Hazard and Disaster: WBBSE Class 9 Geography solutions

Summary

A hazard is a sudden event that harms nature, people’s belongings, and homes on Earth. The word ‘hazard’ comes from old words that meant ‘death’, showing how serious these events can be. Hazards can be grouped into types. Natural hazards happen because of nature, like a big flood. Quasi-natural hazards start from nature but become worse because people are not careful or have old beliefs. Man-made hazards are caused by what people do, such as accidents in factories or too many people living in one place.

A disaster is what happens when a hazard becomes very big and very bad. The word ‘disaster’ comes from old words meaning ‘bad star’. Long ago, people believed that a ‘bad star’ in the sky caused terrible events on Earth. This was their way of understanding why bad things happened. A disaster is a harsh event that stops people from living their normal lives. It causes great harm to people, animals, and plants, happening very quickly and without warning. It can mean loss of life, injuries, and damage to homes and the environment.

Many kinds of disasters come from nature. Floods happen when there is too much rain and water covers the land. Floods can be caused by heavy rain, melting ice, or big storms. Sometimes, things people build, like dams, can also cause floods if they break. Floods can wash away homes and crops and spread diseases. Drought is when there is no rain for a very long time. This makes the land dry, and it’s hard to grow food. Droughts can be caused by nature or by people cutting down too many trees.

Cyclones are big storms with very strong, swirling winds. They have different names in different parts of the world. Earthquakes happen when the ground suddenly shakes. This is usually caused by movements deep inside the Earth. Earthquakes can make buildings fall and are measured on a special scale. A tsunami is a giant wave in the sea, often caused by an earthquake under the ocean. Tsunamis can travel far and cause a lot of damage when they reach land.

Landslides occur when earth, rocks, and soil slide down a hill or mountain. Heavy rain or earthquakes can cause landslides. An avalanche is when a large amount of snow slides down a mountain. A blizzard is a strong, cold wind with a lot of snow, usually in very cold places. Volcanism is when hot liquid rock, gas, and ash burst out from a volcano. Wildfires are large fires that burn in forests or grasslands, spreading very quickly. All these events can change the land and affect many lives.

Textual Questions, Answers (Oriental)

Multiple Choice Questions

1. Loss of human life and property due to environment

A. incident
B. accident
C. danger
D. disaster

Answer: D. disaster

2. Soil erosion is what type of hazard?

A. natural
B. man made
C. quasi-natural
D. extra terrestorial

Answer: C. quasi-natural

3. Tsunami is a disaster like

A. geological
B. water-related
C. atmospheric
D. biological

Answer: A. geological

4. Example of an organic disaster

A. earthquake
B. tsunami
C. volcanism
D. landslide

Answer: D. landslide

True and false

1. In ancient time people believed disaster as evil star on bad star.

Answer: True

Explanation: The word ‘disaster’ originates from the belief that a bad or evil star caused misfortune. Ancient Greeks and other Europeans thought that natural disasters were linked to such celestial influences.

2. In West Bengal two drought prone districts are Bankura & Purulis.

Answer: True

Explanation: The document mentions that 315 out of 725 talukas in 99 districts in India are drought-prone, and Bankura and Purulia in West Bengal are commonly cited examples of such areas.

3. When blocks of ice fall down from high altitude then it is termed as waterfalls.

Answer: False

Explanation: This describes an avalanche, not a waterfall. An avalanche involves the downward movement of large masses of ice or snow, typically on a steep slope.

4. Tsunamies are the effects of cyclones.

Answer: False

Explanation: Tsunamis are caused by undersea earthquakes, volcanic eruptions, or landslides, not by cyclones. Although both are coastal hazards, their causes are completely different.

Fill in the blanks

1. The word ‘Sea tremor’ was first used by the Geographer ______.

Answer: Charles F. Richter

2. In West Bengal the person who looks after district disaster management authority is ______.

Answer: the Secretary

3. The date ______ is celebrated as disaster minimised day.

Answer: October 13

Answer the following very short type question

1. What is natural disaster?

Answer: A natural disaster is a harsh natural incident which affects normal activities of human being. It is the next adverse condition or extreme result of a natural hazard, which happens because of natural calamity and damages life and environment.

2. What do you mean by hazard?

Answer: Hazard may be defined as sudden incidents which damage natural, economic and human properties on the surface of the earth. According to dictionary, Hazard is such a condition which destroyes life, property and creates a serious threat in the environment.

3. What types of disaster is flood?

Answer: Flood is a climate-related extreme hazard which sometimes may be a disaster. The different types of flood are (a) Natural flood and (b) Man-made flood.

4. What is flash flood?

Answer: A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice or snow flowing over ice sheets or snowfields.

5. What do you mean by cloud burst?

Answer: A cloudburst is an extreme amount of precipitation in a short period of time, sometimes accompanied by hail and thunder, which is capable of creating flood-like conditions. It is a sudden, very heavy rainfall, usually local in nature and of brief duration.

6. Define drought.

Answer: 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.

7. Define Tsunami.

Answer: Tsunamis are popularly called tidal ‘waves’ although they actually have nothing to do with the tides. These waves often affect distant shores and originate by rapid displacement of water from the lake or the sea either by seismic activity, landslides, volcanic eruptions or large meteoroid impacts.

8. Name the most destructive and biggest tsunami, when and where did it happened?

Answer: One of the most destructive and biggest tsunamis in recorded history was the Indian Ocean tsunami, which occurred on December 26, 2004. It was triggered by a massive undersea earthquake off the west coast of Sumatra, Indonesia, and affected 14 countries, causing widespread devastation and loss of life.

9. What is avalanche?

Answer: When a huge bulk of ice move downward due to steep rock slope then it is termed as avalanche.

10. What is blizzard?

Answer: During prolonged winter season in Tundra region there is a continuous cold wind along with snow fall which is termed as blizzard.

11. What is ice fall?

Answer: An icefall is a portion of a glacier characterized by rapid flow and a chaotic, crevassed surface. It occurs where the glacier bed steepens and/or narrows. It is essentially a frozen waterfall, where large blocks of ice can break off and fall.

12. What is wild fire?

Answer: When there is a sudden fire, in the forest area on grassland regions or bushes it is called wild fire.

Essay type questions

1. Classify natural hazard describe it in brief.

Answer: Hazard may be classified into three types: (1) Natural Hazard: It happens because of natural calamity and damages life and environment. For an example in West Bengal most areas are often affected by flood during summer. (2) Quasi-natural Hazard: There are some hazards which occur mainly due to natural causes but due to lack of human consciousness and superstitions it becomes very much dangerous. For an example flood, soil erosion etc. (3) Man made Hazard: There are some hazards which are caused by unscrupulous activities of human being such as Bhopal gas leakage, (chemical hazard) Chernobil (Russia) atomic hazard, organic hazard (increase of population).

2. Mention the differences between natural hazard and man-made disaster.

Answer: Natural Hazard happens because of natural calamity and damages life and environment. For an example in West Bengal most areas are often affected by flood during summer. Man made Hazard are some hazards which are caused by unscrupulous activities of human being such as Bhopal gas leakage, (chemical hazard) Chernobil (Russia) atomic hazard, organic hazard (increase of population).

3. As a hazard or disaster define, classify and mention the causes of flood.

Answer: Hazard may be defined as sudden incidents which damage natural, economic and human properties on the surface of the earth. ‘Disaster’ is the next adverse condition or extreme result of hazard. Disaster is such a harsh natural incident which affects normal activities of human being.

According to Indian Meteorological Department when a particular area experiences average annual rainfall of more than 125% and becomes waterlogged then it is termed as flood. Different types of flood: (a) Natural flood (b) Man-made flood.

(a) Natural flood caused due to (i) heavy rainfall with in a short period (ii) melting of ice (iii) cyclonic storm (iv) tsunami (v) excessive rainfall during long time, (vi) sinuous river course (vii) steep slope of land. etc.
(b) Man made causes like (i) Multipurpose river valley project (ii) breaking down of dams etc.

4. Describe the causes of drought and drone prone areas.

Answer: Causes of drought: (A) Natural causes: (i) due to insufficient rainfall (ii) high rate of evaporation (iii) delayed arrival of monsoonal rain (iv) early departure of monsoon (v) during monsoon season if there is continuous rainless days (vi) increase of temperature due to effect of green house gases. (B) Man made causes: (i) deforestation for which rainfall decreases and CO₂ increases (ii) urbanisation etc.

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

5. Write in brief about nature of hazard and disaster in West Bengal and also describe its impact on people.

Answer: In West Bengal most areas are often affected by flood during summer. In West Bengal two drought prone districts are Bankura & Purulia.

The impact of hazard and disaster on people includes loss of human life and property due to environment incident/accident/danger/disaster. Disasters cause great damage to human beings as well as plants and animals. Disasters occur rapidly, instantaneously and indiscriminately. Disaster is such a physical phenomenon which cause the loss of life or injury, property damage, social & economic disruption or environmental degradation. According to some researchers of Colorado University of U.S.A. disasters means loss of hundreds of life, wastage of one million dollar and injuries of one million people.

6. Mention the strategies adopted for disaster management in West Bengal.

Answer: Key disaster management strategies in West Bengal generally include:

Risk Assessment: Identifying hazard-prone areas (floods, cyclones, landslides, droughts) and assessing community and infrastructure vulnerability.
Prevention & Mitigation: Implementing structural measures like embankments and cyclone shelters, alongside non-structural approaches such as afforestation, land-use planning, and public awareness.
Preparedness: Strengthening early warning systems, training response teams and communities, establishing Emergency Operations Centers, stockpiling relief supplies, and conducting mock drills.
Coordinated Response: Ensuring rapid search and rescue, timely evacuation, provision of immediate relief (food, water, shelter, medical aid), and quick restoration of essential services.
Recovery & Reconstruction: Conducting damage assessments, rebuilding infrastructure with disaster-resilient features (“building back better”), and supporting livelihood restoration for affected communities.
Institutional Framework: Strengthening State and District Disaster Management Authorities and integrating Disaster Risk Reduction into development plans.

Extras

Additional MCQs

1. Which term is defined as sudden incidents which damage natural, economic and human properties on the earth’s surface?

A. Hazard
B. Disaster
C. Risk
D. Vulnerability

Answer: A. Hazard

2. The word ‘hazard’ is derived from the Arabic ‘az-zahr’, which means what?

A. Chance
B. Death
C. Luck
D. Fortune

Answer: B. Death

3. Which of the following is classified as a man-made hazard?

A. Bhopal gas leakage
B. Flood
C. Tsunami
D. Volcano eruption

Answer: A. Bhopal gas leakage

4. Soil erosion due to lack of human consciousness is an example of which hazard type?

A. Natural hazard
B. Quasi-natural hazard
C. Man-made hazard
D. Extra-terrestrial hazard

Answer: B. Quasi-natural hazard

5. Which term refers to the extreme result of a hazard affecting normal human activities?

A. Emergency
B. Disaster
C. Accident
D. Risk

Answer: B. Disaster

6. In the origin of the word ‘disaster’, the component ‘astre’ means what?

A. Star
B. Evil
C. Bad
D. Planet

Answer: A. Star

7. Which instrument records the seismic waves generated by an earthquake?

A. Seismometer
B. Seismograph
C. Barometer
D. Richter scale

Answer: B. Seismograph

8. Who devised the Richter scale in 1935?

A. Charles F. Richter
B. Beno Gutenberg
C. Savindra Singh
D. Alfred Wegener

Answer: A. Charles F. Richter

9. On the Richter scale, a tremor of magnitude 3 is classified as what?

A. Light tremor
B. Moderate quake
C. Significant quake
D. Major quake

Answer: A. Light tremor

10. Approximately 95% of earthquakes in India occur near which region?

A. Himalayan region
B. Deccan Plateau
C. Indo-Gangetic Plain
D. Western Ghats

Answer: A. Himalayan region

11. According to the Indian Meteorological Department, a flood is declared when annual rainfall exceeds what percentage of the average?

A. 100%
B. 125%
C. 150%
D. 175%

Answer: B. 125%

12. Which of the following is a natural cause of floods?

A. Heavy rainfall
B. Dam construction
C. Urbanisation
D. Deforestation

Answer: A. Heavy rainfall

13. Which of the following is a man-made cause of floods?

A. Dam failure
B. Tsunami
C. Cyclone
D. Melting ice

Answer: A. Dam failure

14. The National Flood Management Programme in India was announced following the devastating flood of which year?

A. 1954
B. 1958
C. 1962
D. 1970

Answer: A. 1954

15. In which year was the first flood forecasting station established by the Central Water Commission?

A. 1954
B. 1956
C. 1958
D. 1960

Answer: C. 1958

16. Which term describes the absence or deficiency of rainfall leading to general suffering?

A. Drought
B. Flood
C. Cyclone
D. Blizzard

Answer: A. Drought

17. Which type of drought occurs when soil moisture is insufficient to maintain average crop yield?

A. Meteorological drought
B. Hydrological drought
C. Agricultural drought
D. Socio-economic drought

Answer: C. Agricultural drought

18. The Sahel region, known for severe droughts during 1905–1909 and other periods, lies at the edge of which desert?

A. Sahara
B. Gobi
C. Mojave
D. Kalahari

Answer: A. Sahara

19. Approximately what percentage of India’s total area is classified as drought-prone?

A. 50%
B. 68%
C. 75%
D. 82%

Answer: B. 68%

20. Which term denotes a region of low atmospheric pressure with swirling winds in tropical and temperate zones?

A. Tornado
B. Cyclone
C. Blizzard
D. Hurricane

Answer: B. Cyclone

21. In the Northern Hemisphere, cyclone winds rotate in which direction?

A. Clockwise
B. Anticlockwise
C. Inward only
D. Outward only

Answer: B. Anticlockwise

22. What name is given to cyclonic storms in the West Indies?

A. Hurricane
B. Typhoon
C. Tornado
D. Willy-willy

Answer: A. Hurricane

23. Which term describes the downward and outward movement of slope-forming materials?

A. Avalanche
B. Landslide
C. Subsidence
D. Creep

Answer: B. Landslide

24. The French component ‘aval’ in the word ‘avalanche’ means what?

A. Snow
B. Ice
C. Valley
D. Mountain

Answer: C. Valley

25. A blizzard is characterised by continuous cold winds and snowfall in which region?

A. Tropics
B. Tundra
C. Temperate plains
D. Deserts

Answer: B. Tundra

26. Volcanism involves the eruption of magma, gas and smoke from which layer of the Earth?

A. Crust
B. Mantle
C. Core
D. Lithosphere

Answer: B. Mantle

27. Which of the following is a primary volcanic hazard?

A. Tsunami
B. Landslide
C. Pyroclastic flows
D. Drought

Answer: C. Pyroclastic flows

28. Which volcanic hazard can trigger a tsunami following an eruption?

A. Lava flow
B. Pyroclastic flow
C. Landslide
D. Air fall tephra

Answer: C. Landslide

29. What term describes sudden uncontrolled fires in forest and grassland areas?

A. Wild fire
B. Brush burn
C. Urban fire
D. Industrial fire

Answer: A. Wild fire

30. Which mode of wild fire spread involves fire moving from lower vegetation to higher vegetation?

A. Crown fire
B. Crawling fire
C. Jumping fire
D. Surface fire

Answer: B. Crawling fire

31. Which spread mechanism of wild fires involves embers being carried by wind igniting fires ahead of the main front?

A. Jumping fire
B. Crawling fire
C. Crown fire
D. Surface fire

Answer: A. Jumping fire

32. In 2003, which country experienced the destruction of 4,249 sq km of forest due to wildfires?

A. Portugal
B. France
C. Indonesia
D. United States

Answer: A. Portugal

33. Which country lost 97,550 sq km of forest area to wildfires in 1997?

A. Indonesia
B. Australia
C. Brazil
D. Russia

Answer: A. Indonesia

34. According to Colorado University researchers, a disaster is defined by the loss of hundreds of lives and what financial loss?

A. One million dollars
B. One hundred thousand dollars
C. Ten million dollars
D. One billion dollars

Answer: A. One million dollars

35. Which human activity is noted as a cause of earthquakes in the chapter?

A. Deep underground mining
B. Surface irrigation
C. Road construction
D. Deforestation

Answer: A. Deep underground mining

36. Absolute drought is defined by which condition during the rainy season?

A. Continuous lack of rainfall
B. Rainfall below 25%
C. Daily rainfall of 0.2 mm
D. Excessive rainfall

Answer: A. Continuous lack of rainfall

37. Partial drought is defined when daily average rainfall during the rainy season equals what?

A. 0.2 mm
B. 2 mm
C. 20 mm
D. 0 mm

Answer: A. 0.2 mm

38. Which phase of the National Flood Management Programme focused on intensive data collection immediately after its launch?

A. Immediate phase
B. Short-term measures
C. Long-term measures
D. Planning phase

Answer: A. Immediate phase

39. Which agency is responsible for flood forecasting in India?

A. Central Water Commission
B. Indian Meteorological Department
C. National Disaster Management Authority
D. Central Pollution Control Board

Answer: A. Central Water Commission

40. What term is used for cyclonic storms in the Philippines?

A. Bagui
B. Typhoon
C. Hurricane
D. Tornado

Answer: A. Bagui

Additional Questions, Answers

1. What is the origin and meaning of the word “hazard”?

Answer: The word ‘Hazard’ is originated from ancient Anglo-French word ‘hasard’ or Arabic word ‘az-zahr’ means ‘death’. According to dictionary Hazard is such a condition which destroyes life, property and creates a serious threat in the environment.

2. Into which three types may hazards be classified?

Answer: Hazard may be classified into three types: (1) Natural Hazard, (2) Quasi-natural Hazard, and (3) Man made Hazard.

3. What is a quasi-natural hazard?

Answer: Quasi-natural Hazard: There are some hazards which occur mainly due to natural causes but due to lack of human consciousness and superstitions it becomes very much dangerous. For an example flood, soil erosion etc.

4. Name one example of a man-made hazard.

Answer: One example of a man-made hazard is Bhopal gas leakage (chemical hazard).

5. How did Savindra Singh define disasters?

Answer: According to Geographer Savindra Singh, “Disasters are rather, adverse unfortunate extreme events which cause great damage to human beings as well as plants and animals. Disasters occur rapidly, instantaneously and indiscriminately”.

6. According to WHO, what constitutes a disaster?

Answer: According to WHO Disaster is such a physical phenomenon which cause the loss of life or injury, property damage, social & economic disruption or environmental degradation.

7. According to researchers at Colorado University, what criteria define a disaster?

Answer: According to some researchers of Colorado University of U.S.A. disasters means loss of hundreds of life, wastage of one million dollar and injuries of one million people.

8. What is the etymology of the word “disaster”?

Answer: The word disaster is originated from either French word ‘Disastro’ or Italian word ‘Diasastro’ or Greek word ‘Disaster’. French word ‘des’ or Latin word ‘dis’ or ‘de’ or ‘di’ which mean bad evil and ‘astre’ mean star. So bad star or evil star. [dis/de/di] + [astron/star] = disaster. In ancient times people of Greece & other European countries believed that there was a bad star behind each and every natural disaster.

9. According to the Indian Meteorological Department, when is an area considered to be experiencing a flood?

Answer: According to Indian Meteorological Department when a particular area experiences average annual rainfall of more than 125% and becomes waterlogged then it is termed as flood.

10. What are the two broad categories of flood?

Answer: The two broad categories of flood are: (a) Natural flood and (b) Man-made flood.

11. Name two natural causes of floods.

Answer: Two natural causes of floods are (i) heavy rainfall within a short period and (ii) melting of ice. Other causes include cyclonic storm, tsunami, excessive rainfall during long time, sinuous river course, and steep slope of land.

12. Name two man-made causes of floods.

Answer: Two man-made causes of floods are (i) Multipurpose river valley project and (ii) breaking down of dams etc.

13. List two effects of floods on human health.

Answer: Two effects of floods on human health are (i) loss of life and (iii) spread of diseases like typhoid, cholera, diarrhoea etc.

14. Mention one remedial measure that can be taken before a flood.

Answer: One remedial measure that can be taken before a flood is the creation of forest. Other measures include construction of dams, dykes and reservoirs, regular removal of silt from the river bed, digging of waterbodies, forecasting about flood, and renovation of river bed & river banks.

15. What are the three phases of the National Flood Management Programme?

Answer: The National Flood Management Programme, announced after the devastating flood in 1954, was divided into three phases: (a) Immediate, (b) Short term, and (c) Long term.

16. Where was the first flood-forecasting station established, and in which year?

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

17. How is drought defined in hydrological terms?

Answer: Hydrological drought often leads to a reduction of natural stream flow or ground water level plus stored water supplies.

18. What is agricultural drought?

Answer: Agricultural drought occurs when the moisture level in soil is insufficient to maintain average crop yield.

19. What is socio-economic drought?

Answer: Socio-economic drought correlates the supply and demand of goods and services with meteorological, hydrological, and agricultural drought.

20. What percentage of India’s total area is drought-prone?

Answer: Around 68% of India’s total area is drought-prone.

21. What phenomenon constitutes absolute drought?

Answer: Absolute drought is when continuously there is no rainfall during rainy season.

22. What is a cyclone?

Answer: Cyclone is a region of low atmospheric pressure surrounded by high atmospheric pressure resulting in swirling atmospheric disturbance accompained by powerful winds.

23. How do cyclonic winds circulate in the Northern Hemisphere?

Answer: In the Northern Hemisphere, cyclonic winds blow in an anticlockwise direction.

24. Give two regional names for cyclonic storms outside India.

Answer: Two regional names for cyclonic storms outside India are:

(i) Hurricane in West Indies
(ii) Typhoon in China & Japan

25. What are seismic waves?

Answer: The waves generated by an earthquake are called seismic waves.

26. What is the name of the instrument used to record seismic waves?

Answer: Seismic waves are recorded by an instrument called seismograph.

27. What scale is used to measure the magnitude of earthquakes?

Answer: The magnitude or intensity of energy released by an earthquake is measured by the Richter scale.

28. Who devised the Richter scale, and in which year?

Answer: The Richter scale was devised by Charles F. Richter, in 1935.

29. What does the Japanese term “tsunami” mean?

Answer: The term ‘Tsunami’ has been derived from a Japaneese word, ‘Tsu’ meaning harbour and ‘nami’ meaning ‘waves’.

30. Name two causes of tsunamis.

Answer: Tsunamis originate by rapid displacement of water from the lake or the sea either by:

(i) seismic activity
(ii) landslides

31. What is a landslide?

Answer: The term ‘landslide’ includes all varieties of mass movements of hill slopes and can be defined as the downward and outward movement of slope forming materials composed of rocks, soils, artificial fills or combination of all these materials along surfaces of seperation by falling, sliding and flowing, either slowly or quickly from one place to another.

32. Name two physical causes of landslides.

Answer: Two physical causes of landslides are:

(i) Prolonged precipitation
(ii) rapid draw-down

33. Name two man-made causes of landslides.
Answer: Two man-made causes of landslides are:
(i) Excavation (particularly at the toe of the slope).
(ii) loading of slope crest

34. What safety measures are recommended during a blizzard?

Answer: During a blizzard, it is recommended:

(i) To take shelter in inside the ice caves.
(ii) to keep away from wind
(iii) to put fire
(iv) to keep proper ventilation in fire place etc.

35. What is volcanism?
Answer: The process by which magma, gas and smoke erupt from the mantle of the earth, it is known as volcanism.

36. What are two primary volcanic hazards?

Answer: Two primary volcanic hazards are:

(i) Pyroclastic flows
(ii) Air fall tephra (volcanic bomb)

37. List two types of wild fire.

Answer: Two types of wild fire are:

(i) forest fire
(ii) grass fire

38. Explain the origin and etymology of the terms “hazard” and “disaster.”

Answer: The word ‘Hazard’ is originated from ancient Anglo-French word ‘hasard’ or Arabic word ‘az-zahr’ means ‘death’.

The word disaster is originated from either French word ‘Disastro’ or Italian word ‘Diasastro’ or Greek word ‘Disaster’. French word ‘des’ or Latin word ‘dis’ or ‘de’ or ‘di’ which mean bad evil and ‘astre’ mean star. So bad star or evil star. [dis/de/di] + [astron/star] = disaster.

39. Outline the classification of hazards into natural, quasi-natural, and man-made, providing one example of each.

Answer: Hazard may be classified into three types:

(1) Natural Hazard : It happens because of natural calamity and damages life and environment. For an example in West Bengal most areas are often affected by flood during summer.
(2) Quasi-natural Hazard : There are some hazards which occur mainly due to natural causes but due to lack of human consciousness and superstitions it becomes very much dangerous. For an example flood, soil erosion etc.
(3) Man made Hazard : There are some hazards which are caused by unscrupulous activities of human being such as Bhopal gas leakage, (chemical hazard) Chernobil (Russia) atomic hazard, organic hazard (increase of population).

40. Describe the criteria, features, and classification of floods, including its types and effects.

Answer: According to Indian Meteorological Department when a particular area experiences average annual rainfall of more than 125% and becomes waterlogged then it is termed as flood.

Feature of flood : (i) In recent environmental science flood is a cumulative hazard (ii) Flood is climate-related extreme hazard. Sometimes it may be disaster. Eg. cyclonic storm appeared near coasts of Orissa in the year 1990. It was a kind of disaster as there was flood.

Different types of flood : (a) Natural flood (b) Man-made flood.

Effect of flood : (i) loss of life and property (ii) loss of crops (iii) spread of diseases like typhoid, cholera, diarrhoea etc. (iv) Natural disbalance of ecosystem.

41. Discuss the phases and objectives of the National Flood Management Programme in India.

Answer: After a devastating flood in 1954, the government of India announced a National Flood Management Programme. The programme was divided into three phases: (a) Immediate, (b) Short term, and (c) Long term.

The (a) Immediate phase, extending over a period of 2 years, was adopted for intensive collection of data and execution of emergent flood protection measures. (b) Short term measures, covering the next 4 to 5 years, included construction of spurs and embankments at selected sites. (c) 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.

42. Analyze the classification of drought, including its various forms and their impacts on society.

Answer: 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. Its impacts are spread across different domains as listed below:

(A) Meteorological drought: It is simple deficit of rainfall from the normal. It can be classified into (i) Severe drought: When rainfall is <50-75% (ii) Medium drought: Rainfall less than 25-50%: (iii) Less severe drought: Rainfall more then 60%. (iv) Partial drought: when daily average rainfall is 0.2mm during rainy season (v) Absolute drought: When continuously there is no rainfall during rainy season.
(B) Hydrological drought: It often leads to reduction of natural stream flow or ground water level plus stored water supplies.
(C) Agricultural drought: It occurs when moisture level in soil is insufficient to maintain average crop yield.
(D) Socio-economic drought: It correlates the supply and demand of goods and services with the three above mentioned types of drought.

43. Explain the causes and management strategies for drought-prone areas in India.

Answer: Causes of drought are:

(A) Natural causes: (i) due to insufficient rainfall (ii) high rate of evaporation (iii) delayed arrival of monsoonal rain (iv) early departure of monsoon (v) during monsoon season if there is continuous rainless days (vi) increase of temperature due to effect of green house gases.
(B) Man made causes: (i) deforestation for which rainfall decreases and CO₂ increases (ii) urbanisation etc.

Regarding drought-prone areas in India, around 68% of India’s total area is drought-prone. 315 out of a total of 725 talukas in 99 districts are prone. In 2001 more than eight states suffered the impact of severe drought.

Remedies for drought include: (i) Public awareness and education (ii) restoration of ecological balance by conserving, developing and harvesting land, water, livestock and human resources. (iii) to minimise the adverse effects of drought on production of crops and livestock.

44. Define a cyclone and illustrate its characteristics and regional names.

Answer: Cyclone is a region of low atmospheric pressure surrounded by high atmospheric pressure resulting in swirling atmospheric disturbance accompanied by powerful winds blowing in anticlockwise direction in the Northern Hemisphere and in the clockwise direction in the Southern Hemisphere. They occur mainly in the tropical and temperate regions of the world. In different regions cyclonic storm are known by different names like (i) Hurricane in West Indies (ii) Typhoon in China & Japan (iii) Tornado in U.S.A. (iv) Willy willy in Australia (v) Bagui in Phillippines (vi) Catrina Rita in Mexican coast (U.S.A) (vii) Aaila, Pilin, Helen Lahar etc. in Bay of Bengal coast.

45. Explain how earthquakes are measured, including the roles of seismic waves, seismographs, and the Richter scale.

Answer: The waves generated by an earthquake are called seismic waves which are recorded by an instrument called seismograph. Earthquake is measured by two ways—(i) the instrument that measures different seismic waves (ii) the instrument that measures intensity of earthquake. The magnitude or intensity of energy released by an earthquake is measured by the Richter scale devised by Charles F. Richter, in 1935. This scale ranges between 0 and 10. According to this scale if the magnitude of tremor is 6 then the destruction will be very high. If it is 3 then it is light tremor and if it is 8-9 then it may be very much destructive.

46. Discuss the formation, causes, effects, and preventive measures of tsunamis.

Answer: The term ‘Tsunami’ has been derived from a Japaneese word, ‘Tsu’ meaning harbour and ‘nami’ meaning ‘waves’. Tsunamis are Popularly called tidal ‘waves’ although they actually have nothing to do with the tides. These waves which often affect distant shores, originate by rapid displacement of water from the lake or the sea either by seismic activity, landslides, volcanic eruptions or large meteoroid impacts.

Results of tsunamis include: (i) formation of new waterbodies on land surface near the coast. (ii) destruction of coastal mangrove forest as well as ecological disbalance. (iii) Death of aquatic animals along with human being. (iv) Huge destruction of resources, life and property.

Preventive measures for tsunamis are: (i) regional warning systems through modern satellites. (ii) rescue & removal of people from the coastal regions to higher places. (iii) quick supply of adequate drinking water, medicines, food, etc.

47. Evaluate the causes, effects, and mitigation measures of landslides.

Causes: Landslide can be caused by poor ground conditions, geomorphic phenomena, natural physical forces and quite often due to heavy spells of rainfall coupled with impeded drainage.

Physical causes: (i) Prolonged precipitation, (ii) rapid draw-down (iii) earthquake (iv) volcanic eruption (v) thawing (vi) shrink and swell (vii) artesian pressure.
Man made causes: (i) Excavation (particularly at the toe of the slope). (ii) loading of slope crest (iii) draw-down (of reservoir) (iv) deforestation (v) irrigation (vi) mining etc.

Effects: (i) Destroyed roads, railway lines, settlements (for an eg. 1980 there was a severe landslide near Tunsung basti in Darjeeling) loss of life & property.

Mitigation measures are not explicitly detailed under the landslide section, but general preventive measures for hazards like deforestation prevention in hilly regions (mentioned under earthquake preventive measures) could be relevant.

48. Compare and contrast avalanches and blizzards, including their characteristics and safety recommendations.

Answer: An avalanche is when a huge bulk of ice move downward due to steep rock slope. The French word ‘Avaler’ = descend (aval = to the valley). So in English Avalanche means Ice descending down the valley. Normally it happens during winter and spring. Causes include: (i) Due to gravitational pull (ii) undercutting (iii) releases of debris. Types of avalanche include: (i) Powder avalanche (ii) slab avalanche (iii) debris avalanche (iv) rock avalanche etc. Remedies for avalanche involve removing people from snow covered regions during winter and spring.

A blizzard occurs during prolonged winter season in Tundra region; it is a continuous cold wind along with snow fall. It is a dangerous natural hazard or disaster in Tundra or polar region. Safety recommendations during a blizzard are: (i) To take shelter in inside the ice caves. (ii) to keep away from wind (iii) to put fire (iv) to keep proper ventilation in fire place etc.

49. Examine the nature of volcanic hazards, distinguishing between primary and secondary hazards, with examples.

Answer: The process by which magma, gas and smoke erupt from the mantle of the earth, it is known as volcanism.

Nature of disaster: (i) It is an endogenetic sudden process (ii) it is the second highest destructive type of disaster. Due to volcanism disaster may be caused in two ways like—
(A) Primary volcanic hazard: (i) Pyroclastic flows (ii) Air fall tephra (volcanic bomb) (iii) Lava flows (iv) Volcanic gases (CO₂, Sulphur, Boric acid, Water vapour & gas)
(B) After volcanic hazard (secondary hazards): (i) landslide for an example due to landslide of St. Helena volcano in Pacific ocean in the year 1980 there was a great loss of life. (ii) tsunami : sometimes tsunami may happen due to volcanism although it occurs mostly due to earthquake on the sea floor.

50. Describe the spread of wild fires globally, mentioning the area destroyed in any two countries.

Answer: When there is a sudden fire, in the forest area on grassland regions or bushes it is called wild fire. Wild fire spreads from one place to another immediately in three ways: (i) crawling fire from lower level to upper (ii) crown fire from upper level to lower. (iii) jumping fire: fire spreads fast due to blowing of wind.

In U.S.A. 17,400 sq km area (0.18%) were destroyed due to massive volume of wild fire. In France 211 sq km forest area (0.04%) were destroyed due to massive volume of wild fire. In 2003 due to wild fire 4,249 sq km area in Portugal and in Indonesia 97,550 sq km area in 1997, in 1999, 440-90 sq km area and in 2001 143-51 sq. km, in 2005 133-28 sq km, in 2003 37.45 sq km forest area was destroyed.

Ron'e Dutta

Ron'e Dutta is a journalist, teacher, aspiring novelist, and blogger who manages Online Free Notes. An avid reader of Victorian literature, his favourite book is Wuthering Heights by Emily Brontë. He dreams of travelling the world. You can connect with him on social media. He does personal writing on ronism.

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