MSBSHSE Class 8 Science Chapter 9 Disaster Management Important

Q1. What do you mean by disaster?

Answer: A disaster is defined as a disruption on a massive scale, either natural or man-made, occurring in short or long periods of time. Disasters can lead to human, material, economic or environmental hardships, which can be beyond the bearable capacity of the affected society. As per statistics, India as a whole, is vulnerable to 30 different types of disasters that will affect the economic, social and human development potential to such an extent that it will have long-term effect on productivity and macro-economic performance.

Q2. What are the different types of disaster?

Answer: Disasters can be classified into the following categories:

• Water and Climate Disaster: Flood, hail storms, cloudburst, cyclones, heat waves, cold waves, droughts, hurricanes.
• Geological Disaster: Landslides, earthquakes, volcanic eruptions, tornadoes
• Biological Disaster: Viral epidemics, pest attacks, cattle epidemic and locust plagues
• Industrial Disaster: Chemical and industrial accidents, mine shaft fires, oil spills
• Nuclear Disasters: Nuclear core meltdowns, radiation poisoning
• Man-made disasters: Urban and forest fires, oil spill, the collapse of huge building structures

Q3. Answer the following in your own words.

a. Explain the relation between continuous rains and landslide. Give reasons.

b. Prepare a chart showing ‘Do’s’ and ‘don’ts’ at the time of earthquake.

c. What are the specifications of an earthquake – proof building?

d. Explain the effects of a landslide.

e. Is there any relation between dam and earthquake? Explain.

Answer a: After effects of heavy rains cause landslides. Plants and small trees are uprooted from the soil due to continuous heavy rains. The rain water enters the cracks and fissures present in hard rocks causing their weathering. Due to these factors, soil and rocks run off on a slopy region. This running of soil, rocks along with other debris causes landslide. This proves that there is a strong relation between continuous rains and landslide.

Answer b: Do’s at the time of earthquake:

• Stay under the lintel of an inner door, in the corner of a room, under a table or under a bed.
• Keep yourself away from glass, windows, outside doors and walls, and anything that could fall.
• Hold on and protect your head with a pillow, unless you are under a heavy light fixture that could fall.
• Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, load bearing doorway.

Avoid doing following things during earthquake:

• Avoid using the lift in the multistoried building, instead use the 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, lantern, or matchbox, instead use torch or battery.

Answer c: The constructions, which do not get damaged due to earth movements up to 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 earthquake, modern equipment like lasers ranging very long baseline, geiger counter, creep meter, strain meter, tide gauge, tiltmeter, volumetric strain gauge etc. are used.

Answer d: The effects of landslide are:

• Rivers get flooded and change their paths.
• Displacement of waterfalls, formation of artificial water reservoirs.
• There is life and financial loss on a large scale, as trees, buildings, rocks on sloppy areas collapse on low-lying land.
• Landslides affect the traffic.
• Landslide destroys plant life on it.

Answer e: The main purpose of constructing a dam is to impound flowing water. Due to storage of tons of water in the dam, there is weakening of the faults and the stress caused by it is enough to induce earthquakes. The platonic plates are disturbed and when they move, they cause an earthquake.

Q4. Give scientific reasons.

a. It is safer to find shelter under things like a bed, table at the time of earthquake.

b. In monsoon, don’t take shelter near hillside.

c. Don’t use lifts at the time of earthquake.

d. The foundation of earthquake-proof building is separated from other land.

Answer a: During an earthquake, it is safer to find shelter under things like a bed, table because due to high vibrations, heavy things may fall on us and we might get injured. If any heavy things hit us, we might die or have any other injuries. So, staying under things like a bed, table is the safest way to protect ourselves at the time of an earthquake.

Answer b: During monsoon season slipping is a common issue. Slipping happens due to various reasons, but the two most relevant ones are gravity and water. Gravity pulls soils and sand downwards and rain can help to do it fast. Thus, it ’s risky to take shelter near hillsides during monsoons.

Answer c: During an earthquake, we should not use lift because if the earthquake is too strong on the Ritcher ’s scale, it may cut the power. Due to which, you might get trapped inside the lift for an uncertain period of time, till it is reconnected. Thus, it is better to avoid it before and after the shocks.

Answer d: The simple way to structure more resistance to these lateral forces is to tie the walls, floor, roof, and foundations into a rigid box that holds together when shaken by a quake. From an earthquake point of view, the most dangerous building construction is unreinforced brick or concrete block.

Q5.If a crowd gathers at the place of earthquake, what would be the difficulties in relief work?

Answer: If a crowd gathers at the place of earthquake, there would be following difficulties in relief work:

• It would be difficult for the relief team in finding the victims
• The gathering might misuse the relief resources
• The help might get delayed towards the victims because of the crowd gathering.
• The targeted area might get havoced due to crowd gathering, which will make it hard to pinpoint the area that needs more help.
• The gathering can misguide the relief workers.
• The severity of the situation can be easily misjudged.

Q6. Make a list of the institutes and organizations who provide help for disaster management. Collect more information about their work.

Answer: The list of institutes and organizations who provide help for disaster management are:

• National Disaster Response Force (NDRF)
• National Disaster Management Authority (NDMA)
• National Institute of Disaster Management (NIDM)
• International Strategy for Disaster Reduction (ISDR)

Q7. Define earthquake.

Answer: Sudden vibrations of the earth and shaking of the earth ’s surface /ground is called an earthquake. These causes seismic waves leading to movements of the earth’s surface like tremors, shaking or it goes up-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 epicentre on the earth ’s surface. Strong convulse or waves at first reach the epicentre, therefore major loss occurs near to that area.

Q8. Name the machine or instrument used to record the earthquakes and how it is measured?

Answer: The machine / Instrument, which records the earthquakes is called ‘Seismograph’ or ‘Seismometer’, and the accentuation (intensity) is measured in ‘Richter Scale’. This is one of the mathematical measuring units.

Q9. What are the effects of an earthquake?

Answer: The effects of an earthquake are:

• 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.
• Direction of flow of rivers, streams changes.
• Possibility of fire in cities increases.
• If there is an earthquake at the bottom of the ocean, it may create tsunami waves and thereby the large scale destruction of the coastal region.
• Level of water-table changes.

Q10. What are the causes of an earthquake?

Answer: The causes of an earthquake are:

• Volcanic eruption.
• 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 surface causing earthquakes.

Q11. What precautions should be taken during an earthquake?

Answer: Following are the precautions that should be taken during an earthquake:

• If you are at home, then, do not get scared and instead of running here and there, stand still in one place.
• Sit on the floor or below the bed or any other furniture and cover yourself until the movement of 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 in a safe place and sit inside it.
• Do not wait near or below tall buildings, trees or electric poles.

Q12. Explain the causes of landslides?

Answer: The causes of landslides are:

• After effects of natural disasters like earthquake, tsunami, heavy rains, storms, floods cause landslides.
• Unlimited cutting of trees causes soil erosion.
• While building roads in mountains, there is a lot of digging that makes the mountain weak.

Q13. What are the methods of fire extinction?

Answer: There are 3 main methods to stop the spread of fire or to control the fire.

• Cool Out (Use of Water): To extinguish fire, water is most common and effective solution which is easily available everywhere. If you spray water on the fire or around the fire it creates cooling effect and helps to control the fire.
• 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.
• 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. Stirrup pump is the best device to put off small fires. It sprays water in all directions around the fire.

Q14. What is the difference between seismograph and Richter scale?

Answer: Following is the table explaining the difference between seismograph and Richter scale:

Seismograph	Richter scale
Used for measuring and recording the vibrations of earthquakes	Used for indicating the intensity of an earthquake
Used for measuring the motions related to the ground like seismic waves resulting in an earthquake and volcanic eruptions	Used for quantifying the energy that is released during an earthquake

Q15. Explain the earthquake zones in India?

Answer: There are total 5 earthquake zones in India and they are:

• Zone 5: Highly prone to earthquakes. Punjab, Kashmir and North-East India.
• Zone 4: Parts of Delhi, Jammu, Bihar and Indo-Gangetic basin.
• Zone 3: Moderate damage risk. Western Himalayan plains, Andaman and Nicobar islands.
• Zone 2 and 1: Low damage risk.

Q16. Explain the types of fire?

Answer: The types of fire are:

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 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 temperature. When both these groups combine with water, it explodes.

Class E Fire (Electrical): A fire caused due to electrical components is class E fire. To extinguish such fire, power is cut off and non-conductive fire extinguishers like carbon dioxide are used.

Q17. What is called the collapse of rift?

Answer: 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 collapse of rift.

Q18. What are the types of earthquakes?

Answer: The types of earthquakes are:

• Tectonic earthquakes: The most common form of earthquakes, it is caused by the movement of loose fragmented pieces of land on the earth’s crust known as tectonic plates.
• Volcanic earthquake: The less prevalent compared to the tectonic variety, these earthquakes have happened before or after the eruption of a volcano. It is caused when magma leaving the volcano is filled with rocks being pushed to the surface.
• Collapse earthquake: This earthquake occurs in underground mines. The main cause is due to pressure generated within the rocks.
• Explosion earthquakes: The occurrence of this type of earthquake is artificial in nature. High-density explosions such as nuclear explosions are the primary cause.

Q19. What are seismic waves?

Answer: When an earthquake occurs, it releases waves of energy, which are known as Seismic waves. It is like the ripples created in water if you throw a stone in it. Seismic waves are like those ripples which can travel through the inside of the earth, as well as on the surface.

Q20. What are the types of landslides?

Answer: Following are the types of landslides:

Falls –Falls are sudden movements of loads of soil, debris, and rock that break away from slopes and cliffs. Falls landslides occur as a result of mechanical weathering, earthquakes and force of gravity.

Slides –It is a kind of mass movement which breaks away the sliding material from the underlying stable material. During this type of landslide rotational and transitional kinds of slides are experienced.

Topples –This type of landslides occurs when the topple fails. The failure of the topple encompasses the forward spinning and movement of huge masses of rock, debris, and earth from a slope. This type of slope failure takes place around an axis near or at the bottom of the block of rock.

Spreads –They are commonly known as lateral spreads and take place on gentle terrains via lateral extension followed by tensile fractures.

Flows –This type of landslide is categorised into five; earth flows, debris avalanche, debris flow, mudflows and creep, which include seasonal, continuous and progressive.