Selina Textbook Solutions: Rocks | Geography Class 9 ICSE PDF Download

 Page 1


Rocks 
Exercises 
I. Short Answer Questions  
Question 1. 
State two points of distinction between rocks and minerals. 
Answer: 
Rocks : 
1. Rocks contain minerals. 
2. Rocks are the aggregates of minerals and other rock material. 
Minerals : 
1. Minerals do not contain rocks. 
2. Mineral are the compounds of pure elements with a definite chemical 
Composition. 
Question 2. 
Name any three elements of the earth’s crust. 
Answer: 
These are silicon, aluminium, iron, magnesium, calcium, potassium, sodium and nickel. 
Question 3. 
Name three types of rocks. 
Answer: 
Three types of rocks are sedimentary, igneous and metamorphic rocks. 
Question 4. 
Why are the igneous rocks also called the primary rocks? 
Answer: 
The igneous rocks were the first to be formed. They form the basis of formation of other 
types of rocks. Thus, they are called primary rocks. 
Question 5. 
Give one difference between Extrusive igneous and Intrusive igneous rocks. 
Answer: 
? Extrusive igneous rocks are formed by the cooling of molten magma on the earth’s 
surface. 
Page 2


Rocks 
Exercises 
I. Short Answer Questions  
Question 1. 
State two points of distinction between rocks and minerals. 
Answer: 
Rocks : 
1. Rocks contain minerals. 
2. Rocks are the aggregates of minerals and other rock material. 
Minerals : 
1. Minerals do not contain rocks. 
2. Mineral are the compounds of pure elements with a definite chemical 
Composition. 
Question 2. 
Name any three elements of the earth’s crust. 
Answer: 
These are silicon, aluminium, iron, magnesium, calcium, potassium, sodium and nickel. 
Question 3. 
Name three types of rocks. 
Answer: 
Three types of rocks are sedimentary, igneous and metamorphic rocks. 
Question 4. 
Why are the igneous rocks also called the primary rocks? 
Answer: 
The igneous rocks were the first to be formed. They form the basis of formation of other 
types of rocks. Thus, they are called primary rocks. 
Question 5. 
Give one difference between Extrusive igneous and Intrusive igneous rocks. 
Answer: 
? Extrusive igneous rocks are formed by the cooling of molten magma on the earth’s 
surface. 
? Intrusive igneous rocks are formed when the magma solidifies within the earth’s 
crust forming coarse texture. 
Question 6. 
Name any two chief characteristics of Igneous Rocks. 
Answer: 
Igneous rocks are formed by cooling of magma and these are crystalline rocks and full 
of mineral compounds. 
Question 7. 
What is the main characteristics of Basic Igneous Rocks? 
Answer: 
Basic igneous rocks have higher percentage of oxides of denser elements and dark in 
colour, e.g. Basalt, dolerite etc. 
Question 8. 
Name two important landforms made by Igneous Rocks. 
Answer: 
Conical mountains and extensive lava plateaus. 
Question 9. 
What are Sills ? 
Answer: 
The magma takes place in between the layers of rocks and hardens after cooling, which 
is called Sill. 
Question 10. 
Which rocks are associated with ores of metals ? 
Answer: 
Igneous rocks are associated with ores of metals due to their origin by cooling magma 
resulting in crystalline rocks rich in mineral content. 
Question 11. 
Which rocks are associated with fossil fuels ? 
Answer: 
Sedimentary rocks are associated with fossil fuels due to fossils trapped in between 
layers of these rocks. 
Question 12. 
Mention any two chief characteristics of Sedimentary Rocks. 
Answer: 
? Sedimentary rocks are formed from material derived from other rocks including 
plant and animal remains. These rocks thus contain fossils. 
Page 3


Rocks 
Exercises 
I. Short Answer Questions  
Question 1. 
State two points of distinction between rocks and minerals. 
Answer: 
Rocks : 
1. Rocks contain minerals. 
2. Rocks are the aggregates of minerals and other rock material. 
Minerals : 
1. Minerals do not contain rocks. 
2. Mineral are the compounds of pure elements with a definite chemical 
Composition. 
Question 2. 
Name any three elements of the earth’s crust. 
Answer: 
These are silicon, aluminium, iron, magnesium, calcium, potassium, sodium and nickel. 
Question 3. 
Name three types of rocks. 
Answer: 
Three types of rocks are sedimentary, igneous and metamorphic rocks. 
Question 4. 
Why are the igneous rocks also called the primary rocks? 
Answer: 
The igneous rocks were the first to be formed. They form the basis of formation of other 
types of rocks. Thus, they are called primary rocks. 
Question 5. 
Give one difference between Extrusive igneous and Intrusive igneous rocks. 
Answer: 
? Extrusive igneous rocks are formed by the cooling of molten magma on the earth’s 
surface. 
? Intrusive igneous rocks are formed when the magma solidifies within the earth’s 
crust forming coarse texture. 
Question 6. 
Name any two chief characteristics of Igneous Rocks. 
Answer: 
Igneous rocks are formed by cooling of magma and these are crystalline rocks and full 
of mineral compounds. 
Question 7. 
What is the main characteristics of Basic Igneous Rocks? 
Answer: 
Basic igneous rocks have higher percentage of oxides of denser elements and dark in 
colour, e.g. Basalt, dolerite etc. 
Question 8. 
Name two important landforms made by Igneous Rocks. 
Answer: 
Conical mountains and extensive lava plateaus. 
Question 9. 
What are Sills ? 
Answer: 
The magma takes place in between the layers of rocks and hardens after cooling, which 
is called Sill. 
Question 10. 
Which rocks are associated with ores of metals ? 
Answer: 
Igneous rocks are associated with ores of metals due to their origin by cooling magma 
resulting in crystalline rocks rich in mineral content. 
Question 11. 
Which rocks are associated with fossil fuels ? 
Answer: 
Sedimentary rocks are associated with fossil fuels due to fossils trapped in between 
layers of these rocks. 
Question 12. 
Mention any two chief characteristics of Sedimentary Rocks. 
Answer: 
? Sedimentary rocks are formed from material derived from other rocks including 
plant and animal remains. These rocks thus contain fossils. 
? Sedimentary rocks are generally not crystalline. They are soft and layered as they 
are formed by deposition of sediments. 
Question 13. 
Give two examples of Sedimentary Rocks. 
Answer: 
1. Sandstone 
2. Limestone 
Question 14. 
Name the rocks which are most widespread on the earth. 
Answer: 
Sedimentary rocks are most widespread on the earth. 
Question 15. 
Name the three stages of lithification of Sedimentary rocks. 
Answer: 
Lithification is the process of turning loose rock material into hard rock through 
evaporation, compaction and cementation. 
Question 16. 
Name the types Sedimentary rocks based on agents of formation. 
Answer: 
There are five main types of rocks on the basis of agents of formation: 
1. Riverine Rocks These are formed by the sediments deposited by running water or 
river. 
2. Lacustrine Rocks These are formed by the deposition of silt etc on the bed of 
lakes. 
3. Glacial Rocks These are formed by the debris carried on and deposited by 
glaciers. 
4. Aeolean Rocks These are formed by the deposition sand accumulation by the 
wind. 
5. Marine Rocks These are formed by the deposition of sediments at the ocean floor. 
These types are Calcarious and Carbonaceous sedimentary Rocks. 
Question 17. 
Which agents are responsible for deposition of sediments? 
Answer: 
There are three main agents of deposition i.e., water, wind and ice, which mainly act as 
agents of change on the surface of earth for deposition of sediments. 
Page 4


Rocks 
Exercises 
I. Short Answer Questions  
Question 1. 
State two points of distinction between rocks and minerals. 
Answer: 
Rocks : 
1. Rocks contain minerals. 
2. Rocks are the aggregates of minerals and other rock material. 
Minerals : 
1. Minerals do not contain rocks. 
2. Mineral are the compounds of pure elements with a definite chemical 
Composition. 
Question 2. 
Name any three elements of the earth’s crust. 
Answer: 
These are silicon, aluminium, iron, magnesium, calcium, potassium, sodium and nickel. 
Question 3. 
Name three types of rocks. 
Answer: 
Three types of rocks are sedimentary, igneous and metamorphic rocks. 
Question 4. 
Why are the igneous rocks also called the primary rocks? 
Answer: 
The igneous rocks were the first to be formed. They form the basis of formation of other 
types of rocks. Thus, they are called primary rocks. 
Question 5. 
Give one difference between Extrusive igneous and Intrusive igneous rocks. 
Answer: 
? Extrusive igneous rocks are formed by the cooling of molten magma on the earth’s 
surface. 
? Intrusive igneous rocks are formed when the magma solidifies within the earth’s 
crust forming coarse texture. 
Question 6. 
Name any two chief characteristics of Igneous Rocks. 
Answer: 
Igneous rocks are formed by cooling of magma and these are crystalline rocks and full 
of mineral compounds. 
Question 7. 
What is the main characteristics of Basic Igneous Rocks? 
Answer: 
Basic igneous rocks have higher percentage of oxides of denser elements and dark in 
colour, e.g. Basalt, dolerite etc. 
Question 8. 
Name two important landforms made by Igneous Rocks. 
Answer: 
Conical mountains and extensive lava plateaus. 
Question 9. 
What are Sills ? 
Answer: 
The magma takes place in between the layers of rocks and hardens after cooling, which 
is called Sill. 
Question 10. 
Which rocks are associated with ores of metals ? 
Answer: 
Igneous rocks are associated with ores of metals due to their origin by cooling magma 
resulting in crystalline rocks rich in mineral content. 
Question 11. 
Which rocks are associated with fossil fuels ? 
Answer: 
Sedimentary rocks are associated with fossil fuels due to fossils trapped in between 
layers of these rocks. 
Question 12. 
Mention any two chief characteristics of Sedimentary Rocks. 
Answer: 
? Sedimentary rocks are formed from material derived from other rocks including 
plant and animal remains. These rocks thus contain fossils. 
? Sedimentary rocks are generally not crystalline. They are soft and layered as they 
are formed by deposition of sediments. 
Question 13. 
Give two examples of Sedimentary Rocks. 
Answer: 
1. Sandstone 
2. Limestone 
Question 14. 
Name the rocks which are most widespread on the earth. 
Answer: 
Sedimentary rocks are most widespread on the earth. 
Question 15. 
Name the three stages of lithification of Sedimentary rocks. 
Answer: 
Lithification is the process of turning loose rock material into hard rock through 
evaporation, compaction and cementation. 
Question 16. 
Name the types Sedimentary rocks based on agents of formation. 
Answer: 
There are five main types of rocks on the basis of agents of formation: 
1. Riverine Rocks These are formed by the sediments deposited by running water or 
river. 
2. Lacustrine Rocks These are formed by the deposition of silt etc on the bed of 
lakes. 
3. Glacial Rocks These are formed by the debris carried on and deposited by 
glaciers. 
4. Aeolean Rocks These are formed by the deposition sand accumulation by the 
wind. 
5. Marine Rocks These are formed by the deposition of sediments at the ocean floor. 
These types are Calcarious and Carbonaceous sedimentary Rocks. 
Question 17. 
Which agents are responsible for deposition of sediments? 
Answer: 
There are three main agents of deposition i.e., water, wind and ice, which mainly act as 
agents of change on the surface of earth for deposition of sediments. 
Question 18. 
What are known as metamorphic rocks ? Give two examples. 
Answer: 
Metamorphic rocks are formed by complete change of texture of rocks through 
volcanism and diastrophism, e.g., limestone is converted to marble and shale is 
transformed to slate. 
Question 19. 
What is Mechanical Metamorphism ? 
Answer: 
This is a mechanical Transformation in which texture of rocks is changed by crushing 
and rubbing processes associated with heat and compression created by mechanical 
action. 
Question 20. 
What is meant by Rock Cycle ? 
Answer: 
The earth is said to be 4700 million years old and the rocks came into existence 3400 
years ago. Since then these rocks have undergone various changes by which multiple 
transformation took place within the rocks. This continuous process of transformation of 
old rocks into new rocks is known as rock cycle for figure See Page no. of this book. 
Question 21. 
What processes are involved in the formation of Igneous Rocks ? 
Answer: 
Igneous rocks are associated with volcanic activity, cooling of magma and mechanical 
weathering etc. 
II. Explain these terms associated with rocks. 
Question 1. 
Extrusive Igneous Rocks. 
Answer: 
These rocks are formed by consolidation of erupted magma on the surface of earth. 
Question 2. 
Laccoliths and Batholiths. 
Answer: 
Laccoliths is formed by the intrusion of magma in the erupting channel just below the 
crust. Batholiths are deep seated dome shaped formation of magma intrusion, generally 
forming the base of mountain ranges, e.g., Ranchi Batholiths. 
 
Page 5


Rocks 
Exercises 
I. Short Answer Questions  
Question 1. 
State two points of distinction between rocks and minerals. 
Answer: 
Rocks : 
1. Rocks contain minerals. 
2. Rocks are the aggregates of minerals and other rock material. 
Minerals : 
1. Minerals do not contain rocks. 
2. Mineral are the compounds of pure elements with a definite chemical 
Composition. 
Question 2. 
Name any three elements of the earth’s crust. 
Answer: 
These are silicon, aluminium, iron, magnesium, calcium, potassium, sodium and nickel. 
Question 3. 
Name three types of rocks. 
Answer: 
Three types of rocks are sedimentary, igneous and metamorphic rocks. 
Question 4. 
Why are the igneous rocks also called the primary rocks? 
Answer: 
The igneous rocks were the first to be formed. They form the basis of formation of other 
types of rocks. Thus, they are called primary rocks. 
Question 5. 
Give one difference between Extrusive igneous and Intrusive igneous rocks. 
Answer: 
? Extrusive igneous rocks are formed by the cooling of molten magma on the earth’s 
surface. 
? Intrusive igneous rocks are formed when the magma solidifies within the earth’s 
crust forming coarse texture. 
Question 6. 
Name any two chief characteristics of Igneous Rocks. 
Answer: 
Igneous rocks are formed by cooling of magma and these are crystalline rocks and full 
of mineral compounds. 
Question 7. 
What is the main characteristics of Basic Igneous Rocks? 
Answer: 
Basic igneous rocks have higher percentage of oxides of denser elements and dark in 
colour, e.g. Basalt, dolerite etc. 
Question 8. 
Name two important landforms made by Igneous Rocks. 
Answer: 
Conical mountains and extensive lava plateaus. 
Question 9. 
What are Sills ? 
Answer: 
The magma takes place in between the layers of rocks and hardens after cooling, which 
is called Sill. 
Question 10. 
Which rocks are associated with ores of metals ? 
Answer: 
Igneous rocks are associated with ores of metals due to their origin by cooling magma 
resulting in crystalline rocks rich in mineral content. 
Question 11. 
Which rocks are associated with fossil fuels ? 
Answer: 
Sedimentary rocks are associated with fossil fuels due to fossils trapped in between 
layers of these rocks. 
Question 12. 
Mention any two chief characteristics of Sedimentary Rocks. 
Answer: 
? Sedimentary rocks are formed from material derived from other rocks including 
plant and animal remains. These rocks thus contain fossils. 
? Sedimentary rocks are generally not crystalline. They are soft and layered as they 
are formed by deposition of sediments. 
Question 13. 
Give two examples of Sedimentary Rocks. 
Answer: 
1. Sandstone 
2. Limestone 
Question 14. 
Name the rocks which are most widespread on the earth. 
Answer: 
Sedimentary rocks are most widespread on the earth. 
Question 15. 
Name the three stages of lithification of Sedimentary rocks. 
Answer: 
Lithification is the process of turning loose rock material into hard rock through 
evaporation, compaction and cementation. 
Question 16. 
Name the types Sedimentary rocks based on agents of formation. 
Answer: 
There are five main types of rocks on the basis of agents of formation: 
1. Riverine Rocks These are formed by the sediments deposited by running water or 
river. 
2. Lacustrine Rocks These are formed by the deposition of silt etc on the bed of 
lakes. 
3. Glacial Rocks These are formed by the debris carried on and deposited by 
glaciers. 
4. Aeolean Rocks These are formed by the deposition sand accumulation by the 
wind. 
5. Marine Rocks These are formed by the deposition of sediments at the ocean floor. 
These types are Calcarious and Carbonaceous sedimentary Rocks. 
Question 17. 
Which agents are responsible for deposition of sediments? 
Answer: 
There are three main agents of deposition i.e., water, wind and ice, which mainly act as 
agents of change on the surface of earth for deposition of sediments. 
Question 18. 
What are known as metamorphic rocks ? Give two examples. 
Answer: 
Metamorphic rocks are formed by complete change of texture of rocks through 
volcanism and diastrophism, e.g., limestone is converted to marble and shale is 
transformed to slate. 
Question 19. 
What is Mechanical Metamorphism ? 
Answer: 
This is a mechanical Transformation in which texture of rocks is changed by crushing 
and rubbing processes associated with heat and compression created by mechanical 
action. 
Question 20. 
What is meant by Rock Cycle ? 
Answer: 
The earth is said to be 4700 million years old and the rocks came into existence 3400 
years ago. Since then these rocks have undergone various changes by which multiple 
transformation took place within the rocks. This continuous process of transformation of 
old rocks into new rocks is known as rock cycle for figure See Page no. of this book. 
Question 21. 
What processes are involved in the formation of Igneous Rocks ? 
Answer: 
Igneous rocks are associated with volcanic activity, cooling of magma and mechanical 
weathering etc. 
II. Explain these terms associated with rocks. 
Question 1. 
Extrusive Igneous Rocks. 
Answer: 
These rocks are formed by consolidation of erupted magma on the surface of earth. 
Question 2. 
Laccoliths and Batholiths. 
Answer: 
Laccoliths is formed by the intrusion of magma in the erupting channel just below the 
crust. Batholiths are deep seated dome shaped formation of magma intrusion, generally 
forming the base of mountain ranges, e.g., Ranchi Batholiths. 
 
Question 3. 
Fossil fuels. 
Answer: 
These are the fuels accumulated between two impermeable layers of the sedimentary 
rocks, e.g. peat, coal and petroleum etc. 
Question 4. 
Lithification of Rocks. 
Answer: 
It is the process of turning the loose material into hard rock, which helps in the formation 
of the sedimentary rocks found in different layers one upon another. 
Question 5. 
Metamorphism. 
Answer: 
It is the process of transformation of sedimentary and igneous rocks into metamorphic 
rocks through extreme temperature and compression by volcanism and diatrophism by 
physical and Chemical changes. 
III. Distinguish between each of the following 
P Q. Lava and Magma. 
Answer: 
Lava : Lava is the black molten material erupted in a volcano. 
Magma : Magma is the compound of lava, stones, ash, debris etc. erupting out in a 
volcano. 
Question 1. 
Plutonic and Volcanic rocks. 
Answer: 
Plutonic rocks : 
1. These are intrusive igneous rocks. 
2. These cool down very slowly due to heat in the interior 
Volcanic rocks : 
1. These are extrusive igneous rocks. 
2. These cool down abruptly due to less temperature on the surface region.