridged) by groundwater, long furrows are formed and these are called Lappies.
Sinkhole:
- A funnal shaped depressions formed due to dissolution of limestone rock is called sinkholes.
Caves and Caverns:
- Caves are hollows that are formed by the dissolution of limestone rocks when Carban di oxide in air turns into carbonic acid after its reaction with water
- Caverns are the caves with irregular floors.
- All types of deposits in the caves and caverns are collectively called Speleothems.
3. What is a glacier? Explain its types.
A glacier is large mass of ice that moves slowly over the land form its place of accumulation. It is also known as ‘River of ice’. The place of accumulation is called snowfield. Glaciers are broadly divided into two types based on the place of occurrence such as Continental glacier and Valley glacier.
Continental glacier:
Thick sheets of ice that covers vast areas of a continent is called Continental glacier. These glaciers cover large swaths of land.
Valley glacier:
The glacier which takes its origin from a snow covered mountain range is known as a Valley
glacier.
4. Describe the depositional work of winds.
Deposition occurs when the speed of wind is reduced by the presence of obstacles like bushes, forests and rock structures. The sediments carried by wind get deposited on both the wind ward and leeward sides of these obstacles. Some of the depositional landforms are sand dunes, barchans and loess.
Sand dune:
In deserts, during sandstorms, wind carries loads of sand. When the speed of wind decreases, huge amount of sand gets deposited. These mounds or hills of sand are called sand dunes.
Barchan:
Barchans are isolated, crescent shaped sand dunes. They have gentle slopes on the windward side and steep slopes on the leeward side.
Transverse Dunes :
These are asymmetrical in shape. They are formed by alternate slow and fast winds that blow form the same direction.
Longitudinal Dunes :
These are long narrow ridges of sand, which extend in a direction paralled to the prevailing winds.
Loess:
The tem loess refers to the deposits of find silt and porous sand over a vast region.
5. Give a detailed account on the three orders of land forms.
- Landform is a natural feature of the solid surface of the Earth or other planetary body.
- Typical landforms include hills, mountains, plateaus, canyons, valleys as well as shoreline features such as bays, peninsulas, and seas.
- Land forms are grouped into three orders. They are first order land form, second order land form, and third order land form.
First order land form:
First order land forms are continents and oceans.
Second order land form:
Mountains, plateaus and plains in both continents and oceans are the Second order land forms.
Third order land form:
Third order land forms are called as Minor land forms. They are deltas, fjords, coasts, sand dunes, beaches, valleys, cirques, mushroom rocks and limestone caves.
VI. Consider the given statements and choose the right option given below
1. i) ‘I’ Shaped valley is an erosional feature of the river.
ii) ‘U’ Shaped valley is an erosional feature of the glacier.
iii) ‘V’ Shaped valley is an erosional feature of the glacier.
- i, ii & iii are right
- i & ii are right
- i & iii are right
- only I is right
Ans : b) i & ii are right
2. Statement I : Running water is an important agent of gradation.
Statement II : The work of the river depends on the slop of land on which if flows.
- Statement I is false II is true
- Statement I and II are false
- Statement I is true II is false
- Statement I and II are true
Ans: d) Statement I and II are true
3. Statement : Limestone regions have less underground water.
Reason : Water does not percolate through limestone.
- The statement is right reason is wrong.
- The statement is wrong Reason is right.
- The statement and reason are wrong.
- The statement and reason are right.
Ans: b) The statement is wrong Reason is right.
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