Gujarat Board Textbook Solutions Class 8 Social Science Chapter 5 Natural Disasters

Gujarat Board GSEB Solutions Class 8 Social Science Chapter 5 Natural Disasters Textbook Exercise Important Questions and Answers, Notes Pdf.

Gujarat Board Textbook Solutions Class 8 Social Science Chapter 5 Natural Disasters

GSEB Class 8 Social Science Natural Disasters Textbook Questions and Answers

Answer the following questions:
Question 1.
Can the disasters mentioned in this unit be called as ‘geographical events’ ? Why ?
Answer:
Yes. The disasters mentioned in this unit can be called ‘geographical events’.
Earthquake, volcano, tsunami, flood, drought, landslide, etc. are disasters which occur on the surface of the Earth, so these can be called ‘geographical events’.

Question 2.
How can you get information about disasters from government?
Answer:
Information regarding disasters and their management can be collected from the following address by post or by E-mail:
Gujarat State Disaster Management Authority
Block No. 11, Fifth floor, Udyog Bhavan,
Gandhinagar : 382 017.
Telephone : +917923259220 Fax : +917923259275
E-mail: info@gsdma.org

Question 3.
What are the advantages of living in a volcanic region ? How ?
Answer:
If I live in a region of a dead volcano, I shall get the following benefits:

As magma soil is very fertile, substantial crops can be grown.
There will be abundant farm production in the volcanic soil on the slopes of the volcano.
Minerals such as mercury, lead, antimony, lead, zinc, tungsten, tin, etc. also available from lava rocks, which are used in industries.
Diamonds are found in these areas.
At a few places, there are hot water springs and geysers. Such water is useful in curing certain skin diseases.

Question 4.
Your friend’s village has been affected by flood. What will you do to help him?
Answer:

I shall provide food grains, clothes, medicines, utensils for kitchen, and beds, etc. to him.
I shall arrange for his stay.
I shall instruct my friend and the villagers to drink only boiled water.
I shall arrange to provide enough grass and drinking water for the cattle in his house.
With the help of friends, I shall clean up the filth deposited in his home due to flood.
I shall join the labour camps to repair the roads damaged due to the flood.
Some NGOs work in flood affected areas to provide relief. I shall join such an institution.
I shall contribute as much money as I can to the Chief Minister’s Relief Fund or to some fund raising institution.

Question 5.
Which areas experience landslides more frequently ? Why ?
Answer:
Landslides occur more in the regions of heavy rainfall and in tectonic zones. This is so because surface rocks are broken due to heavy rainfall or due to an earthquake.

Question 6.
What efforts should be made to prevent drought / famine from occurring?
OR
What efforts should be made for protection against drought ?
Answer:
The following efforts should be made to prevent drought/famine :

Every year, more and more trees should be planted and nurtured.
Prevent atmospheric pollution to maintain the humidity in the atmosphere.
Wells should be deepened or should be recharged to get water for drinking and for irrigation. (4 ) Water storage tanks or reservoirs should be built to store rainwater and storm water.
Water should be stored by constructing check dams across small rivers, streams or water creeks.
Attempts should be made to store rainwater and increase ground water volume.
Length of canals, attached to main dam, should be increased.
Lakes should be made deeper to store more rainwater.

Fill in the blanks with a proper word:

1. The origin of an earthquake is known as ………………… .
Answer:
focus

2. Forest resources get depleted due to ………………… .
Answer:
Forest fires

3. Often ………………. strikes in the coastal regions of India.
Answer:
cyclone

4. Due to landslide, ……………… railway gets obstructed frequently.
Answer:
Konkan

Activities
(1) Arrange a group discussion or an elocution competition on ‘Be Safe from Natural Disasters’.
(2) If possible, meet people from Disaster Management Committee and discuss ‘Natural Disaster Management’ with them.
(3) Project:
Prepare a chart with information and pictures of any one natural disaster that has occurred in the recent past.

GSEB Class 8 Social Science Natural Disasters Intext Questions and Answers

Question 1.
How will you be helpful to others if there is an earthquake in your area?
Answer:

I shall arrange for residential accommodation of earthquake-affected people.
I shall provide them with food, clothes, medicine, utensils for cooking, beds, etc.
I shall try to get financial help from government and other NGOs for repairing or buying new houses for the earthquake-affected people who lost their homes due to the earthquake.
I shall help to rescue the people buried under the debris.
I shall hand over household goods and other things obtained from the debris to the authorised officer of government.
If possible, I shall accommodate earthquake-affected people in my house for some days.
I shall offer consolation, show patience and try to give them courage.

Question 2.
Would you like to live in a region of volcano ? Why?
Answer:
See the answer of sub-question (6) of the main Question 1. of guestions And Answers section.

Question 3.
If your house is near the seashore and the government warns you about tsunami, what will you do for your protection?
Answer:

I shall pick up my valuable things and go to a higher place.
I shall avoid the fascination of watching the tsunami at the seacoast.
I shall listen to the radio and television for more safety instructions about tsunami.
I shall take benefits offered by social service organizations for safety from tsunami.

Question 4.
How will you respond to the situation if the warning for a cyclone is given?
Answer:
I shall immediately:

Go to a safer place.
Switch off all electric connections and stand away from electric poles, large trees, buildings, etc.
Shift my cattle to a safe place.
Put the valuable things in my house in a safe place.
Have enough quantity of food and water.
Maintain patience and courage.
Listen to the weather news on radio and television and follow safety instructions strictly.
I will not be carried away by rumours.
After the cyclone is over, I shall participate in the rescue work and show compassion for the affected persons.

GSEB Class 8 Social Science Natural Disasters Additional Important Questions and Answers

Choose the correct alternative from those given below each question:

Question 1.
What is the place nearest to the focus of an earthquake on the surface of Earth called ?
A. Earthquake centre
B. Epicentre
C. Focal centre
D. Landslide centre
Answer:
B. Epicentre

Question 2.
Due to how many reasons are volcanic eruptions caused ?
A. Two
B. Five
C. Three
D. Four
Answer:
D. Four

Question 3.
How many types of volcanic mountains are there ?
A. Three
B. Four
C. Two
D. Five
Answer:
A. Three

Question 4.
What is the approximate length in kilometres of a tsunami wave ?
A. 800 to 1200
B. 500 to 1500
C. 700 to 1600
D. 600 to 900
Answer:
C. 700 to 1600

Question 5.
In which year did the tsunami disaster occur in Japan ?
A. 2004
B. 2008
C. 2010
D. 2011
Answer:
D. 2011

Question 6.
Which pollution should be reduced for reducing the possibility of drought?
A. River
B. Atmospheric
C. Water
D. Land
Answer:
B. Atmospheric

Fill in the blanks with a proper word:

1. Earthquake is caused due to internal …………….. in the earth.
Answer:
disturbance

2. Maximum effect of an earthquake is near the ……………… on the surface.
Answer:
epicentre

3. Effect of an earthquake depends on its ……………… .
Answer:
intensity

4. Lava soil is fertile because it contains ……………….. .
Answer:
potassium

5. The fast flow of water in a river is called ‘ ……………….. ’.
Answer:
flood

6. An earthquake is recorded with a …………….. .
Answer:
Seismograph

7. Tsunamis and cyclones cause destruction near ……………….. .
Answer:
coastal regions

State whether the following statements are true or false:

1. Focus (of an earthquake) is on the surface of the Earth.
Answer:
False

2. Effect of an earthquake depends on its speed.
Answer:
True

3. Heavy gases below the lava push it downwards.
Answer:
False

4. Diamonds are found at few volcanic regions.
Answer:
True

5. More trees should be grown to prevent droughts.
Answer:
True

6. Heavy damage is caused to forests due to forest fire.
Answer:
True

Match the pairs correctly:

Section ‘A’	Section ‘B’
(1) Lava	(1) Tsunami
(2) Powerful and devastating	(2) Forest fire sea waves
(3) Drought	(3) Heavy damage to forest resources
(4) Earth	(4) Shortage of food and water quake
	(5) Volcano

Answer:
(1 – 5), (2 – 1), (3 – 2), (4 – 3).

Write answers to the following questions in one or two sentences:

Question 1.
Name the natural disasters.
Answer:
Names of natural disasters :

Earthquake,
Volcano,
Tsunami,
Flood,
Drought,
Storm (Cyclone),
Forest fire and
Landslides.

Question 2.
What is an earthquake ?
Answer:
Due to catastrophic (sudden) movements like collision of plates in the interior of the Earth or heavy pressure, the weak upper crust of Earth experiences sudden tremors. This is called ‘earthquake’.

The place from where these movements start is called ‘Focus’. The focus of the earthquake is in the interior of the earth.

The seismic waves caused due to an earthquake ; travel at different velocities in different directions. The nearest place on the surface of Earth, perpendicular to the focus of the earthquake is called its ‘Epicentre’. The area around the epicentre suffers maximum damage. The impact of the earthquake becomes less as we go away from the epicentre. The effect of an earthquake depends on its intensity.

Seismographs placed at various centres on the surface? record the earthquake very minutely. The locations o. the focus and the intensity of the earthquake can be ascertained with the help of a seismograph. There are ‘ three types of earthquakes :

Volcanic,
Tectonic and
Plutonic.

Question 3.
What is an Epicentre ?
Answer:
The nearest place from the focus on the surface of the Earth, perpendicular to the Focus, is called Epicentre.

Question 4.
Which instrument records earthquakes ?
Answer:
Earthquakes are recorded with a Seismograph.

Question 5.
What are the reasons for an earthquake ?
Answer:
There are three reasons for earthquakes.
They are :

Earthquakes caused by volcanic eruptions (Volcanic Earthquakes),
Earthquakes caused by strike-slip faults (Tectonic Earthquakes) and
Earthquakes caused by subduction in an active subduction zone (Plutonic Earthquakes).

Question 6.
What is a volcanic mountain ?
Answer:
When a volcanic eruption takes place, ash, big . rocks and lava, etc. are deposited around the volcanic crater and a cone-shaped small or big hill is formed. Frequent eruptions raise the height of the hill and it turns into a volcanic mountain.

Question 7.
What are the reasons for the volcanic eruption ?
Answer:
When the tectonic balance is disturbed, hot magma, “Jrock material, ash, water vapour and other gases rush towards the surface with great speed. These are thrown out through a fissure or a vent in the rock strata. This process is called ‘volcanic eruption’.

There are four reasons for volcanic eruptions :

Very high temperature in the interior of the Earth,
Formation of liquid magma,
Formation of gases and water vapour and
Movement of magma towards the surface of the Earth.

Question 8.
How many types of volcanoes are there ? Which are they?
Answer:
There are three types of volcanoes. They are:

Active volcano,
Latent (dormant) volcano and
Extinct (dead) volcano.

Question 9.
What is a Tsunami ?
Answer:
Tsunami is a Japanese word. ‘Tsu’ means a ports and ‘nami’ means waves. Due to volcanic eruption or an earthquake on the sea/ocean floor, huge, very strong and abnormally high and unimaginably long waves are created. These are called ‘Tsunami’.

Their length is approximately 700 to 1600 km and they travel with great speed and force. By the time these waves reach coast, they become very destructive. They attain great height and power which causes a great deal of destruction on the coast.

Tsunami waves are generated one after another. As a result, devastation near the coastal area continues for many hours. India experienced a tsunami disaster on 26th December, 2004 and Japan on 11th March, 2011.

Question 10.
What is a ‘flood’? Which areas are more affected due to floods ?
Answer:
Due to heavy and continuous rainfall in the upper course of a river, or due to bursting of a dam causes water to flow at great speed. This is called a ‘flood’. Low-lying areas along the river bed are most affected by floods.

Question 11.
What is a ‘drought’?
Answer:
A drought means the non-occurrence of rains. Such a condition is created when there is no rainfall or scanty rainfall which leads to the drying up of ground water. This is called ‘drought’.
Droughts create shortage of food grains and water.

Question 12.
When is a storm created?
Answer:
When a low pressure area develops over land or sea, powerful winds blow towards this area from the surrounding regions. When these winds blow powerfully along with rainfall, a storm is developed.

Question 13.
What is a ‘forest fire’?
Answer:
In dense forests, dry branches of larger trees come into friction with each other frequently due to winds. This generates fire which spreads quickly within the forest. Such fires occur due to other reasons also. Such a fire is called ‘forest fire’. A lot of damage is caused due to forest fire.

Answer the following questions:

Question 1.
What is an earthquake ? Explain the process of an earthquake.
Answer:
Due to catastrophic (sudden) movements like collision of plates in the interior of the Earth or heavy pressure, the weak upper crust of Earth experiences sudden tremors. This is called ‘earthquake’.

The place from where these movements start is called ‘Focus’. The focus of the earthquake is in the interior of the earth.

Volcanic,
Tectonic and
Plutonic.

Question 2.
What is a volcanic eruption ?
OR
What is the process of a volcano ? State the reasons for a volcanic eruption.
Answer:
When the tectonic balance is disturbed, hot magma, “•Jrock material, ash, water vapour and other gases rush towards the surface with great speed. These are thrown out through a fissure or a vent in the rock strata. This process is called ‘volcanic eruption’.

There are four reasons for volcanic eruptions :

Very high temperature in the interior of the Earth,
Formation of liquid magma,
Formation of gases and water vapour and
Movement of magma towards the surface of the Earth.

Question 3.
How is a volcanic mountain formed ? What are the types of volcanoes ?
OR
Write short notes: Composition of a volcano
Answer:
Due to internal pressure there is a lot of movement within the molten lava situated in the interior of the Earth. The temperature of water which has percolated into the upper layers of the soil rises, and the water eventually turns into water vapour. Water vapour requires much more space than water. So it exerts tremendous pressure in all directions. Due to this, the weaker sections of the Earth’s crust break with big sound and create fissures. First of all, water vapour is thrown out through these fissures. It is followed by ash, rock fragments, mud and then the hot magma. This magma spreads in all directions and forms a cone-shaped hill or a mountain. Such a mountain is called a ‘volcano’. This is how a volcano is formed.

There are three types of volcanoes:

Active volcano,
Dormant (latent) volcano and
Extinct (dead) volcano.

Question 4.
State the benefits of a volcanic eruption.
Answer:
The benefits of a volcanic eruption are :

Due to such eruptions, a large layer of lava spreads on the surface of the Earth and lava soil is formed. This lava soil is very fertile and is useful for agriculture.
Abundant crop can be obtained with the help of potassium-rich soils of volcanic residues.
Volcanic regions are composed of igneous rocks. Precious minerals like mercury, antimony, lead, zinc, tungston, tin, etc. are available from these rocks.
When the lava cools down and solidifies in the volcanic pipe and carbon comes under heavy pressure, it turns into diamonds.
At few places in the volcanic region, there are hot water springs and geysers which are useful in curing certain skin diseases.
Small pebbles thrown out from the volcano are known as ‘Lapilli’. These can be moulded and given desired shapes easily.

Question 5.
What is a tsunami ? Explain.
Answer:
Tsunami is a Japanese word. ‘Tsu’ means a ports and ‘nami’ means waves. Due to volcanic eruption or an earthquake on the sea/ocean floor, huge, very strong and abnormally high and unimaginably long waves are created. These are called ‘Tsunami’.

Write short notes:
Devastating waves
Question 1.
Answer:
When a storm or a cyclone emerges in the ocean, large and powerful waves are generated. After the storm is over, the shape of the waves changes. They attain height, develop longer length and spread up to hundreds of kilometres from the place of their origin. When they reach the seacoast, they cause heavy damage. So these waves are called ‘devastating waves’.

When a large boulder or a glacier breaks near the seacoast and falls into the sea, or a shooting star falls in the sea, similar large waves occur.

Gujarat Board Textbook Solutions Class 8 Social Science Chapter 5 Natural Disasters

Gujarat Board Textbook Solutions Class 8 Social Science Chapter 5 Natural Disasters