Samacheer Kalvi 8th Social Science Geography Solutions Term 1 Chapter 1 Rock and Soil

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Samacheer Kalvi 8th Social Science Geography Solutions Term 1 Chapter 1 Rock and Soil

Samacheer Kalvi 8th Social Science Rock and Soil Textbook Evaluation

I. Choose the correct answer

Question 1.
Which of the following is known as sphere of rocks –
(a) Atmosphere
(b) Biosphere
(c) Lithosphere
(d) Hydrosphere
Answer:
(c) Lithosphere

Question 2.
World soil day is observed on –
(a) 15th August
(b) 12th January
(c) 15th October
(d) 5th December
Answer:
(d) 5th December

Question 3.
Fossils are found in –
(a) Sedimentary rocks
(b) Igneous rocks
(c) Metamorphic rocks
(d) Plutonic rocks
Answer:
(a) Sedimentary rocks

Question 4.
The first layer of soil is called as –
(a) Regur
(b) Regolith
(c) Unweathered rock
(d) Partially weathered rock
Answer:
(b) Regolith

Question 5.
Ideal soil for growing cotton is –
(a) Red soil
(b) Black soil
(c) Alluvial soil
(d) Mountain soil
Answer:
(b) Black soil

Question 6.
The major component of soil is –
(a) Rocks
(b) Gas
(C) Water
(d) Minerals
Answer:
(d) Minerals

Question 7.
Which one of the following is the most widespread most and productive category of soil –
(a) Alluvial soil
(b) Black soil
(c) Red soil
(d) Mountain soil
Answer:
(a) Alluvial soil

II. Fill in the Blanks

1. The scientific study of rocks is called ………………
2. …………… soil is highly suitable for cotton cultivation.
3. The “skin of the earth” is ……………..
4. ……………. is the kind of metamorphic rock using which the Taj Mahal was built.
5. ……………. is known as the primary rocks.

Answer:

1. Petrology
2. Black
3. Soil
4. White Marble
5. Igneous rock

III. State whether the following statements are true or false

Question 1.
Igneous rocks are called primary rocks.
Answer:
True

Question 2.
Slate is formed from shale.
Answer:
True

Question 3.
Red soil is formed by the process of leaching.
Answer:
False
Correct statement:
Laterites soils is formed by the process of leaching.

Question 4.
M – sand is used as an alternative for natural sand in construction.
Answer:
True

Question 5.
Volcanic mountains are covered with sedimentary rocks.
Answer:
False
Correct statement:
Sedimentary rocks are formed from broken pieces of rocks.

IV. Match the following

Question 1.

Answer:

a. 2
b. 1
c.  4
d. 3.

Question 2.

Answer:

a. 2
b. 4
c.  1
d.  3.

V. Choose the incorrect statement from the following

Question 1.

1. Igneous rocks are called the primary rocks.
2. Soil is the product of the weathering of rocks.
3. Sedimentary rocks are the hardest ones.
4. Deccan plateau is the region of Igneous rocks.

Answer:
3. Sedimentary rocks are the hardest ones.

Question 2.

1. Soil erosion decreases its fertility.
2. Dynamic metamorphism is caused by high temperature.
3. Soil is a renewable source.
4. Humus is a part of the top layer of soil.

Answer:
2. Dynamic metamorphism is caused by high temperature.

VI. Consider the following statements and choose the right option from the given ones

Statement (1) – Sedimentary rocks consist of many layers.
Statement (2) – Sedimentary rocks are formed by the sediments deposited at different points in time.

1. 1 and 2 are correct and 2 explains 1
2. 1 and 2 are correct but, 2 does not explain 1
3. 1 is correct but, 2 is incorrect
4. 2 is correct but, 1 is incorrect.

Answer:
1. 1 and 2 are correct and 2 explains 1

VII. Give reasons for the following 

Question 1.
Chemical sedimentary rocks are found in the beds of reservoirs.
Answer:

• Because these are formed by the precipitation of minerals from water.
• It is formed usually through evaporation of chemical-rich solutions.

Question 2.
Igneous rocks are found in the regions of volcanoes.
Answer:
The igneous rocks are formed by the solidification of molten magma.

VIII. Distinguish the following

Question 1.
Metamorphic rock and sedimentary rock.
Answer:
Metamorphic Rocks:

• Formed when Igneous and Sedimentary rocks are subjected to high temperature and pressure.
• Mostly crystalline in nature
• Fossils do not survive in these rocks
• Example Gneiss, Slate, quartz

Sedimentary Rocks:

• Formed by the sediments derived and deposited by various agents.
• They are non – crystalline rocks
• Contain fossils., Example Coal, Oil, natural gas
• Example Chalk, Sandstone, Rock Salt

Question 2.
Soil conservation and Soil erosion.
Answer:

Soil conservation:

• The process of protecting the soil from erosion to maintain its fertility.
• Methods of soil conservation are afforestation, controlled grazing, construction of dams, crop rotation etc.,

Soil erosion:

• Removal or destruction of the top layer of soil by natural forces and human activities.
• Running water and wind are the major agents of Soil erosion.
  Rill erosion and Gully erosion are the major types of soil erosion

IX. Give short answers

Question 1.
How are igneous rocks formed?
Answer:
Igneous rocks are the primary rocks formed by the solidification of the molten magma.

Question 2.
Describe the composition of the soil.
Answer:
The basic components of soil are mineral, organic matter, water and air. It consists of about 45% mineral, 5% organic matter, 25%  of water and 25% air. It is only a generalized fact. The composition of soil varies from place to place and time to time.

Question 3.
Define ‘rock’.
Answer:

• The rocks are the solid mineral materials forming a part of the surface of the earth and other similar planets.
• The earth is the crust is composed of rocks.

Question 4.
State the types of soils.
Answer:
Alluvial soil, Black soil, Red soil, Laterite soil, Mountain soil, Desert soil.

Question 5.
What is soil conservation?
Answer:
Soil Conservation is the process of protecting the soil from erosion to maintain its fertility.

X. Give a detailed answer for the following

Question 1.
Explain the process of soil formation.
Answer:

1. Soil is a mixture of organic matter, minerals, gases, liquids and organisms that together support life.
2. Soil minerals form the basis of soil. It forms on the surface of the earth. It is known as the ‘skin of the earth’.
3. Soils are produced from rocks (parent material) through the processes of weathering and natural erosion.
4. Water, wind, temperature change, gravity, chemical interaction, living organisms and pressure differences all help break down parent material. It leads to the formation of loose material.
5. In course of time, they further break down into fine particles. This process release the minerals locked in the rock fragments.
6. Later on, the vegetative cover which develop in that region forms humus content in the soil. This way the soil gets matured gradually.

Question 2.
Classify and explain the rocks.
Answer:

• Soil is a mixture of organic matter, minerals, gases, liquids and organisms that together support life.
• Soils are produced from rocks through the processes of weathering and natural erosion.
• Water, wind, temperature changes, gravity, chemical interaction, living organisms and pressure break down parent material.
• It leads to the formation of loose material.
• In the course of time, they further break down into fine particles and releases the locked minerals in the rock.

2. Classify and explain the rocks.

• The rocks are the solid minerals material forming a part of the surface of the earth and other similar planets.
• The earth’s crust is composed of rocks.

Classification of Rocks:
Rocks are classified into three types namely,

• Igneous Rocks
• Sedimentary Rocks
• Metamorphic Rocks

Igneous Rocks:
These rocks are formed by the solidification of molten magma. These rocks are also called as Primary or Parent Rocks. There are two types of igneous rocks:

• Extrusive Igneous Rocks
• Intrusive Igneous Rocks

Sedimentary Rocks:
The Sedimentary rocks are formed by the sediments derived and deposited by various agents. It is also known as stratified rocks. There are three types of sedimentary rocks namely,

• Organic Sedimentary Rocks
• Mechanical Sedimentary Rocks
• Chemical Sedimentary Rocks

Metamorphic Rocks:
When Igneous and Sedimentary rocks subject to high temperature and pressure, the original rocks get altered to form a new kind of rock called metamorphic rocks.
There are two types of Metamorphism rocks namely,

• Thermal Metamorphism
• Dynamic Metamorphism

Question 3.
Give an account of different layers of soil.
Answer:

Question 4.
Classify and explain the soil.
Answer:
Soil is classified on the basis of its formation, colour, physical and chemical properties Based on these, the soil is classified into six major types. They are:

• Alluvial Soil
• Black soil
• Red Soil
• Laterites Soil
• Mountain Soil
• Desert soil

Alluvial Soil:

• It found in the regions of river valleys, flood plains, and coastal regions.
• It is formed by the disposition of silt by the running water. It is suitable for the cultivation of sugarcane, jute, rice, wheat, and other food crops.

Black Soil:

• These soils are formed by the weathering of igneous rocks.
• It is ideal for growing cotton.

Red Soil:

• It is formed by the weathering of metamorphic and crystalline rocks.
• The presence of iron oxide makes this soil red in color. It is suitable for millet cultivation.

Laterite soil:

• It is formed by the process of leaching.
• It is found in the tropical region.
• It is suitable for the cultivation of tea and coffee.

Mountain soil:

• These soils are found over the slopes of mountains.
• Soils in these regions are thin and acidic.
• It differs from region to region based on the altitude.

Desert soil:

• There is the sandy soil found in the hot desert regions.
  These soils are porous and saline. It is infertile for agriculture.

IX. Activity Corner

Question 1.
Complete the following table with the help of an internet source

Answer:

Question 2.
Map Work:
Mark the areas of black soil on the outline map of India.
Answer:

Samacheer Kalvi 8th Social Science Geography Rock and Soil Additional Questions

I. Choose the correct answer 

Question 1.
……………. rocks are also called Primary rocks.
(a) Sedimentary
(b) Igneous
(c) Metamorphic
(d) Stratified
Answer:
(b) Igneous

Question 2.
…………….. rocks are also known as stratified rocks.
(a) Igneous
(b) Metamorphic
(c) Sedimentary
(d) Hypabysal
Answer:
(c) Sedimentary

Question 3.
The oldest sedimentary rocks of the world have been identified in
(a) Green land
(b) India
(c) France
(d) Australia
Answer:
(a) Green land

Question 4.
…………….. soil is suitable for milled cultivation.
(a) Alluvial
(b) Black
(c) Latente
(d) Red
Answer:
(d) Red

Question 5.
……………. soil is porous and saline.
(a) Mountain
(b) Desert
(c) Alluvial
(d) Red
Answer:
(b) Desert

Question 6.
The time needed to form soil depends on the ……………..
(a) altitude
(b) rainfall
(c) climate
(d) fertility
Answer:
(c) climate

II. Fill in the blanks

1. ……………. refer to rock in Greek.
2. Out of 2,000 different types, only ……………. are the basic minerals commonly found all over the earth.
3. ……………. are chemical substances which exist in nature.
4. Minerals exist in nature ¡n the form of ……………. or …………..
5. The world Igneous is derived from the Latin word ……………. meaning …………….
6. Intrusive Igneous rocks are also called ………….. rocks.
7. Meta means ………….. and morpha means ………………
8. In wet tropical area, soil formation is ………………

Answer:

1. Petrus
2. 12
3. Minerals
4. Elements, compounds
5. Ignus, fire
6. Crystallins
7. Change, shape
8. Faster

III. Match the following

a. iiii
b. iv
c. i
d. ii

IV. Choose the incorrect statement from the following 

Question 1.

1. Igneous rocks do not contain fossils
2. The oldest sedimentary rock in the world is 3.9 billion years old.
3. Soil consists of 5% Organic matter.
4. Laterite soil is thin and acidic.

Answer:
4. Laterite soil is thin and acidic

V. Consider the following statement and choose the right option from the given ones 

Question 1.
Statement 1: Proper management of soil resources will lead to sustainable food production.
Statement 2: India is an Agricultural country.

1. 1 and 2 are correct but 2 does not explain.
2. 1 is correct but 2 is incorrect.
3. 1 and 2 are correct and 2 explains 1.
4. 1 is incorrect but 2 is correct.

Answer:
3. 1 and 2 are correct and 2 explains 1

VI. Give Reason for the following

Question 1.
The Laterite soil is infertile.
Answer:
Laterite is the typical soils of tropical regions. These soils are found in the regions which experienced the alternate wet and dry condition. As these soils are formed by the process of leaching, it is in fertile.

Question 2.
Sedimentary rocks are called stratified rocks.
Answer:
Sedimentary rocks consist of many layers which were formed by the sediments deposited at different periods. As it consists of many strata, it is also known as ‘Stratified rocks’.

VII. Distinguish the following

Question 1.
Igneous rock and sedimentary rock.
Answer:
Igneous rocks:

• Formed by the solidification of molten magma.
• Classified into 2 types: Extrusive and Intrusive Igneous rocks.
• Crystalline in nature.
• Hard in nature.

Sedimentary rocks:

• Formed by the sediments derived and deposited by various agents.
• Classified into 3 types: Organic, Mechanical, Chemical sedimentary rocks.
• Non – crystalline rocks
• Soft and get eroded easily.

VIII. Give short answers

Question 1.
Name the four realms of earth.
Answer:
Four realms of the earth, are the lithosphere, hydrosphere, atmosphere, and biosphere.

Question 2.
What is the Lithosphere composed of?
Answer:
The lithosphere is composed of solid rocks and unconsolidated materials.

Question 3.
What is lava?
Answer:
Lava is actually a fiery red molten magma that comes out from the interior of the earth on its surface.

Question 4.
Why are crystalline rocks called so?
Answer:
The intrusive Igneous rocks consist of large crystals, and so they are also called ‘Crystalline rocks’.

Question 5.
Name a few Major Active Volcanoes.
Answer:
Major Active Volcanoes:
Mount Vesuvius, Mt. Stromboli and Mt. Etna in Italy and Mauna Loa and Mauna Kea in Hawaii Islands.

Question 6.
What are the characteristics of Sedimentary rocks?
Answer:

1. They have many layers.
2. They are non-crystalline rocks.
3. They contain fossils.
4. They are soft and get eroded easily.

Question 7.
What is Thermal Metamorphism?
Answer:
If the change in the rocks is mainly caused by high temperature, the process is called thermal metamorphism.

Question 8.
Explain Dynamic Metamorphism.
Answer:
If the change in the rock is mainly caused by high pressure, the process is called Dynamic Metamorphism.

Question 9.
State the characteristics of Metamorphic rocks.
Answer:

1. Metamorphic rocks are mostly crystalline in nature.
2. They consist of alternate bands of light and dark minerals.

Question 10.
Mention some uses of rocks.
Answer:

1. Cement
2. Writing chalk
3. Fire
4. Building materials
5. Bath scrub
6. Kerbstone
7. Ornament
8. Roofing materials
9. Decorative materials
10. These are valuable sources of minerals such as gold, diamond, sapphire, etc.

IX. Give Detailed Answer

Question 1.
Explain the different types of sedimentary rocks.
Answer:
Types of Sedimentary Rocks
1. Organic Sedimentary Rocks:

• These rocks are formed as a result of the decomposition of dead plants and animals.
• It contains fossils. Chalk, Talc, Dolomite, and Limestone rocks are of this category.

2. Mechanical Sedimentary Rocks:

• These rocks are formed from the disintegration of igneous and metamorphic rocks.
• The natural agents erode and transport these rocks and deposit them at some places. After a long period of time, they cemented to form rocks.
• Sandstone, Shale, and Clay are examples of rocks of this type.

3. Chemical Sedimentary rocks:

• These are formed by the precipitating minerals from water. It is formed usually through evaporation of chemical-rich solutions.
• These rocks are also called evaporates.
• Rock Salt is an example of this kind.

Question 2.
Explain the Rock cycle with a diagram.
Answer:
1. Igneous rocks are the primary rocks formed first on the earth. These rocks are weathered, eroded, transported, and deposited at some places to form sedimentary rocks.

2. The Igneous and Sedimentary rocks are changed into metamorphic rocks under the influence of temperature and pressure.

3. The metamorphic rocks also get disintegrated and deposited to form sedimentary rocks.

4. Formation of igneous rocks take place when there is an outflow of molten materials. Like this, the rocks of the earth’s crust keeps on changing from one form to another form under various natural forces and agents.

5. The endless process is referred to as Rock Cycle.

Question 3.
Mention the uses of soils.
Answer:
Uses of soils: Soil is one of the important natural resources. It is a basic requirement for plant growth and supports various life forms on the earth.

1. The minerals present in the soil enhance and nourishes the crops and plants.
2. It is used in the making of ceramics or pottery.
3. It is a source of material for construction and handicraft works.
4. It acts as a natural filter of water and purifies it.
5. Soil supports the ecosystem and plays an important role in land management.