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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

Rock And Soil Class 8 Question 1.
Which of the following is known as sphere of rocks –
(a) Atmosphere
(b) Biosphere
(c) Lithosphere
(d) Hydrosphere
Answer:
(c) Lithosphere

Rocks And Soils 8th Standard Question 2.
World soil day is observed on –
(a) 15th August
(b) 12th January
(c) 15th October
(d) 5th December
Answer:
(d) 5th December

Samacheer Kalvi Guru 8th Social Question 3.
Fossils are found in –
(a) Sedimentary rocks
(b) Igneous rocks
(c) Metamorphic rocks
(d) Plutonic rocks
Answer:
(a) Sedimentary rocks

Social Samacheer Kalvi 8th Question 4.
The first layer of soil is called as –
(a) Regur
(b) Regolith
(c) Unweathered rock
(d) Partially weathered rock
Answer:
(*) Horizon

8th Social Guide Samacheer Kalvi Question 5.
Ideal soil for growing cotton is –
(a) Red soil
(b) Black soil
(c) Alluvial soil
(d) Mountain soil
Answer:
(b) Black soil

Samacheer Kalvi 8th Social Book Question 6.
The major component of soil is –
(a) Rocks
(b) Gas
(C) Water
(d) Minerals
Answer:
(d) Minerals

Samacheer Kalvi Guru 8th Social Science 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. Scientific study of rocks is called ………………
  2. …………… soil is highly suitable for cotton cultivation.
  3. The “skin of earth” is ……………..
  4. ……………. is the kind of metamorphic rock using which 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

Samacheer Kalvi 8th Social Question 1.
Igneous rocks are called primary rocks.
Answer:
True

Samacheer Kalvi 8th Social Science Question 2.
Slate is formed from shale.
Answer:
True

Samacheer Kalvi 8th Books Solutions Social Science Question 3.
Red soil is formed by the process of leaching.
Answer:
False
Correct statement:
Laterites soils i s formed by the process of leaching.

8th Social Samacheer Kalvi Question 4.
M – sand is used as alternative for natural sand in construction.
Answer:
True

Samacheer Kalvi.Guru 8th Social 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

Samacheer Kalvi Social Science 8th Question 1.
Rock And Soil Class 8 Samacheer Kalvi Science Geography Solutions Term 1 Chapter 1Answer:

a. 2
b. 1
c.  4
d. 3.

Samacheer Kalvi 8 Social Question 2.
Rocks And Soils 8th Standard Samacheer Kalvi Science Geography Solutions Term 1 Chapter 1 Rock And Soil
Answer:

a. 2
b. 4
c.  1
d.  3.

V. Choose the incorrect statement from the following

Kalvi Guru 8th Social Question 1.

  1. Igneous rocks are called the primary rocks.
  2. Soil is the product of 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.

8th Samacheer Kalvi Social 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 of 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

Social Guide For Class 8 Samacheer Kalvi Question 1.
Chemical sedimentary rocks are found in the beds of reservoirs.
Answer:
Chemical Sedimentary rocks are formed by precipitating of minerals from water. It is formed usually through evaporation of chemical rich solutions.

Samacheer Kalvi Guru 8 Social Science 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

Samacheer Kalvi 8th Books Social Science 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 donot 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:
The igneous rocks are formed by the solidification of molten magma.

Question 2.
Describe about the composition of 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:

  1. The rocks are the solid mineral materials forming a part of the surface of the earth and other similar planets.
  2. A rock is an aggregate of one or more minerals. Rock is an important natural resource and is found in solid state.
  3. It may be hard or soft in nature.

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 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:
Samacheer Kalvi Guru 8th Social Science Geography Solutions Term 1 Chapter 1 Rock And Soil
Igneous:
(i) The igneous rocks are formed by the solidification of molten magma. Also called Primary or Parent Rocks.
(ii) Types:

  • Extrusive Igneous Rocks.
  • Intrusive Igneous Rocks

1. Extrusive Igneous Rocks:
Molten magma which comes out from the interior of the earth’s surface, gets solidified and forms such rocks. Fine grained and glassy in nature. Eg., Basalt, found in north western peninsular India.

2. Intrusive Igneous rocks:
Molten magma cools down deep inside the earth’s crust, becomes solid and forms such rocks. Form large grains. Deep seated rocks are plutonic rock and ones at shallow depths – Hypabysal rocks. Example Granite, Diorite.

Sedimentary:
(i) Formed by the sediments derived and deposited by various agents. Also called stratified rocks.
(ii) Types:

  • Organic sedimentary rocks
  • Mechanical sedimentary rocks,
  • Chemical sedimentary rocks

1. Organic sedimentary rocks:
Formed due to decomposition of dead Plants and Animals. Contains fossils. Example Chalk, Talc

2. Mechanical sedimentary rocks:
Formed from the disintegration of Igneous and metamorphic rocks. Get deposited due to erosion by natural agents. Get cemented after a long time to form rocks. Example Sandstone, Shale.

3. Chemical sedimentary rocks: Formed by precipitating of minerals from water. Formed due to evaporation of chemical rich solution. Example Rock Salt.

Metamorphic:
(i) Formed when Igneous and sedimentary rocks are subjected to high temperature and pressure.
(ii) Types:

  • Thermal
  • Dynamic

1. Thermal Metamorphic:
If the change in rocks is caused by high temperature.

2. Dynamic Metamorphic:
If the change in rock is caused by high pressure. Formed from Igneous rocks. Eg., Granite into gneiss
Formed from Sedimentary rocks. Eg., Shale into Slate

Question 3.
Give an account on different layers of soil.
Answer:
Social Samacheer Kalvi 8th Science Geography Solutions Term 1 Chapter 1 Rock And Soil
8th Social Guide Samacheer Kalvi Science Geography Solutions Term 1 Chapter 1 Rock And Soil

Question 4.
Classify and explain the soil.
Answer:
Definition:
Soil is a mixture of Organic matter, minerals, gases, liquids and organisms that together support life.

Classification of soils:
Soils are classified on the basis of their formation, colour, physical and chemical properties. Based on these, soil is classified into six major types. They are: Alluvial soil, Black soil, Red soil, Laterite soil, Mountain soil, Desert soil.

Alluvial soil:

  • Found in the regions of river valleys, flood plains and coastal regions.
  • Formed by the deposition of silt by the running water.
  • Most productive of all soils.
  • Suitable for the culitivation of sugarcane, jute, rice, wheat.

Black soils:

  • Formed by weathering of igneous rocks.
  • Clayey in nature.
  • Retains moisture.
  • Ideal for growing cotton.

Red Soils:

  • Formed by weathering of metamorphic rocks and crystalline rocks.
  • Found in semi – arid regions.
  • Not a fertile.
  • Is soil brown red in colour due to the presence of iron oxide
  • Suitable for millet cultivation.

Laterite soils:

  • Formed by the process of leaching.
  • Found in trophical regions, which experienced alternate wet and dry condition.
  • Infertile soil.
  • Suitable for plantation of tea and coffee.

Mountain soils:

  • Found in slopes of mountains.
  • Thin and acidic in nature.
  • Nature of soil differs based on the altitude.

Desert soils:

  • Found in hot desert region.
  • Porous and saline in nature.
  • Infertile in nature.
  • Agriculture not successful.

IX. Activity Corner

Question 1.
Complete the following table with the help of internet source
Samacheer Kalvi 8th Social Book Science Geography Solutions Term 1 Chapter 1 Rock And Soil
Answer:
Samacheer Kalvi Guru 8th Social Science Geography Solutions Term 1 Chapter 1 Rock And Soil

Question 2.
Map Work:
Mark the areas of black soil on the outline map of India.
Answer:
Samacheer Kalvi 8th Social Science Geography Solutions Term 1 Chapter 1 Rock And Soil

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.
Oldest sedimentary rocks of the world have been identified in
(a) Green land
(b) India
(c) France
(d) Australia
Answer:
(a) Creen landi

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) Deserti

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, firel
  6. Crystallins
  7. Change, shape
  8. Faster

III. Match the following

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

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

IV. Choose the incorrect statement from the following

Question 1.

  1. Igneous rocks donot 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 resource 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 are the typical soils of trophical regions. These soils are found in the regions which experienced 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 lithosphere, hydrosphere, atmosphere and biosphere.

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

Question 3.
What is lava?
Answer:
Lava is actually a fiery red molten magma 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 as ‘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 as thermal metamorphism..

Question 8.
Explain Dynamic Metamorphism.
Answer:
If the change in the rock is mainly caused by high pressure, the process is called as 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. Kerb stone
  7. Ornament
  8. Roofing materials
  9. Decorative materials
  10. These are valuable source 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 the examples of rocks of this type.

3. Chemical Sedimentary rocks

  • These are formed by precipitating of minerals from water. It is formed usually through evaporation of chemical rich solutions.
  • These rocks are also called as 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 are 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 crust keeps on changing from one form to another form under various natural forces and agents.

5. The endless process is referred as Rock Cycle.

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

Question 3.
Mention the uses of soils.
Answer:
Uses of soils:
Soil is one of the important natural resource. 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 making of ceramics or pottery.
  3. It is a source of material for construction and handicraft works.
  4. It acts as natural filter of water and purifies it.
  5. Soil supports ecosystem and play an important role in land management.

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