Science Textbook Solutions for Class 8 Science Chapter 9 - Disaster Management


Important points to remember :

  1. Sudden vibrations  on the  earth  and shaking of the  earth  surface  /ground  is called an earthquake. 
  2. 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 unit.


Question 1: Answer the following in your own words.
A. Explain the relation between continuous rains and landslide. Give reasons.
Answer : Continuous rain and landslid relationship:

  1. Landslides usually occurs when the slope happen to change from a stable to an unstable condition. Therefore, the change in slope stability can be caused by numerous factors which are acting alone or together.
  2. The most important factor for landslide includes rainwater (pore water) pressure acting to destabilize or detaining the slope by its huge pressure.
  3. When continuous rain occur more and more landslides occurs which causes when water will continuously get inside the soil which in turn leaving the soil wet and heavy.
  4. Then when the rainwater enters these dents or cracks, it causes weathering of these rocks in a gradual manner.
  5. The weight of this rock increases, and this rocks slides on these particular sloppy region and settle down at the lower region.
  6. Then the heavy rainfall leads down-slope to the soil and rock under the direct influence of gravity which in turn leads to the birth of landslides.


B. Prepare a chart showing 'Do's' and 'don'ts' at the time of earthquake.
Answer :
Stay away from glass, window doors, walls and any other weak structure that may fall. Try to keep your cool and don't run around here and there, coming out of your houses. Move away from tall buildings, trees, streetlights and utility wires. Once out of your houses, stay in open space till the shaking stops.

C. What are the specifications of an earthquake proof building ?
Answer : Earthquake-resistant structures are structures designed to protect buildings from earthquakes. While no structure can be entirely immune to damage from earthquakes, the goal of earthquake-resistant construction is to erect structures that fare better during seismic activity than their conventional counterparts.

D. Explain the effects of landslide.
Answer : The negative economic effects of landslides include the cost to repair structures, loss of property value, disruption of transportation routes, medical costs in the event of injury, and indirect costs, such as lost timber and fish stocks. Water availability, quantity, and quality can be affected by landslides.

E. Is there any relations between dam and earthquake? Explain.
Answer : Dams by itself do not cause any earthquake. The purpose of any dam is to impound the flowing water. This leads to formation of reservoir in which a large portion of land is submerged along with the river course on which the dam is made. This leads to increase in the pore-water-pressure of that area.


Question 2: Give scientific reasons.
A. It is safer to find shelter under things like a bed, table at the time of earthquake. 
Answer : It is safer to find shelter under things like a bed, table at the time of earthquake because heavy things may fall on us due to high vibrations and we can get severe injuries. So, staying under things like a bed, table is the safest way to protect ourselves at the time of earthquake.

B. In Monsoons, don't take shelter near hillside.
Answer : In monsoon, shelter should not be taken near hillside because slipping during monsoon is a common issue. There are several reasons of slipping of a land but the 2 most relevant ones are gravity and water.

C. Don't use lifts at the time of earthquakes.
Answer : Lifts should not be used at the time of earthquake, because if the earthquake is too strong on the Richter's scale, it may cut the power. And, in this case, a person may be trapped in there for an uncertain period of time, till it is reconnected.

D. The foundation of earthquake-proof building is separated from other land.
Answer : Earthquake is the cause of humongous disaster. To prevent this disaster we are constantly building earthquake proof buildings. Structure of this kind of earthquake buildings are made in separate land to avoid the tectonic plate's vibration and avoid the impact of the earthquake.


Question 3 : 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, following are the difficulties faced during relief work:

  1. Hindrance to the clearance of debris
  2. Hindrance to the passage of ambulance carrying earthquake victims
  3. Aggravation of fear and panic in victims Chances of stampede and theft
  4. Quarrels amongst people for food and other resources.



Question 4: Make a list of the institutes and organizations who provide help for disaster managment. Collect more information about their work.
Answer : International government organisations working for disaster management are:

(a) The United Nations and its organisations:

The Food and Agricultural Organisation of the UN (FAO): It gives early warning of impending food crises, and keep tracks of global food supply problems.

The United Nations Development Programme (UNDP): It helps disaster-prone countries with disaster mitigation, prevention and preparedness measures.

The World Food Programme (WFP): It is the main supplier of relief food aid.

The World Health Organisation (WHO): It gives global public health leadership by setting standards, monitoring health trends, and providing direction on emergency health issues.

(b) The International Committee of the Red Cross ( ICRC): It gives physical rehabilitation to people injured by explosive weapons or other types of incident.

(c) The International Federation of Red Cross and Red Crescent Societies ( IFRC): It coordinates and gives international help to victims of natural and technological disasters, to refugees and in health emergencies.

Indian organisations and institutes working for disaster management are:
(a) National Disaster Response Force (NDRF):

(b) National Disaster Management Authority (NDMA):

(C) National Institute of Disaster Management (NIDM):


Question 5: Make a survey of your school according to the plan of disaster managment an write the pointwise information.
Answer : This an activity based questions. Kindly do it yourself.

Question 7: With the help of following pictures, explain your role in the disaster management.
Answer : Your local government has first-hand knowledge of your community's social, economic, infrastructure, and environmental needs, helping them to provide support in a disaster. The role of local government under the Disaster Management Act 2003 is to: have a disaster response capability.


# Can you Tell 
1. What do you mean by disaster ? 
Answer : A disaster is a sudden, calamitous event that seriously disrupts the functioning of a community or society and causes human, material, and economic or environmental losses that exceed the community's or society's ability to cope using its own resources.

2. What are the different types of disaster?
Answer : Types of Disaster

  1. Geophysical (e.g. Earthquakes, Landslides, Tsunamis and Volcanic Activity)
  2. Hydrological (e.g. Avalanches and Floods)
  3. Climatological (e.g. Extreme Temperatures, Drought and Wildfires)
  4. Meteorological (e.g. Cyclones and Storms/Wave Surges)
  5. Biological (e.g. Disease Epidemics and Insect/Animal Plagues)


3. What is an earthquake ? what are the effects of earthquake ?
Answer :  Sudden vibrations  on the  earth  and shaking of the  earth  surface  /ground  is called an earthquake. These cause 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 earthquake  is the point above the epicenter on the earth surface. Strong convulse or waves at first reach to the epicenter,  therefore major loss occurs near to that area.

4. What are the reasons for ‘Malin’ mishap in Pune district?  What are its effects? 
Answer : A catastrophic landslide occurred in the village of Malin in Pune on 30th July, 2014. It was caused as a result of heavy rainfalls and killed about 151 people in that area. The effects of the landslide were severe as it caused huge number of death and many of them were also burried in the landslide.

5. What is the landslide ?
Answer : A landslide is defined as the movement of a mass of rock, debris, or earth down a slope. Landslides are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity. ... Earthquake shaking and other factors can also induce landslides under
water.

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