Science textbook solutions for Class 7 Chapter 10 Disaster Management

Important points to remember :
  1. We have studied two types of disasters, namely, manmade and  natural disasters.  Natural disasters such as famine, lightning strikes, cloudbursts, storms, etc. occur due to changes in the weather.  
  2. The condition that arises due to long term and severe scarcity  of foodgrains and water is called famine. 
  3. Famines can be very severe. 
  4. Government of India established the National Flood Commission in 1976. 
  5. The Commission has made special efforts towards the control of floods. Such a wave, generated  by an earthquake or volcano occurring on the ocean floor, is called a ‘tsunami’. ‘Tsunami’ is a Japanese word which means ‘harbour wave’. 
  6. 13th  October International Day for Disaster Reduction.

Question 1: Find the odd one out.
a) Famine, earthquake, cloudburst, railway accident
Answer : Railway accident is the odd one. Famine, earthquake and cloudburst are natural disaster whereas railway accident is not.

b) Drought, heavy rains, storm, tsunami.
Answer : Drought is the odd one. Drought is the main cause of famine whereas heavy rains, storm and tsunami are the secondary factors.

c) Lava, hot mud, ash, locusts.
Answer : Locusts is the odd one. It is an insect which destroys crops. Lava, hot mud and ash are the substances released during volcanic eruption.

d) Washing away of crops, attack of pests on crops, volcano, singeing of crops
Answer : Volcano is the odd one. Washing away of crops, attack of pests on crops and singeing of crops are causes of famine.

Question 2: What are the remedial measures for the following calamities?
a) Famine 
Answer :
1. Planned usage of water and reuse of water.
2. Proper planning of water conservation and harvesting at the local level.
3. Large scale plantation of trees and prevention  of deforestation.
4. Making appropriate  changes in plans, taking into account the weather  forecasts.

b) Lightning strike
Answer : Do not stand on open ground or below a tree. Do not go to a high location  or climb  a tree.

2. Do not stand near an electric  pole, a telephone  pole, a tower, etc.

3. Do not lean  on wired  fences  around a farm,  a compound,  a garden or a house.

4. If you are on a two-wheeler, a bicycle, a tractor or a boat, get off immediately  and go to a safe place.

5. Do not gather all together  in one place.

6. Take care to keep a distance  of 15 feet between  any two persons.

7. Do not  use  plugged  in  electrical  appliances.  Do not  use  a mobile  or telephone.

8. Stand on dry wood, a plastic  sheet, sack or jute  cloth  or dry leaves.

c) Storm
Answer : Do not stand on open ground or below a tree. Do not go to a high location  or climb  a tree.

2. Do not stand near an electric  pole, a telephone  pole, a tower, etc.

3. Do not lean  on wired  fences  around a farm,  a compound,  a garden or a house.

4. If you are on a two-wheeler, a bicycle, a tractor or a boat, get off immediately  and go to a safe place.

5.Do not gather all together  in one place.

d) Cloudburst
Answer :
  1. Introduce better flood warning systems. 
  2. Modify homes and businesses to help them withstand floods.
  3. Construct buildings above flood levels.
  4. Tackle climate change.
  5. Increase spending on flood defences. 
  6. Protect wetlands and introduce plant trees strategically. 
  7. Restore rivers to their natural courses. 
  8. Introduce water storage areas.

Question 3: True or false ? Give reasons for your answer.
a) Information about a forthcoming storm is to be kept secret.
Answer: False. You should alert everyone about forthcoming storm so that they'll prepared for crisis.

b) You should not swim when there is lightning in the sky.
Answer: True. As lightning frequently strikes water & conducts through it, you should avoid swimming during lighting.

c) It is possible to prevent the eruption of a volcano.
Answer: False. As volcanoes are natural phenomenon, we cant stop it from eruption.

d) Heavy rains result in famine.
Answer : True. Heavy rains causes flood which destroys food storages. Thus it results in famine.

Question 4: Write answers to the following question in your own words.

a) What is a tsunami? What gives rise to a tsunami?
Answer : A tsunami is a series of large waves generated by an abrupt movement on the ocean floor that can result from an earthquake, an underwater landslide, a volcanic eruption or - very rarely - a large meteorite strike. However, powerful undersea earthquakes are responsible for most tsunamis.

b) What is a cloudburst?
Answer : due to very high temperature  near the  land, it  vapourizes and goes back into the same clouds. As  a result the  amount  of vapour in those  clouds  becomes very high. Due to rapid condensation, it rains suddenly  over  a specific  and small  region  at a rate of 100 mm per hour or more. This is known as a cloudburst

c) Explain the effects of a volcano.
Answer : The  chemical  substances such as lava, vapour, hot mud, sulphur, etc. get collected  on the surface of the earth and thereby  mountains and hills are created. The atmosphere gets polluted due to the ash  and gases ejected  by the volcano. Often, it rains as a result of a volcanic  eruption. Temperature  rises due to hot gases. Forests and settlements get buried under the hot mud.

d) What are the measures to prevent loss of life due to lightning?
Answer : The following measures should be taken to avoid fatality during lightning:

i) On all tall and high-rise buildings, there must be lightning arrestors on the roof which will send lightning surge to ground.

ii) We should stay away from the mountains in the rainy days because mountains are potential risks during lightning days.

iii) Tall trees are connected with the ground. So, we should stay away from them because when lightning will fall on it you may come in contact with that lightning.

Question 5: What measures have been taken to deal with calamities such as floods and landslides under the disaster management programme in Maharashtra?
Answer : The Disaster management department under the Maharashtra government has put into immediate plans as the people of the region faced floods.

The plans have a unique effective operation strategy to deal with such calamities as they aim in protecting the lives of their residents. They also warn about incoming earthquakes prior.

Question 6 : With reference  to disaster management what are the things in your house that you will check?
Answer :
1)we should check the ceiling fans.
2)we should check that the house's base is strong or not.
3)Have some extra medication on hand for times when disaster strikes.
4)Teach family members how to turn off electricity, gas, etc.
5)Identify places in the house that can provide cover during an earthquake.

#use your brain power
1. Why shouldn’t we wait at the foothill  while it is raining heavily ? 
Answer : We should not wait at the foothill while it is raining heavily because there are chances of heavy mudslide or landslide any moment. There might be potential for dangerous mud flow occurrence in the foothill which is very dangerous and not safe. The areas along the trough line can receive very heavy rain any moment.