9th Std Social Science Term 1 Solution | Lesson.5 Lithosphere – I Endogenetic Processes

Lesson.5 Lithosphere – I Endogenetic Processes

Lesson.5 Lithosphere – I Endogenetic Processes

I. Choose the correct answer

1. …………… is the rigid outer layer of the Earth.

1. Core
2. Mantle
3. Crust
4. Inner core

Ans: c) Crust

2. …………… layer is made up of liquid iron.

1. Inner core
2. Outer core
3. Mantle
4. Crust

Ans: b) Outer core

3. Magma is found in the ……………

1. crust
2. mantle
3. Core
4. None of the above

Ans: b) mantle

4. Diastrophism is connected to ……………

1. Volcanism
2. Earthquakes
3. Tectonics
4. Fold/Fault

Ans: c) Tectonics

5. The movement of tectonic plates is induced by …………… energy.

1. Hydel
2. Thermal
3. Wave
4. Tidal

Ans: b) Thermal

6. In the ancient period, Gondwana land moved towards …………… direction.

1. North
2. South
3. East
4. West

Ans: a) North

7. Many million years ago , India was a part of the super continent ……………

1. Gondwana
2. Laurasia
3. Panthalasa
4. Pangea

Ans: a) Gondwana

8. The movement of plates that creates stress and tension in the rocks causing them to stretch and cracks result in ……………

1. Fold
2. Fault
3. Mountain
4. Earthquake

Ans: b) Fault

9. …………… refers to a bowl-shaped depression found at the top of the volcano.

1. Crater
2. Vent
3. Chamber
4. Volcanic cone

Ans: a) Crater

10. The point of origin of an Earthquake is called the ……………

1. Epicentre
2. Focus
3. Seismic wave
4. Magnitude

Ans: b) Focus

II. Match the following

1. i) Mt. Fuji is a dormant volcano.

ii) Mt. Kilimanjaro is a dormant volcano.

iii) Mt. Tanzania is a dormant volcano.

Which of the statement(s) is are true?

1. i is true
2. ii is true
3. iii is true
4. i, ii, iii are true

Ans: a) i is true

2. Statement : Magma gushes out when it finds vents.

Reason : Interior of the Earth contains compressed hot magma

Which of the statement(s) is are true?

1. Statements & reason are true
2. Statements is true, reason is false
3. Statement is false reason is true
4. Statement & reason are false

Ans: a) Statements & reason are true

3. Statement I : Mountain ranges are formed by the collision of tectonic plates.

Statement II : The movement of tectonic plates is due to the thermal energy from the mantle.

1. Statement I is false II is true
2. Statement I and II are false
3. Statement I is true II is false
4. Statement I and II are true

Ans: d) Statement I and II are true

IV. Answer the following in one or two sentences

1. Write a brief note on the various spheres of the Earth.

The Earth surface is a vast area which contains four spheres.

They are-

• Lithosphere – It is the solid outer part of the Earth.
• Atmosphere – It is a thin layer of gases that surrounds the Earth.
• Hydrosphere – It is the watery part of the Earth’s surface.
• Biosphere – This is the layer of the Earth where life exists.

2. Mention the layers of the interior of the Earth.

The structure of the Earth’s interior is divided into three layers namely the crust, the mantle and the core.

Crust

Crust is the outer layer of the Earth. It is also known as the ‘Skin of our Earth’. It is the solid and rigid layer.

Mantle

The interior part beneath the curst is called Mandle. The major elements of the Mantle are Silica (si) and Magnesium (Mg). So, this layer is also known SIMA.

Core

The Core is the innermost and hottest layer of the Earth. It is composed mainly of Nickel (Ni) and Iron(Fe). So, This layer is called as NIFE.

3. Define : Plate tectonics.

• Tectonic plates are huge slabs of rocks which float independently over the mantle.
• Collisions of these plates produce mountain ranges and other irregular surface features both on land and ocean floor.
• This phenomenon is called ‘Plate tectonics.

4. Write a note on Fold and Fault?

• Tectonic plates float independently over the mantle. Due to the lateral compressional forces, they are forced to move upwards and downwards. At that time, the sedimentary beds become bent or curved. This is called Fold.
• The movement of plates creates stress and tension in the rocks, causing them to stretch and crack. This is called ‘Fault’.

5. What is Tsunami?

• The word ‘Tsunami’ is a Japanese term meaning harbor waves.
• It is adopted to describe large seismically generated sea waves caused by Earthquakes and landslides.
• These waves travel at a great speed (more than 500 km per hour) and the length of 600 km.
• These waves reach to a height of more than 15 m near the sea shore.
• The waves are capable of causing destruction along the coastal areas.

6. What is a Volcano? Mention its major components.

A volcano is a vent an opening on the surface of the Earth crust through which hot solid, liquid and gaseous materials (magma) erupt out to the surface from the Earth’s interior.

Its major components are-

1. Magma chamber
2. Volcanic cone
3. Vents
4. Creater

7. What is an Earthquake and how it occurs?

A sudden movement of the earth’s crust caused by the release of stress accumulated along geologic faults or by volcanic activity is known as Earthquake.

It occurs mainly because of-

• The sudden vibration in the Earth’s crust which spreads outward in all the direction as waves from the source of disturbance.
• The time when rocks underneath the Earth surface push over each other or pull apart from one another.
• The time when the tectonic plates colliding with each other.

8. What are seismic waves and mention its types?

The Seismic waves are generated by the earthquakes. The nature, force and speed of these seismic waves depend on the nature of the medium through which it passes.

Its types are –

1. Primary waves or P-waves.
2. Secondary waves or S-waves and
3. Surface waves or L-waves.

9. Write about the Pacific Ring of fire.

• The Pacific Ring of Fire or Ring of Fire is an area where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean.
• The Ring of Fire contains more than 450 volcanoes and is home to over 75 percent of the world’s active and dormant volcanoes.
• Approximately 90 percent of the world’s earthquakes and 81 percent of the world’s largest earthquakes happen along the Ring of Fire.

V. Give Reasons for the following

1. SIAL floats over SIMA.

• Crust is the outer layer of the Earth. It is the skin of our Earth. The major elements of crust are Silica (Si) and Aluminum (Ai) and thus, it is termed as SIAL.
• The interior part beneath the crust is called Mandle. The major elements of the mantle are Silica (Si) and Magnesium (Mg).
• So, we say SIAL floats over SIMA.

2. Igneous rocks are also called Primary Rocks or Mother rocks.

• The interior of the Earth contains very hot molten material called ‘Magma’.
• When the magma reaches the Earth’s surface, it is referred to as ‘Lava’.
• The lava on the surface cools down and gets solidified as rocks called igneous rocks.
• All other rocks are directly or indirectly formed from igneous rocks.
• So Igneous rocks are called Primary rocks or Mother rocks.

VI. Distinguish between

1. Core and crust.

2. Epi centre and Hypo centre:

3. Divergent and convergent boundaries:

4. Primary waves and Secondary waves.

5. Shield volcano and volcanic Dome.

1. Describe the structure of the Earth.

The Crust:

• Crust is the outer layer of the Earth.
• It is also known as the skin of our Earth
• It is the slid and rigid layer of the Earth which is between 5 and 30 km.
• The crust is classified as Continental crust and Oceanic crust.
• The major elements of crust are Silica (Si) and Aluminium (Al). Thus, it is termed as SIAL.

The Mantle:

• The interior part beneath the Crust is called Mantel which is about 2900 km thick.
• The major elements of the mantle are Silica (Si) and Magnesium (Mg). Hence, it is also termed as SIMA.
• In the upper part of the mantle, the rock remains solid. In the lower part of mantle, rocks are in molten form.
• This molten rock inside the Earth is called ‘Magma’.

The Core:

• The core is the innermost and hottest layer of the Earth.
• It is composed mainly of Nickel (Ni) and Iron (Fe). Hence, it is called NIFE.
• The core divided into Solid inner core and Liquid outer core.
• The presence of large quantities of iron in the core is responsible for the Earth’s gravitational force.

2. Write a note on the internal and external processes of Earth.

The formation and deformation of landforms on the surface of the Earth is a continuous activity of two broad processes. These processes are referred as Geomorphic Processes. The two processes are: Internal processes, External processes.

Internal processes:

The forces that act from the Earth’s interior towards the surface of the Earth are called Internal Processes or Endogenetic Processes. These forces build the landscape and create topographic relief.

External processes:

The forces that act on the surface of the Earth due to natural agents like running water, glacier, wind, waves etc., are called External Processes or Exogenetic Processes. These external processes tear the landscape down into relatively low elevated plains.

3. How are volcanoes classified based on the periodicity of their eruptions?

Volcanoes are classified into three based on the periodicity of eruptions. They are-

1. Active Volcano
2. Dormant Volcano and
3. Extinct volcano.

Active Volcano:

• Active volcanoes are those which constantly eject volcanic lava, gases and fragmented materials.
• Volcano at Mount St. Helens in the USA is an example for Active Volcano.

Dormant Volcano:

• Volcanoes that do not show any sign of volcanic activity for a long period of time are known as dormant volcanoes.
• Sometimes, there may be a sudden explosion which may cause unimaginable loss to life and property.
• Example – Mt. Fuji in Japan.

Extinct Volcano:

• A volcano which stopped permanently its volcanic activity is known as Extinct Volcano.
• It is also called as Dead Volcano.
• Example: Mt Kilimanjaro, Tanzania and Tiruvannamalai, Tamil Nadu.

4. Explain the effects of Volcanoes.

The effects of volcanoes can be divided into Constructive effects and Destructive effects of volcano are given below.

Constructive effects:

• Volcanic materials enrich the soil fertility that promotes agricultural activities.
• The hot volcanic region helps in generating geothermal energy.
• Many active and dormant volcanoes are the most attractive tourist spots of the world.
• Most of the volcanic materials are used as building materials.

Destructive effects:

• Volcanic eruption causes Earthquakes, fast floods, mud slide and rock fall.
• Lava can travel very far and burn, bury or damage anything in its path.
• The large amount of dust and ash makes breaking hard and irritable.
• Volcanic eruptions can alter the weather conditions.
• It disrupts transport in and around the volcanic region.

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