Hazards – Detailed Summary | Samacheer Kalvi 8th Social Science | Geography

Hazards – Detailed Summary

Book: Samacheer Kalvi 8th Social Science

Subject: Geography

Unit: Unit 5

Lesson Name: Hazards

About the Lesson

“Hazards” is an important Geography lesson in the Samacheer Kalvi 8th Social Science book. This lesson explains the meaning of hazard, disaster and catastrophe. It also teaches us about different types of hazards, their causes, effects and prevention measures.

Hazards may be natural or human-made. Some hazards become disasters when they cause serious damage to human life, property, environment and economic activities. Therefore, awareness and prevention measures are very important.

Learning Objectives

To understand the meaning of hazard, disaster and catastrophe.
To learn the major types of hazards.
To understand natural hazards and human-made hazards.
To know the causes and effects of earthquakes, floods, cyclones, droughts, landslides and tsunamis.
To learn about hazardous wastes.
To understand air pollution and water pollution as hazards.
To create awareness about hazard prevention measures.
To prepare for textbook-back one-mark, short-answer and paragraph questions.

Detailed Summary of the Lesson

1. Introduction

The earth supports living and non-living things. Human beings live in different environments such as plains, mountains, coastal areas, river valleys and cities.

Sometimes, natural events or human activities threaten human life, property, environment and economic assets. Such threatening events are called hazards.

2. Meaning of Hazard

A hazard is a thing, person, event or factor that poses a threat to people, structures or economic assets and may cause a disaster.

Hazards may occur naturally in the environment or may be caused by human activities.

3. Origin of the Word Hazard

The word “hazard” comes from the old French word “hasart”, meaning a game of dice.

It is also connected with the Arabic word “az-zahr” and the Spanish word “azar”.

4. Natural Hazard

A natural hazard is a natural process or event that becomes a potential threat to human life and property.

Earthquakes, floods, cyclonic storms, droughts, landslides, tsunamis and volcanic eruptions are examples of natural hazards.

5. Disaster

A disaster is a hazardous event that occurs over a limited time span in a defined area and causes great damage to property and loss of life.

A disaster usually needs assistance from others because the affected people may not be able to manage the situation alone.

6. Catastrophe

A catastrophe is a massive disaster.

It causes very great damage and requires huge expenditure of money and a long time for recovery.

Types of Hazards

7. Classification of Hazards

Hazards are classified in two main ways:

Based on their causes of occurrence
Based on their origin

8. Hazards Based on Causes of Occurrence

Based on causes of occurrence, hazards are broadly classified into three types:

Natural hazards
Human-made hazards
Socio-natural hazards

9. Natural Hazards

Natural hazards are caused by natural processes. Human beings have no direct role in the origin of these hazards.

Examples include earthquakes, floods, cyclones, droughts, landslides, tsunamis and volcanic eruptions.

10. Human-Made Hazards

Human-made hazards are caused by undesirable human activities.

Industrial chemical leaks, oil spills, fire accidents, nuclear accidents, transport accidents, war, terrorism and bomb blasts are examples of human-made hazards.

11. Socio-Natural Hazards

Socio-natural hazards are natural hazards that are intensified by human activities.

For example, landslides may become worse because of road construction, house construction, tunnel excavation, mining and quarrying in mountain areas.

Storm surge hazards may become worse due to the destruction of mangroves.

Hazards Based on Origin

12. Eight Categories of Hazards

Based on origin, hazards can be grouped into eight categories:

Atmospheric hazard
Geologic or seismic hazard
Hydrologic hazard
Volcanic hazard
Environmental hazard
Biological hazard
Technological hazard
Human-induced hazard

13. Atmospheric Hazard

Atmospheric hazards are caused by atmospheric conditions.

Tropical storms, thunderstorms, lightning, tornadoes, avalanches, heat waves, fog and forest fire are examples of atmospheric hazards.

14. Geologic or Seismic Hazard

Geologic or seismic hazards are connected with earth movements and geological processes.

Earthquakes, tsunami, landslides and land subsidence are examples.

15. Hydrologic Hazard

Hydrologic hazards are connected with water.

Floods, droughts, coastal erosion and storm surges are examples of hydrologic hazards.

16. Volcanic Hazard

Volcanic hazards are caused by volcanic activities.

Volcanic eruptions and lava flows are examples of volcanic hazards.

17. Environmental Hazard

Environmental hazards are connected with damage to the natural environment.

Pollution of soil, air and water, desertification, global warming and deforestation are examples.

18. Biological Hazard

Biological hazards are caused by living organisms and disease-causing agents.

Chickenpox, smallpox, AIDS, HIV and killer bees are examples of biological hazards.

19. Technological Hazard

Technological hazards are caused by failure or misuse of technology.

Hazardous material incidents, fires, bridge failures, tunnel failures, dam failures, nuclear accidents and radiological accidents are examples.

20. Human-Induced Hazard

Human-induced hazards are caused by human actions.

Terrorism, bomb blasts, war, transportation accidents and civil disorder are examples of human-induced hazards.

Major Hazards in India

21. Important Hazards

India is affected by many types of hazards because of its physical, climatic and human conditions.

The major hazards in India are:

Earthquakes
Floods
Cyclonic storms
Droughts
Landslides
Tsunami
Hazardous wastes
Pollution of air
Pollution of water

Earthquakes

22. Meaning of Earthquake

An earthquake is a violent tremor in the earth’s crust.

It sends shock waves in all directions from its place of origin.

23. Earthquake Zones in India

The Bureau of Indian Standards has grouped India into four seismic zones:

Zone II
Zone III
Zone IV
Zone V

No area of India is classified as Zone I.

24. Effects of Earthquakes

Loss of human life.
Damage to buildings, roads and bridges.
Landslides in mountain regions.
Tsunami in coastal regions if the earthquake occurs under the sea.
Disruption of transport and communication.

Floods

25. Meaning of Flood

Flood is an event in which a part of the earth’s surface gets inundated.

Heavy rainfall and large waves in seas are common causes of floods.

26. Major Causes of Floods

The major causes of floods are grouped into three types:

Meteorological factors
Physical factors
Human factors

27. Meteorological Factors of Floods

Heavy rainfall
Tropical cyclones
Cloud burst

28. Physical Factors of Floods

Large catchment area
Inadequate drainage arrangement

29. Human Factors of Floods

Deforestation
Siltation
Faulty agricultural practices
Faulty irrigation practices
Collapse of dams
Accelerated urbanisation

30. Flood-Prone Areas in India

The Gangetic plains covering Punjab, Haryana, Uttar Pradesh, North Bihar, West Bengal and the Brahmaputra valley are major flood-prone areas.

Coastal Andhra Pradesh, Odisha and southern Gujarat are also often affected by floods.

Cyclonic Storms

31. Meaning of Cyclonic Storm

A cyclonic storm is a strong wind circulating around a low-pressure area in the atmosphere.

It rotates in an anti-clockwise direction in the Northern Hemisphere and clockwise direction in the Southern Hemisphere.

32. Effects of Tropical Cyclones

Tropical cyclones are associated with destructive winds, storm surges and heavy rainfall.

They may cause flooding, destruction of houses, loss of trees, damage to crops and danger to coastal communities.

33. Storm Surge

A storm surge is a sudden rise of seawater caused by a tropical cyclone.

It is more common in shallow coastal water regions.

34. Cyclone-Prone Coastal Areas

The east coast of India is more vulnerable to storm surges than the west coast.

North Odisha and West Bengal coasts, Andhra Pradesh coast between Ongole and Machilipatnam, and Tamil Nadu coast are vulnerable to storm surges. In Tamil Nadu, Nagapattinam and Cuddalore districts are frequently affected.

Droughts

35. Meaning of Drought

Drought is a condition of lack of water to satisfy the normal needs of agriculture, livestock, industry or human population.

In India, droughts generally occur due to the failure of monsoons.

36. Types of Drought

Droughts are classified into three major types:

Meteorological drought
Hydrological drought
Agricultural drought

37. Meteorological Drought

Meteorological drought occurs when there is a reduction in rainfall for a specific period below a specific level.

38. Hydrological Drought

Hydrological drought is associated with reduction of water in streams, rivers and reservoirs.

It may be divided into surface water drought and groundwater drought.

39. Agricultural Drought

Agricultural drought refers to the condition in which agricultural crops are affected due to lack of rainfall.

40. Drought-Prone Areas in India

The arid and semi-arid region from Ahmedabad to Kanpur and from Kanpur to Jalandhar is highly prone to drought.

The dry region lying on the leeward side of the Western Ghats is also highly drought-prone.

Landslides

41. Meaning of Landslide

Landslide is the rapid downward movement of rock, soil and vegetation down a slope under the influence of gravity.

Landslides are generally sudden and infrequent.

42. Causes of Landslides

Steep slopes
Heavy rainfall
Weak ground structure
Deforestation
Earthquakes
Volcanic eruptions
Mining
Construction of roads and railways in mountains

43. Landslide-Prone Areas

Landslides are very common along the steep slopes of the Himalayas, the Western Ghats and river valleys.

In Tamil Nadu, Kodaikanal in Dindigul district and Ooty in The Nilgiris district are frequently affected by landslides.

Tsunami

44. Meaning of Tsunami

Tsunami refers to huge ocean waves caused by an earthquake, landslide or volcanic eruption under the sea.

It is generally noticed in coastal regions and poses serious danger to people living near the coast.

45. Origin of the Word Tsunami

The word “Tsunami” is derived from Japanese words.

“Tsu” means harbour and “nami” means wave. Therefore, tsunami means harbour wave.

46. Indian Ocean Tsunami of 2004

The Indian Ocean tsunami took place on 26th December 2004.

It was caused by an undersea earthquake near Sumatra. It affected many countries including Indonesia, Sri Lanka, India, Thailand, Somalia and Maldives.

Hazardous Wastes

47. Meaning of Hazardous Waste

Hazardous wastes are wastes that may cause adverse health effects on ecosystems and human beings.

They are dangerous because they may be toxic, radioactive, flammable, explosive or chemically harmful.

48. Major Hazardous Wastes

Radioactive substances
Chemicals
Medical wastes
Flammable wastes
Explosives
Household hazardous wastes

49. Examples of Hazardous Wastes

Unused fuel pipes of nuclear power plants
Synthetic chemicals
Acids and bases
Hypodermic needles
Bandages
Outdated drugs
Waste oil
Automobile batteries
Household batteries
Pesticides

50. Chernobyl Nuclear Accident

The Chernobyl nuclear accident took place on 26th April 1986.

It is remembered as one of the largest nuclear accidents in history.

Pollution of Air

51. Air and Its Composition

Air is a mixture of several gases.

The main gases are nitrogen, oxygen and carbon dioxide. Nitrogen forms about 78.09% of air, oxygen forms about 20.95%, and carbon dioxide forms about 0.03%.

52. Air Pollution

Air pollution is the contamination of indoor or outdoor air by gases and solid particles that modify its natural characteristics and percentage.

53. Air Pollutants

Air pollutants are mainly classified into:

Primary pollutants
Secondary pollutants

54. Primary Pollutants

Primary pollutants are air pollutants emitted directly from a source.

Oxides of sulphur, oxides of nitrogen, oxides of carbon and particulate matter are examples.

55. Secondary Pollutants

Secondary pollutants are not directly emitted.

They are formed when primary pollutants react in the atmosphere. Ground-level ozone and smog are examples.

56. Smog

Smog is a serious problem in most big urban areas.

It is formed when emissions from vehicles and industries, combustion of wood and coal combine with fog.

Pollution of Water

57. Water Pollution

Water pollution is the alteration in the physical, chemical and biological characteristics of water.

It causes harmful effects on human beings and aquatic life.

58. Causes of Water Pollution in India

Urbanisation
Industrial effluents
Sewage
Agricultural runoff
Improper agricultural practices
Seawater intrusion
Solid wastes

Need for Prevention Measures

59. Meaning of Prevention

Prevention means activities taken to prevent a natural calamity or potential hazard from causing harmful effects on people or economic assets.

60. Prevention Planning

Prevention planning consists of:

Hazard identification
Vulnerability assessment

61. Importance of Prevention

Delayed action may increase economic losses.

For developing countries like India, prevention is one of the most critical components in managing disasters.

62. General Prevention Measures

Create awareness among people.
Identify hazard-prone areas.
Prepare disaster management plans.
Follow early warning systems.
Avoid construction in unsafe areas.
Protect forests and mangroves.
Keep emergency kits ready.
Train people in first aid and rescue methods.
Dispose hazardous wastes safely.
Reduce air and water pollution.

Central Idea of the Lesson

The central idea of the lesson is that hazards are dangerous events or factors that threaten people, property, economic assets and the environment. Hazards may be natural, human-made or socio-natural. When a hazard causes great damage and loss of life, it becomes a disaster. If the disaster is massive and needs a long time for recovery, it is called a catastrophe. Awareness, preparedness and prevention measures are necessary to reduce the harmful effects of hazards.

Hazard, Disaster and Catastrophe – Difference

Term	Meaning
Hazard	A thing, person, event or factor that poses a threat to people, structures or economic assets.
Disaster	A hazardous event that causes great damage to property and loss of life in a defined area.
Catastrophe	A massive disaster that requires huge money and long time for recovery.

Hazards Based on Causes

Type	Meaning	Examples
Natural Hazards	Hazards caused by natural processes.	Earthquake, flood, cyclone, drought, landslide, tsunami, volcanic eruption.
Human-Made Hazards	Hazards caused by undesirable human activities.	Industrial leak, oil spill, nuclear accident, fire, terrorism, war.
Socio-Natural Hazards	Natural hazards intensified by human activities.	Landslide worsened by road construction, mining and quarrying.

Hazards Based on Origin

Category	Examples
Atmospheric Hazard	Tropical storms, thunderstorms, lightning, tornadoes, avalanches, heat waves, fog and forest fire.
Geologic / Seismic Hazard	Earthquakes, tsunami, landslide and land subsidence.
Hydrologic Hazard	Floods, droughts, coastal erosion and storm surges.
Volcanic Hazard	Eruptions and lava flows.
Environmental Hazard	Pollution of soil, air and water, desertification, global warming and deforestation.
Biological Hazard	Chickenpox, smallpox, AIDS, HIV and killer bees.
Technological Hazard	Hazardous material incidents, fires, infrastructure failures, nuclear and radiological accidents.
Human-Induced Hazard	Terrorism, bomb blast, war, transportation accidents and civil disorder.

Major Hazards in India – Quick Table

Hazard	Meaning / Cause
Earthquake	Violent tremor in the earth’s crust sending shock waves in all directions.
Flood	Inundation of part of the earth’s surface due to heavy rainfall or large sea waves.
Cyclonic Storm	Strong wind circulating around a low-pressure area.
Drought	Lack of water to satisfy the normal needs of agriculture, livestock, industry or human population.
Landslide	Rapid downward movement of rock, soil and vegetation down a slope.
Tsunami	Huge ocean waves caused by earthquake, landslide or volcanic eruption under the sea.
Hazardous Wastes	Wastes that cause harmful effects on ecosystem and human beings.
Air Pollution	Contamination of air by harmful gases and particles.
Water Pollution	Alteration in physical, chemical and biological characteristics of water.

Flood Causes – Quick Table

Type of Cause	Examples
Meteorological Factors	Heavy rainfall, tropical cyclones and cloud burst.
Physical Factors	Large catchment area and inadequate drainage arrangement.
Human Factors	Deforestation, siltation, faulty agricultural practices, faulty irrigation practices, collapse of dams and accelerated urbanisation.

Types of Drought

Type	Meaning
Meteorological Drought	Reduction in rainfall for a specific period below a specific level.
Hydrological Drought	Reduction of water in streams, rivers and reservoirs.
Agricultural Drought	Crops are affected due to lack of rainfall.

Air Pollutants

Type	Meaning	Examples
Primary Pollutants	Pollutants directly emitted from a source.	Oxides of sulphur, oxides of nitrogen, oxides of carbon, particulate matter.
Secondary Pollutants	Pollutants formed when primary pollutants react in the atmosphere.	Ground-level ozone, smog.

Hazardous Wastes – Quick Table

Waste Type	Examples
Radioactive Substances	Tools and unused fuel pipes of nuclear power plants.
Chemicals	Synthetic organics, inorganic metals, salts, acids, bases, flammables and explosives.
Medical Wastes	Hypodermic needles, bandages and outdated drugs.
Flammable Wastes	Organic solvents, oils, plasticisers and organic sludges.
Household Hazardous Wastes	Pesticides, waste oil, automobile battery and household battery.

Important Exam Points from the Lesson

Question Focus	Answer
Percentage of nitrogen in air	78.09%.
Indian Ocean tsunami occurred in	2004.
The word tsunami is derived from	Japanese language.
Example of surface water	Lake.
Event due to failure of monsoons	Drought.
Hazards may lead to	Disaster.
Landslide is an example of	Natural hazard / geologic or seismic hazard.
On the basis of origin, hazards are grouped into	Eight categories.
Terrorism is an example of	Human-induced hazard.
Oxides of nitrogen are	Primary pollutants.
Chernobyl nuclear accident took place in	26th April 1986.
Primary pollutant example	Oxides of sulphur.
Hazardous waste example	Outdated drugs.
Earthquake may cause	Tsunami.
Meteorological drought means	Reduction in rainfall.
Storm surge is common in	Shallow coastal water regions.
East coast districts of Tamil Nadu often affected	Nagapattinam and Cuddalore.
In Tamil Nadu, landslide-prone places	Kodaikanal and Ooty.

Vocabulary to Remember

Hazard – a threatening event or factor that may cause disaster.
Disaster – hazardous event causing great damage and loss of life.
Catastrophe – massive disaster requiring long recovery.
Natural Hazard – hazard caused by natural processes.
Human-Made Hazard – hazard caused by human activities.
Socio-Natural Hazard – natural hazard worsened by human activities.
Atmospheric Hazard – hazard caused by atmospheric conditions.
Geologic Hazard – hazard connected with earth movements.
Hydrologic Hazard – hazard connected with water.
Biological Hazard – hazard caused by living organisms or diseases.
Technological Hazard – hazard caused by failure or misuse of technology.
Earthquake – violent tremor in the earth’s crust.
Flood – inundation of land by water.
Cyclone – strong wind system around a low-pressure area.
Storm Surge – sudden rise of seawater due to tropical cyclone.
Drought – lack of water for normal needs.
Landslide – downward movement of rock, soil and vegetation.
Tsunami – huge ocean waves caused by undersea disturbance.
Hazardous Waste – waste harmful to humans and environment.
Primary Pollutant – pollutant directly emitted from a source.
Secondary Pollutant – pollutant formed by chemical reaction in the atmosphere.
Smog – smoke and fog mixed with pollutants.
Prevention – activities taken to reduce harmful effects of hazards.
Vulnerability Assessment – study of how much people or places are at risk.

TET / Exam Focus Areas

Very Important Focus: These are the most expected textbook-based areas from this lesson.

Define hazard.
Differentiate hazard, disaster and catastrophe.
What are the major types of hazards?
Explain hazards based on their origin.
List out atmospheric hazards.
What is earthquake?
What is flood? What are the major causes of flood?
Write a note on cyclonic storms.
What is storm surge?
Define drought and explain its types.
List out the major drought-prone areas of India.
What is landslide?
What do you mean by tsunami?
Write a brief note on hazardous wastes.
Differentiate primary and secondary pollutants.
What are the causes of water pollution in India?
Why are prevention measures needed?

Short Answer Questions and Answers

1. Define hazard.

Hazard is a thing, person, event or factor that poses a threat to people, structures or economic assets and may cause a disaster.

2. What is disaster?

A disaster is a hazardous event that occurs in a defined area and causes great damage to property and loss of life.

3. What is catastrophe?

Catastrophe is a massive disaster that requires huge expenditure of money and a long time for recovery.

4. What are the major types of hazards based on causes?

Based on causes, hazards are classified into natural hazards, human-made hazards and socio-natural hazards.

5. What are natural hazards?

Natural hazards are hazards caused by natural processes. Earthquakes, floods, cyclones, droughts, landslides, tsunamis and volcanic eruptions are examples.

6. What are human-made hazards?

Human-made hazards are hazards caused by undesirable human activities such as industrial accidents, oil spills, fire accidents, war and terrorism.

7. What are socio-natural hazards?

Socio-natural hazards are natural hazards intensified by human activities. Landslides worsened by construction, mining and quarrying are examples.

8. Name the eight categories of hazards based on origin.

Atmospheric, geologic or seismic, hydrologic, volcanic, environmental, biological, technological and human-induced hazards are the eight categories.

9. List out atmospheric hazards.

Tropical storms, thunderstorms, lightning, tornadoes, avalanches, heat waves, fog and forest fire are atmospheric hazards.

10. What is earthquake?

Earthquake is a violent tremor in the earth’s crust that sends shock waves in all directions from its place of origin.

11. What is flood?

Flood is an event in which a part of the earth’s surface gets inundated due to heavy rainfall, large waves or other causes.

12. What are the major causes of floods?

Heavy rainfall, tropical cyclones, cloud burst, large catchment area, inadequate drainage, deforestation, siltation, faulty agricultural practices, collapse of dams and rapid urbanisation are major causes of floods.

13. What is a cyclonic storm?

A cyclonic storm is a strong wind circulating around a low-pressure area in the atmosphere.

14. What is storm surge?

Storm surge is the sudden rise of seawater due to a tropical cyclone.

15. What is drought?

Drought is a lack of water to satisfy the normal needs of agriculture, livestock, industry or human population.

16. Name the three types of drought.

Meteorological drought, hydrological drought and agricultural drought are the three types of drought.

17. What is meteorological drought?

Meteorological drought is a condition in which rainfall is reduced below a specific level for a specific period.

18. What is hydrological drought?

Hydrological drought is associated with reduction of water in streams, rivers and reservoirs.

19. What is agricultural drought?

Agricultural drought is a condition in which agricultural crops are affected due to lack of rainfall.

20. What is landslide?

Landslide is the rapid downward movement of rock, soil and vegetation down a slope under the influence of gravity.

21. What do you mean by tsunami?

Tsunami refers to huge ocean waves caused by an earthquake, landslide or volcanic eruption under the sea.

22. From which language is the word tsunami derived?

The word tsunami is derived from the Japanese language.

23. What are hazardous wastes?

Hazardous wastes are wastes that may cause adverse health effects on ecosystems and human beings.

24. Give examples of hazardous wastes.

Radioactive substances, chemicals, medical wastes, flammable wastes, explosives, pesticides, waste oil and batteries are examples of hazardous wastes.

25. When did the Chernobyl nuclear accident take place?

The Chernobyl nuclear accident took place on 26th April 1986.

26. What is air pollution?

Air pollution is the contamination of indoor or outdoor air by harmful gases and solid particles that modify its natural characteristics.

27. What are primary pollutants?

Primary pollutants are air pollutants emitted directly from a source. Oxides of sulphur, oxides of nitrogen and oxides of carbon are examples.

28. What are secondary pollutants?

Secondary pollutants are formed when primary pollutants react in the atmosphere. Ground-level ozone and smog are examples.

29. What is water pollution?

Water pollution is the alteration in the physical, chemical and biological characteristics of water, causing harmful effects on humans and aquatic life.

30. Why are prevention measures needed?

Prevention measures are needed to reduce the harmful effects of hazards on people, property, environment and economic assets.

How to Write This in Exam

For a short answer, write the direct definition first. For example, if the question asks “Define hazard”, write “Hazard is a thing, person, event or factor that poses a threat to people, structures or economic assets and may cause a disaster.”

For a paragraph answer, divide the answer into headings such as meaning of hazard, types of hazards, major hazards in India, effects and prevention measures.

Sample Exam Answer

“Hazards” is an important Geography lesson in 8th Social Science. A hazard is a thing, person, event or factor that poses a threat to people, structures or economic assets and may cause a disaster. A disaster is a hazardous event that causes great damage to property and loss of life. A catastrophe is a massive disaster that needs huge money and long time for recovery.

Hazards are classified based on causes and origin. Based on causes, hazards are divided into natural hazards, human-made hazards and socio-natural hazards. Natural hazards are caused by natural processes. Earthquakes, floods, cyclones, droughts, landslides, tsunamis and volcanic eruptions are examples. Human-made hazards are caused by undesirable human activities such as industrial accidents, oil spills, war and terrorism. Socio-natural hazards are natural hazards made worse by human actions.

Based on origin, hazards are grouped into eight categories. They are atmospheric, geologic or seismic, hydrologic, volcanic, environmental, biological, technological and human-induced hazards. Atmospheric hazards include tropical storms, thunderstorms, lightning, tornadoes, heat waves and fog. Geologic hazards include earthquakes, tsunami and landslides. Hydrologic hazards include floods, droughts, coastal erosion and storm surges.

India faces many major hazards such as earthquakes, floods, cyclonic storms, droughts, landslides, tsunami, hazardous wastes, air pollution and water pollution. Floods are caused by heavy rainfall, cyclones, cloud burst, poor drainage, deforestation, siltation, faulty irrigation and rapid urbanisation. Droughts occur due to the failure of monsoons. Landslides occur due to steep slopes, heavy rainfall, deforestation, earthquakes, mining and construction in mountain regions.

Tsunami refers to huge ocean waves caused by earthquake, landslide or volcanic eruption under the sea. The Indian Ocean tsunami occurred in 2004. Hazardous wastes such as chemicals, radioactive substances, medical wastes and batteries affect human health and the environment. Air pollution and water pollution are also serious hazards.

Prevention measures are very important to reduce the harmful effects of hazards. Prevention planning includes hazard identification and vulnerability assessment. Awareness, early warning, safe construction, protection of forests and mangroves, safe disposal of hazardous wastes and disaster preparedness can reduce losses.

One Mark Important Points

Chapter Name – Hazards
Hazard Origin Word – Hasart
Hasart Meaning – Game of dice
Hazard May Lead To – Disaster
Massive Disaster – Catastrophe
Types Based on Causes – Natural, human-made and socio-natural hazards
Origin-Based Hazard Categories – Eight
Atmospheric Hazard Example – Tropical storm / lightning / heat wave
Geologic Hazard Example – Earthquake / tsunami / landslide
Hydrologic Hazard Example – Flood / drought / storm surge
Environmental Hazard Example – Pollution / deforestation / global warming
Human-Induced Hazard Example – Terrorism
Percentage of Nitrogen in Air – 78.09%
Percentage of Oxygen in Air – 20.95%
Carbon Dioxide in Air – 0.03%
Indian Ocean Tsunami Year – 2004
Tsunami Word Language – Japanese
Tsu Means – Harbour
Nami Means – Wave
Surface Water Example – Lake
Failure of Monsoon Causes – Drought
Earthquake Zones in India – Zone II, III, IV and V
No Seismic Zone in India – Zone I
Storm Surge – Sudden rise of seawater due to tropical cyclone
Tamil Nadu Cyclone-Affected Districts – Nagapattinam and Cuddalore
Tamil Nadu Landslide-Prone Places – Kodaikanal and Ooty
Chernobyl Nuclear Accident – 26th April 1986
Oxides of Nitrogen – Primary pollutants
Primary Pollutant Example – Oxides of sulphur
Secondary Pollutant Example – Smog
Hazardous Waste Example – Outdated drugs
Prevention Planning Includes – Hazard identification and vulnerability assessment

Short Conclusion

“Hazards” teaches us about dangerous events and factors that may affect people, property, environment and economic assets. Hazards may be natural, human-made or socio-natural. They may also be classified as atmospheric, geologic, hydrologic, volcanic, environmental, biological, technological and human-induced hazards. India faces hazards such as earthquakes, floods, cyclones, droughts, landslides, tsunamis, hazardous wastes, air pollution and water pollution. Awareness and prevention measures are necessary to reduce the impact of hazards and disasters.