WBBSE Solutions For Class 9 Geography And Environment Chapter 6 Hazards And Disasters

Class ix Geography Book WBBSE Chapter 6 Hazards And Disasters Multiple Choice Questions With Answers

Question 1. The dangerous condition or situation that causes threat or damage to human property is called :
(1) Disaster
(2) Hazard
(3) Danger
(4) Catastrophe

Answer: (2) Hazard

Question 2.________ is an example of a natural hazard.
(1) Cyclone
(2) Forest fire
(3) Food poisoning
(4) Deforestation

Answer: (1) Cyclone

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Question 3. An example of a geological hazard is :
(1) Earthquake
(2) Forest fire
(3) Landslide
(4) Deforestation

Answer: (1) Earthquake

Question 4. The intensity of an earthquake is measured by :
(1) Barograph
(2) Seismograph
(3) Richter scale
(4) Linear scale

Answer: (3) Richter scale

Question 5. The series of sea waves triggered by tremendous sea quakes is called :
(1) Earthquake
(2) Volcanism
(3) Tsunami
(4) Drought

Answer: (3) Tsunami

Question 6. Strong winds and heavy rain are usually associated with :
(1) Earthquake
(2) Landslide
(3) Drought
(4) Cyclone

Answer: (4) Cyclone

Class ix Geography Book WBBSE

Question 7. The flow of water that submerges dry lowland areas is called :
(1) Cyclone
(2) Tsunami
(3) Flood
(4) Drought

Answer: (3) Flood

Question 8. The rapid flow of snow along a sloping surface is called :
(1) Landslide
(2) Avalanche
(3) Flood
(4) Cyclone

Answer: (2) Avalanche

Question 9. What type of hazard is soil erosion?
(1) Natural
(2) Man-made
(3) Quasi-natural
(4) Extra terrestorial

Answer: (2)Manmade

Question10. Tsunami is a disaster like—
(1) Geological
(2) Water-related
(3) Atmospheric
(4) Biological

Answer: (2) Water-related

Question 11. The place on the surface of the earth lying vertically above the focus of an earthquake is called
(a) Centre
(b) Anticentre
(c) Epicentre
(d) Call center of the earthquake

Answer: (c) Epicentre

Question 12. Richter. Scale was discovered by
(1) H.F. Ride
(2) Charles F. Richter
(3) Wegener
(4) None

Answer: (2) Charles F. Richter

Question 13. The point of origin of earthquake in the earth’s interior is known as –
(1) Centre
(2) Epicentre
(3) Tsunami
(4) None of these

Answer: — (1) Centre

Question 14. When earthquake occurs in the ocean, it is called-
(1) Tsunami
(2) Plate movement
(3) Tectonic earthquake
(4) None of these

Answer: (1) Tsunami

Question 15. The place where shocks of earthquake is at first felt is known as
(1) Epicentre
(2) Focus
(3) None
(4) Centre

Answer: (2) Focus

Question 16. Focus is situated in the
(1) Interior of the earth
(2) Surface of the earth
(3) None
(4) Above the surface of the earth

Answer: (1) Interior of the earth

Question 17. The place on the surface of the earth lying vertically above the forces of an earthquake is called
(1) Centre
(2) Anticentre
(3) Epicentre
(4) Focus

Answer: (3) Epicentre

Question 18. Imaginary lines passing through place of equal intensity of shaking are called :
(1) Coseismal line
(2) Siesmolay line
(3) Isoseismal line
(4) Siesmal line

Answer: (3) Isoseismal line

Question 19. Instrument used for measuring earthquake shock is
(1) Richter scale
(2) Seismograph
(3) None
(4) Earthgraph

Answer: (2) Seismograph

Question 20. A majority of earthquake occur along
(1) Plate Boundaries
(2) River valleys
(3) Ocean beds
(4) Plateau region

Answer: (1) Plate Boundaries

Question 21. Destructive Tsunamis bring about
(1) Earthquake
(2) Destructive coastal flood
(3) Lava flow
(4) Volcanic eruption

Answer: (2) Destructive coastal flood

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Question 22. The belt accounts about 65 percent of the total earthquakes in the world is-
(1) Mid-continental belt
(2) Mid-Atlantic belt
(3) Circum pacific belt
(4) Other belts

Answer: (3) Circum pacific belt

Question 23. Sea waves caused by the submarine earthquakes are called-
(1) Hypocentre
(2) Epic entre
(3) Seismic waves
(4) Tsunamis

Answer: (4) Tsunamis

Question 24. A natural hazard is :
(1) A flood, earthquake or similar unpredictable natural event
(2) An extreme natural phenomenon that causes death and destruction
(3) People located in a natural environment that may disrupt or threaten their safety and property
(4) An unpredictable event that disturbs the natural order of the environment

Answer: (4) an unpredictable event that disturbs the natural order of the environment

Question 25. Pre-disaster planning will make possible :
(1) The prevention of the disaster
(2) The effective application of aid where prevention is not possible
(3) Anticipating the consequences of a disaster
(4) All of the above

Answer: (4) All of the above

Question 26. A disaster is defined according to :
(1) Its human consequences
(2) Its cause
(3) The number of deaths it causes
(4) Its measurable severity

Answer: (1) Its human consequences

Question 27. Although each type of disaster can have a different cause, they all cause predictable problems in the following areas :
(1) Environment and health —
(2) Administration and managerial
(3) Social and economic
(4) 1, 2, and 3

Answer: (4) 1, 2, and 3

Question 28. The majority of lives lost in an earthquake are caused by :
(1) Floods
(2) Landslides
(3) Fire
(4) Building collapse

Answer: (4) Building collapse

Question 29. During an earthquake the walls of buildings without lateral bracing :
(1) Create a whiplash effect
(2) Fall outward
(3) Fall inward
(4) Remain standing

Answer: (2) Fall outward

Question 30. A house most vulnerable to an earthquake would typically be :
(1) Built of flimsy wood materials
(2) Built of heavy materials without frame reinforcement
(3) Built of heavy materials without a solid foundation
(4) Built with a weak roof and weak walls

Answer: (2) built of heavy materials without frame reinforcement

Question 31. Intensity is a measure of :
(1) Human experience during an earthquake as measured on the Richter scale
(2) Energy released during an earthquake as measured on the Mercalli scale
(3) Human experience during an earthquake as measured on the Mercalli scale
(4) Energy released during an earthquake as measured on the Richter scale

Answer: (3) Human experience during an earthquake as measured on the Mercalli scale

Question 32. The basis for the theory of continental drift is :
(1) Plate tectonics
(2) Pressure building up within the earth’s crust
(3) The earth’s land area once was a single mass
(4) Divergent rifts between continental land masses

Answer: (3) The earth’s land area once was a single mass

Question 33. The best method for avoiding loss of life from tsunamis is :
(1) Human-made seawalls of adequate size and length
(2) Participation in a tsunami warning system
(3) Timely evacuation of people from areas prior to flooding
(4) An extensive program of emergency medical assistance

Answer: (3) Timely evacuation of people from areas prior to flooding

Class ix Geography Book WBBSE

Question 34. The majority of tsunamis take place in :
(1) Earthquake zones
(2) The Pacific Ocean
(3) The Indian Ocean
(4) The coastline of Indonesia

Answer: (2) The Pacific Ocean

Question 35. Tsunamis travel at a speed :
(1) That can exceed 1,000 kilometers per hour
(2) That increases as they approach land
(3) That allows ample time for warning populations
(4) Proportional to the vertical depth of the displaced column of water

Answer: (1) That can exceed 1,000 kilometers per hour

Question 36. The majority of volcanoes are located in :
(1) The circum-Pacific belt
(2) The mid-Atlantic line
(3) East Africa
(4) The African Rift Valley

Answer: (1) The circum-Pacific belt

Question 37. The basic ingredients of a volcanic eruption are :
(1) Gases and molten rock
(2) Gases and pumice
(3) Ash and gases
(4) Magma and lava

Answer: (1) Gases and molten rock

Question 38. A dangerous secondary effect of an island volcanic eruption may be :
(1) Ash fall on nearby islands
(2) Lava flows into the waterfront
(3) Tsunamis on nearby coastal areas
(4) Severe oceanic wave disturbances

Answer: (3) Tsunamis on nearby coastal areas

School Geography Class 9 Solutions WBBSE

Question 39. A  sudden break in volcanic activity during an eruption period generally means :
(1) The danger is over
(2) Immediate evacuation of the area may be necessary
(3) An increased need for monitoring
(4) Increased earthquake activity within the plate area

Answer: (2) Immediate evacuation of the area may be necessary

Question 40. Useful volcanic prediction methods currently under study use :
(1) Frequency of tremors
(2) Upward movement of magma
(3) Analysis of chemical content of volcanic gases
(4) Infrared air photographs

Answer: (1) Frequency of tremors

Question 41. A volcanic disaster will pose both :
(1) An immediate and a long-term disease problem
(2) Loss of crops and disruption of migration
(3) Deaths and high surgical needs
(4) Loss of crops and disruption of markets.

Answer: (4) Loss of crops and disruption of markets.

Question 42. Cyclones cannot develop when the ocean temperature is below 24 degrees Centigrade (76°F) because :
(1) Of insufficient heat
(2) Of insufficient temperature difference between the air and water
(3) Cooler water temperatures prevent doldrums
(4) Of insufficient evaporation

Answer: (4) Of insufficient evaporation

Question 43. When two wind currents travel side by side, the faster current :
(1) Curls away from the slower one
(2) Curls away from the vorticity of the earth’s force
(3) Curls in the directon of the earth’s rotation
(4) Curls around the slower one

Answer: (4) Curls around the slower one

Question 44. Wind velocity is measured :
(1) On the Saffir/Simpson scale.
(2) By the National Hurricane Center in the Hawaiian Islands.
(3) On the Richter scale.
(4) On the Beaufort scale.

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Answer: (4) On the Beaufort scale.

Question 45. Tropical cyclones often generate :
(1) High rates of injured people
(2) Tidal floods
(3) Very heavy rainfall
(4) Agricultural soil erosion

Answer: (3) Very heavy rainfall

Question 46. Modern technology usually first identifies and follows a cyclone using :
(1) World Weather Watch
(2) Satellite photos
(3) Weather radar
(4) Automatic weather stations

Answer: (2) Satellite photos

Question 47. Errors in cyclone forecasting are ;
(1) Seldom
(2) Frequent
(3) Increasing
(4) Declining

Answer: (4) Declining

Question 48. Cyclone disasters can create a climate :
(1) Different from previous temperatures and humidity
(2) That will cause more cyclones within six months
(3) That will induce long-term rainfall
(4) Where negative social changes will result

Answer: (1) Different from previous temperatures and humidity

Question 49. Houses damaged in a cyclone usually :
(1) Explode
(2) Get blown over
(3) Collapse
(4) Remain standing

Answer: (4) Remain standing

Question 50. The primary measurement of flood damage is :
(1) The quantity of water discharged
(2) How high the water goes above normal restraints
(3) The dollar amount of economic damage
(4) The number of deaths

School Geography Class 9 Solutions WBBSE

Answer: (2) How high the water goes above normal restraints

Question 51. Flash floods may result from :
(1) Dam failures or cloudbursts
(2) Riverine terrain and conditions
(3) Rainfall due to tropical cyclones
(4) Inadequate catchment areas

Answer: (1) Dam failures or cloudbursts

Question 52. Timing and reliability of flood warnings: Timing and reliability of flood warnings :
(1) Are difficult to insure
(2) Decrease as the downstream distance increases
(3) Increase as the downstream distance increases
(4) Are easy to insure using Landsat technology

Answer: (3) Increase as the downstream distance increases

Question 53. A severe flood in a rural area could cause :
(1) A substantial increase in snakebite victims
(2) A housing shortage in the cities
(3) Little damage if the waters stagnate
(4) Little effect on the national economy of an industrial nation

Answer: (2) A housing shortage in the cities

Question 54. Active floodproofing is most effective : .
(1) With long warning lead times
(2) In flash-flood areas
(3) If it is permanent
(4) In floodplain areas

Answer: (1) With long warning lead times

Question 55. An effective flood-control master plan will have :
(1) A public information program
(2) Local government support
(3) Insufficient funding
(4) 1, 2, and c

Answer: (4) 1, 2, and c

Question 56. One reason why misery due to drought is increasing on a worldwide basis is :
(1) An increase in world population
(2) A decrease in rainfall worldwide
(3) An increase in human activities that aggravate drought conditions
(4) a decrease in water table levels

Answer: (3) An increase in human activities that aggravate drought conditions

Question 57. Long-term drought can cause changes in social and living patterns.
(1) Temporary
(2) Major ecological
(3) Permanent
(4) Minor

Answer: (3) Permanent

Question 58. During a drought, it is important that :
(1) People get relief supplies as near to their homes as possible
(2) People leave their homes and migrate to a water source
(3) Livestock is reduced to allow ample supplies for humans
(4) That a program be implemented to impress the public with the seriousness of the problem

Answer: (1) People get relief supplies as near to their homes as possible

Question 59. The study of earthquake is :
(1) Seismology
(2) Siesmology
(3) Etomology
(4) Phorosics

Answer: (1) Seismology

Question 60. During tsunamis, the largest wave is the wave.
(1) First
(2) Second
(3) Unpredictable, could be any of them
(4) Third

Answer: (3) Unpredictable, could be any of them

School Geography Class 9 Solutions WBBSE

Question 61. Tsunamis are destructive due to their :
(1) height of the wave
(2) Uncertainty
(3)Momentumandlongwavelength
(4) Temperature

Answer: (3) Momentum and long wavelength

Question 62. Drought is :
(1) A year without rainfall
(2) A week without rain
(3) Water scarcity over a long period
(4) A season without rain

Answer: (3) Water scarcity over a long period

Question 63. Flood is :
(1) Excessive rain
(2) Water overflows to submerge land
(3) Excess water
(4) Excessive water depth

Answer: (2) Water overflows to submerge land

Question 64. The naming of tropical cyclones is useful :
(1) For reporting
(2) for the forecasters
(3) For research
(4) For tracking, forecasting, and reporting

Answer: (4) For tracking, forecasting, and reporting

Question 65. Pre-disaster management includes :
(1) Prevention
(2) Mitigation
(3) Response
(4) (1) and (2)

Answer: (4) (1) and (2)

Question 66. The charge of disaster management just after independence was with :
(1) Ministry of Water Resource
(2) Ministry of Home Affairs
(3) Relief Commissioners
(4) Ministry of Human Resource

Answer: (3) Relief Commissioners

Question 67. The Disaster Management Act was enacted in :
(1) 2005
(2) 2002
(3) 2006
(4) 2000

Answer: (1) 2005

Question 68. Match the following meteorological scales with the phenomena :
1. Richter A. Hurricane
2. Fujit B. Wind
3. Saffir- Simpson C. Earthquake
4. Beaufort D. Tornado
(1) 1A, 2D, 3A, 4B
(2) 1A, 2D, 3B, 4C
(3) 1D, 2C, 3B, 4A
(4) 1C, 2A, 3B, 4D

Answer: (1) 1A, 2D, 3A, 4B

Question 69. Ambutia in Darjeeling was known for
(1) landslide
(2) Earthquake
(3) Flash flood
(4) None

Answer: (1) landslide

Question 70. The intensity of earthquake by observation is measured by :
(1) Richter scale
(2) Mercalli scale
(3) Both Richter and Mercalli scale
(4) None

Answer: (2) Mercalli scale

School Geography Class 9 Solutions West Bengal Board

Question 71. The threshold for a quake to cause damage on a Richter scale is :
(1) 2
(2) 3
(3) 6
(4)7
Answer:(4)7

Question 72. Turbidity is measured by :
(1) Solarimeter
(2) Nephelometer
(3) Pyranometer
(4) None

Answer: (2) Nephelometer

Question 73. Tsunamis literally mean :
(1) Huge wave
(2) Wave series
(3) Tremors
(4) Harbour wave

Answer: (4) Harbour wave

School Geography Class 9 Solutions West Bengal Board Chapter 6 Hazards And Disasters Short Questions With Answers:

Question 1. What is seismology?
Answer:

Seismology

The science of earthquakes is known as Seismology (from the Greek word seismos, meaning earthquakes).

Question 2. What do you refer to as hypocentre or focus?
Answer:

Hypocentre

The place of origin of an earthquake inside the earth is called its hypocentre or focus.

Question 3. What do you mean by volcanic eruptions?
Answer:

Volcanic eruptions

Volcanic eruptions are often very violent and cause earthquakes.

Question 4. What are Artificial Earthquakes?
Answer:

Artificial Earthquakes

These are caused by human activities. Minor tremours due to running trains, heavy machines, and bomb explosions are of this type.

Question 5. What is meant by Richter Scale?
Answer:

Richter Scale

The scale which measures the magnitude of an earthquake is called Richter Scale..

Question 6. Explain the following: Seismograph.
Answer:

Seismograph

Seismograph is the instrument which is used for recording earthquake waves and earthquake vibrations.

Question 7. Explain the following: Seismic Focus
Answer:

Seismic Focus

Seismic Focus is the point beneath the crust from where seismic waves originate.

Question 8. What are two belts of earthquakes and volcanoes in the world?
Answer:

The two belts of earthquakes and volcanoes in the world are :

(1) Ring of the Pacific Ocean
(2) Alpine Himalayan region.

Question 9. What is called the ring of fire?
Answer:

Ring of fire

The ring of Pacific Ocean (ring of earthquakes and volcanoes) is also called ring of fire.

Question 10. What is avalanche?
Answer:

Avalanche: A fall or slide of a large mass of snow or rock, down from a mountain.

Question 11. what is Blizzard?
Answer:

Blizzard: Blizzards are severe winter storms that pack a combination of blowing snow and wind resulting in very low visibilities.

Question 12. What is Cyclone?
Answer:

Cyclone: It’s an atmospheric pressure distribution characterized by the rapid, spiraling inward circulation of air masses about a low-pressure centre.

School Geography Class 9 Solutions West Bengal Board

Question 13. What do you mean by Drought?
Answer:

Drought: Drought is said to happen when extremely dry weather pre-vails at an area due to less rainfall than its normal amount, over months together or even years, causing a hurdle for agriculture.

Question 14. Define Earthquake.
Answer:

Earthquake: An earthquake is the result of a sudden release of Earth’s internal energy in the crust that creates seismic waves.

Question 15. Define Flood.
Answer:

Flood: A flow of water from a water body like sea, ocean, river etc., deviating the normal path of flow of water into a dry land.

Question 16. Define Forest fire.
Answer:

Forest fire: A forest fire is an uncontrolled fire occurring in forest.

Question 17. What is Landslide?
Answer:

Landslide: “Landslide” describes a large mass of rocks and earth that suddenly and quickly slides down along the slope of a mountain or hill.

Question 18. What is Tsunami?
Answer:
Tsunami: An unusual and very large ocean wave caused by an underwater earthquake at the ocean-bed or underwater volcanic eruption.

Question 19. Define Volcanism.
Answer:

Volcanism: A volcano is a rupture on the crust of the Earth (either in land or at ocean) from where hot lava, volcanic ash, and gases emerge from magma chamber due to increase in internal pressure the of the Earth.

Question 20. Define Hazard.
Answer:

Hazard

Hazard, a naturally occurring physical phenomenon, may be defined asa dangerous condition or situation, which threat to or cause havoc damage to human property including casualties in a large scale.

Question 21. Which natural disaster claims maximum number of human lives on a regular basis?
Answer: Floods.

Question 22. How many people were killed by Krakatoa eruption in Sunda strait in 1883?
Answer: 50,000.

Question 23. Which scale is used to measure the magnitude of earthquakes?
Answer: Richter scale.

Question 24. Intensity of earthquakes is measured by which scale.
Answer: Mercalli scale.

Question 25. Which part of India is most prone to earthquakes?
Answer: The Himalayan region. :

Question 26. Which part of South India is frequently influenced by droughts?
Answer: Rain-shadow area of the Western Ghats.

Question 27. Name the area in North-East India which is affected by floods almost every year.
Answer: The Brahmaputra valley.

Question 28. Name two areas in India which have high incidence of landslides.
Answer: The Himalayas and the Western Ghats.

School Geography Class 9 Solutions West Bengal Board Chapter 6 Hazards And Disasters True Or False Blanks

Question 1. Earthquakes may cause vertical and lateral displacement of the earth’s crust.
Answer: True

Question 2. Volcanic activity may cause earthquakes.
Answer: True

Question 3. Volcanic activities is very common in the Pacific Ocean area.
Answer: True

Question 4. Earthquake causes landslides.
Answer: True

Question 5. Gigantic sea waves are known as tsunamis.
Answer: True

Question 6. Himalayas is an earthquake-prone area.
Answer: True

Question 7. Richter Scale records earthquake.
Answer: False

Question 8. Tsunamis are caused by earthquake under the Sea.
Answer: True

Question 9. Epicentre is the shortest distance between the focus and the earth-crust_.
Answer: True

Question 10. In ancient time people believe disaster as evil star on bad star.
Answer: True

Question 11. In West Bengal, two drought-prone districts are Bankura & Purulia.
Answer: True

Question 12. When blocks of ice fall down from high altitude then it is termed as waterfalls.
Answer: False

Question 13. Tsunamies are the effects of cyclones.
Answer: False

School Geography Class 9 Solutions West Bengal Board

Question 14. The cyclones of Caribbean islands are called typhoons.
Answer: False

Question 15. Forest fires are un controlled spread of fire occurring in a forest.
Answer: True

Question 16. The phenomenon of eruption of molten magma on to the surface is calledflood.
Answer: False

Question 17. The severe winter storm that is associated with blowing snow and wind is called avalanche.
Answer: False

WBBSE Solutions Guide Class 9 Chapter 6 Hazards And Disasters Distribution Volcanoes, Earthquake Belt And Lava Plateaus Fill In The Blanks

Question 1. The point where slip or rupture of plates takes place is called the __________________ of the earthquake.
Answer: Focus.

Question 2. ___________ is a situation which occurs by acute deficiency of rainfall in a region.
Answer: Drought.

Question 3. The movement of soil, rock or other earth materials downhill by gravity is called a________________.
Answer: Landslide.

Question 4. ______________measures the severity of earthquake.
Answer: Richtre scale.

Question 5. ______________ is an earthquake recording instruments.
Answer: Seismograph.

Question 6. ________________ is a huge sea wave.
Answer: Tsunami.

Question 7. ________________mountains are the weak portion of earth.
Answer: Fold.

WBBSE Solutions Guide Class 9 Chapter 6 Hazards And Disasters 2 Marks Questions And Answers

Question 1. What do you mean by cyclone?
Answer:

Cyclone

Cyclone ’is a region of low atmospheric pressure surrounded by high at- mospheric pressure resulting in swirling atmospheric disturbance accompained by powerful winds blowing in anticlockwise direction in the Northern Hemisphere and in the clockwise direction in the Southern Hemisphere.

Question 2. Mention the flood-prone area in West Bengal.
Answer:

The flood-prone area in West Bengal

In West Bengal, flood-prone areas include, the Ganga delta in the South, and the northern plains drained by the Tista and Torsa in the northern parts of West Bengal. There are occasional floods in Damodar and Kanshaboti basin. Dams have been constructed on them to control flood condition as well as to irrigate land during dry season.

Question 3. State the types of hazards.
Answer:

Types of hazards

There are two types of hazards we often see. One is Natural Hazard and the other is Manmade Hazard.

Natural hazards :

Hazards, which are caused by natural phenomena or events, are called natural hazards.

Examples: cyclones, tsunamis, earthquakes, volcanic eruptions which are exclusively of natural origin. Somethimes forest fire may also pose as natural hazard caused by lightning or volcanic eruption.

Manmade hazards :

Hazards which are caused due to human negligence are called manmade hazards.

Example : Deforestation, Forest fire, Food poisioning, Environmental pollution etc.

Question 4. From where does the word disaster came from?
Answer: The word disaster is originated from either French word ‘Disastro’ or Ital- ian word ‘Diasastor’ or Greek word ‘Disaster’. French word ‘des’ or Latin word ‘dis’ or ‘de’ or ‘di’ mean bad/evil and ‘astre’ mean star. So bad star or evil star. {dis/de/di] + [astron/star] = disaster.

Question 5. What do you mean by a blizzard?
Answer:

Blizzard

A blizzard is a severe snowstorm characterized by strong sustained winds of at least 56 km/h (35 mph) and lasting for a prolonged period of time – typically three hours or more. A ground blizzard is a weather condition where snow is not

Question 6. What are the effects of blizzard?
Answer:

Blizzards

Blizzards can be dangerous, especially when driving an automobile. It creates a fog like mist called a “white out” which is thicker than a fog. Many accidents happen because of the thick mist.

If a blizzard is cold enough it could cause a person with proper clothing to get frosbite or hypothermia, It can cause power outage that can last for hours and also causes snow to pile a more than 10 inches.

Question 7. What do you mean by landslides? OR, Write a short note-on landslide.
Answer:

Landslides

A landslide, also known as a landslip, is a geological phenomenon that includes a wide range of ground movements, such as rockfalls, deep failure of slopes and shallow debris flows. Landslides can occur in offshore, coastal and onshore environments.

Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released.

Class 9 Geography Solution WBBSE

Question 8. What is Epicentre?
Answer:

Epicentre

The place or point in the interior of the earth, where an earthquake takes its origin is called Focus or Centre. Vertically above the centre, the point or place on the surface of the earth is known as epicentre.

Here at the epicentre the quaking of the earth is first experienced and the intensity of the quake is most severe. The earthquake waves move in other directions from this epicentre and farther away from this epicentre, the intensity decreases.

 

Question 9. What is the function of seismograph?
Answer:

Function of seismograph

It is used to measure earth-quake.

Question 10. Why do earthquakes frequently strike both the coasts of Pacific Ocean ?
Answer: It is known that plates which are boundaring, are very much unstable in characte- ristic. They are always sliding or moving to each other. This movement generate earthquake. The coast of Pacific Ocean lies in plate boundaries. So, earthquakes are frequent strike both the coasts of the Pacific Ocean.

Question 11. What is the difference between an earthquake and an earth movement? (S.Question)
Answer:

The difference between an earthquake and an earth movemen

The sudden shaking of earth’s crust for a short duration due to several causes (such as plate movements, volcancity, making of dams on rivers etc.) is called earthquake. On the other hand, due to internal disturbances of the earth’s interior, the crust of the earth may be uplifted, down wraped or folded.

This is known as earth movement. Both are closely associated but earthquake is just the shaking of earth’s crust, whereas, earth movement involves lateral or vertical movement of the earth’s crust.

Question 12. At which depth do most earthquakes occur?
Answer:

An earthquake is a shaking of the crust of the earth. Itis a sudden jerk or movement of the earth’s crust. It is a great shock or tremor of the crust of the earth that originate naturally beneath the earth’s surface.

Class 9 Geography Solution WBBSE

Question 13. What is Seismograph?
Answer:

Seismograph

Seismograph is an instrument which records earthquake shocks. In this instruments, vibrations are recorded by a pen tracing on a revolving drum attached with graph. Modern Seismographs are so sensitive that they record vibrations of earthquakes thousands of kilometers away.

 

Question 14. What is ‘Pacific Ring of Fire’?
Answer:

Pacific Ring of Fire

Circum Pacific Earthquake Belt is known as the ‘Pacific Ring of Fire’. There are a large number of active and dormant volcanoes in this belt. It encircles the Pacific Ocean including Western coast of North and South America, the Aleution Islands, and the Islands of Asia like Japan, Philippines, and Indonesia etc.

This is a region of young fold mountains. This belt has weak earth’s crust due to whichn the crustal movements and eruptions volcanoes are frequent. Fujiyama of Japan, Krakatoa in Indonesia, Chimborazo, and Cotap in South America are within this belt. About 70% earthquakes of the world occur in this belt.

Chapter 6 Hazards And Disasters 2 Marks Questions And Answers (Short Notes)

Question 1. Earthquake waves
Answer:

The earthquake waves are of three types –

(1) Primary Waves –
These are the fastest waves. These waves create maximum disaster. SPEED: 7.8 km/Sec.

(2) Secondary waves –
These are the second fast waves. These travel in opposite direction to that of primary waves. SPEED :5-6 km./Sec.

(3) Surface waves –
These are slowest of all the waves. These waves are capable of travelling at the Earth’s surface. SPEED : 3 – 4 km./Sec.

Class 9 Geography Solution WBBSE

Question 2. What is Ritchter scale? :
Answer:

Ritchter scale

Ritchter Scale is the scale which measures the intensity of an earthquake. The Ritcher Scale was devised by Prof. Ritcher, an eminent American Seismologist. The scale measures the intensity of an earthquake, the scale is based on instrumental recordings of a seismograph.

Question 3. The effects of earthquakes.
Answer:

The effects of earthquakes

The effects of eartnquakes are both destructive and constructive, although destructive effects are much more.

Destructive effects :(1) It can alter the course of a river. The earthquake of 1950 changed the course of the Brahmaputra river.
(2) Sea waves reach greater heights and speed sometimes 500 to 800 km. per hour. These disastrous sea waves are known as “Tsunamis” (along the Japanese sea coast). Due to this adjoining coastal region is suddenly flooded and there is unimaginable loss of lives and property.
(3) Landslides occur in the mountainous areas.
(4) The ground rises and falls resulting in the cracks of rocks and buildings collapse resulting in the death of thousands of people.
(5) Bridges, roads etc. are damaged.
(6) Dislocation of electric wiring takes place and fire breaks out.

Constructive effects :
(1) From the interior of the earth, variety of unknown minerals come out on the surface.
(2) Lava comes out and after consolidation above the earth’s surface make the soil fertile.
(3) Coastal plains and lakes are created. These are useful for human.

Question 4. Tsunamis.
Answer:

Tsunamis

When a submarine earthquake causes a considerable movement of sections of the ocean floor, great mass of water come into motion and waves of a peculiar kind called Tsunami are formed on the surface of the ocean (In Japan, ‘tsu’ means harbour and ‘nami’ means waves).

Tsunami move along the ocean surface at a very high speed of upto 400 to 800 km per hour and cover tremendous distances. In open ocean the Tsunami waves are very long but they are not high but as they approach the shore, their height increases to almost 9 metres above normal tide level. These waves cause wide spread destruction crashing on the shore and travelling far inland in coastal areas.

Class 9 Geography Chapter 6 WBBSE

Question 5. Centre and epicentre of an earthquake.
Answer:

Centre and epicentre of an earthquake

The place or point, in the interior of the earth, where an earthquake takes its origin is called Focus or Centre. Vertically above the centre, the point or place on the surface of the earth is known as epicentre.

Here at the epicentre the quaking of the earth is first experienced and the intensity of the quake is most severe. The earthquake waves move in other directions from this epicentre and farther away from this epicentre, the intensity decreases.

Question 6. Recent Earthquakes.
Answer:

Some of the most destructive earthquakes of the world in the recent past are :

(1) The earthquake of Mexico City which occured on 19th September in 1995.
(2) The earthquake of Armenia (Russian Federation) on December, 1988.
(3) The earthquake of Hokkaido in Japan in 1993 and
(4) The earthquake of Kobe in Japan on 17th January, 1995.

Chapter 6 Hazards And Disasters 3 Marks Questions And Answers

Question 1. State the cause of occurrence of Drought.
Answer:

Cause of occurrence of Drought.

(1) Drought is defined as a deficit of rain water. We know that deficiency of water vapour in the atmosphere of an area cause less rainfall. If high pressure and dry air prevails in an area for a prolonged time period, less moisture is generated in that area which is burden to produce precipitation (because these systems cannot hold as much water vapour). This results in a deficit of water for those areas.

(2) Sometimes, warm, dry, continental air moves over an area in contrary to cooler, moist, oceanic air, due to shifting of air masses by wind. El Nino, which affects the ocean’s water temperature, also has an impact on precipitation levels, because it can shift the air masses above the ocean, often making wet places
dry (drought prone).

(3) Deforestation for agriculture and/or building combined with the resultant erosion can also cause drought. As soil is moved away from an area it is less able to absorb moisture when it falls.

Class 9 Geography Chapter 6 WBBSE

Question 2. State the flood prone regions in India.
Answer:

The flood prone regions in India

The lower plain region of India specially Bihar, Uttar Pradesh and West Bengal in respect of the Ganga and Assam in respect of Brahmaputra suffer from the adverse effects of flood every year. The Ganga Brahmapuitra Basin receives maximum run off within the three monsoon months. Based on hydrological studies carried out, it is estimated that only 18% of the rain water can be stored in dams, reservoirs, etc. While 82% of the rain water flows through rivers ultimately into the sea.

Question 3. State the drought-prone areas in the world.
Answer:

Drought-Prone Area :

(1) Sahal region of Africa :

Sahal means the edge of Sahara desert which is excessive drought prone area of the world. This region was affected by drought during 1905-1909, 1950-1969, 1973, 1984, 1990 and 2007.

(2) Drought-Prone region of India :
Around 68% of India’s total area is droughtprone. 315 out of a total of 725 talukas in 99 districts are drought prone. In 2001 more than eight states suffered the impact of severe drought.

Question 4. State three remedies of Drought.
Answer:

Remedies :

(1) Public awareness and education
(2) restoration of ecological balance by conserving, developing and harvesting land, water, livestock and human resources.
(3) to minimise the adverse effects of drought on production of crops and livestock.

Question 5. Mention the remedies to be taken for flood prevention.
Answer:

Remedies: As flood is a natural hazard we can take few types of measures for remedies. Some measures can be taken
(1) Before flood such as creation of forest, construction of dams, dykes and reservoirs etc., regular removal of silt from the river bed, digging of waterbodies, forecasting about flood, renovation of river bed and river banks etc.

(2) After flood supply of adequate drinking water, dry food, rescue of flood-prone people, sufficient supply of geoline, bleaching powder etc., recovery of dead bodies and their disposal, proper medical care for people, temporary shelter like camps, metal sheds, tents etc.

After devastating flood in 1954, the government of India announced a National Flood Management Programme, The programme was divided into three phases—
(1) Immediate,
(2) Short-term and
(3) Long-term.

(1) Immediate phase :
Extending over a period of 2 years was adopted for intensive collection of data and execution of emergent flood protection measured.

(2) Short terms measures :
Covering next 4 to 5 years, included construction of spurs and embankments at selected sites.

(3) Long-term measures :
Included the construction of storage, reservoirs on rivers/tributaries and additional embankments.

The Central Water Commission (C.W.C) started flood forecasting in 1958 when the first forecasting station was established at old Railway Bridge, Delhi.

Class 9 Geography Chapter 6 WBBSE

Question 6. Briefly explain hazard & disaster. Or, Hazared is the cause and disaster is the effect. Explain.
Answer:

Hazard

Hazard, a naturally occurring physical phenomenon, may be defined asa dangerous condition or situation, which threat to or cause havoc damage to human property including casualties in a large scale.

Disater, happens when a hazard impacts on the population resulting in substantial and significant physical damage or destruction, loss of life, or drastic change to the environment. Due to a disaster a serious disruption happens to the functioning of a society of mankind.

The losses occur due to such disaster some times may exceed the ability of the affected society to recover the situation by using its own resources. Ahazard becomes a disaster only when it affects human settlements and causes loss of life and damage to property. So Hazard is the cause and the Disaster is the effect.

Question 7. What are the different names of cyclone?
Answer:

Cyclones are known by different names in different parts of the world:

1. Typhoons in the Northwest Pacific Ocean west of the dateline

2. Hurricanes in the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean.

3. Tropical cyclones – the Southwest Pacific Ocean and Southeast Indian Ocean.

4. Severe cyclonic storm (the North Indian Ocean)

5. Tropical cyclone (the Southwest Indian Ocean)

6. Willie-Willie in Australia

7. Tornado in Gulf of Mexico

Question 8. What are the characteristics of a cyclone?
Answer:

Cyclones in India are moderate in nature.Some of the general characteristics of a cyclone are :

(1) Strong winds
(2) Exceptional rain
(3) Storm surge
Cyclones are generally accompanied by strong winds which cause a lot of de- struction. In some cases it is accompanied by heavy downpour and also the rise in the sea which intrudes inland thereby causing floods.

Question 9. What do you mean by disaster ?
Answer:

Disaster

Disaster is an incident or series of events that gives rise to casualties and loss or destruction of surroundings, buildings, properties, infrastructural facilities and all other vital services or survival means to such an extent that is a far from the normal means and competence of the people affected in order to deal with it.

WBBSE Class 6 Geography Chapter 6 Question Answer

Disaster can be defined as “catastrophic situation in which the normal pattern of life or eco-system has been disrupted and extra-ordinary emergency interventions are required to save and preserve lives and or the environment”.

The United Nations defines disaster as “the occurrence of sudden or major misfortune which disrupts the basic fabric and normal functioning of the society or community”.

As per the Disaster Management Act, 2005, disaster is defined as “a catastrophe, mishap, calamity or grave occurrence in any area, arising from natural or manmade causes, or by accident or negligence which results in substantial loss of life or human suffering or damage to, and destruction of, property, or damage to, or degradation of, environment, and is of such a nature or magnitude as to be beyond the coping capacity of the community of the affected area”.

Question 10. State the characteristics of disaster.
Answer:

The major characteristics of a disaster are :
(1) Inevitability or certainty.
(2) Ability to be forbidden.
(3) Pace of onset.
(4) Span of forewarning.
(5) Extent of impact.
(6) Scope and intensity of impact.

Question 11. State the objectives of disaster management plan.
Answer:

General Objectives of a Disaster Management Plan are :
(1) To guarantee the safety, security and stability- to secure business sites and facilities, to safeguard and make available critical resources, to ensure supply of equipments, to make sure security and resurgence of accounts from expected disasters, to protect all the vital information and records.

(2) To reduce the risk of disasters caused by human error. To be well equipped in order to pull through from a major natural disaster.

(3) To recover lost or damaged records or information ensuring the organization’s capacity to carry on its operation and service even post- disaster period (sustainability).

Question 12. State the principles of disaster management.
Answer:

Principles of Disaster Management are :

(1) Disaster management is the accountability at all levels of government.

(2) Disaster management arrangements must identify the contribution and pro- spective role of non-government agencies.

(3) Disaster management to utilize existing resources for daily purpose.

(4) The concerned organizations should work and endeavor as a supplement to their central business.

(5) Persons are to be responsible for their own safety.

(6) Planning of disaster management should be focusing on large-scale episodes.

WBBSE Class 6 Geography Chapter 6 Question Answer

Question 13. What is a Hazard? How is it classified ?
Answer:

Hazard

Hazard may be defined as “a dangerous condition or event, that threaten or have the potential for causing injury to life or damage to property or the environment.” The word ‘hazard’ owes its origin to the word ‘hasard’ in old French and ‘az-zahr’ in Arabic meaning ‘chance’ or ‘luck’.

Hazards can be grouped into two broad categories namely natural and manmade

(1) Natural hazards are hazards which are caused because of natural phenomena (hazards with meteorological, geological or even biological origin). Examples of natural hazards are cyclones, tsunamis, earthquake and volcanic eruption which are exclusively of natural origin. Landslides, floods, drought, fires are socionatural hazards since their causes are both natural and man-made. For example flooding may be caused because of heavy rains, landslide or blocking of drains with human waste.

(2) Manmade hazards are the hazards which are due to human negligence. Manmade hazards are associated with industries or energy generation facilities and include explosions, leakage of toxic waste, pollution, dam failure, wars or civil strife etc.

Question 14. Give a chart explaining various types of hazards.
Answer:

Types of Hazards :

Geological Hazards

1. Earthquake
2. Tsunami
3. Volcanic eruption
4. Landslide
5. Dam burst
6. Mine Fire

Water And Climatic Hazards

1. Tropical Cyclone
2. Tornado and Hurricane
3. Floods
4. Drought
5. Hailstorm
6. Cloudburst
7. Landslide
8. Heat And Cold wave
9. Snow Avalanche
10.Sea erosion

Environmental Hazards

1. Environmental pollutions
2. Deforestation
3. Desertification
4. Pest Infection

Biological Hazards

1. Human / Animal Epidemics
2. Pest attacks
3. Food poisoning
4. Weapons of Mass Destruction

WBBSE Class 6 Geography Chapter 6 Question Answer

Question 15. Describe different types of earthquakes.
Answer:

Earthquakes have main two types –

(1) Natural Earthquake –

Those earthquakes that are caused due to nature are called natural earthquakes. Natural earthquake has 3 main sub – divisions.

(1) Tectonic Earthquakes.
(2) Volcanic Earthquakes.
(3) Isostatic

(2) Artificial Earthquakes –

Those earthquakes that originaes due to human activities are called Artificial Earthquakes. Explosion of Atom bomb, Rail, Running of elephants etc. causes these types of Earthquakes.

Question 16. What are the factors responsible for earthquakes?
Answer:

The factors responsible for earthquakes

(1) Volcanic activity:-

Due to volcanic eruptions, earthquakes take place. Thus, in volcanic belts they are common. In 1883 severe earthquake occured due to the Krakatoa eruption and in 1985 Nevado Del Ruz eruption caused earthquake in Columbia. Lava flowing within crust may cause tremors on the surface.

(2) Tectonic movement:-

This is related to the Plate Tectonic Theory. When two plates converge each other from opposite directions or they scrape past against other an earthquake takes place. (This takes place by rubbing together the land masses). In 1967 the earthquake in Koyna was caused in this way. This happened along 400 km long Kurdawadi Rift (from SE of Sholapur to North of Pune).

At present the Gondawana plate is moving North at the rate of 5 centimetres a year. And it is feared that a mammoth earthquake measuring 8.5 on the richter scale is likely to occur in the next 10 to 15 years.

(3) isostatic Adjustment or Plutonic Earthquake :-
This is caused by the adjustment of sial and sima (sima – silica and magnesium and sial — silica and aluminium). Where the equilibrium is disturbed due to gradation by natural agent.

WBBSE Class 6 Geography Chapter 6 Question Answer Hazards And Disasters 5 Marks Questions And Answers

Question 1. Define the concept of volcanicity.
Answer:

Volcanicity

According to F.J. Monkhouse, the term volcanicity includes in its widest sense all the processes by which solid, liquid or gases materials are forced into the earth’s crust or escape on to the surface. In the words of S.W.

Wooldridge and R.S. Morgan, the term ‘Volcanicity’ covers all those processes in which molten rock materials or magma rises into crust or is poured out on its surface, there to solidity as a crystalline or semi crystalline rock. P.G.

Worcuster has used the term volcanism in place of volcanicity. According to him, volcanism includes all phenomenon connected with the movement of heated material from the interior to or towards the surface of the earth.

This activity has a greater effect on the surface features. The materials injected into the earth’s crust are known as intrusive rocks while in molten rock and other material which reaches in surface is called extrusive rocks.

Extrusive rocks build a variety of landforms varying from tiny cones to widespread sheets of lava. The molten rock material beneath the earth’s crust is known as magma which is normally maintained by overlying pressure. But when the pressure is locally relieved by the earth’s movements, various phenomena of volcanicity take place and magma comes out as lava.

Question 2. Describe the causes of volcanic eruptions.
Answer:

Causes of Volcanic Eruptions : Our knowledge regarding the causes of volcanic eruptions is very limited because these eruptions have their origin in the interior of the earth to which we do not have direct access. However, following causes are assigned to volcanic eruptions on the basis of indirect observations:

(1) High Temperature in the interior of the Earth :
The temperature increases with the increase in depth below the surface of the earth. This results in melting of rock material at high pressure in the earth. This molten material is ejected at the surface of the earth.

(2) Weak Points in Earth’s Crust :
The existence of weak points in the earth’s crust is a necessary condition for a volcanic eruption. The world distribution of
volcanoes is that most of the volcanoes have erupted in the weaker zones of the earth. The coastal areas are its best example.

(3) Gases :
The presence and formation of gases in the interior of the earth also cause volcanic eruption. Among the gases, water vapour is most effective. The rain water in contact with the hot interior of the earth after its percolation through the coast becomes water vapour. Sea water also percolates near the sea coast and becomes vapour. The heat and pressure increase many fold when water is converted into vapour. This water vapour comes to the surface through a weak point.

(4) Earthquakes :
The earthquakes are also responsible for crustal dislocations giving rise to the formation of faults. The release of pressure from the earth’s interior under dislocations causes the magma to escape to the surface.

(5) Plate Tectonics :
The rigid lithospheric slabs or rigid and solid crystal layers are known as plates. These plates keep on moving in different directions. Individual plates may have continental crust, oceanic crust or both. When an oceanic plate collides with continental plate, the denser oceanic plate is forced below the lighter continental plate. The overrun plate is thrust into the mantle and part of the plate is melted.

Melting also takes place due to heat created by pressure of rocks from above. The molten rock (magma) rises to the surface and a volcanic eruption takes place.

Question 3. What are different types of volcano according to their frequency ?
Answer:

(1) Active Volcanoes :
These volcanoes keep on ejecting volcanic mate- rial at frequent intervals. The Etna volcano of Italy has been active for the last 2500 years. The Stromboli volcano of Sicily island explodes after every 15 minutes and is known as the Light House of the Mediterranean.

(2) Dormant Volcanoes :
The dormant volcanoes are those in which eruption has not occurred regularly for a long time. But they cause great damage to life and property when they suddenly become active after remaining dormant for a sufficiently long time. Vesuvius volcano of Italy has exploded only 10 times in about 1500 years. The volcano of Barren Island to the East of Andamans in India exploded in 1991 after remaining dormant for several years.

(3) Extinct Volcanoes :
The volcanoes which have not recorded any eruption in historic times are called extinct volcanoes. The vent of an extinct volcano is blocked and its crater is filled with rain water to form a crater lake. Vegetation starts growing on it. The possibility of future explosion becomes remote. Popa of Myanmar is its outstanding example. Many a time, an extinct volcano suddenly becomes active.

This has happened in case of Krakatao volcano. The island of Krakatao is situated in the Sunda Strait between the islands of Java and Sumatra. Its eruption in the year 1883 blew off the top of the mountain by an explosion which caused tidal waves about 16 metres high, killing 36,000 people in West Java. The volcanic dust, ashes and smoke spread in about 27 km. the rock fragments and lava rose to a height of about 800 metres.

The sound of explosion was heard as far as Istanbul (Turkey) in the West and Tokyo in the East. The volcanic dust and gases encircling the globe in the atmosphere caused strange sunrise and sunset conditions for about three years. Today Krakatao is only a low island with a lake inside its crater.

Question 4. Describe the effects of Volcanic activities.
Answer:

Effects of volcanic activities :– Effects of volcanic activities are put into two categories as described below :

1. Destructive Effects :
Volcanoes are destructive. They cause untellable miseries to men and property. In the vesuvius explosion the whole of Pompeii city was destroyed. Thousands of people lost their lives in the recent explosion of a volcano in Columbia. More than 1,00,000 people lost lives in the Etna volcanic eruption in 1693. The entire island of Krakatao was removed from the face of the world due to volcanic explosion in 1883.

2. Constructive Effects :
Where there are huge damages to life and property of men, there are also numerous constructive effects of volcanic eruption onthe life of men. During transformation of the face of earth’s surface men are benefitted in the following manner.

(1) Due to the flow of lava over large areas, fertile land is obtained and various agricultural crops are raised on it. Cotton is the important agricultural crop which is grown on the Deccan Trap of Peninsular India.

(2) During volcanic activities shale is formed. It is used in building activities.

(3) Owing to volcanic eruption numerous valuable minerals come near the surface and we can avail them at much lesser expenses.

(4) Volcanic lakes provide irrigational facilities and also provide drinking water in their adjoining areas. ‘

(5) Area of volcanic lakes, hot spring and geysers add scenic beauty to the landscape and thus are helpful in developing and increasing tourism activities.

(6) Hot springs and geysers are used to generate geothermal electricity. New Zealand, Italy, |reland, Mexico, Japan, U.S.A and Russia, produce geothermal electricity on local scale. India also produces electricity around hot springs in Laddakh.

(7) Volcanic eruptions help us to understand, the geology and geological history of the earth and its interior.

Question 5. Discuss the global pattern of volcanism.
Answer:

Global pattern of volcanism

Global Pattern of Volcanism : Weak zones, where continents and ocean meet each other, abound in volcanoes, fold mountain regions and some islands are famous for volcanic activities owing to number of volcanoes and occurrence of volcanic activities. Their global pattern is described below :

(1) The Circum-Pacific Belt :
There are 522 active volcanoes and volcanic eruptions. Out of these 403 are located in and around the Pacific Ocean. The belt encircling the Pacific Ocean is the largest region of volcanic activities. It includes western coasts of the two Americas and the eastern coasts of Asia. Because of the largest number of volcanoes this belt is truly known as the ‘Ring of fire’.

(2) The Mid-world (Alpine-Himalayan) Belt :
The mid-world volcanoes belt extend East to West along the Alpine and the Himalayan fold mountains and their extensions. The belt occupies second place in the distribution of volcanoes after the circum-pacific belt.

It covers the Caucasus, Iran, Baluchistan, India Myanmar and Iceland. Sicily and Japan have the largest number of active and dormant volcanoes and are counted among the biggest volcanic island of the world. The Etna of Sicily has exploded on the X-Mas day of 1985 and damaged houses and agricultural land greatly.

(3) The African Belt :
Volcanoes are situated in the Rift valley lake belt and on the eastern coast of Africa. The Rift valley lake belt of volcanoes passes through the Red Sea and extends up to Palestine. Mt. Kilimanjaro in Tanzania is an extinct volcano situated on the east coast of Africa. The belt occupies third place in the world.

(4) The Atlantic and Indian Oceans :
Several volcanoes are also found in theridge belt of the Atlantic ocean, Indian ocean and South Pacific ocean.

(5) Hawaiian and Alentian islands were formed due to eruption in the ocean

 

Question 6. Briefly mention the concept and definition of earthquakes.
Answer:

Earthquakes

Earthquakes are tremors which are produced by the passage of vibratory waves through the rocks of the earth. If you throw a stone in a pond of still water, a series of concentric waves are produced on the surface of water.

These waves spread out in all directions from the point where the stone strikes the water. Similarly, any sudden disturbance in the earth’s crust may produce vibrations in the crust which travel in all directions from the point of disturbance.

The science of earthquakes is known as Seismology (from the Greek word seismos, meaning earthquake) and the instrument which records earthquake waves is called Seismograph. The Seismographic records indicate that about 8,000 to 10,000 earthquakes occur annually in the different parts of the world which means that earth experiences an earthquake every hour on an average.

In addition, there are many more earthquakes in the vast area of oceans which are not recorded due to lack of recording stations there. In fact, our earth vibrates continuously. Most of the earthquakes originate at a depth of 50 to 100 km below the earth’s surface.

The place of origin of an earthquake inside the earth is called its hypocentre or foc@s. The point on the earth’s surface vertically above the focus is called the epicentre. The shock waves travel in all directions from the focus. On the earth’s surface the shaking is the strongest near the epicentre.

Question 7. Explain in brief the distribution of earthquake-prone zone.
Answer:

Earthquake-prone zone

The distribution of earthquakes is more or less similar to that of volcanoes. The earthquakes mostly occur in weak crustal areas of the earth.

(1) Circum-Pacific Belt :

About 68% of world’s earthquakes are observed along the coasts of the vast Pacific Ocean. This is known as the ‘ring of fire’. This is the area of intense volcanic activity also.

This area is closely linked with the region of crustal dislocations and volcanic phenomenon. Chile, California, Alaska, Japan, Philippines, New Zealand, and the Mid-ocean area have many minor and major earthquakes in this belt.

Mountains here run along the border of continents and nearly parallel to the depressions in one answer: It causes a sharp break in relief which becomes a cause for the earthquake.

(2) Mid-world Mountain Belt :

Nearly 21% of the world’s earthquakes occur in the Mid-world mountain belt. It extends parallel to the equator from Mexico across Atlantic Ocean, the Mediterranean Sea from Alpine-Caucasus ranges to the Caspian, Himalayan mountains and the adjoining lands. This zone has folded mountains, large depressions and active volcanoes.

(3) Minor Belts :

The remaining 11% of the shocks are recorded outside these two belts. Only a few occur along the fracture in African lakes, Red and the Dead Sea zone.

Earthquakes in India :

Earthquakes in India are mainly confined to the Hima- layan region and its foothills. They are also felt in the Ganga Valley. There have been a number of violent earthquakes in India in historic times.

The Kutch earthquake (1819), the Assam earthquake (1877), the Kangra earthquake (1905), the Bihar earthquake (1934), the Assam earthquake (1950), Himachal earthquake (1975) and Uttarkashi earthquake (1991) are some of the well-known examples.

The Peninsular Plateau has remained practically free from earthquakes. But the earthquake of Koyna Dam region in Maharashtra in 1968 is an important exception. This was most probably caused due to large quantity of water in the reservoir which resulted in fissures and cracks. The other major earthquakes of the Peninsular India are those of Lattur (1993) and Jabalpur (1997).

The earthquake which shook Bhuj in 2001 was one of the most devastating which turned Bhuj, Anjar, Bhachau, Gandhidham and Ratnel into mounds of rubble.

Question 8. Write a detailed account of impact of earthquakes on environment.
Answer:

Impact of Earthquakes on Environment :

(1) Human Life :

Earthquake of high intensity, usually over 7 on the richter scale cause heavy damage to human life particularly if the earthquake strikes a thickly populated area. Table gives an area of loss of human lives by earthquakes striking different parts of the world in the last 25 years.

The most hazardous earthquakes claiming more than one lakh human lives in the history of the world are those of Chibli (China) in 1290 AD. (100,000 deaths), Shen Shu (China) in 1556 AD. (8,30,000 deaths), Kolkata in 1737 AD. (3,00,000 deaths).

(2) Damage to Buildings :

Buildings are often damaged during earthquakes, especially the weak buildings constructed with brick, mud, or timber. Reinforced concrete buildings are less damaged. Projecting cornices, balconies, towers and arcades render buildings more vulnerable to earthquake shocks. Damage to buildings is caused by the oscillation (backward and forward) motion of the ground.

The foundation of the building moves with the ground oscillation whereas upper part of the building fails to move as quickly as the lower portion. This leads to differntial stress and subsequent cracking in the building

(3) Fires :

Severe earthquake cause strong seismic waves which cause fires in buildings, mines and factories. Most of the fires are caused by short-circuit in electric fittings. The earthquake of Sagami bay (Japan) in 1923 claimed a total of 1,63,000 lives out of which 38,000 casualties were due to fire alone.

(4) Floods :
Strong seismic waves often cause damage to dams and water stored behind the dam flows rapidly downstream and vast areas are flooded there. However, timely action by the civil authorities prevented breach in the dam and avoided the flood fury in the density populated area.

Sometimes, floods are caused due to blocking of flow of river water caused by rock-fall. The blockade of the river leads to accumulation of huge quantities of water in the upstream area of the site of blockade and possible change in the river course. When the debris are removed by water pressure, the river water gushes down stream and vast areas are flooded.

(5) Topographical changes :
Topographical effects of earthquakes are conspicious along faults, fissures, scarps, etc. Cracks and fissures occurring due to earthquake facilitate landslides. The severe earthquake of Uttarkashi (1991) caused many cracks and fissures in the Varunavrat Parvat. This gave birth to landslides which caused heavy damage to Uttarkashi town in the year 2003.

(6) Liquefaction :
Soil liquefaction is a phenomenon where low density satu- rated sands of relatively uniform size inside the earth start behaving like a jelly with no strength to hold a building up and the building just sinks or gets tilled on one side.

(7) Damage to Transport System: Damage to transport system includes high- ways, railways, airports, marine and river systems, water supply and sewage, fuel and oil, energy transmission and communication systems. In the event of a strong earthquake, these systems are damaged as the earthquake waves cross them. Damage to transport system brings economic activities to a standstill and leads to heavy financial losses.

Question 9. What do you mean by sea quakes and Tsunamis?
Answer:

Sea quakes and Tsunamis

Earthquakes occurring in the sea are called sea quakes. Whenever an earthquake hits the sea bed, it results in violent movements in the oceanic water. Seismic sea waves occur following violent movement of the seafloor.

These waves ing harbour and ‘nami’ meaning wave. According to Report of High Powered Com- mittee on Disaster Management (2001), “Tsunami is an ocean wave produced by an event at the sea, like an earthquake, landslide or volcanic eruption”.

A tsunami is not a single wave but a series of waves generated by the geologicalm changes near or below the ocean floor. These waves may reach enormous size and have been known to travel across the oceAnswer:

Question 10. Give an account of formation of Tsunamis.
Answer:

Formation of Tsunamis :

(1) Undersea earthquakes :
Although tsunami may be caused by landslides, volcanic eruptions or even by the impact of a large meteorite falling on the ocean, most destructive tsunamis are generated by massive undersea earthquakes, occurring at depth less than 50 km with the epicentre or fault line near or on the ocean floor.

A strong undersea earthquake with magnitude greater than 7.5 on the Richter Scale tilts and deforms large areas of the seafloor ranging from a few kilometres to 1000 kilometres and even more. As the sea floor is tilted or deformed by the tectonic earthquake (earthquake associated with the earth’s crustal deformation), the sea water above is displaced from its equilibrium position.

Waves are formed as the displaced water attempts to regain its equilibrium under the influence of gravity. It is this vertical movement of the entire water column that generates destructive tsunami waves.

The displacement of sea floor and occurrence of an earthquake and formation of tsunamis can best be explained on the basis of plate tectonics. When two converging lithospheric plates come closer together, the heavier plate is thrust under the lighter plate and displacement of the crust takes place at the subduction zone. A fault is created and an earthquake occurs, giving rise to tsunamis.

It must be noted that a tsunami is usually not generated if the sea floor move- ment is horizontal. Besides, not all undersea earthquakes create tsunami, as it depends upon the nature and degree of displacement of seawater column.

It is only the vertical displacement of the seawater due to abrupt, jerky movements of fault blocks on seabed that gives birth to tsunamis. Once formed, the monstrous waves soon begin their journey towards the nearest coastline, ringing the bells of doom.

(2) Landslides :
Tsunami waves are also generated by displacement of seawater resulting from landslides as well as rock falls, icefalls, etc. Construction work of an airport runway along the coast of Southern France in the 1980’s caused an underwater landslide.

This triggered the destructive tsunami waves in the harbour of Thebes. Underwater landslides may also occur when a strong earthquake shakes the sea floor, thus forming tsunamis. These waves rapidly travel away from the source due to dissipation of energy and create havoc in the nearby coastlines.

(3) Volcanic Eruptions :

Whenever a violent volcanic eruption takes place under the sea, it causes a sudden displacement of a large volume of seawater and tsunami waves are formed. Similarly, when the roof of a volcano collapses that has a large empty magma chamber owing to continuous flow of lava, a crater sometimes as large as one kilometre in diameter is formed. As the seawater gushes into this crater, the water column of the sea is disturbed which gives rise to tsunami waves.

(4) Meteorites and Asteroids :

There is a potential danger of tsunami being formed by the fall of meteorites and asteroids in the ocean. Researchers in Cali fornia have developed a computer simulation depicting the ocean impact of asteroid 1950 DA, a gigantic space rock that would be very close to the earth in 2880.

Although the possibility of such an impact is very remote, the computer model definitely gives the researcher an insight into the destructive power of tsunami caused by near-earth object. Some of the meteorites have been uncomfortably close to the earth and could wreck havoc in different forms including tsunamis.

Question 11. Give an account of the types of Earthquakes.
Answer:

Types of Earthquakes :

Tectonic Earthquake:

1.Tectonic earthquakes are generated due to = sliding of rocks along a fault plane.
Example: Volcanic Earthquakes.

2.They.are confined to the areas of active volcanoes.

Collapse Earthquakes:

1.These earthquakes are minor and are caused due to the falling of roofs of mines.

Explosion Earthquakes:

(1) Earthquakes caused by chemical explosions are termed as explosion earthquakes.

(2) Nuclear device causes these earthquakes.

Induced Earthquake:

Human activities also cause earthquake.
(1) The pumping of fluids into the oil fields to raise the hydrostatic pressure and to increase oil recovery is responsible for setting off minor earthquakes.

(2) Human beings build large dams on major rivers. The load of water impounded (reservoirs) behind the large dams triggers earthquakes.

Question 12. Describe the role of students in Disaster management.
Answer:

The role of students in Disaster management

The basic role of the student is awareness of what to do during and after disasters. Students, by nature have a great deal of courage and stamina in collective sense.

Their combined effort are very helpful to the society in case of dire need. Our educational system should include the training programmes to the students from school level to get them acquainted with the helping nature at times when voluntary and spontaneous approaches are essential for the sake of relief for distressed or afflicted persons. A disaster is a calamity which affect the society to a great extent.

It needs united efforts to overcome the disaster. Thus disaster management is essential, where youth plays a vital role in tacking the situation as fast as possible. If the students are properly trained, they can rush to the disaster spot and can help the disaster management team for quick rehabilitation and resettlement of victims at times of floods, earthquakes and drought etc. They also can spread awareness to the precautions to be taken at times of disasters.

Question 13. What do you mean by Drought ? Explain its types.
Answer:

Drought

Drought is either absence or deficiency of rainfall from its normal pattern in a region for.an extended period of time leading to general suffering in the society. Drought proceeds in sequential manner.

Its impacts are spread across different domains as listed below—

(1) Meteorological:

It is simple deficit of rainfall from the normal. It can be classified into
(1) Seuere drought : When rainfall is <50—-75%
(2) medium drought: rainfall less than 25-50% :
(3) Extreme drought : rainfall more then 60%.
(4) Partial drought ; when daily average rainfall is 0.2mm during rainy season
(5) Absolute drought : When continuously there is no rainfall during rainy season.

(2) Hydrological drought :
It often leads to reduction of natural stream flow or ground water level plus stored water supplies. }

(3) Agricultural drought :
It occurs when moisture level in soil is insufficient to maintain average crop yield. :

(4) Socio-economic drought :
It correlates the supply and demand of goods and services with the three above mentioned types of drought.

Question 14. What do you mean by flood ? State its causes.
Answer:

Flood

A flood is flow of water that submerges land which is usually dry. Flood is a state of high water level that leads to inundation of land, which is not usually submerged. Floods may happen due to breach in the embankment of a river, spill over or due to heavy rains.

There are several causes of floods which differ from place to place. Some of the major cause of flood are :

(1) Heavy rainfall
(2) heavy siltation which reduces the water carrying capacity of the rivers/stream
(3) strong winds along with storm surge
(4) Construction of dams and reservoirs on the course of a river
(5) Landslides blocking the flow of the stream ete.

Question 15. Write a note on forest fire.
Answer:

Forest fire

A forest fire is an uncontrolled fire occuring in forest. Sometimes, the forest fire is so large that it takes a long time for the firefighting crews to gain control over the situation. This could result in massive destruction. A wildfire differs from other fires by its extensive size, the speed at which it can spread out from its original source.

Types of Forest Fires :

Forest or wildfires can be broadly classified into three types —

1. Ground fires.
2. Surface fires.
3. And crown fires.
4. Depending on the type of fuel

1. Ground fires :
Are usually fueled by subterranean roots, buried organic matter, and dead vegetative parts like leaves, branches, and bark and stems of trees that exist on the soil surface at various stages of decomposition.

2. Surface fires :
On the other hand, are fed by low-lying vegetation, shrubbery, leaves, grass, and other debris. A surface fire is usually less intense as compared to a ground fire, and it does not pose major risks to mature trees and their roots.

3. Crown or aerial fires :
Can reach the level of tree canopy. A crown fire can blow embers and tree branches to unburned areas, and thus, spread the fire rapidly.

4. Causes of Forest Fires :
Right from lightning and volcanic eruptions to unattended campfires can cause forest fires. Sometimes, a lighted cigarette left in the forest can also ignite a wildfire.

The following are some of the most important factors that can cause forest fires :
Lightning and Volcanic Eruptions, Underground Coal Fires, Spontaneous Forest Fires.

Question 16. Write a note on avalanche.
Answer:

Avalanche

An avalanche (also called a snowslide or snowslip) is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack (slab avalanche) when the forces on the snow exceed its strength but sometimes only with gradually widening (loose snow avalanche). After initiation, avalanches usually acceierate rapidly and grow in mass and volume as they entrain more snow.

If the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. Slides of rocks or debris, behaving in a similar way to snow, are also referred to as avalanches.

Cause :
The load on the snowpack may be only due to gravity, in which case failure may result either from weakening in the snowpack or increased load due to precipitation. Avalanches that occur in this way are known as spontaneous avalanches.

Avalanches can also be triggered by other loads such as skiers, snowmobilers, animals or explosives. Seismic activity may also trigger the failure in the snowpack and avalanches.

Avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack. Avalanches are most common during winter or spring but glacier movements may cause ice and snow avalanches at any time of year.

In mountainous terrain, avalanches are among the most serious objective natural hazards to life and property, with their destructive capability resulting from their potential to carry enormous masses of snow at high speeds.

Question 17. State the process of formation of blizzard.
Answer:

Step One:

The first step in the formation of any blizzard is that cold air must be present. Warm air should start to flow over it. This first step can occur when winds pull cold air toward the equator and away from the North or South poles.

This pulling motion will also bring warm air in the direction of the poles and away from the equator. As the warm air from the equator is brought into contact with the cold air from the poles, a weather phenomenon called a “front” is formed; clouds begin to take shape, gaining more and more moisture, which will eventually be released as snow.

Step  Two :

As the moisture is added to the clouds, it starts to form into water vapor which is a mixture of gaseous water and liquid water. Generally, blizzards that are high intensity are formed near some sort of body of water. Bodies of water such as lakes and rivers are excellent sources of moisture for a blizzard and can lead to some very large snowstorms.

As the blowing winds associated with a front pick up more and more water, the storm strengthens and the blizzard becomes a much more formidable force of nature than a simple snowstorm.

Step Three :

Most storms with large amounts of water built up will simply cause torrential rainfall. A blizzard releases its moisture in the form of snow. This is because of the third necessary requirement for a blizzard, cold air near the ground.

As the water vapour begins to clump together to form small particles of ice, the particles begin to fall to the ground. In a rainstorm, the ice particles will thaw and become raindrops.

In a blizzard, however, because of the below-freezing temperatures near the ground, the ice will not thaw and will instead stay frozen as they hit the ground in the form of snow, sleet, or hail.

Question 18. What are the conditions necessary for forming of cyclones?
Answer:

The conditions necessary for forming of cyclones

Cyclones, also known as hurricanes or typhoons, are primarily caused by high ocean temperatures, broad-scale wind systems and clustered thunderstorms, which liberate the heat energy from the ocean surface and transfer it to the cyclone.

Ocean temperatures must be higher than 80 degrees Fahrenheit to a depth of at least 150 feet. This heat from the ocean combines with the Earth’s rotation to create the cyclone’s spin and propulsion. As the cyclone moves across cooler waters, land or into unfa- vorable wind systems, it gradually begins to dissipate as it loses energy.

There are a number of additional atmospheric conditions that must be present in order for a cyclone to form, including moisture layers in the mid-troposphere, approximately 3 miles above the Earth’s surface, and low vertical wind shear. between the Earth’s surface and the upper troposphere.

Cyclones also need to be at least 310 miles from the equator, where the deflective Coriolis force of the planet’s rotation begins to take effect. Depending on the caliber of these conditions, a cyclone’s center, or eye, can grow to be more than 62 miles in diameter, although 25 miles is more typical.

Question 19. Explain the stages of formation of cyclone.
Answer:

The development of a cyclone covers three stages namely-

(1) Formation and initial development state :
Four atmospheric/ oceanic conditions are necessary for the formation of a cyclone namely :

1. A warm sea temperature in excess of 26 degree centigrade, to a depth of 60 meters, which provides abundant water vapour in the air by evaporation.

2. High relative humidity (degree to which the air is saturated by water vapour) of the atmosphere to a height of about 7000 metres, facilitates condensation of
water vapour into droplets and clouds, releases heat energy and induces drop in pressure.

3. Atmospheric instability (an above average decrease of temperature with altitude) encourages considerable vertical cumulus cloud convection when condensation of rising air occurs.

4. A location of at least 4-5 latitude degrees from the Equator allow the influence of the force due to the earth’s rotation (Coriolis force) to take effect in inducing cyclonic wind circulation around low-pressure centers.

(2) Fully matured :
The main feature of a fully mature tropical cyclone is a spiral pattern of highly turbulent giant cumulus thundercloud bands. These bands spiral inwards and form a dense highly active central cloud core which raps around a relatively calm zone.

This is called the “eye” of a cyclone. The eye looks like a black hole or a dot surrounded by thick clouds. The outer circumference of the thick cloud is called the ‘eye wall’.

c) Weakening or decay :
A tropical cyclone begins to weaken as soon as its source of warm moist air is abruptly cut off. This is possible when the cyclone hits the land, on the cyclone moves to a higher altitude or when there is the interference of another low pressure.

Depending on their track on the warm tropical sea and proximity to land a cyclone may last for less than 24 hours to more than 3 weeks. On an average, the life cycle of a cyclone (a cyclone to complete these three stages mentioned above) takes six days. The longest cyclone is typhoon John which lasted for 31 days (August to September 1994 in the northeast and northwest pacific basins).

Question 20. What are the harmful effects caused by cyclones?
Answer:

1. Typical Adverse effect :
First, in a sudden, brief onslaught, high winds cause major damage to infrastructure and housing, in particular fragile constructions. They are generally followed by heavy rains and floods and, in flat coastal areas by storm surge riding on tidal waves and inundating the land over long distances of even up to 15 kilometers inland.

2. Physical damage :
Structures will be damaged or destroyed by the wind force, flooding and storm surge. Light-pitched roofs of most structures especially the ones fitted onto industrial buildings will suffer severe damage.

3. Casualties and public health :
Caused by flooding and flying elements, contamination of water supplies may lead to viral outbreaks, diarrhea, and malaria.

4. Water supplies :
Ground and pipe water supply may get contaminated by flood waters.

5. Crops and food supplies :
High winds and rains ruin the standing crop and food stock lying in low lying areas. Plantation-type crops such as banana and coconut are extremely vulnerable. Salt from the seawater may get deposited on the agricultural land and increase the salinity. The loss of the crop may lead to acute food shortage.

6. Communication :
Severe disruption in the communication links as the wind may bring down the electricity and communication towers, telephone poles, telephone lines, antennas, and satellite disk and broadcasting services. Transport lines (road and rail) may be curtailed, Lack of proper communication affects effective distribution of relief materials.

Question 21. What are the possible measures to be taken to control or minimize the effects of cyclone?
Answer:

Possible Risk Reduction Measures :

Coastal belt plantation :
Green belt plantation along the coastal line in a scientific interweaving pattern can reduce the effect of the hazard. Providing a cover through green belt sustains less damage. Forests act as a wide buffer zone against strong winds and flash floods.

Without the forest the cyclone travel freely inland. The lack of protective forest cover allows water to inundate large areas and cause destruction. With the loss of the forest cover each consecutive cyclone can penetrate further inland.

Hazard mapping :
Meteorological records of the wind speed and the directions give the probability of the winds in the region. Cyclones can be predicted several days in advance. The onset is extensive and often very destructive. Past records and paths can give the pattern of occurrence for particular wind speeds.

A hazard map will illustrate the areas vulnerable to cyclone in any given year. It will be useful to estimate the severity of the cyclone and various damage intensities in the region. The map is prepared with data inputs of past climatological records, history of wind speed, frequency of flooding etc

Land use control designed so that least critical activities are placed in vulnerable areas. Location of settlements in the floodplains is at utmost risk. Siting of key facilities must be marked in the land use. Policies should be in place to regulate land use and building codes should be enforced.

Engineered structures :
structures need to be built to withstand wind forces. Good site selection is also important. Majority of the buildings in coastal areas are built with locally available materials and have no engineering inputs. Good construction practice should be adopted such as :

1. Houses can be strengthened to resist wind and flood damage. All elements holding the structures need to be properly anchored to resist the uplift or flying off of the objects. For example, avoid large overhangs of roofs, and the projections should be tied down.

2. A row of planted trees will act as a shield. It reduces the energy.

3. Buildings should be wind and water-resistant.

4. Buildings storing food supplies must be protected against the winds and water.

5. Protect river embankments. Communication lines should be installed underground.

6. Provide strong halls for community shelter in vulnerable locations.

Flood management :
Torrential rains, strong wind, and storm range leads to flooding in the cyclone-affected areas. There are possibilities of landslides too. Flood mitigation measures could be incorporated.

Improving vegetation cover :
The roots of the plants and trees keep the soil intact and prevent erosion and slow runoff to prevent or lessen flooding. The use of tree planted in rows will act as a windbreak. Coastal! shelterbelt plantations can be developed to break severe wind speeds.

It minimizes devastating effects. The Orissa calamity has also highlighted the need for urgent measures like shelterbelt plantation along cyclone-prone coastal areas. Species chosen for this purpose should not only be able to withstand the impact of strong cyclonic winds but also check soil erosion.

Question 22. What do you mean by disaster management?

Answer:

Disaster management

Basically, the process of disaster management involves dynamism. Its mission includes the duty of making a plan, systematizing the entire process, employing and training crews, leading, administering and supervising.

It involves multiple organizations that should act concertedly in order to avert (prevent), alleviate (mitigate), prepare for (arrange), respond (react) and recover (recuperate) from the consequences of a disaster.

Thus it includes prompt response, regaining or retrieval, avoidance, diminution, alertness; the cycle gets repeated on and on. Disaster management is a complex humanitarian process involving international, national, and local organizations each with a distinct role to play. A coordinated effort is required in order to respond to a disaster.

It is defined as “an applied science which seeks, by the systematic observation and analysis of disasters, to improve measures relating to prevention, mitigation, preparedness, emergency response and recovery”.

Disaster management can be referred to the organizing and managing of the resources and responsibilities in order to handle all emergency situations with a humanitarian approach; especially, its prevention, mitigation, preparedness, response and the recovery so as to reduce the impact of disasters.

Any sort of disaster is likely to disrupt the essential services, health care facilities, supply of electricity and water, sewerage systems, removal of wastes and garbage, transport and communication systems.

Such interruption heavily affects the health, the socio-economic set up of the local people and countries. Even if the immediate impacts have been mitigated, it usually leaves a predominant long-lasting effect in its people.

The ill planned assistance and rescue activities negatively affect both the victims of disaster and the donors and aids organization; hence it is foremost that the physical therapists should also participate collective and recognized efforts rather than individual programs

Geography Class 9 West Bengal Board

Question 23. What are the effects of drought?
Answer:

Effects of drought

Periods of droughts can have significant environmental, agricultural, health, economic and social consequences. The effect varies according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations that depend on as a major food source are more vulnerable to famine.

(1) Drought can also reduce water quality because lower water flows reduce dilution of pollutants and increase contamination of remaining water sources. Common consequences of drought include:

(2) Diminished crop growth or yield production and carrying capacity for livestock.

(3) Dust bowls, themselves a sign of erosion, which further erode the landscape.

(4) Dust storms, when drought hits an area suffering from desertification and erosion.

(5) Famine due to lack of water for irrigation.

(6) Habitat damage, affecting both terrestrial and aquatic wildlife.

(7) Hunger, drought provides too little water to support food crops.

(8) Malnutrition, dehydration and related diseases.

(9) Mass migration, resulting in internal displacement and international refugees.

(10) Reduced electricity production due to reduced water flow through hydroelectric dams.

(11) Shortages of water for industrial users.

(12) Snake migration, which results in snakebites.

(13) Social unrest.

(14) War over natural resources, including water and food. Wildfires, such as Australian bushfires, are more common during times of drought and even death of people.

(15) Exposure and oxidation of acid sulfate soils due to falling surface and groundwater levels.

Question 24. What are the effects of flood?
Answer:

The effects of flood can be categorized in two parts-

Primary effects :
The primary effects of flooding include loss of life, damage to buildings and other structures, including bridges, sewerage systems, roadways, and canals.

Floods also frequently damage power transmission and sometimes power generation, which then has knock-on effects caused by the loss of power. This includes loss of drinking water treatment and water supply, which may result in loss of drinking water or severe water contamination.

It may also cause the loss of sewage disposal facilities. Lack of clean water combined with human sewage in the flood waters raises the risk of waterborne diseases, which can include typhoid, giardia, cryptosporidium, cholera and many other diseases depending upon the location of the flood.

Damage to roads and transport infrastructure may make it difficult to mobilize aid to those affected or to provide emergency health treatment.

Flood waters typically inundate farm land, making the land unworkable and preventing crops from being planted or harvested, which can lead to shortages of food both for humans and farm animals. Entire harvests for a country can be lost in extreme flood circumstances. Some tree species may not survive pro- longed flooding of their root systems

Secondary and long-term effects :
Economic hardship due to a temporary decline in tourism, rebuilding costs, or food shortages leading to price increases is a common after-effect of severe flooding. The impact on those affected may cause psychological damage to those affected, in particular where deaths, serious injuries, and loss of property occur.

Urban flooding can lead to chronically wet houses, which are linked to an increase in respiratory problems and other illnesses. Urban flooding also has significant economic implications for affected neighborhoods.

Question 25. What are the causes of landslides?
Answer:

The causes of landslides

Landslides occur when the stability of the slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone.It can be divided into two categories-

1. Natural causes of landslides include :

1. Groundwater (pore water) pressure acting to destabilize the slope
2. Loss or absence of vertical vegetative structure, soil nutrients, and soil structure (e.g. after a wildfire – a fire in forests lasting for 3-4 days)
3. Erosion of the toe of a slope by rivers or ocean waves
4. Weakening of a slope through saturation by snow melt, glaciers melting, or heavy rains
5. Earthquakes adding loads to barely stable slope
6. Earthquake-caused liquefaction destabilizing slopes
7. Volcanic eruptions

2. Landslides are aggravated by human activities, such as-

1. Deforestation, cultivation, and construction, which destabilize the already fragile slopes.
2. Vibrations from machinery or traffic
3. Blasting
4. Earthwork which alters the shape of a slope, or which imposes new loads on an existing slope
5. In shallow soils, the removal of deep-rooted vegetation that binds colluvium to bedrock
6. Construction, agricultural or forestry activities (logging) which change the amount of water which infiltrates the soil.

Geography Class 9 West Bengal Board

Question 26. State the measures to be taken to minimize the effects of landslides.
Answer:

Vulnerability to landslide hazards is a function of location, type of human activity, use, and frequency of landslide events. The effects of landslides on people and structures can be lessened by total avoidance of landslide hazardareas or by restricting, prohibiting, or imposing conditions on hazard-zone activity. Local governments can reduce landslide effects through land-use policies and regulations.

Individuals can reduce their exposure to hazards by educating themselves on the past hazard history of a site and by making inquiries to planning and engineering departments of local governments. They can also obtain the professional services of an engineering geologist, a geotechnical engineer, or a civil engineer, who can properly evaluate the hazard potential of a site, built or unbuilt.

The hazard from landslides can be reduced by avoiding construction on steep slopes and existing landslides, or by stabilizing the slopes. Stability increases when groundwater is prevented from rising in the landslide mass by

(1) Covering the landslide with an impermeable membrane,
(2) Directing surface water away from the landslide,
(3) Draining groundwater away from the landslide, and
(4) Minimizing surface irrigation. Slope stability is also increased when a retaining structure and/ or the weight of a soil/rock berm are placed at the toe of the landslide or when mass is removed from the top of the slope.

Question 27. Explain the disaster management cycle.
Answer:
The Disaster Management Cycle consists of the following broad stages :

(1) The Disaster Event :
This refers to the “real-time” event of a hazard occur- ring and affecting elements at risk. The duration of the event will depend on the type of threat; ground shaking may only occur for a matter of seconds during an earthquake while flooding may take place over a longer sustained period.

(2) Response and Relief :
This refers to the first stage response to any calamity, which include setting up control rooms, putting the contingency plan in action, issue warning, action for ecacuation, taking people to safer areas, rendering medical aid to the neeby, etc.,

simultaneously rendering relief to the homeless, food, drinking water, clothing, etc. to the needy, restoration of communication, and disbursement of assistance in cash or kind.

(3) Recovery :
Recovery is used to describe the activities that encompass the three overlapping phases of emergency relief, rehabilitation, and reconstruction.

Emergency relief :
Activities undertaken during and immediately following a disaster, which include immediate relief, resuce, damage and needs assessment, and debris clearance.

Rehabilitation ;
Rehabilitation includes the provision of temporary public utilities and housing as interim measures to assist longer-term recovery.

Class 9 Geography Solution WBBSE

Reconstruction :
Reconstruction attempts to return communities to improved pre-disaster functioning. It includes the replacement of building, infrastructure, and lifeline facilities so that long-term development prospects are enhanced rather than reproducing the same conditions which made an area or population vulnerable in the first place.

(4) Development :
In an evolving economy, development process is an ongoing activity. Long-term prevention/disaster reduction measures like construction of embankments against flooding, irrigation facilities as drought proofing measures, increasing plant cover to reduce the occurrences of landslides, land use planning, construction of houses capable of withstanding the onslaught of heavy rains/wind speed and shocks of earthquakes are some of the activities that can be taken up as part of development plans.

(5) Prevention :
Reducing the risk of disasters involves activities, which either reduce or modify the scale and intensity of the threat faced or by improving the conditions of elements at risk.

Although the term ‘prevention’ is often used to embrace the wide diversity of measures to protect persons and property its use is not recommended since t is misleading in its implicit suggestion that natural disasters are preventable, The use of term reduction to describe protective or preventive actions that reduce the scale of impact is therefore preferred.

(6) Mitigation :
Mitigation embraces all measures taken to reduce both the effect of the hazard itself and the vulnerable conditions to it to reduce the scale of future disaster.

(7) Preparedness :
Preparedness embraces the measures that enable us to respond quickly to disaster situation to cope with them effectively. It includes the formation of viable emergency plans, the development of warning systems, the maintenance of inventories, and training of personnel. It may also embrace search and rescue measures as well as evacuation plants for areas that may be at risk from a recurring disaster.

Question 28. Give an account of the major landslides in India.

Answer: Major Landslides in India :

 

Date/year	Location	Effects
1993	Ratighat (Uttarakhand)	The Nainital hill area remained cut off for about a week. It took five days to clear the debris.
1993	Nilgiri Hills (Tamil Nadu)	Forty people died, and over 600 families shifted to safer places. Roads and houses destroyed.
August 12-18yl998	Malpa (Uttarakhand)	The entire village was washed away. About 384 persons including 60 pilgrims going to Lake Mansarovar were killed.
Sept. 24 to Oct.10.2003	Uttarkashi (Uttarakhand)	Boulders from Varunavat Parvat razed several parts of Uttarkashi town. Landslides affected 362 families and nearly 3,000 people were evacuated. Several portions of the national highway leading to Gangotri were damaged.
July 6, 2004	Badrinath (Uttarakhand)	The landslide blocked the pilgrimage route to Badrinath. Over 2,000 pilgrimages were stranded in the hills near Badrinath. Nearly 1,000 shopkeepers and 2,500 villagers were trapped and remained cut off for 3 days. Roads were blocked. Massive rescue work had to be launched.

 

Question 29. Give an account of the flood control programs And policies taken by the Government of India.

Answer: After devastating floods in 1954, the Government of India announced a National Flood Management Programme. The program was divided into three- phases—immediate, short-term, and long-term.

(1) Immediate phase :
Extending over a period of 2 years was adopted fo intensive collection of data and execution of emergent flood protection measures.

(2) Short-term measure :
Covering next 4 to 5 years, included construction of spurs and embankments at selected sites.

(3) Long-term measures :
included the construction of storages, reservoirs on rivers/tributaries and additional embankments. It has been estimated that out of 40 million hectares, only 32 million hectares can be provided with reasonable degree of flood protection by structural measures.

Since the lanuching of the National Flood Control Programme in 1954, nearly, 45.81 million hectares of land has been provided with reasonable degree of flood protection. About 33,630 km near of embankments, 37,904 km. of drainage channels, 2,337 town-protection works and raising the level of about 4,713 villages had been completed upto March, 2000.

These achievements have been executed with a cumulative expenditure of Rs. 7,239.45 crore. Besides a number of reservoir projects have been completed which have helped in mitigating flood-peak in the downstream reaches.

Notable among these are Tilaiya, Konar, Maithon and Panchet Hill dams in the Damodar Valley System, Bhakra Dam on the Satluj, Hirakud Dam on the Mahanadi, Pong Dam on the Beas, Nagarjun Sagar and Junghbhadra on the Krishna and Ukai Dam on the Tapi. All these dams have afforded reasonable degree of protection to about 13.64 lakh hectares of land.

Question 30. Suggest some steps reduce the impact of drought.
Answer:

The following steps are helpful in reducing the impact of drought :
(1) Immediate steps should be taken to provide safe drinking water, medicines for the victims, and availability of fodder and water for the cattle and shifting of the people and their livestock to safer places.

(2) Various devices of remote sensing, satellite mapping, and GIS (Geographical Information System) may be used for identifying water aquifers.

(3) Rainwater harvesting should be encouraged as far as possible.

(4) Steps should be taken for inter-basin transfer of river water from surplus to deficient areas.

(5) Small dams can help in collecting the water.

(6) Afforestation retains water and helps in reducing the frequency and intensity of droughts.

(7) Drought-resistant crops should be grown in areas of deficient rainfall.

Class 9 Geography Chapter 6 WBBSE

Question 31. What are the factors responsible for earthquakes?
Answer:

The main causes that are responsible for earthquakes are –

(1) Volcanic Activity :
Due to volcanic eruptions, earthquake takes place. Thus, in volcanic belts they are common. In 1883 severe earthquake occurred due to the Krakatoa eruption and in 1985 Nevado Del Ruz eruption caused earthquake in Columbia. Lava flowing within crust may cause tremors on the surface.

(2) Tectonic Movement :
This is related to the Plate Tectonic Theory. When two plates converge each other from opposite directions or they scrape past against other an earthquake takes place. (This takes place by rubbing together the land masses). In 1967 the earthquake in Koyna was caused in this way.

This happened along 400 km long Kurdawadi Rift (from SE of Sholapur to North of Pune). At present, the Gondwana plate is moving North at the rate of 5 centimeters a year. And it is feared that a mammoth earthquake measuring 8.5 on the richter scale is likely to occur in the next 10 to 15 years.

(3) Isostatic Adjustment :
This is caused by the adjustment of sial and sima (sima – silica and magnesium and sial — silica and aluminum). Where the equilibrium is disturbed due to gradation by natural agent.

(4) Dislocation of the earth’s crust :
Earthquakes may be caused due to the dislocation of the crust or the rock bed beneath the surface of the earth.

(5) Gases in the Interior :
Sudden shaking of the earth’s surface is felt when in the interior of the earth’s surface expansion and contraction of gases takes place.

(6) Minor Causes :
(1) Faulting and folding in the rock strata.
(2) Landslides and avalanches.
(3) Submarine Slides.

(7) Man-Made Causes :
(1) The impounding of large quantities of water behind dams disturbs the crustal balance.
(2) The shock waves through bomb testing originates earthquakes.