Samacheer Kalvi Class 7 Social Science Solutions Term 1 Chapter 1 Interior of the Earth

I. Choose the correct answer:

 

Question 1. Nife is made up of ..........
(a) Nickel and ferrous
(b) Silica and aluminum
(c) Silica and magnesium
(d) Iron and magnesium
Answer: (a) Nickel and ferrous
In simple words: The core of the Earth has two main metals, Nickel and Iron (which is also called ferrous). That is why it is named Nife.

🎯 Exam Tip: Remember Nife stands for NI-ckel and FE-rrous (Iron) for the Earth's core composition.

 

Question 2. Earthquake and volcanic eruption occur near the edges of ..........
(a) Mountain
(b) Plains
(c) Plates
(d) Plateaus
Answer: (c) Plates
In simple words: Earthquakes and volcanoes happen a lot where the large tectonic plates of the Earth meet. These areas are usually unstable.

🎯 Exam Tip: Understanding plate tectonics helps explain why geological events like earthquakes and volcanoes happen at specific locations.

 

Question 3. The magnitude of an earthquake is measured by ..........
(a) Seismograph
(b) Richter scale
(c) Ammeter
(d) Rotameter
Answer: (b) Richter scale
In simple words: The Richter scale is used to find out how strong an earthquake is. A seismograph is the tool that records the ground shaking.

🎯 Exam Tip: Distinguish between the seismograph (the instrument) and the Richter scale (the measurement unit) when answering questions about earthquakes.

 

Question 4. The narrow pipe through which magma flow out is called a ..........
(a) Vent
(b) Crater
(c) Focus
(d) Caldera
Answer: (a) Vent
In simple words: When a volcano erupts, the hot melted rock, called magma, comes out through a narrow opening. This opening is called a vent.

🎯 Exam Tip: Remember that the vent is the passageway, while the crater is the basin-like opening at the top of the volcano.

 

Question 5. .......... Volcano is known as light house of Mediterranean Sea.
(a) Stromboli
(b) Krokota
(c) Fujiyana
(d) Kilinanjaro
Answer: (a) Stromboli
In simple words: Stromboli is a volcano that erupts regularly, making it look like a lighthouse guiding ships. It is a famous active volcano in Italy.

🎯 Exam Tip: Specific examples like Mount Stromboli often appear in general knowledge or geography questions. Learn its unique characteristic.

 

Question 6. .......... belt is known as the "Ring of Fire”.
(a) Circum – Pacific
(b) Mid – Atlantic
(c) Mid – Continental
(d) Antarctic
Answer: (a) Circum – Pacific
In simple words: The Pacific Ring of Fire is an area in the Pacific Ocean where many earthquakes and volcanic eruptions happen. This area is shaped like a horseshoe.

🎯 Exam Tip: The Pacific Ring of Fire is a key geographical term indicating a major zone of seismic and volcanic activity.

II. Fill in the blanks:

 

Question 1. The core is separated from the mantle by a boundary called.............
Answer: Weichart-Gutenberg discontinuity
In simple words: The line that divides the Earth's core from its mantle is called the Weichart-Gutenberg discontinuity. It helps us understand Earth's internal structure.

🎯 Exam Tip: Learn the names of the major discontinuities within the Earth, as they define boundaries between layers.

 

Question 2. The earthquake waves are recorded by an instrument known as ..........
Answer: Seismograph
In simple words: A seismograph is a special machine that detects and records the shaking caused by earthquakes. It helps scientists study how strong earthquakes are and where they come from.

🎯 Exam Tip: Remember the instrument (seismograph) that records the waves, not the scale (Richter scale) that measures the magnitude.

 

Question 3. Magma rises to the surface and spreads over a vast area is known as ..........
Answer: Lava
In simple words: Magma is melted rock found deep inside the Earth. When it comes out onto the surface, it is called lava. It cools down and forms new land.

🎯 Exam Tip: Distinguish between magma (inside the Earth) and lava (on the Earth's surface).

 

Question 4. An example for active volcano ..........
Answer: Mauna Loa in Hawaii / Mt. Stromboli / St. Helens / Pinatubo
In simple words: Active volcanoes are those that erupt often. Mauna Loa, Mt. Stromboli, St. Helens, and Pinatubo are all good examples of active volcanoes.

🎯 Exam Tip: Memorize at least two or three examples of active, dormant, and extinct volcanoes for quick recall.

 

Question 5. Seismology is the study of ..........
Answer: Earthquakes
In simple words: Seismology is the scientific study of earthquakes and how seismic waves travel through the Earth. This helps in predicting and understanding these natural events.

🎯 Exam Tip: Many 'ology' words refer to the study of something; 'seismology' specifically pertains to seismic activity and earthquakes.

III. Circle the odd one:

 

Question 1. crust, magma, core, mantle
Answer: magma
In simple words: The crust, core, and mantle are the three main layers that make up the Earth. Magma is the melted rock found inside the Earth, not a layer itself.

🎯 Exam Tip: Identify the category that most items belong to, and then find the one that doesn't fit the category.

 

Question 2. focus, epicenter, vent, seismic waves
Answer: vent
In simple words: Focus, epicenter, and seismic waves are all terms related to earthquakes. A vent, however, is an opening on a volcano where lava comes out.

🎯 Exam Tip: Group related terms mentally. If three items are about earthquakes and one is about volcanoes, the volcanic term is the odd one out.

 

Question 3. Uttar Kashi, Chamoli, Koyna, Krakatoa
Answer: Krakatoa
In simple words: Uttar Kashi, Chamoli, and Koyna are places in India known for earthquakes. Krakatoa is a famous volcano located in Indonesia.

🎯 Exam Tip: Knowledge of geographical locations and their associated natural disasters is crucial for such questions.

 

Question 4. lava, caldera, silica, crater
Answer: silica
In simple words: Lava, caldera, and crater are all features or outputs related to volcanoes. Silica is a mineral found in rocks, not a volcanic feature.

🎯 Exam Tip: Understand the basic vocabulary for both volcanoes and minerals to differentiate between them.

 

Question 5. Stromboli, Helens, Hawaii, Fujiyama
Answer: Hawaii
In simple words: Stromboli, St. Helens, and Fujiyama are all names of famous volcanoes. Hawaii is a state or island chain, not a single volcano itself, though it has volcanoes.

🎯 Exam Tip: Pay attention to whether the item is a specific volcano name or a general geographical area that might contain volcanoes.

IV. Match the following:

 

Question. Match the following:

Answer:
1. Earth quake - (c) Sudden movement
2. Sima - (d) Silica and magnesium
3. Pacific Ring of Fire - (e) World volcanoes
4. Tsunami - (a) Japanese term
5. Mt. Kenya - (b) Africa
In simple words: An earthquake is a sudden movement of the Earth. Sima is a layer made of silica and magnesium. The Pacific Ring of Fire is a zone with many volcanoes. A tsunami is a large sea wave, a Japanese word. Mount Kenya is a mountain in Africa.

🎯 Exam Tip: For match the following questions, draw lines or write down the correct pairs clearly to avoid confusion.

V. Consider the following statement and (✓) Tick the appropriate answer:

 

Question 1. Assertion (A) : There structure of the earth may be compared to that of an Apple.
Reason (R) : The interior of the earth consists of crust, mantle and core.
(a) A and R are correct and A explains R
(b) A and R are correct but A does not explain R
(c) A is incorrect but R is correct
(d) Both A and R are incorrect
Answer: (b) A and R are correct but A does not explain R
In simple words: The Earth's structure is like an apple with layers, and it does have a crust, mantle, and core. However, the reason given (about the layers) does not fully explain why it's compared to an apple's structure.

🎯 Exam Tip: In Assertion-Reason questions, first check if both statements are true. Then, check if the reason correctly explains the assertion.

 

Question 2. Assertion (A): The Pacific Ocean includes two thirds of the world's volcanoes.
Reason (R) : The boundary along the Eastern and Western coast areas of the Pacific Ocean is known as the Pacific Ring of Fire.
(a) A and R are correct and A explains R
(b) A and R are correct but A does not explain R
(c) A is incorrect but R is correct
(d) Both A and R are incorrect A
Answer: (a) A and R are correct and A explains R
In simple words: It is true that most of the world's volcanoes are found in the Pacific Ocean. This is because the edges of the Pacific Ocean form a special zone called the Pacific Ring of Fire, which explains why so many volcanoes are there.

🎯 Exam Tip: Look for a cause-and-effect relationship between the assertion and the reason. If the reason directly causes or explains the assertion, option (a) is often correct.

VI. Answer in a word:

 

Question 1. Name the outermost layer of the earth.
Answer: The crust
In simple words: The Earth's surface, where we live, is called the crust. It's the thinnest and outermost layer.

🎯 Exam Tip: Know the order of Earth's layers: crust, mantle, and core, from outermost to innermost.

 

Question 5. The radius of the earth is ..................kms.
(a) 6731
(b) 6421
(c) 6371
(d) 6571
Answer: (c) 6371
In simple words: The Earth has a rounded shape, and its middle part from the center to the outside edge measures about 6371 kilometers. This distance helps us understand the size of our planet.

🎯 Exam Tip: Remember specific values like the Earth's radius, as they are common knowledge questions in geography.

 

Question 6. The mantle forms ................... of the earth's volume
(a) 1%
(b) 15%
(c) 75%
(d) 84%
Answer: (d) 84%
In simple words: The mantle is the big middle layer of the Earth, and it makes up most of the Earth's total size. It is where most of the heat from the core is transferred.

🎯 Exam Tip: Knowing the relative proportions of the Earth's layers (crust, mantle, core) is key to understanding its structure.

 

Question 7. The crust forms .................. of the earth's volume
(a) 15%
(b) 1%
(c) 84%
(d) 54%
Answer: (b) 1%
In simple words: The Earth's crust is like a thin skin on the outside. It is the smallest part of the Earth's volume, even though it's where we live.

🎯 Exam Tip: Understand that while the crust is where life exists, it's a very tiny part of the Earth's overall structure.

 

Question 8. How many active volcanoes in the world?
(a) 500
(b) 600
(c) 700
(d) 800
Answer: (b) 600
In simple words: There are about 600 active volcanoes around the world. These are volcanoes that have erupted recently or could erupt again soon.

🎯 Exam Tip: Be aware of the approximate number of active volcanoes, as it highlights the dynamic nature of Earth's geology.

 

Question 9. How many major zones of volcanic activities in the world?
(a) one
(b) two
(c) three
(d) Four
Answer: (c) three
In simple words: Volcanoes are not found everywhere equally; they are mainly located in three big areas or belts around the world. These zones are usually at the edges of tectonic plates.

🎯 Exam Tip: Knowing the main volcanic zones helps explain why some areas have more eruptions than others.

 

Question 10. The upper part of the earth's crust
(a) SIMA
(b) core
(c) SIAL
(d) Mantle
Answer: (c) SIAL
In simple words: The top part of the Earth's outer layer, called the crust, is known as SIAL. This name comes from the main materials it's made of: Silica and Aluminium.

🎯 Exam Tip: Understand the composition of SIAL and SIMA to differentiate between the upper and lower crust layers.

 

II. Fill in the blanks:

 

1. The oceanic crust is composed mostly of .................. rocks.
Answer: dense
In simple words: The part of the Earth's crust under the oceans is made of heavy, packed rocks. This makes it different from the crust under land.

🎯 Exam Tip: Remember that oceanic crust is typically thinner and denser than continental crust, primarily composed of basalt.

 

2. The upper part of the crust consists of ....................rocks.
Answer: granite
In simple words: The top layer of the Earth's crust, especially under the continents, is mostly made of granite rock. Granite is a common type of igneous rock.

🎯 Exam Tip: Knowing that continental crust is largely granitic helps explain why it is less dense than oceanic crust.

 

3. The sial and the sima together form the earth...................
Answer: Crust
In simple words: The two parts, SIAL (Silica and Aluminium) and SIMA (Silica and Magnesium), make up the entire outer shell of the Earth. This outer shell is what we call the crust.

🎯 Exam Tip: Understand SIAL and SIMA as the components that define the Earth's crust and their respective compositions.

 

4. Mantle is separated from the crust by a boundary called...................
Answer: Mohorovicic discontinuity
In simple words: There is a clear line that separates the Earth's crust from the mantle below it. Scientists call this boundary the Mohorovicic discontinuity, or Moho for short.

🎯 Exam Tip: Discontinuities like the Moho are crucial for identifying distinct layers within the Earth based on seismic wave changes.

 

5. The core is also known as ....................
Answer: barysphere
In simple words: The very center of the Earth, which is called the core, has another scientific name. It is also known as the barysphere, meaning "heavy sphere."

🎯 Exam Tip: Learn alternative names for Earth's layers, as they might be used interchangeably in questions.

 

6. The outer core is rich in ....................
Answer: iron
In simple words: The outer part of the Earth's core is mostly made of melted iron. This liquid iron moves around and creates Earth's magnetic field.

🎯 Exam Tip: Recall that the outer core's liquid iron content is responsible for generating Earth's magnetic field.

 

7. The crust forms .................... of the earth's volume.
Answer: 1%
In simple words: The crust is like a very thin peel on an apple, making up only a tiny fraction of the Earth's total size. This shows how vast the inner layers are compared to the surface.

🎯 Exam Tip: Differentiate between the percentage of volume and mass when describing Earth's layers.

 

8. The movement of the Earth's lithospheric plates is termed as .................. movements.
Answer: tectonic
In simple words: The large, hard pieces of Earth's surface are always slowly moving. These movements are called tectonic movements, and they cause many changes on our planet.

🎯 Exam Tip: Understanding plate tectonics is fundamental to explaining earthquakes, volcanoes, and mountain formation.

 

9. A................... is formed between two plates.
Answer: trench
In simple words: When two of Earth's big plates push together and one slides under the other, it creates a very deep ditch in the ocean floor. This deep cut is called an oceanic trench.

🎯 Exam Tip: Recognize trenches as key features at convergent plate boundaries where subduction occurs.

 

10. The earthquake is measured by the .................... scale.
Answer: Richter
In simple words: We use a special scale called the Richter scale to tell how strong an earthquake is. The higher the number on this scale, the more powerful the earthquake.

🎯 Exam Tip: Know that the Richter scale measures the magnitude (energy released) of an earthquake, not its intensity (felt effects).

 

11. The earthquake is a .................... activity.
Answer: Volcanic
In simple words: Earthquakes can happen when volcanoes are active and magma moves underground. These are often smaller earthquakes related to the volcano's activity.

🎯 Exam Tip: Remember that volcanic activity is one of the causes of earthquakes, often leading to smaller, localized tremors.

 

12. Tsunami is a .................... term.
Answer: Japanese
In simple words: The word "Tsunami" comes from the Japanese language. It refers to the very large ocean waves caused by earthquakes under the sea.

🎯 Exam Tip: Understanding the origin of scientific terms can sometimes provide clues about the phenomenon itself.

 

13. On .................... A tsunami occured in Tamil Nadu.
Answer: 26th Dec 2004
In simple words: A very big tsunami hit Tamil Nadu and other parts of the Indian Ocean on December 26, 2004. This event caused a lot of damage and loss of life.

🎯 Exam Tip: Specific dates of major natural disasters are often important to remember for historical and geographical context.

 

14. The opening of the Volcano is usually .................... in form,
Answer: circular
In simple words: The hole at the top of a volcano, where lava and ash come out, is usually round. This circular opening is called a crater.

🎯 Exam Tip: Distinguish between a volcano's vent (the actual opening) and its crater (the basin-shaped depression).

 

15. The semi-molten state of interior earth is called...................
Answer: Magma
In simple words: Deep inside the Earth, where it is very hot, rocks melt into a thick, gooey liquid. This melted rock material is called magma, and it flows beneath the surface.

🎯 Exam Tip: Remember that molten rock is called magma when underground and lava when it erupts onto the surface.

 

III. Circle the odd one:

 

1. Active volcano, Dormant volcano, Extinct volcano, Cinder cone volcano
Answer: Cinder cone volcano
In simple words: Active, Dormant, and Extinct describe how often a volcano erupts. A Cinder cone volcano describes its shape or type. The Cinder cone volcano is the one that is different in this group.

🎯 Exam Tip: Classify volcanoes correctly based on their activity (active, dormant, extinct) versus their structural shape (cinder cone, shield, composite).

 

2. Stratosphere, Troposphere, Bary-sphere, Exosphere
Answer: Bary-sphere
In simple words: Stratosphere, Troposphere, and Exosphere are all layers of the Earth's atmosphere, which is the air around our planet. Bary-sphere is a layer deep inside the Earth (the core), so it is the odd one out.

🎯 Exam Tip: Pay close attention to the scientific terms and their contexts; some words sound similar but refer to different parts of Earth or its atmosphere.

 

3. Shield volcano, Cinder cone volcano, Composite volcano, Dormant volcano
Answer: Dormant volcano
In simple words: Shield, Cinder cone, and Composite describe the different shapes and types of volcanoes. Dormant describes a volcano that is sleeping and not erupting right now. So, Dormant volcano is the odd one because it talks about activity, not shape.

🎯 Exam Tip: Ensure you can distinguish volcano classifications based on morphology (shape) from those based on eruptive status (activity).

 

IV. Match the following:

 

1. Earth quake
2. Sima
3. Pacific Ring of Fire
4. Tsunami
5. Mt. Kenya
Answer:
1. Earth quake - (c) Sudden movement
2. Sima - (d) Silica and magnesium
3. Pacific Ring of Fire - (e) World volcanoes
4. Tsunami - (a) Japanese term
5. Mt. Kenya - (b) Africa
In simple words: Earthquakes are sudden shakes of the ground. Sima is made of silica and magnesium. The Pacific Ring of Fire is where many volcanoes are found. Tsunami is a Japanese word for huge sea waves. Mount Kenya is a mountain in Africa.

🎯 Exam Tip: For matching questions, connect each term with its most defining characteristic or location.

 

V. Consider the following statement and (√) Tick the appropriate answer:

 

Question 1. Assertion (A) : The structure of the earth may be compared to that of an Apple. Reason (R) : The interior of the earth consists of crust, mantle and core.
(a) A and R are correct and A explains R
(b) A and R are correct but A does not explain R
(c) A is incorrect but R is correct
(d) Both A and R are incorrect
Answer: (b) A and R are correct but A does not explain R
In simple words: Both the statement that Earth's structure is like an apple and the statement about its layers (crust, mantle, core) are true. However, the reason about the layers doesn't directly explain why it's like an apple. The apple comparison is about how it has distinct layers.

🎯 Exam Tip: In assertion-reason questions, first check if both statements are true individually, then evaluate if the reason directly explains the assertion.

 

Question 2. Assertion (A) : The Himalayan region and the Ganga Brahmaputra valley are prone to earthquakes. Reason (R) : A number of earthquakes have been experiencing in Brahmaputra valley,
(a) A and R are correct and A explains R
(b) A and R are correct but A does not explain R
(c) A is incorrect but R is correct
(d) Both A and R are incorrect
Answer: (a) A and R are correct and A explains R
In simple words: The Himalayan area and the Ganga Brahmaputra valley often experience earthquakes. This is true because many earthquakes have indeed happened in the Brahmaputra valley. So, the reason clearly explains why this area is prone to earthquakes.

🎯 Exam Tip: When evaluating geographical statements, look for evidence of activity (like frequent earthquakes) that supports the assertion of proneness to such events.

 

VI. Answer in a word:

 

Question 1. What is the three concentric layers of the earth?
Answer:
The crust
The mantle
The core
In simple words: Our Earth is like an onion with three main layers, one inside the other. These layers are called the crust, the mantle, and the core.

🎯 Exam Tip: Listing the Earth's layers in order from outside to inside is often expected in questions about its structure.

 

Question 2. What are the causes of the Earthquake?
Answer:
The main cause of earthquakes is the sudden movement of the Earth's crust along cracks or faults.
Also, the shifting of large landmasses can cause big ground movements.
Volcanic activity can also lead to smaller earthquakes.
In simple words: Earthquakes happen when big pieces of Earth's skin (crust) suddenly slip past each other. They can also be caused by large land shifts or by volcanoes erupting.

🎯 Exam Tip: Focus on plate tectonics and fault lines as the primary causes of earthquakes, and remember volcanic activity as a secondary cause.

 

Question 3. What are the types of earthquake waves?
Answer: There are three main kinds of earthquake waves:
1. P waves or longitudinal waves
2. S waves or transverse waves
3. L waves or surface waves
In simple words: When an earthquake happens, it sends out three different types of shaking waves. These are P waves (which move like a spring), S waves (which shake side-to-side), and L waves (which travel along the surface).

🎯 Exam Tip: Understand the characteristics and relative speeds of P, S, and L waves, as they are used to locate earthquake epicenters.

 

Question 4. What is Magma?
Answer: Magma is molten rock material found deep inside the Earth. It is mixed with gases.
In simple words: Magma is very hot, melted rock that is still inside the Earth. It also has gases trapped in it.

🎯 Exam Tip: Clearly differentiate between magma (underground) and lava (on the surface) when describing molten rock.

 

Question 5. What is a caldera?
Answer: A caldera is a very large, basin-shaped hollow at the top of a volcano. These are formed when strong explosions blow away the entire top part of big cones.
In simple words: A caldera is a huge, bowl-shaped dip on top of an old volcano. It forms after a very powerful eruption causes the volcano's top to collapse inwards.

🎯 Exam Tip: Understand that a caldera is much larger than a typical volcanic crater and results from a catastrophic collapse rather than a simple eruption opening.

 

VII. Answer the following briefly:

 

Question 1. What is the crust?
Answer:
The crust is the Earth's outermost layer.
It is about 35 km thick on land (continental masses) and about 5 km thick under the oceans (oceanic floors).
The crust has two parts: the upper part called SIAL and the lower part called SIMA. SIAL is lighter than SIMA.
In simple words: The crust is the thin outer skin of the Earth where we live. It's thicker under land and thinner under the sea, and it's made of two main parts: SIAL on top and SIMA below.

🎯 Exam Tip: When defining the crust, include its location, average thickness, and the two major compositional layers (SIAL and SIMA).

 

Question 2. What is tectonic Movement?
Answer:
The large, rigid pieces of Earth's surface, called lithospheric plates (both continental and oceanic), constantly move over the semi-fluid layer known as the asthenosphere.
This slow, continuous movement is known as tectonic movement. These movements reshape Earth's surface over long periods.
In simple words: Tectonic movement is the slow sliding of Earth's big, hard plates on top of a softer layer underneath. This movement causes things like earthquakes and mountains.

🎯 Exam Tip: Explain tectonic movement by mentioning the lithospheric plates, the asthenosphere, and the resulting geological activity.

 

Question 3. What is Asthenosphere?
Answer: The Asthenosphere is a part of the Earth's mantle that is very hot and flows slowly like thick syrup. It is this soft, moving layer that allows the tectonic plates above it to shift and slide.
In simple words: The Asthenosphere is a soft, flowing layer deep inside the Earth's middle part (mantle). It helps the big plates on Earth's surface move around.

🎯 Exam Tip: Emphasize the semi-fluid nature of the asthenosphere, which is crucial for plate movement.

 

Question 4. How the earthquake can be recorded?
Answer:
Earthquake waves are recorded by a machine called a seismograph, and their strength is measured using the Richter Scale.
An earthquake of 2.0 or less on the Richter Scale is usually very small.
Over 5.0 on the Richter Scale can cause damage, like things falling down.
Above 6.0 on the Richter Scale is considered very strong, and 7.0 or more is a major earthquake.
In simple words: We use a special machine called a seismograph to record earthquake shakes. The Richter Scale then gives us a number to say how strong the earthquake was, from small shakes to very big ones that cause damage.

🎯 Exam Tip: Remember both the instrument (seismograph) for detection and the scale (Richter) for measuring magnitude when explaining earthquake recording.

 

Question 5. Give a note on Tsunami 2004
Answer:
On December 26, 2004, a powerful tsunami struck many coastal areas around the Indian Ocean, including Indonesia, India, Sri Lanka, and Thailand.
This event caused huge loss of life and property in all the affected coastal regions. It was one of the deadliest natural disasters in recorded history.
In simple words: A giant sea wave, called a tsunami, hit many countries around the Indian Ocean on December 26, 2004. It caused a lot of harm to people and buildings near the sea.

🎯 Exam Tip: Include the date, affected regions, and the significant impact (loss of life/property) when describing major natural disasters like the 2004 Tsunami.

 

Question 6. What is a Tsunami?
Answer:
A tsunami is a huge ocean wave caused by an earthquake or other disturbance under the sea. The word "Tsunami" is a Japanese term.
These large waves are quite common along the coasts of Japan and other areas in the Pacific Ocean, which is known for its frequent seismic activity.
In simple words: A tsunami is a very big wave in the ocean that happens because of an earthquake under the water. The word comes from Japan, where these waves often hit the coast.

🎯 Exam Tip: Define tsunami by its cause (undersea earthquake), its nature (huge wave), and mention its etymology and common locations.

 

Question 7. Write a note on Barren Island.
Answer:
Barren Island is located in the Andaman Sea, about 138 km northeast of the capital of the territory.
It is the only active volcano from Sumatra to Myanmar, meaning it is the only one in that large region that has erupted in recent times. Its last eruption was in 2017.
In simple words: Barren Island is an island in the Andaman Sea that has the only active volcano in a big area, stretching from Sumatra to Myanmar. It last erupted in 2017.

🎯 Exam Tip: Note the unique characteristic of Barren Island (only active volcano in a large region) and its geographical location.

 

X. Answer the following questions in detail:

 

Question 1. Explain the divisions of Earth Movements?
Answer: The movement of the Earth's lithospheric plates creates changes and forces on the Earth's surface. These movements are divided into two main types:
1. Endogenic forces
2. Exogenic forces

Endogenic forces:
These are the forces that work from deep inside the Earth. They cause things like earthquakes and volcanoes, which build up landforms.
Exogenic forces:
These are the forces that work on the Earth's surface. They cause things like erosion and weathering, which wear down landforms.
In simple words: Earth's surface moves due to two types of forces: Endogenic forces come from inside the Earth and create features like mountains and volcanoes. Exogenic forces come from outside (like wind and water) and break down these features.

🎯 Exam Tip: Clearly define and provide examples for both endogenic (internal, constructive) and exogenic (external, destructive) forces to score well.

 

Question 2. What are the causes of Volcanic Activity?
Answer: Volcanic activity is caused by several factors:
The temperature deep inside the Earth increases rapidly, by about 10°C for every 35 meters, due to pressure.
Because of this intense heat and pressure, the Earth's interior is in a semi-molten state, called magma.
This magma is under great pressure and contains dissolved gases that make it buoyant.
This pressure and the gases cause the volcanic material to burst through weak spots in the Earth's crust.
In simple words: Volcanoes erupt because it's super hot and pressurized inside the Earth, melting rocks into magma. This magma, full of gases, pushes up through weak spots in the Earth's surface, causing an eruption.

🎯 Exam Tip: Focus on the role of heat, pressure, magma formation, and the release of gases through crustal weaknesses as primary causes of volcanism.

 

Question 3. Describe the distribution of Earthquakes and Volcanoes in the world.
Answer:
Distribution of Earthquakes:
1. About 68% of earthquakes happen in the Pacific Ring of Fire. Another 31% of earthquakes occur in the Mediterranean-Himalayan belt and Asia Minor.
2. The remaining percentage of earthquakes are found in Northern Africa and Rift Valley areas, as well as the Ganga-Brahmaputra Valley.

Distribution of Volcanoes:
1. Volcanoes are found in areas where the Earth's crust is intensely folded or faulted, typically along plate boundaries.
2. There are around 600 active volcanoes and thousands of dormant and extinct ones across the globe.
3. They appear along coastal mountain ranges, offshore islands, and in the middle of oceans.
4. The main volcanic belts in the world are also the principal earthquake belts, showing a strong connection between the two phenomena.
In simple words: Most earthquakes happen in two main areas: the Pacific Ring of Fire and the Mediterranean-Himalayan belt. Volcanoes are also found in these same areas, especially where Earth's plates meet, forming mountain ranges and islands. This means that places with many volcanoes also tend to have many earthquakes.

🎯 Exam Tip: Highlight the correlation between earthquake and volcano distribution, emphasizing their occurrence along plate boundaries like the Pacific Ring of Fire and specific continental belts.