1. Is it possible to prevent the loss of life caused by lightning?
2. What should be done to prevent the bunds on a farm from getting washed away in the rainy season?
3. Why do we experience water-scarcity?
We have studied two types of disasters, namely, manmade and natural disasters. Into which categories do the disasters shown in the news items above, fall ?
We can prevent certain disasters, while it is necessary to take precautions in the case of some other disasters. Natural and manmade disasters are related to each other. Natural disasters such as famine, lightning strikes, cloudbursts, storms, etc. occur due to changes in the weather. There is the possibility of damage to property in such natural calamities. Who is to be held responsible for that ? What can we do to deal with these losses ?
The condition that arises due to long term and severe scarcity of foodgrains and water called famine. Famines can be very severe. Although the main cause of famine is natural phenomena, yet a famine condition is created by some human activities besides some natural events.
There are records of loss of life caused by severe famines in various parts of the world. Asia has turned out to be the most famine affected continent of the world. A majority of the famines occurred in drought prone and flood affected regions. Among the most dreadful famines that have occurred in the world, are the famines that affected India and China.
Are we responsible for famine?
- Water shortage is increasing as the balance between rainfall and population is disturbed.
- Though there has been a very high rise in the production of foodgrains as a result of the green revolution, the balance of the environment has been lost due to use of chemical fertilizers, pesticides and weedicides.
- Unlimited lifting of water.
- Erosion of land.
- Misuse of water.
Sometimes the water coming down from rain clouds does not reach the land in the form of rain. Instead, 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.
We have already learnt about floods and the effects of floods. Collect information about the floods that have occurred at various places in Maharashtra in the last few years.
Protective measures in view of floods
- Construction of small dams in mountainous regions
2. Construction of percolation tanks
3. Making river beds flat
4. Cultivation of new forests
5. Connecting rivers
You have learnt about generation of electric charge and lightning strikes in the lesson on static electricity. In this lesson we shall learn something more about lightning and the measures for protection from it.
A volcano is a natural event or phenomenon. The interior of the earth is very hot. Movement of hot substances continuously occur from the interior towards the surface of the earth. As a result, sometimes the solid, liquid and gaseous substances below the earth’s crust are pushed towards the crust. When these substances come out of the earth’s crust in an eruption and start flowing, it is called a volcano.
What are the effects of a volcano?
- 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.
2. The atmosphere gets polluted due to the ash and gases ejected by the volcano.
3. Often, it rains as a result of a volcanic eruption.
4. Temperature rises due to hot gases.
5. Forests and settlements get buried under the hot mud.
Volcanoes erupt in the sea as they do on land. The same substances that come out during the eruption of a volcano on the land are ejected during the eruption of a volcano in the sea. Some islands are created due to the eruption of volcanoes in the sea. It is not possible to prevent the eruption of a volcano, to stop it after it erupts or to control it. However, by means of science and technology, it is possible to predict an eruption and to take immediate steps for disaster management.
As on land, earthquakes and volcanic eruptions occur at the bottom of the sea, too. If an earthquake occurs at the bottom of ocean, the energy released pushes the water upwards. As a result of this, a peculiar type of waves are formed. These waves are not very high near the source, but they start spreading very fast to long distances. The velocity of these waves is 800 to 900 kilometre per hour. When they reach a coastal area, their velocity is reduced, but their height is found to have increased tremendously, even to about 30 metres 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’.
Destructive effects of tsunami
- Buildings and other constructions are destroyed.
2. There is large scale loss of life and financial loss.
3. Boats and ships near the coast get damaged.
4. Trees get uprooted. Landslides take place on a large scale.
5. Changes take place in the original land near the coast giving rise to swamps.
6. Traffic obstructions arise.
7. The business/industry related to the sea are adversely affected and normal day-to-day life is disrupted.
8. Large scale damage is caused to harbours.
We have already learnt about the formation of storms and their effects. Suppose, you are caught in a storm. What will you do to keep yourself safe
With the help of your teacher prepare a power point presentation on ‘Effects of Natural Calamities and Measures for their Management’ and present it in the class.