Hazards

Class 8 | Social Science — Geography | Unit 5

Class 8 Unit 5 Geography

Unit 5 Hazards

Learning Objectives

1. To learn the meanings of hazard, disaster and catastrophe.

2. To describe the major types of hazards, their causes and effects.

3. To develop awareness regarding hazards and related prevention measures.

Introduction

Teacher: Good morning students.

Students: Good morning teacher.

Teacher: Are all present today?

Krithika: No teacher, Shruthi is absent today.

Teacher: Why is she absent today?

Pavithra: Teacher, don't you know what happened to her?

Teacher: No my dear child, what happened to her?

Theshmitha: Teacher, Yesterday, while returning home, she was struck by a big branch of a tree due to heavy rain and got injured.

Teacher: Oh my God what a pity? Students, you all must be very careful while moving around to avoid the problems from hazards.

Kamalesh: Teacher, what do you mean by hazards? You mean the Belgian football player 'Hazard'?

Teacher: No no, it is an event which can affect the living and non-living things of earth. I think today is the right day to get into the interesting chapter 'hazards.'

Hazards

In the beginning of twenty-first century, the earth supported a human population that was more numerous and found healthier and wealthier than ever before. At the same time, there were a lack of awareness on the risks that faced by the people. By keeping this in mind, the present lesson of hazards is intended to familiarise the different types of hazards to promote awareness among students regarding hazards.

Hazards are defined as a thing, person, event or factor that poses a threat to people, structures or economic assets and which may cause a disaster. They could be either human made or naturally occurring in the environment. The word 'hazard' owes its origin to the word 'hasart' in old French meaning a game of dice (in Arabic – az-zahr; in Spanish – azar). Though the society experiences several types of hazards, it is important for a region to be aware of those threats that are most likely to affect the community most severely.

Do You Know

A natural hazard is a natural process and event that is a potential threat to human life and property. The process and events themselves are not a hazard but become of human use of the land

A disaster is a hazardous event that occurs over a limited time span in a defined area and causes great damage to property by loss of life, also needs assistance from others.

A catastrophe is a massive disaster that requires significant expenditure of money and a long time for recovery.

Types of Hazards

Some hazards occur frequently and threat the people. Hazards are classified in different ways.

1. Based on their causes of occurrence.

2. Based on their origin.

1. Based on their causes of occurrence

Hazards can be broadly classified into three types: natural, human-made and socio-natural hazards.

1. Natural hazards: These are the results of natural processes and man has no role to play in such hazards. The main examples of natural hazards are earthquakes, floods, cyclonic storms, droughts, landslides, tsunamis and volcanic eruptions.

2. Human-made hazards: these are caused by undesirable activities of human. It can be the result of an accident, such as an industrial chemical leak or oil spill, or an intentional act. Such hazards can disturb the safety. health, welfare of people and cause damage or destruction to property. The following are the examples of human-made hazards. They are explosions, hazardous wastes, pollution of air, water and land, dam failures, wars or civil conflicts and terrorism.

3. Socio-natural hazards (Quasi-natural hazards): these are caused by the combined effect of natural forces and misdeeds of human. Some of the examples are:

1. The frequency and intensity of floods and droughts may increase due to indiscriminate felling of trees, particularly in the catchment areas of the rivers.

2. Landslides are caused by natural forces and their frequency, and impact may be aggravated as a result of construction of roads, houses etc., in mountainous areas, excavating tunnels and by mining and quarrying.

3. Storm surge hazards may be worsened by the destruction of mangroves.

4. Smog is a serious problem in most big urban areas. The emissions from vehicles and industries, combustion of wood and coal together combined with fog leads to smog.

2. Based on their origin

Hazards can be grouped into eight categories

1. Atmospheric hazard – Tropical storms, Thunderstorms, Lightning, Tornadoes, Avalanches, Heat waves, Fog and Forest fire.

2. Geologic/Seismic hazard – Earthquakes, Tsunami, Landslide and Land subsidence.

3. Hydrologic hazard – Floods, Droughts, Coastal erosion and Storm surges.

4. Volcanic hazard – Eruptions and Lava flows.

5. Environmental hazard – Pollution of soil/ air/water, Desertification, Global warming and Deforestation.

6. Biological hazard – Chickenpox, Smallpox, AIDS [HIV] and Killer bees.

7. Technological hazard – Hazardous material incidents, Fires, Infrastructure failures [Bridges, Tunnels, Dams, Nuclear and Radiological accidents].

8. Human-induced hazard – Terrorism, Bomb blast, War, Transportation accidents and Civil disorder.

Major Hazards in India:

1) Earthquakes

Earthquake is a violent tremor in the earth's crust, sending out a series of shock waves in all directions from its place of origin. Earthquake prone regions of the country have been identified on the basis of scientific inputs relating to seismicity, earthquakes occurred in the past and tectonic setup of the region. Based on these inputs, Bureau of Indian Standards has grouped the country into four seismic zones: Zone 2, Zone 3, Zone 4 and Zone 5 (No area of India is classified as Zone 1).

Seismic Zones of India (Source: National Institute of Disaster Management, New Delhi)

Table-Earthquake-prone Zones of India

Seismic Zones	Level of Risk	Regions
Zone V	Very High	Comprises entire northeastern India, parts of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Rann of Kutch in Gujarat, part of North Bihar and Andaman & Nicobar Islands.
Zone IV	High	Covers remaining parts of Jammu and Kashmir and Himachal Pradesh, National Capital Territory (NCT) of Delhi, Sikkim, northern parts of Uttar Pradesh, Bihar and West Bengal, parts of Gujarat and small portions of Maharashtra near the west coast and Rajasthan.
Zone III	Moderate	Comprises Kerala, Goa, Lakshadweep Islands, remaining parts of Uttar Pradesh, Gujarat and West Bengal, parts of Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Odisha, Andhra Pradesh, Tamil Nadu and Karnataka
Zone II	Low	Covers remaining parts of country

2) Floods

Flood is an event in which a part of the earth's surface gets inundated. Heavy rainfall and large waves in seas are the common causes of flood. The major causes of floods are:

A. Meteorological factors

1) Heavy rainfall

2) Tropical cyclones

3) Cloud burst

B. Physical factors

1) Large catchment area

2) Inadequate drainage arrangement

C. Human factors

1) Deforestation

2) Siltation

3) Faulty agricultural practices

4) Faulty irrigation practices

5) Collapse of dams

6) Accelerated urbanization

Activity

Discuss in the classroom about the actions to be taken before, during and after flood.

The following map shows the major flood prone areas in India. Gangetic plains covering the states of Punjab, Haryana, Uttar Pradesh, North Bihar, West Bengal and Brahmaputra valley are the major flood prone areas in north and northeast India. Coastal Andhra Pradesh, Odisha and southern Gujarat are the other regions which are also prone to flood often. (Source: National Institute of Hydrology, New Delhi)

3) Cyclonic Storms

A cyclonic storm is a strong wind circulating around a low pressure area in the atmosphere. It rotates in anti-clockwise direction in Northern Hemisphere and clockwise in the Southern Hemisphere. Tropical cyclones are characterised by destructive winds, storm surges and exceptional levels of rainfall, which may cause flooding. Wind speed may reach up to 200 kilometer per hour and rainfall may record up to 50 centimeter per day for several consecutive days. A sudden rise of seawater due to tropical cyclone is called storm surge. It is more common in the regions of shallow coastal water.

East coastal areas vulnerable to storm surges

1) North Odisha and West Bengal coasts.

2) Andhra Pradesh coast between Ongole and Machilipatnam.

3) Tamil Nadu coast (among 13 coastal districts, Nagapattinam and Cuddalore districts are frequently affected).

West coastal areas vulnerable to storm surges

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

1) Maharashtra coast, north of Harnai and adjoining south Gujarat coast and the coastal belt around the Gulf of Cambay.

2) The coastal belt around the Gulf of Kutch.

(Source: Mohapatra et al., 2015)

4) Droughts

Any lack of water to satisfy the normal needs of agriculture, livestock, industry or human population may be termed as a drought. Further, the drought could be classified into three major types as,

1) Meteorological drought: it is a situation where there is a reduction in rainfall for a specific period below a specific level.

2) Hydrological drought: it is associated with reduction of water in streams, rivers and reservoirs. It is of two types, a) Surface water drought, and b) Groundwater drought.

3) Agricultural drought: it refers to the condition in which the agricultural crops get affected due to lack of rainfall.

Droughts in India occur in the event of a failure of monsoon. Generally monsoon rainfall is uneven in India. Some areas receive heavy rainfall while other regions get moderate to low rainfall. The areas which experience low to very low rainfall are affected by drought. (Source: Khullar, 2014)

Fact

About one third area of the country is affected by drought. It severely affects 16 Percentage of the land area and 12 Percentage of the total population of India. The areas that receive an annual rainfall of less than 60 cm are the drought prone regions of India.

The major areas highly prone to drought are:

1) The arid and semi-arid region from Ahmedabad to Kanpur on one side and from Kanpur to Jalandhar on the other.

2) The dry region lying in the leeward side of the Western Ghats.

5) Landslides

Landslide is a rapid downward movement of rock, soil and vegetation down the slope under the influence of gravity. Landslides are generally sudden and infrequent. Presence of steep slope and heavy rainfall are the major causes of landslides. Weak ground structure, deforestation, earthquakes, volcanic eruptions, mining, construction of roads and railways over the mountains are the other causes of landslides. About 15 Percentage of India's landmass is prone to landslide hazard. Landslides are very common along the steep slopes of the Himalayas, the Western Ghats and along the river valleys. In Tamil Nadu, Kodaikanal (Dindigul district) and Ooty (The Nilgiris district) are frequently affected by landslides.

6) Tsunami

Tsunami refers to huge ocean waves caused by an earthquake, landslide or volcanic eruption. It is generally noticed in the coastal regions and travel between 640 and 960 kilometer per hour. Tsunami pose serious danger to the inhabitants of the coastal areas.

Do you know?

The word 'Tsunami' is derived from Japanese word 'tsu' meaning harbour and 'nami' meaning wave (Harbour wave).

Indian Ocean Tsunami of two thousand and four

• On December 26, 2004, at 7:59 a.m. local time, an undersea earthquake with a magnitude of 9.1 struck off the coast of the Indonesian island of Sumatra.

• The tsunami killed at least 2,25,000 people across a dozen countries, with Indonesia, Sri Lanka, India, Thailand, Somalia and Maldives, sustaining massive damage.

7) Hazardous Wastes

The wastes that may or tend to cause adverse health effects on the ecosystem and human beings are called hazardous wastes. The following are the major hazardous wastes.

Radioactive substance: tools and unused fuel pipe of nuclear power plants.

ii) Chemicals: synthetic organics, inorganic metals, salts, acids and bases, and flammables and explosives.

Medical wastes: hypodermic needles, bandages and outdated drugs.

Flammable wastes: organic solvents, oils, plasticisers and organic sludges.

Explosives: the wastes resulting from ordnance manufacturing and some industrial gases.

Household hazardous wastes: pesticides, waste oil, automobile battery and household battery.

Do You Know?

Chernobyl nuclear disaster site (near Pripyat) to become an official tourist spot

Before:

• Chernobyl (then Soviet Union) nuclear accident was happened on 26th April, 1986.

• The radiation emitted was more than 400 times than that released by the atomic bomb dropped on Hiroshima (Japan) in 1945. This accident remains the largest nuclear accident in history.

• More than 3,50,000 people were evacuated from the area and severe restrictions on permanent human settlement are still in that place.

Now:

• 33 years after the accident, the Exclusion Zone, which covers an area now in Ukraine and Belarus is inhabited by numerous animals and more than 200 bird species.

• In 2016, the Ukraine part of this zone was declared as a radiological and environmental biosphere reserve by the government.

8) Pollution of Air

Air is a mixture of several gases. The main gases are nitrogen (78.09%) for forming products such as, fertilisers for plants and for making the air inert, oxygen (20.95%) for breathing and carbon dioxide (0.03%) for photosynthesis. Some other gases like argon, neon, helium, krypton, hydrogen, ozone, zenon and methane are also present. Besides, water vapour and dust particles make their presence felt in one way or the other.

Air pollution is the contamination of the indoor or outdoor air by a range of gases and solids that modify its natural characteristics and percentage. Air pollutants can be categorised into primary and secondary pollutants. A primary pollutant is an air pollutant emitted directly from a source. A secondary pollutant is not directly emitted as such, but forms when other pollutants (primary pollutants) react in the atmosphere.

Primary Pollutants	Secondary Pollutants
Oxides of Sulphur	Ground Level Ozone
Oxides of Nitrogen	Smog
Oxides of Carbon
Particulate Matter
Other Primary Pollutants

9) Pollution of Water

Water pollution may be defined as alteration in the physical, chemical and biological characteristics of water, which may cause harmful effects in human and aquatic life. In India, water pollution has been taking place on a large scale and since a long period. Both surface and groundwater bodies are polluted to a great extent. The major causes of water pollution in India are:

Urbanization

Industrial effluents

Sewages

Agricultural runoff and improper agricultural practices

Seawater intrusion

Solid wastes

Need for Prevention Measures

Prevention is defined as the activities taken to prevent a natural calamity or potential hazard from having harmful effects on either people or economic assets.

1. Prevention planning consists of i) hazard identification, and ii) vulnerability assessment.

2. Delayed actions may increase the economic losses.

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

Nature is emerging as a new weapon of mass destruction, do you agree?

Around 22,000 people have died in India in 10 years until 2017 due to major environmental disasters – Indian Meteorology Department.

In the past two decades (1998-2017) over 5,00,000 people have died due to extreme weather events around the world – stated by Global Climate Risk Index Report Published by Germanwatch (German-based non-profit organisation).

Recap

1. Hazards are defined as the phenomena that pose a threat to people, structures or economic assets and which may cause disaster.

2. There are three types of hazards namely natural hazards, human-made hazards and Socio-natural hazards.

3. Natural hazards are earthquakes, floods, cyclonic storms, droughts, landslides, tsunamis, volcanic eruptions etc.

4. Human-made hazards are explosions, hazardous wastes, pollution of air, land and water, dam collapses, wars or civil conflicts, terrorism etc.

5. Socio- natural hazards are caused by the combined effect of natural forces and misdeeds of human.

GLOSSARY

Earthquake It is a violent tremor in the earth's crust. நிலஅதிர்வு Floods It is a state of high water level along a river channel or on coast that leads to inundation of land. வெள்ளப்பெருக்கு Drought Any lack of water to satisfy the normal needs of agriculture, livestock, industry or human population may be termed as a drought. வறட்சி Tsunami It is a series of waves caused by the earth movements under the sea. ஆழிப்பேரலை

Evaluation

Exercise 1. Choose the correct answer

1. percentage of nitrogen is present in the air.

a) 78.09 Percentage b) 74.08 Percentage c) 80.07 Percentage d) 76.63 Percentage

2. Tsunami in Indian Ocean took place in the year .

a) 1990 b) 2004 c) 2005 d) 2008

3. The word Tsunami is derived from language.

a) Hindi b) French c) Japanese d) German

4. The example of surface water is

a) Artesian well b) Groundwater c) Subsurface water d) Lake

5. Event that occurs due to the failure of monsoons.

a) Condensation b) Drought c) Evaporation d) Precipitation Exercise 2. Fill in the blanks

1. Hazards may lead to .

2. Landslide is an example of hazard.

3. On the basis of origin, hazard can be grouped into categories.

4. Terrorism is an example of hazard.

5. Oxides of Nitrogen are pollutants which affects the human beings.

6. Chernobyl nuclear accident took place in year.

Exercise 3. Match the following

1. Primary pollutant
2. Hazardous waste
3. Earthquake
4. Meteorological drought
5. Human induced hazard

Options: Terrorism, Tsunami, Outdated drugs, Oxides of Sulphur, Reduction in rainfall

Exercise 4. Answer briefly

1. Define 'hazard'.

2. What are the major types of hazards?

3. Write a brief note on hazardous wastes.

4. List out the major flood prone areas of our country.

5. Mention the types of drought.

6. Why should not we construct houses at foothill areas?

Exercise 5. Distinguish between

1. Hazards and disasters.

2. Natural hazard and human-made hazard.

3. Flood and drought.

4. Earthquake and Tsunami.

Exercise 6. Answer in a paragraph

1. Write an essay on air pollution.

2. Define earthquake and list out its effects.

3. Give a detailed explanation on the causes of landslides.

4. Elaborately discuss the effects of water pollution.

Exercise 7. Activities

1. Name the hazards which you have identified.

SL.No	Item	In and around your school	In your residential environs	On the way to school from home
1.	Hazardous factory / Industry
2.	Roads of heavy traffic
3.	Tall buildings
4.	Things which burn easily
5.	Open drainage / Septic tank
6.	Others

2. List out the hazards that occur frequently and occasionally in your place.

Frequent Hazards	Occasional Hazards
1	1
2	2
3	3
4	4
5	5

3. On the map of Tamil Nadu shade the 13 coastal districts in different colours.

REFERENCE BOOKS

1. Central Board of Secondary Education – A Supplementary Text Book in Geography for Class XI (2006). Natural Hazards and Disasters (Unit 11). Natural Hazards and Disaster Management, The Secretary, Central Board of Secondary Education, Delhi.

2. Keller, E.A. and DeVecchio, D.E. (2012). Natural Hazards: Earth's Processes as Hazards, Disasters and Catastrophes (3rd Edition), Pearson Prentice Hall, New Jersey.

3. Khullar, D.R. (2014). India: A Comprehensive Geography, Kalyani Publishers, New Delhi.

4. Manual on Natural Disasters Management in India (2001). National Centre for Disaster Management, Ministry of Home Affairs, Government of India, New Delhi.

5. Mohapatra, M., Mandal, G.S., Bandyopadhyay, B.K., Tyagi, A. and Mohanty, U.C. (2012). Classification of Cyclone Hazard Prone Districts of India. Natural Hazards, 63(3): 1601-1620.

6. Paul, B.K. (2011). Environmental Hazards and Disasters: Contexts, Perspectives and Management, John Wiley & Sons, Oxford.

7. Reed, S.B. (1997). Introduction to Hazards (3rd Edition). Disaster Management Training Programme, National Institute of Disaster Management, New Delhi.

8. Smith, K. and Petley, D.N. (2008). Environmental Hazards: Assessing Risk and Reducing Disaster (5th Edition), Taylor & Francis Group, London.

9. The Report of High Powered Committee on Disaster Management (2002). National Centre for Disaster Management, Indian Institute of Public Administration, New Delhi.

INTERNET RESOURCES

http://www.amssdelhi.gov.in/tropicle_cyclones.htm

http://www.searo.who.int/topics/air_pollution/what-is-air-pollution.pdf?ua=1

https://germanwatch.org/en/cri

https://ndma.gov.in/en/landslides-zonemap.html

https://nidm.gov.in/safety_earthquake.asp

https://nptel.ac.in/courses/120108005/module9/lecture9.pdf

https://theconversation.com

https://www.downtoearth.org.in

https://www.thehindubusinessline.com/news/national/over-12-of-landmass-in-india-prone-to-landslides/article9728811.ece

Book-back Exercises — Questions & Answers

Answers generated strictly from the Samacheer Kalvi textbook content. Attempt each question first, then click "Show Answer" to check.

1. Choose the correct answer

1. ___ percentage of nitrogen is present in the air.

a) 78.09% b) 74.08% c) 80.07% d) 76.63%

Answer: a) 78.09%

Explanation: According to the chapter, nitrogen forms 78.09% of air for forming products such as fertilisers for plants and for making the air inert.

2. Tsunami in Indian Ocean took place in the year ___.

a) 1990 b) 2004 c) 2005 d) 2008

Answer: b) 2004

Explanation: The chapter mentions that on December 26, 2004, an undersea earthquake caused the Indian Ocean Tsunami that killed at least 2,25,000 people across a dozen countries.

3. The word Tsunami is derived from ___ language.

a) Hindi b) French c) Japanese d) German

Answer: c) Japanese

Explanation: The chapter states that the word 'Tsunami' is derived from Japanese word 'tsu' meaning harbour and 'nami' meaning wave (Harbour wave).

4. The example of surface water is

a) Artesian well b) Groundwater c) Subsurface water d) Lake

Answer: d) Lake

Explanation: Among the given options, lake is the only example of surface water, while the others are forms of groundwater or subsurface water.

5. Event that occurs due to the failure of monsoons.

a) Condensation b) Drought c) Evaporation d) Precipitation

Answer: b) Drought

Explanation: The chapter clearly states that droughts in India occur in the event of a failure of monsoon.

2. Fill in the blanks

1. Hazards may lead to ___.

Answer: disaster

2. Landslide is an example of ___ hazard.

Answer: geologic/seismic

3. On the basis of origin, hazard can be grouped into ___ categories.

Answer: eight

4. Terrorism is an example of ___ hazard.

Answer: human-induced

5. Oxides of Nitrogen are ___ pollutants which affects the human beings.

Answer: primary

6. Chernobyl nuclear accident took place in ___ year.

Answer: 1986

3. Match the following

3. Match the Following

Column A	Column B
1. Primary pollutant	Terrorism
2. Hazardous waste	Tsunami
3. Earthquake	Outdated drugs
4. Meteorological drought	Oxides of Sulphur
5. Human induced hazard	Reduction in rainfall

Answers: 1-d, 2-c, 3-b, 4-e, 5-a

4. Answer briefly

1. Define 'hazard'.

Answer: Hazards are defined as a thing, person, event or factor that poses a threat to people, structures or economic assets and which may cause a disaster. They could be either human made or naturally occurring in the environment.

2. What are the major types of hazards?

Answer: Hazards can be broadly classified into three types: natural hazards, human-made hazards and socio-natural hazards. Natural hazards are results of natural processes like earthquakes and floods. Human-made hazards are caused by undesirable activities of humans like pollution and terrorism.

3. Write a brief note on hazardous wastes.

Answer: The wastes that may or tend to cause adverse health effects on the ecosystem and human beings are called hazardous wastes. Major hazardous wastes include radioactive substances, chemicals, medical wastes, flammable wastes, explosives and household hazardous wastes like pesticides and waste oil.

4. List out the major flood prone areas of our country.

Answer: Gangetic plains covering Punjab, Haryana, Uttar Pradesh, North Bihar, West Bengal and Brahmaputra valley are major flood prone areas in north and northeast India. Coastal Andhra Pradesh, Odisha and southern Gujarat are other regions frequently prone to floods.

5. Mention the types of drought.

Answer: Drought can be classified into three major types: Meteorological drought (reduction in rainfall below specific level), Hydrological drought (reduction in water in streams, rivers and reservoirs), and Agricultural drought (condition where agricultural crops get affected due to lack of rainfall).

6. Why should not we construct houses at foothill areas?

Answer: Houses should not be constructed at foothill areas because landslides are common along steep slopes and their frequency may be aggravated due to construction of houses in mountainous areas. About 15% of India's landmass is prone to landslide hazard.

5. Distinguish between

1. Hazards and disasters.

Answer: A hazard is a thing, person, event or factor that poses a threat to people, structures or economic assets which may cause a disaster. A disaster is a hazardous event that occurs over a limited time span in a defined area causing great damage to property and loss of life, needing assistance from others.

2. Natural hazard and human-made hazard.

Answer: Natural hazards are results of natural processes where man has no role to play, like earthquakes, floods and cyclonic storms. Human-made hazards are caused by undesirable activities of humans, such as explosions, pollution, dam failures and terrorism.

3. Flood and drought.

Answer: Flood is an event where part of earth's surface gets inundated due to heavy rainfall and large waves. Drought is any lack of water to satisfy normal needs of agriculture, livestock, industry or human population, occurring due to failure of monsoons.

4. Earthquake and Tsunami.

Answer: Earthquake is a violent tremor in earth's crust sending shock waves in all directions from its origin. Tsunami refers to huge ocean waves caused by earthquake, landslide or volcanic eruption, traveling at 640-960 km/hour and posing danger to coastal inhabitants.

6. Answer in a paragraph

1. Write an essay on air pollution.

Answer: Air is a mixture of nitrogen (78.09%), oxygen (20.95%), carbon dioxide (0.03%) and other gases like argon, neon, helium. Air pollution is contamination of indoor or outdoor air by gases and solids that modify its natural characteristics. Air pollutants are categorised into primary and secondary pollutants. Primary pollutants include oxides of sulphur, nitrogen, carbon, particulate matter and are emitted directly from sources. Secondary pollutants like ground level ozone and smog form when primary pollutants react in atmosphere.

2. Define earthquake and list out its effects.

Answer: Earthquake is a violent tremor in earth's crust, sending out series of shock waves in all directions from its place of origin. India is grouped into four seismic zones based on earthquake risk levels. Zone V has very high risk covering northeastern India, parts of J&K, Himachal Pradesh and Rann of Kutch. Earthquakes cause structural damage, loss of life and property, and can trigger tsunamis and landslides.

3. Give a detailed explanation on the causes of landslides.

Answer: Landslide is rapid downward movement of rock, soil and vegetation down slopes under gravity influence. Presence of steep slopes and heavy rainfall are major causes. Other causes include weak ground structure, deforestation, earthquakes, volcanic eruptions, mining, and construction of roads and railways over mountains. About 15% of India's landmass is prone to landslides, common along steep slopes of Himalayas, Western Ghats and river valleys.

4. Elaborately discuss the effects of water pollution.

Answer: Water pollution is alteration in physical, chemical and biological characteristics of water causing harmful effects on human and aquatic life. In India, both surface and groundwater bodies are polluted extensively. Major causes include urbanization, industrial effluents, sewages, agricultural runoff, improper agricultural practices, seawater intrusion and solid wastes. This pollution affects drinking water quality, destroys aquatic ecosystems, causes waterborne diseases and impacts agricultural productivity.

📝 Summary

1. Hazards are defined as things, persons, events or factors that pose a threat to people, structures or economic assets and may cause disasters, originating from the old French word 'hasart' meaning a game of dice.
2. Natural hazards result from natural processes without human involvement and include earthquakes, floods, cyclonic storms, droughts, landslides, tsunamis and volcanic eruptions.
3. Human-made hazards are caused by undesirable human activities and include explosions, hazardous wastes, pollution of air, water and land, dam failures, wars, civil conflicts and terrorism.
4. Socio-natural hazards (Quasi-natural hazards) result from the combined effect of natural forces and human misdeeds, such as increased floods and droughts due to deforestation in river catchment areas.
5. Understanding the difference between hazards (potential threats), disasters (hazardous events causing damage over limited time), and catastrophes (massive disasters requiring significant money and long recovery time) is essential for awareness and prevention.