RBSE Solutions Class 11 Physical Geography Chapter 7 Earthquakes and Volcanoes

Rajasthan Board RBSE Class 11 Physical Geography Chapter 7 Earthquakes and Volcanoes

RBSE Class 11 Physical Geography Chapter 7 Text Book Questions

RBSE Class 11 Physical Geography Chapter 7 Multiple Choice Questions

 

Question 1. In which category can Etna volcano of Italy be placed?
(a) Active
(b) Extinct
(c) Dead
(d) Dormant
Answer: (a) Active
In simple words: Mount Etna, a volcano in Italy, is considered an active volcano because it erupts regularly.

🎯 Exam Tip: Remember the classification of volcanoes into active, dormant, and extinct types and associate key examples with each.

 

Question 2. In which category do we keep Vesuvius volcano of Italy?
(a) Active
(b) Extinct
(c) Dead
(d) Dormant
Answer: (d) Dormant
In simple words: Mount Vesuvius is a dormant volcano because it has erupted in the past and could erupt again, but it is currently quiet.

🎯 Exam Tip: Distinguish between active (frequent eruptions), dormant (inactive but potential for future eruptions), and extinct (no future eruptions expected) volcanoes.

 

Question 3. Mount Popa volcano of Myanmar is which of the following types?
(a) Active
(b) Extinct
(c) Dead
(d) Dormant
Answer: (b) Extinct
In simple words: Mount Popa in Myanmar is an extinct volcano, meaning it is not expected to erupt again.

🎯 Exam Tip: Know examples of each volcano type (active, dormant, extinct) from around the world.

 

Question 4. Those volcanoes which emit from one vent can be kept under which category of earthquakes?
(a) Rift eruption
(b) Central eruption
(c) Dead
(d) Dormant
Answer: (b) Central eruption
In simple words: Volcanoes that erupt from a single opening are called central eruption volcanoes.

🎯 Exam Tip: Understand the two main types of volcanic eruptions: central and fissure, and their characteristics.

 

Question 5. In India, "The Deccan Plateau” is formed by which type of volcanic eruption?
(a) Fissure eruption
(b) Central eruption
(c) Dead
(d) Dormant
Answer: (a) Fissure eruption
In simple words: The Deccan Plateau in India was formed by lava flowing out from long cracks in the earth, which is known as fissure eruption.

🎯 Exam Tip: Associate fissure eruptions with the formation of large basaltic plateaus, like the Deccan Traps.

RBSE Class 11 Physical Geography Chapter 7 Very Short Answer Type Questions

 

Question 1. Write the definition of earthquake.
Answer: An earthquake is a sudden, violent shaking of the ground. This shaking is typically caused by forces within the Earth's crust and can lead to major destruction.
In simple words: An earthquake is when the ground suddenly shakes very strongly, often causing damage.

🎯 Exam Tip: Define earthquake clearly by mentioning sudden ground shaking and its typical cause (internal earth forces).

 

Question 3. What are Secondary Waves?
Answer: Secondary waves, also known as S-waves, are a type of seismic wave. These waves arrive at the Earth's surface after the primary waves. This is why they are called secondary waves. They cause particles to move perpendicular to the wave direction.
In simple words: S-waves are earthquake waves that come second and shake things sideways.

🎯 Exam Tip: Remember that S-waves are secondary, travel slower than P-waves, and cause sideways motion.

 

Question 4. Write the names of two active volcanoes.
Answer: Two well-known active volcanoes are Etna and Stromboli. These volcanoes are famous for their continuous or frequent eruptions.
In simple words: Etna and Stromboli are two volcanoes that erupt often.

🎯 Exam Tip: Keep in mind prominent examples of active volcanoes for quick recall.

 

Question 5. Write the names of two extinct volcanoes.
Answer: Two examples of extinct volcanoes are Mount Popa in Myanmar and Koh-E-Sultan in Iran. These volcanoes have not erupted for a very long time and are not expected to erupt again.
In simple words: Mount Popa and Koh-E-Sultan are two volcanoes that are no longer active and won't erupt again.

🎯 Exam Tip: Identify key examples of extinct volcanoes to distinguish them from active or dormant ones.

RBSE Class 11 Physical Geography Chapter 7 Short Answer Type Questions

 

Question 1. Explain the Elastic Rebound Theory.
Answer: Professor F. S. Reid proposed the Elastic Rebound Theory to explain seismic faults. This theory states that rocks are elastic, like rubber, and can stretch when stressed. They stretch up to a certain point, then break. When the rocks break, the broken parts quickly spring back to their original positions. This sudden release of energy and movement causes earthquakes, as the rocks expand and contract.
In simple words: Rocks can bend like rubber. When they bend too much and break, they snap back to shape, causing an earthquake.

🎯 Exam Tip: When explaining the Elastic Rebound Theory, focus on the elasticity of rocks, their breaking point, and the sudden rebound as the cause of earthquakes.

 

Question 3. How do earthquakes occur due to water load? Explain.
Answer: When a large amount of water collects on the Earth's surface, like in huge reservoirs behind dams, it puts immense load and pressure on the rocks beneath. This excessive weight can cause the rocks to change rapidly. If this change happens suddenly, it can trigger an earthquake. For example, the Koyna earthquake in Maharashtra is believed to have been caused by the pressure from the Koyna Dam's reservoir. The added weight of water makes the Earth's crust rearrange itself, leading to tremors.
In simple words: Big reservoirs with lots of water push down on the ground. This heavy load can make the ground shift suddenly, causing an earthquake, like at the Koyna Dam.

🎯 Exam Tip: When discussing water load as a cause of earthquakes, highlight the role of large reservoirs and the pressure they exert on the Earth's crust.

 

Question 4. Explain the types of volcanoes.
Answer: Volcanoes differ in how they erupt and how often. Some explode violently, while others erupt quietly. Some become calm quickly, while others stay active for longer. Some volcanoes are quiet for a while and then erupt again. Based on these differences, volcanoes are mainly classified in two ways:
1. On the basis of their eruption period.
2. On the basis of their eruption nature.
In simple words: Volcanoes are grouped by how often they erupt (like active or dormant) and what kind of eruption they have (like explosive or quiet).

🎯 Exam Tip: Remember the two main classification bases for volcanoes: period of eruption and nature of eruption.

 

Question 5. Give examples of active volcanoes.
Answer: Active volcanoes are those that continuously erupt lava, gases, and other materials. There are about 500 such volcanoes worldwide. Major examples include Mount Etna and Stromboli in Italy. Pinatubo in the Philippines is also another notable active volcano. These volcanoes show ongoing activity.
In simple words: Active volcanoes erupt all the time, like Etna and Stromboli in Italy, and Pinatubo.

🎯 Exam Tip: Be ready to name famous active volcanoes as examples to illustrate the concept.

RBSE Class 11 Physical Geography Chapter 7 Essay Type Questions

 

Question 1. State the reasons for the origin of earthquake and describe the types of seismic waves.
Answer: Earthquakes are natural disasters with several causes:
1. Faulting
2. Vulcanicity
3. Water load
4. Contraction of the crust
5. Isostatic Adjustments
6. Elastic Rebound Theory
7. Plate tectonics
8. Human activity (e.g., nuclear explosions, deep mining).

Description of Seismic Waves:
Seismic waves are recorded using a seismograph. Here's a description of these waves:
2. S - Waves: These are known as secondary waves. They reach the Earth's surface after the primary waves, traveling at about 5 km per second. S-waves cause rocks to vibrate at right angles to the wave's direction. Their nature is similar to tidal or light waves, and they fade out when they reach oceanic regions.
3. L - Waves: These are also known as surface waves and travel the longest distance. They spread all around on the surface from the earthquake's epicenter, which is why they are called long waves. L-waves travel at about 3 km per second and cause the most destruction in earthquake-affected areas. They are the last to reach the surface, die out in greater depths, and can pass through water. On a seismograph, they are shown by the symbol 'L'.

This image shows seismic focus and epicenter:

This image illustrates P and S waves motion of particles:

Distribution of Earthquakes in the World:
Most earthquakes worldwide happen in newly folded mountains, volcanic areas, and coastal regions where the ground is unstable. Earthquake distribution is found in the following belts:
1. Circum - Pacific Belt: This is the longest earthquake belt, accounting for about two-thirds (63%) of all global earthquakes. It forms a circle around the Pacific Ocean, extending through islands and continents. This belt has major earthquake conditions, including the joining of ocean and land, folded mountain ranges, destructive volcanic plates, and areas where plates move apart. Western coastal regions of North and South America, and regions from Kamchatka in Asia to islands like Kuril, Japan, Taiwan, and the Philippines are part of this belt.
2. Mid - Continental Belt: Also known as the Mediterranean belt, this region experiences about 21% of the world's earthquakes. Earthquakes here result from geological faults and balancing activities. It includes areas from Portugal to the Himalayas, Tibet, and southeastern island groups. India's earthquake-prone regions also fall within this belt, along with Italy, China, Asia Minor, Hindukush, Himalayas, Alps, and Myanmar.
3. Mid - Atlantic Ridge Belt: This belt lies along the Mid-Atlantic Ridge, extending from the western islands of the Atlantic Ocean. A branch of this belt reaches from the Nile Valley to the Great Rift Valley in Africa.
In simple words: Earthquakes happen because of many things like fault lines, volcanoes, water pressure, and human actions. There are also different types of seismic waves: S-waves (secondary, sideways motion) and L-waves (surface, most destructive). Most earthquakes happen in three main areas: around the Pacific Ocean, across continents through the Mediterranean and Himalayas, and along the Mid-Atlantic Ridge.

🎯 Exam Tip: When explaining earthquake causes, list and briefly describe the main geological processes. For seismic waves, focus on their type, speed, and motion. For distribution, name the major belts and their characteristics.

 

Question 3. Mention the causes for occurrence of volcanic eruptions and classify them.
Answer: Causes of volcanoes:
Many factors contribute to volcanic eruptions. The main factors include:
1. Unbalance: Shifts in the Earth's crust lead to imbalances.
2. Evolution of gases: Gases trapped beneath the surface play a crucial role.
3. Increase in temperature of the crust: Higher temperatures melt rocks, forming magma.
4. Decrease in pressure: A reduction in pressure allows magma to rise.
5. Plate tectonics: Movements of tectonic plates cause magma to emerge.

Classification of Volcanoes:
Volcanoes are primarily classified based on two main factors:
1. On the basis of period of eruption
2. On the basis of nature of eruption

1. Types of volcanoes on the basis of their period of eruption:
Based on how often they erupt, volcanoes are further classified into:
(a) Active or Awake Volcanoes: These volcanoes erupt very frequently. Examples include Etna and Stromboli in Italy.
(b) Dormant Volcanoes: These volcanoes remain inactive for some time but can erupt again. Mount Vesuvius is an example.
(c) Extinct or Dead Volcanoes: These volcanoes have not erupted for a very long time, and their craters are often filled with water. They are not expected to erupt again. Examples include Mount Popa and Koh-i-Sultan.

2. Types of volcanoes on the basis of their nature of eruption:
Volcanoes are also classified by how they erupt:
• Volcanoes with central eruption: These erupt from a single opening (vent). They are further classified into:
1. Hawaiian types of volcanoes: These have less explosive activity and erupt quietly. The lava is thin. Examples are found in the Hawaiian Islands.
2. Strombolian types of volcanoes: These erupt lava fiercely, and sometimes the eruption is explosive. The lava is thick. Stromboli volcano is an example.
3. Volcanian types of volcanoes: These volcanoes erupt with intense explosions and great force. This eruption type is named after Vulcano island.
4. Pelean types of volcanoes: These are the most destructive volcanoes, erupting with extreme violence and causing massive destruction. Pelee volcano in the Martinique Islands is an example.
• Volcanoes with Fissure Eruption: In this type, lava erupts quietly from long cracks (fissures) in the Earth's surface, without any explosion. The lava is usually thin, forming large lava plateaus. The Colombian Plateau and India's Deccan Plateau are examples of areas formed by fissure eruptions.
In simple words: Volcanoes erupt because of things like imbalances in the Earth, gas buildup, temperature changes, pressure drops, and moving tectonic plates. They are grouped by how often they erupt (active, dormant, extinct) and by how they erupt (from a central vent or long cracks, like Hawaiian or Strombolian types).

🎯 Exam Tip: To answer this question fully, first list the main causes of vulcanicity. Then, clearly outline the two primary classification bases for volcanoes and describe each sub-type with an example.

RBSE Class 11 Physical Geography Chapter 7 Other Important Questions

RBSE Class 11 Physical Geography Chapter 7 Multiple Choice Questions

 

Question 1. Cause of earthquake which struck Koyna in Maharashtra was-
(a) Faulting
(b) Water load
(c) Contraction of the crust
(d) Plate tectonics
Answer: (b) Water load
In simple words: The earthquake at Koyna was caused by the heavy weight of water in the dam's reservoir.

🎯 Exam Tip: Remember specific examples like the Koyna earthquake linked to water load to illustrate causes.

 

Question 2. Who propounded the Elastic Rebound Theory?
(a) Prof. F. S. Reid
(b) Morgan
(c) Jeffries
(d) Wegener
Answer: (a) Prof. F. S. Reid
In simple words: Professor F. S. Reid was the one who explained the Elastic Rebound Theory.

🎯 Exam Tip: Associate key theories with their original proponents for higher scores.

 

Question 3. Which type of waves are primary seismic waves?
(a) Compression
(b) Transverse
(c) Shear
(d) Surface
Answer: (a) Compression
In simple words: Primary seismic waves, or P-waves, move through the ground by compressing and expanding it, like a spring.

🎯 Exam Tip: Recall that P-waves are compressional waves, meaning they push and pull material in the direction of wave travel.

 

Question 4. What are primary waves?
(a) P waves
(b) S waves
(c) L waves
(d) Gama Waves
Answer: (a) P waves
In simple words: P waves are the primary waves, the first type of seismic waves to arrive.

🎯 Exam Tip: Clearly identify P waves as primary waves and the first ones to be detected after an earthquake.

 

Question 5. Which waves cause the most destruction?
(a) P waves
(b) S waves
(c) L waves
(d) Alfa Waves
Answer: (c) L waves
In simple words: L waves, which travel along the Earth's surface, are known to cause the most damage during an earthquake.

🎯 Exam Tip: Remember that L-waves, or surface waves, are responsible for the greatest destruction due to their complex motion and travel path.

 

Question 6. Tsunami is a word from which language?
(a) French
(b) Arabian
(c) Hindi
(d) Japanese
Answer: (d) Japanese
In simple words: The word 'Tsunami' comes from the Japanese language.

🎯 Exam Tip: Know the origin of key geological terms like "Tsunami".

 

Question 7. Which belt experiences the most earthquakes?
(a) Mid - Continental Belt
(b) Mid - Atlantic Belt
(c) Circum - Pacific Belt
(d) Himalayan Belt
Answer: (c) Circum - Pacific Belt
In simple words: The Circum-Pacific Belt, also known as the "Ring of Fire," experiences the majority of the world's earthquakes.

🎯 Exam Tip: Identify the Circum-Pacific Belt as the most seismically active region globally due to its plate boundaries.

Matching Type Questions

 

Question A. Match Column A with Column B in the following:

Answer:
1. (c) Faulting is associated with Rift valleys.
2. (a) Vulcanicity (volcanic activity) is associated with Krakatoa.
3. (d) Water load is associated with Koyna.
4. (e) Isostasy (earth's crust balance) is associated with the Himalayan region.
5. (b) Nuclear explosion is linked to Human reasons for earthquakes.
In simple words: Match the earthquake cause from Column A to its related region or reason in Column B.

🎯 Exam Tip: For matching questions, connect each cause of earthquake to its most relevant geographical example or type of origin.

RBSE Class 11 Physical Geography Chapter 7 Very Short Answer Type Questions

 

Question 1. What are endogenetic forces?
Answer: Forces that originate and act beneath the Earth's surface are known as endogenetic forces. These forces are responsible for major landform changes.
In simple words: Endogenetic forces are powers that come from inside the Earth.

🎯 Exam Tip: Define endogenetic forces by their origin (inside the Earth) and impact (shaping landforms).

 

Question 2. What are exogenetic forces?
Answer: Forces that originate on or above the Earth's surface are known as exogenetic forces. These forces typically wear down or change landforms.
In simple words: Exogenetic forces are powers that come from outside or on the Earth's surface.

🎯 Exam Tip: Differentiate exogenetic forces from endogenetic forces by their origin (outside/on the Earth) and their role in erosion/weathering.

 

Question 3. What is the definition of earthquake according to Monk house?
Answer: According to Monk house, an earthquake is "The transmission of elastic shock waves outwards in all directions due to the contraction and adjustment activity in the Earth's crust structure." This definition highlights the wave-like spread of energy.
In simple words: Monk house said an earthquake is when shock waves spread out from the Earth's crust because it shrinks and moves.

🎯 Exam Tip: Quote definitions accurately, focusing on keywords like "elastic shock waves" and "contraction and adjustment."

 

Question 5. What is meant by ocean deposits?
Answer: Ocean deposits are sediments that settle at the bottom of the sea. These deposits can come from various sources, including living organisms (biotic), non-living materials (abiotic), land, ocean floor, or even space (cosmic).
In simple words: Ocean deposits are all the stuff that settles on the bottom of the sea, like sand, mud, and remains of sea life.

🎯 Exam Tip: List the different types of sources for ocean deposits to provide a complete answer.

 

Question 6. What is Seismic Focus?
Answer: The seismic focus refers to the specific point within the Earth's crust where an earthquake actually originates. This is the starting point of the rupture.
In simple words: Seismic focus is the exact place deep inside the Earth where an earthquake starts.

🎯 Exam Tip: Clearly define the seismic focus as the point of origin within the Earth's crust, not on the surface.

 

Question 7. What is Epicenter?
Answer: The epicenter is the central point on the Earth's surface located directly above the seismic focus. It is the place where seismic waves are first felt and often cause the most intense shaking.
In simple words: The epicenter is the spot on the Earth's surface directly above where an earthquake starts underground.

🎯 Exam Tip: Distinguish the epicenter (on the surface) from the focus (below the surface) and explain its significance.

 

Question 8. What are Seismic Waves?
Answer: Seismic waves are the waves of energy generated when a sudden release of energy occurs at the seismic focus, causing the rocks to shake. These waves then travel through the Earth.
In simple words: Seismic waves are the shaking movements that travel through the Earth when an earthquake happens.

🎯 Exam Tip: Define seismic waves as energy waves produced by the shaking of rocks at the focus during an earthquake.

 

Question 10. What is the speed of Primary Waves?
Answer: Primary waves, also known as P-waves, typically travel at a speed of 8 to 10 km per second. They are the fastest seismic waves.
In simple words: Primary waves move very fast, about 8 to 10 kilometers every second.

🎯 Exam Tip: Remember the typical speed range of P-waves and their characteristic as the fastest seismic waves.

 

Question 11. What are land waves?
Answer: Land waves are also known as L-waves, or surface waves. They travel the longest distance on the Earth's surface and are responsible for significant destruction.
In simple words: Land waves are surface waves that travel far and cause a lot of damage.

🎯 Exam Tip: Connect "land waves" with L-waves or surface waves and their role in causing damage.

 

Question 13. Into how many types have natural earthquakes been classified?
Answer: Natural earthquakes are grouped by how they start. They are classified into volcanic earthquakes, tectonic earthquakes, isostatic earthquakes, and plutonic earthquakes.
In simple words: Earthquakes that happen naturally are sorted into four main types based on their cause: volcanic, tectonic, isostatic, and plutonic.

🎯 Exam Tip: Remember the four main types of natural earthquakes and what makes each one distinct.

 

Question 14. What is meant by tectonic earthquakes?
Answer: Tectonic earthquakes are earthquakes that happen because of the movement of tectonic plates. These movements create stress and compression in the Earth's crust, leading to the shaking.
In simple words: Tectonic earthquakes happen when the Earth's plates move, causing stress and shaking in the ground.

🎯 Exam Tip: Key phrases like "tectonic movements" and "stress and compression in the crust" are important for defining tectonic earthquakes.

 

Question 15. What is the meaning of plutonic earthquakes?
Answer: Plutonic earthquakes are those that start deep inside the Earth, much farther below the surface than other types. There is not much information known about how they start or how strong they are.
In simple words: Plutonic earthquakes happen very deep underground. We don't know much about them.

🎯 Exam Tip: Highlight "greater depth" or "significant depths inside the earth" as the defining characteristic of plutonic earthquakes.

 

Question 16. What is meant by Tsunami?
Answer: A Tsunami is a series of very large and destructive ocean waves. These waves are caused by an earthquake that happens under the ocean, creating a strong disturbance in the water.
In simple words: Tsunami means huge, damaging ocean waves caused by underwater earthquakes.

🎯 Exam Tip: Connect "oceanic region earthquake" with "destructive oceanic waves" to fully define a Tsunami.

 

Question 17. Where do most earthquakes occur in the world?
Answer: Most earthquakes in the world happen in the Circum-Pacific Oceanic belt. About 63 percent of all global earthquakes happen in this region.
In simple words: The Circum-Pacific Oceanic belt is where most earthquakes on Earth happen.

🎯 Exam Tip: Identify the "Circum-Pacific Oceanic belt" as the primary location for global earthquake activity.

 

Question 18. Why do earthquakes originate in the Atlantic Ridge belt?
Answer: The intensity of earthquakes is measured on the Richter scale. It contains numbers from 0 to 9.
In simple words: The Richter scale measures how strong an earthquake is, using numbers from 0 to 9.

🎯 Exam Tip: When discussing earthquake intensity, clearly state that the Richter scale is used and its numerical range.

 

Question 20. What is meant by volcano eruption?
Answer: A volcano eruption is a sudden event caused by geological forces. During an eruption, gases, solid rocks, and hot liquid magma are forced out from a crack or opening in the Earth's surface.
In simple words: A volcano eruption is when hot liquid rock, gases, and rocks burst out from an opening in the Earth.

🎯 Exam Tip: Focus on the "sudden activity" and the materials (gases, rocky substances, magma/lava) that come out during an eruption.

 

Question 21. Write the definition of volcano as given by Uldin and Morgan.
Answer: According to Uldin and Morgan, a volcano is defined as a process that includes all the activities taking place both inside and on the outside of the Earth's surface.
In simple words: Uldin and Morgan say a volcano is all the things happening deep inside and on top of the Earth's surface.

🎯 Exam Tip: When quoting a definition, ensure it's accurate and includes the names of the scholars who provided it.

 

Question 22. On which bases has the classification of volcanoes been done?
Answer: Volcanoes have been grouped based on two main things: the time period they erupt and the kind of eruption they have.
In simple words: Volcanoes are classified by when they erupt and how they erupt.

🎯 Exam Tip: The two key classification bases are "period of eruption" and "nature of eruption."

 

Question 23. Into how many types have volcanoes been classified on the basis of period of eruption?
Answer: Based on their eruption period, volcanoes are divided into three types: active volcanoes, dormant volcanoes, and extinct volcanoes.
In simple words: Volcanoes are active, dormant, or extinct, depending on when they last erupted.

🎯 Exam Tip: List the three categories clearly: active, dormant, and extinct volcanoes.

 

Question 24. Into how many categories have volcanoes with central eruption been classified?
Answer: Volcanoes that erupt from a central vent are classified into four categories: Hawaiian type, Stromboli type, Vulcanic type, and Pelean type volcanoes.
In simple words: Central eruption volcanoes are grouped into Hawaiian, Stromboli, Vulcanic, and Pelean types.

🎯 Exam Tip: Remember the four specific types of central eruption volcanoes.

 

Question 25. What is meant by vulcanicity?
Answer: Volcanoes which erupt very frequently are known as active volcanoes.
In simple words: Volcanoes that erupt often are called active volcanoes.

🎯 Exam Tip: Define "active volcanoes" by their frequent eruption activity.

 

Question 27. What is meant by dormant volcanoes?
Answer: Dormant volcanoes are those that have been quiet for some time but are expected to erupt again in the future. They are not currently active but are not extinct.
In simple words: Dormant volcanoes are sleeping volcanoes that can erupt again later.

🎯 Exam Tip: Emphasize that dormant volcanoes are temporarily inactive but have the potential to erupt again.

 

Question 28. Which belts of volcanoes are found to be present?
Answer: The major volcanic belts around the world include the Circum-Pacific Oceanic belt, the Mid-Continental belt, the Mid-Atlantic Ridge belt, and the Eastern African Ridge.
In simple words: Big volcanic areas around the world are the Circum-Pacific, Mid-Continental, Mid-Atlantic Ridge, and Eastern African Ridge belts.

🎯 Exam Tip: Accurately name the main volcanic belts as they are significant geographical features.

 

RBSE Class 11 Physical Geography Chapter 7 Short Answer Type Questions (SA-I)

 

Question 1. What is meant by earthquake? Explain.
Answer: An earthquake is mainly caused by a temporary loss of balance in the Earth's crust at a certain spot. Forces inside the Earth are always at work. When these forces cause a sudden change, the Earth's surface shakes. This shaking is known as an earthquake, which is a natural disaster and produces destructive waves.
In simple words: An earthquake is when the ground shakes suddenly because of a temporary imbalance deep inside the Earth. It's a natural disaster.

🎯 Exam Tip: Explain that earthquakes are a result of internal Earth forces leading to "sudden change" or "imbalance in isostatic equilibrium" causing "shaking."

 

Question 2. How is Isostays helpful in causing earthquakes? Explain.
Answer: Isostasy helps keep the Earth's landforms like mountains, plateaus, and ocean depths balanced. When a lot of material from erosion builds up in ocean areas, it can upset this balance. This temporary imbalance in isostatic equilibrium can cause earthquakes. Such earthquakes often happen in the Himalayan region due to this reason.
In simple words: Isostasy keeps Earth's features balanced. If too much weight builds up in one area, it disturbs this balance and can cause earthquakes, like in the Himalayas.

🎯 Exam Tip: Describe how the disruption of "isostatic equilibrium" due to changes in load (like erosion deposits) directly leads to earthquake events.

 

Question 4. Give a brief introduction of Mid-Continental Belt in context to earthquakes.
Answer: The Mid-Continental belt is also known as the Mediterranean Sea belt. About 21 percent of the world's earthquakes happen in this region. Earthquakes here are caused by geological faulting and changes in the Earth's balance. India is also located within this belt. Other regions included are Italy, China, Asia Minor, Hindukush, Himalayas, and the Alps.
In simple words: The Mid-Continental belt, also called the Mediterranean Sea belt, has about 21% of earthquakes, caused by faults and imbalance. India and regions like the Himalayas are in this belt.

🎯 Exam Tip: Mention the percentage of earthquakes, main causes (faulting, isostatic disequilibrium), and key geographical areas within the belt.

 

Question 5. What is the difference between active and extinct volcanoes?
Answer: Following is the difference between active and extinct volcanoes:

In simple words: Active volcanoes erupt often and are in active areas, while extinct volcanoes haven't erupted in ages, are in quiet areas, and their openings are often blocked.

🎯 Exam Tip: Clearly distinguish between the activity level, tectonic setting, and vent condition for active versus extinct volcanoes.

 

Question 6. What is the difference between Hawaiian Type and Stromboli Type volcanoes?
Answer: Following are the differences between Hawaiian and Stromboli volcanoes:

In simple words: Hawaiian volcanoes erupt gently with thin lava that spreads far, mainly in Hawaii. Stromboli volcanoes erupt violently with thick lava that doesn't spread as far, typical of Stromboli Island.

🎯 Exam Tip: Compare the lava's thickness, eruption intensity, and spread distance to differentiate between Hawaiian and Stromboli types.

 

Question 7. Clarify the difference between Vulcanian volcanoes and Pelean volcanoes.
Answer: Following differences are present between Vulcanian volcanoes and Pelean volcanoes:

In simple words: Vulcanian volcanoes have violent explosions where material doesn't go as high. Pelean volcanoes have the most violent explosions, sending material to the greatest heights.

🎯 Exam Tip: Focus on the comparative violence of the explosion and the height reached by erupted material for Vulcanian versus Pelean types.

 

Question 8. Which is the minor belt of volcanoes?
Answer: The answer text is not provided in the source for this question.
In simple words: No answer is given in the source for this question.

🎯 Exam Tip: For questions asking for specific geographical belts, ensure you can accurately recall and name them.

 

RBSE Class 11 Physical Geography Chapter 7 Short Answer Type Questions (SA-II)

 

Question 1. Describe the contribution of plate tectonics and human reasons in the origination of earthquakes. Or Human activities and plate tectonics are responsible for the origination of earthquakes. Explain.
Answer:
Effect of Plate Tectonics: Plate tectonics play a big part in causing earthquakes. The Earth's surface is made of various plates, and when these plates move apart, come together, or slide past each other, it creates strong forces. This turbulence in the Earth's crust helps to cause earthquakes.
Human Contribution: Human activities also contribute significantly to the occurrence of earthquakes. For example, nuclear explosions, blasts used in mining, deep drilling into the Earth, and building huge dams that hold a lot of water can all increase the chances of earthquakes. Even changes in mine edges or their collapse can lead to earthquakes.
In simple words: Earthquakes happen because of moving tectonic plates pushing or sliding against each other, and also due to human actions like nuclear tests, mining, and building large dams.

🎯 Exam Tip: Remember both natural (plate tectonics, divergence, convergence, shifting) and human-induced (explosions, drilling, dams) causes for earthquakes to provide a complete answer.

 

Question 2. Classify earthquakes on the basis of their condition.
Answer: Earthquakes are mainly classified into two types based on where they occur:
1. Terrestrial earthquakes
2. Oceanic earthquakes.
1. Terrestrial Earthquakes: These are earthquakes that happen on land. Earthquakes that occur in the Mid-Continental belt are typically terrestrial earthquakes. They originate due to tectonic movements, stress, and compression within the Earth's crust.
2. Oceanic Earthquakes: These earthquakes occur under the ocean. They can cause powerful and destructive waves known as Tsunamis. For example, the violent earthquake near Honshu Island in Japan in 2011 caused a Tsunami that destroyed Fukushima city.
In simple words: Earthquakes are grouped into land-based (terrestrial) and ocean-based (oceanic) types. Land earthquakes happen on continents, while ocean earthquakes can cause tsunamis.

🎯 Exam Tip: Distinguish between terrestrial and oceanic earthquakes by their location and their potential effects, such as Tsunamis for oceanic ones.

 

Question 3. What is the difference between central eruption volcanoes and fissure eruption volcanoes?
Answer: Following are the differences between central eruption and fissure eruption volcanoes:

In simple words: Central eruption volcanoes explode from one vent and are common with well-formed cones. Fissure eruption volcanoes leak silently from many cracks, are fewer, and have less developed cones.

🎯 Exam Tip: Pay attention to the number of vents, eruption intensity, global prevalence, and cone development when comparing these two volcano types.

 

Question 4. What are the advantages of earthquakes?
Answer: Although earthquakes are usually destructive, they can sometimes have positive effects:
1. New highlands can form due to earthquakes, which can improve the climate of that region.
2. When coastal land sinks, sea ports become wider and deeper. This creates ideal conditions for large ships to dock.
3. Land that was submerged under the sea can rise up, forming fertile plains, which are good for farming.
In simple words: Earthquakes, while usually harmful, can create new highlands that improve climate, make sea ports deeper for ships, and form fertile plains from risen seabed.

🎯 Exam Tip: While earthquakes are generally seen negatively, remember these three specific advantageous impacts: highland formation, deeper ports, and fertile plains.

 

Question 5. Explain the reasons of vulcanicity.
Answer: Various factors cause volcanoes to erupt in different parts of the world. Here are the main reasons:
1. Isostatic Disequilibrium: When the Earth's crust loses its balance in certain areas, it causes structural changes that lead to volcanic activity.
2. Formation of Gases: Water can get into the Earth's interior through cracks and turns into steam. This steam acts as a powerful force, pushing magma out during an eruption.
3. Increase in Temperature of the Earth's Crust: Continuous splitting of radioactive materials inside the Earth's crust generates heat. This heat weakens rocks and increases their volume, leading to eruptions.
4. Decline in Pressure: When the pressure on the upper layers of the Earth's crust drops, the solid rocks inside can melt. This melting process then leads to volcanic activity.
5. Plate Tectonic: The movement of tectonic plates also causes volcanic activity. If plates move away from each other, it can make volcanic eruptions even more intense.
In simple words: Volcanoes erupt due to Earth's imbalance, steam from water, rising inner heat, less pressure on deep rocks, and tectonic plates moving apart.

🎯 Exam Tip: List the five key reasons for vulcanicity, ensuring you can briefly explain how each factor contributes to volcanic eruptions.

 

Question 6. What are the types of volcanoes on the basis of their period of eruption? Explain.
Answer: Volcanoes are classified into the following main types based on how often they erupt:
1. Active or Awake Volcanoes: These volcanoes erupt very frequently. For example, Etna and Stromboli volcanoes in Italy are active.
2. Dormant Volcanoes: These volcanoes have been quiet for some time but can erupt again. Mount Vesuvius is an example.
3. Extinct or Dead Volcanoes: These volcanoes have not erupted for a very long time, and their craters are often filled with water. Mount Popa in Myanmar and Koh-e-Sultan in Iran are examples of extinct volcanoes.
2. Types of volcanoes on the basis of their nature of eruption:
• Volcanoes with central eruption
• Volcanoes with fissure eruption
Volcanoes with central eruption: These volcanoes erupt from a single opening or vent. They are further classified into:
1. Hawaiian types of volcanoes.
2. Stromboli type of volcanoes.
3. Volcanian types of volcanoes.
4. Pelean types of volcanoes.
1. Hawaiian Type of Volcanoes: These volcanoes erupt quietly with less explosive activity because their lava is thin and gases are not very fierce. Examples are seen in the Hawaiian Islands.
2. Strombolian Type of Volcanoes: These eruptions are relatively fierce. The lava is thick, and eruptions can sometimes be explosive. Stromboli volcano is an example, giving its name to this type.
3. Volcanian Type of Volcanoes: These volcanoes erupt with tremendous explosions and extreme fierceness, often throwing out volcanic ash and large rocks.
In simple words: Volcanoes are grouped by how often they erupt (active, dormant, extinct) and by how they erupt (central or fissure). Central eruptions are further split into Hawaiian (calm), Strombolian (fierce), Volcanian (explosive), and Pelean types.

🎯 Exam Tip: Differentiate between the three types based on eruption period and be able to list the four central eruption types with a brief characteristic for each.

 

Question 7. Describe the substances which are secreted from volcano.
Answer: During a volcanic eruption, various materials come out from inside the Earth. These mainly include:
1. Gases and Water Vapour: Volcanoes release water vapor, along with gases like carbon dioxide, sulfur dioxide, carbon monoxide, hydrogen chloride, and ammonium chloride.
2. Solid Material: Large rocks, small fragments called lapilli, ash, and dust are ejected from the volcano.
3. Liquid Material: The hot, molten rock inside the Earth is called magma. When it reaches the surface through the volcano, it is known as lava.
In simple words: Volcanoes release hot gases (like water vapor and carbon dioxide), solid materials (rocks, ash), and liquid material (magma from inside Earth becomes lava on the surface).

🎯 Exam Tip: Categorize the erupted materials into gases/vapour, solid material, and liquid material, giving examples for each.

 

Question 8. Explain the impact of vulcanicity. Describe the advantageous and harmful impacts of volcanoes.
Answer: Volcanic activity on Earth is a natural phenomenon with both destructive and beneficial impacts:
1. Creative Impact: After lava spreads, it cools and creates fertile soil, which is good for farming. The black soil found in the Indian subcontinent is an example of the positive impact of volcanism. Volcanic activity also helps bring valuable minerals to the surface.
2. Harmful Impact: Volcanic eruptions can be very destructive, causing widespread damage. They can destroy homes, agricultural land, and infrastructure. Hot gases, ash, and lava flows pose serious threats to life and property. Changes in climate and atmospheric conditions can also occur due to large eruptions.
In simple words: Volcanic eruptions can be good by making fertile soil and bringing up minerals, but they are also very harmful, destroying land, homes, and affecting the climate.

🎯 Exam Tip: Remember to discuss both the "creative" (beneficial, e.g., fertile soil, minerals) and "harmful" (destructive, e.g., property damage, environmental impact) aspects of vulcanicity.

 

RBSE Class 11 Physical Geography Chapter 7 Essay Type Questions

 

Question 1. Explain the causes for origination of earthquakes.
Answer: Earthquakes mainly happen because of a temporary imbalance in the Earth's crust at a specific location. The following factors cause this imbalance, leading to earthquakes:
1. Faulting: Stress and pressure from forces inside the Earth can create cracks and breaks in rocks, forming faults. Earthquakes happen when these faults move, especially along the edges of new mountain ranges and rift valleys.
2. Vulcanism: Volcanic eruptions are a major cause of earthquakes. When gases and molten rock (magma) are forcefully pushed out during an eruption, it causes sudden and violent shaking of the ground. Earthquakes often occur during major volcanic events, like the eruptions of Etna, Krakatoa, and Vesuvius.
3. Water Load: Sometimes, large amounts of water collect on the Earth's surface, such as in big dams. This huge weight and pressure can change the rocks beneath, causing them to shift and resulting in earthquakes. The Koyna earthquake in Maharashtra in December 1967 is believed to have been caused by the Koyna Dam.
4. Contraction of the Earth: Some scientists believe that the Earth is slowly shrinking due to continuous cooling and the decay of radioactive elements. When this contraction happens quickly and forcefully, it can lead to earthquakes.
5. Elastic Rebound Theory: Professor F. S. Reid proposed this theory. It states that rocks are elastic, like rubber, and can stretch to a certain limit. When they are stretched too much, they break, and the broken parts snap back into place. This sudden release of energy causes earthquakes. The expansion and contraction of rocks in this way lead to seismic activity.
7. Plate Tectonic: The Earth's surface is divided into large plates. When these plates pull apart, push together, or slide sideways, it creates disturbances. This turbulence causes earthquakes to occur.
8. Other Reasons: Besides the above, other factors like expanding gases, collapsing cliffs in ocean regions, and falling cave ceilings can cause minor earthquakes. Human activities such as nuclear explosions, mining explosions, and deep drilling also lead to localized earthquakes.
In simple words: Earthquakes happen because of several reasons: rock faults, volcanic eruptions, the weight of large water bodies (like dams), the Earth slowly shrinking, rocks snapping back after being stretched (elastic rebound), moving tectonic plates, and human actions like explosions or deep drilling.

🎯 Exam Tip: For an essay question, provide a comprehensive list of earthquake causes. Ensure you explain each point clearly, linking it to seismic activity.

 

Question 2. Give a detailed description of the types of earthquakes.
Answer: Earthquakes are classified in various ways, primarily based on their origin and how they occur:
Types of Earthquakes:
1. Artificial Earthquake: These earthquakes are caused by human activities and usually have a localized impact with lower intensity. Examples include earthquakes from deep mining operations, nuclear explosions, or underground nuclear tests.
2. Natural Earthquake: These earthquakes occur due to natural processes within the Earth. They are further divided into:
(a) Volcanic Earthquakes: These happen because of volcanic activity or eruptions. Examples include those near Vesuvius, Etna, and Krakatoa volcanoes.
(b) Tectonic Earthquake: These earthquakes are caused by the movement of tectonic plates, which create stress and compression in the Earth's crust.
(c) Isostatic Earthquake: These occur due to an imbalance in the Earth's surface equilibrium, often in mountainous regions like the Himalayas. The Hindukush and Nepal earthquake of 2015 is an example.
(d) Plutonic Earthquake: These earthquakes originate at significant depths inside the Earth. Less is known about their exact origin and intensity.
3. Earthquakes on the basis of condition: Based on their location, earthquakes can be classified into two types:
(a) Terrestrial Earthquake: These are earthquakes that occur on land. Many earthquakes in the Mid-Continental belt are terrestrial.
(b) Marine Earthquake: These earthquakes occur in the oceans. They often create large, destructive ocean waves called Tsunamis. For example, the powerful earthquake near Honshu Island in Japan in 2011 caused a Tsunami that destroyed Fukushima city.
In simple words: Earthquakes are grouped into artificial (human-caused) and natural types. Natural earthquakes include volcanic, tectonic, isostatic, and plutonic. Also, earthquakes are classified by location as terrestrial (on land) or marine (in oceans, which can cause tsunamis).

🎯 Exam Tip: For a detailed description, remember the primary classification into artificial and natural, and then the sub-types of natural earthquakes. Also, include the classification based on location (terrestrial/marine) and their distinct characteristics.