Disaster Management Class 8 Science Notes Maharashtra State Board
Earthquake
Sudden vibrations on the earth and shaking of the earth’s surface /ground is called an earthquake. These cause seismic waves leading to movements of the earth’s surface like tremors, shaking, or going down. The shocks and waves formed in the interior of the earth spread on the surface in all directions. The central point of an earthquake is the point above the epicenter on the earth’s surface. Strong convulse or waves at first reach the epicenter, therefore major loss occurs near that area.
Shocks that occur due to an earthquake can be mild or intensified (acute). On the earth, mild earthquakes occur in a larger number than the intensified or Runners. Every day, earthquakes are noticed at some or the other places on the earth. According to the observation of ‘The National Earthquakes Information Center’ every year nearly 12,400 to 14,000 earthquakes occur on the Earth. From this, it is noticed that the earth is continuously vibrating.
The machine/Instrument which records the earthquakes is called a seismograph’ or ‘Seismometer’, and the accentuation (intensity) is measured on ‘Richter Scale’. This is one of the mathematical measuring units. The effects of earthquakes are mentioned below. Study them carefully.
Causes of an Earthquake
- Volcanic eruption.
- The stress of big dams on the earth.
- Mining.
- Underground atomic tests.
- Water percolates through the cracks of the earth. Due to tremendous heat, the water converts into steam.
- The steam formed tries to come out from the loosened earth’s surface causing earthquakes.
Effects of an Earthquake
- Loss of human beings, wild animals, and pets.
- Economic loss at large scale (Electric poles, pipelines, houses, buildings, roads, railway tracks are destroyed).
- Ecosystem destruction due to the loss of Biodiversity.
- The direction of the flow of rivers, and streams changes.
- The possibility of fire in cities increases.
- If there is an earthquake at the bottom of the ocean, it may create tsunami waves and thereby large-scale destruction of coastal regions.
- Level of water-table changes.
Precautions to be taken at the time of Earthquake
- If you are at home, then, do not get scared, and instead of running here and there, stand still in one place. Either sit on the floor or below the bed or any other furniture and cover yourself until the movement of the earth stops. If there is no table or any other shelter then sit in any corner of the room and cover your head by folding your hands around it.
- If you are in the vehicle or outside the house, then park your vehicle at a safe place and sit inside it. Do not wait near or below tall buildings, trees, or electric poles.
Avoid doing the following things during an earthquake
- Avoid using lifts in the multistoried building, instead use a staircase.
- Do not sit in discomfort for long. Do some physical movements.
- After the earthquake there is a possibility of fire, hence, to avoid it carefully switch off the main electric supply.
- Do not use candles, lanterns, or matchboxes, instead use a torch or battery.
Earthquake Resistant/Proof Buildings:
The constructions which do not get damaged due to earth movements upto a certain limit are called earthquake-resistant buildings. To construct tall buildings, ‘Indian Standard Institute’ has made some code of conduct. Buildings are constructed as per I.S. 456 and earthquake-resistant constructions are performed as per IS 1893 (Criteria for earthquake-resistant design of structure) and IS 13920 (Ductile detailing of reinforced concrete structures subjected to seismic forces). Advanced technology is used for earthquake-resistant construction. To get prior intimation about earthquakes, modern equipment like laser ranging very long baseline, Geiger counter, creep meter, strain meter, tide gauge, tilt meter, volumetric strain gauge, etc. are used.
Fire – Types of Fire
- Class A Fire (Solid Substances): Commonly flammable materials are their fuel source. (wood, clothes, coal, papers, etc.) This fire can be put out with water.
- Class B Fire (Liquid Substances): Fires caused due to flammable liquid substances (petrol, oil, varnish, solvents, cooking oil,
paints, etc.) All these substances are lighter than water, therefore, fire extinguishers can be used to extinguish the fire. - Class C Fire (Gaseous Substances): Fires caused due to acetylene, household gas (L.P.G.)
- Class D Fire (Chemical Substances): Fires caused due to combustible metals like potassium, sodium, and calcium, which react with water at normal room temperature. Magnesium, aluminum, and zinc react with water at high temperatures. When both these groups combine with water, it explodes.
- Class E Fire (Electrical): A fire caused due to electrical components is a class E fire. To extinguish such fire, power is cut off and non-conductive fire extinguishers like carbon dioxide are used.
Methods of Fire Extinction:
There are 3 main methods to stop the spread of fire or to control the fire.
1. Cool Out (Use of Water):
To extinguish fire water is the most common and effective solution which is easily available everywhere. If you spray water on the fire or around the fire it creates a cooling effect and helps to control the fire.
2. Suppress the Fire:
To control the fire which is caused due to electricity or oil, sand or soil can be used. If we spread a froth-like substance on the fire, it cuts off the contact between air and fire. This method is more useful to extinguish the fire spread due to oil.
3. Keep Away Flammable Substances:
In this method, all flammable substances are kept away from the fire. Any wooden article or flammable substances must be kept away so that no source is left for the fire to spread. The stirrup pump is the best device to put off small fires. It sprays water in all directions around the fire.
Precautions and Safety Measures
- Develop the habit of switching off the gas regulator when not in use, especially during the night. Switch off the electrical appliances when you are going out of the house.
- To make others alert and call them for help, shout.
- Call the fire brigade.
- Provide information on how to use fire extinguishers.
- First Aid: Let the patient sit/sleep in a comfortable position and call the doctor immediately.
Landslides – Rift Collapse
Natural cracks and fissures present in hard rocks cause their breaking. Especially, at the time of heavy rains, water entering these cracks causes weathering of these rocks. Weight increases, these rocks slide on the sloppy region and settle at the lower side. This is called the collapse of the rift.
Causes of Landslide:
- After-effects of natural disasters like earthquakes, tsunamis, heavy rains, storms, and floods cause landslides.
- Unlimited cutting of trees causes soil erosion.
- While building roads in mountains, there is a lot of digging, which makes the mountain weak.
Effects of Landslide:
- Rivers get flooded and change their paths.
- Displacement of waterfalls, and formation of artificial water reservoirs.
- There is live and financial loss on a large scale, as trees, buildings, and rocks on sloppy areas collapse on low-lying land.
- Landslide affects the traffic.
- Landslide destroys plant life on it.
Disaster Relief – Planning:
If the plan is prepared, it will help with any disaster relief in the school. For that prepare a chart as given below.
| Main Points | The things to be Noted |
| Primary Information of the School |
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| School Disaster Management Committee |
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| Detailed Information about School Building |
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| Information about School Ground |
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| Daily Routine of the School |
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| Possible Hazards in the School |
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| Disaster Management Map of the School | The map must have the following contents: All buildings of the school, their structure, grounds, entrances, places of probable danger in the school, safe places at the time of the disaster, and the nearest road. This map must be at the entrance of the school and all students must be given detailed knowledge about it. |
| Mock Drill in the School | Every month a mock drill must be conducted in the school. It should include possible hazards and the measures taken against them. The date, time, number of students, and shortfalls must be noted down. |
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