Chapter 6 – Hazard and Disasters | Class 9 School Geography Solution

Answer in word or words

Question 4 (a)

When did Aila’ hit the coast of West Bengal ?

Answer

2009.

Question 4 (b)

Name a man-made hazard.

Answer

Nuclear accidents.

Question 4 (c)

What is used to measure the magnitude of seismic waves ?

Answer

Seismometer or seismograph.

Question 4 (d)

Which part of the world is worst affected by Tsunamis?

Answer

The Pacific Rim, also known as the Ring of Fire.

Question 4 (e)

Which two plates collided to cause the disastrous Tsunami in the Indian Ocean on 26th December 2004?

Answer

The Indian Plate and the Burma Plate.

Question 4 (f)

Which kind of flood occurs rapidly with little warning?

Answer

Flash flood.

Correct the following sentences

Question 5 (a)

Volcanic activity is one of the causes of flood.

Answer

Volcanic activity is one of the causes of earthquakes.

Question 5 (b)

Undersea earthquake is the root cause of drought.

Answer

Undersea earthquake is the root cause of Tsunami.

Question 5 (c)

Creep is a very slow but steady downslope movement of snow and ice. 

Answer

Creep is a very slow but steady downslope movement of rock and soil.

Question 5 (d)

Ground blizzard is usually fueled by buried organic matter, leaves etc.

Answer

Fire is usually fueled by buried organic matter, leaves etc.

Short answer type questions

Question 6 (a)

What are the causes of drought?

Answer

Drought is a period of abnormally dry weather that can last for weeks, months, or even years. It can occur anywhere in the world, but it is most common in arid and semi-arid regions.

There are two main causes of drought: natural causes and human causes.

Natural causes

1. Climate change: Climate change is making droughts more frequent and severe. This is because climate change is causing the Earth’s atmosphere to warm, which leads to more evaporation and less precipitation.
2. Ocean temperatures: Ocean temperatures can also play a role in drought. For example, when the El Niño weather pattern occurs, it can cause warmer-than-average sea surface temperatures in the Pacific Ocean. This can lead to below-average precipitation in the southwestern United States.
3. Changes in atmospheric circulation: Changes in atmospheric circulation can also lead to drought. For example, when a high-pressure ridge stalls over a region, it can block precipitation from reaching the area.

Human causes

1. Deforestation: Deforestation reduces the amount of water that is returned to the atmosphere through evapotranspiration. Evapotranspiration is the process by which plants release water vapor into the air through their leaves.
2. Overgrazing: Overgrazing can damage vegetation and reduce the soil’s ability to absorb water.
3. Poor water management: Poor water management practices, such as over-irrigation and water pollution, can also contribute to drought.

Question 6 (b)

What is Landslide?

Answer

A landslide is a mass movement of rock, debris, or earth down a slope. Landslides can occur suddenly or slowly over time. They can be triggered by a variety of factors, including heavy rainfall, earthquakes, volcanic eruptions, and human activity.

Landslides can be very destructive. They can damage or destroy homes, roads, and other infrastructure. They can also cause injuries and deaths.

There are five main types of landslides:

• Falls: Falls are landslides that involve the sudden collapse of rock or debris from a steep slope.
• Topples: Topples are landslides that involve the rotation of a mass of rock or debris around a fixed point.
• Slides: Slides are landslides that involve the movement of a mass of rock or debris down a slope along a relatively planar surface.
• Spreads: Spreads are landslides that involve the lateral spreading of a mass of rock or debris.
• Flows: Flows are landslides that involve the rapid movement of a mass of rock or debris down a slope in a fluid-like manner.

Question 6 (c)

What is Avalanche? 

Answer

An avalanche is a natural disaster that occurs when a mass of snow, ice, and debris rapidly descends down a mountainside or slope. Avalanches can be triggered by various factors, such as snowfall, temperature changes, or human activity like skiing or snowmobiling. They are highly dangerous and can cause significant destruction and loss of life.

Question 6 (d)

What is Blizzard?

Answer

A blizzard is a severe and hazardous weather event characterized by a combination of frigid temperatures, strong winds, and either falling or blowing snow. It results in significantly reduced visibility due to the blowing snow. The key distinction between a blizzard and a regular snowstorm is the strength of the wind, not the amount of snowfall.

Question 6 (e)

What are the causes of floods?

Answer

Floods are caused by an overflow of water onto land that is normally dry. They can occur in any area, but they are most common in low-lying areas and near rivers and streams.

There are a number of factors that can contribute to floods, including:

• Heavy rainfall: Heavy rainfall can cause rivers and streams to overflow, leading to flooding.
• Snowmelt: Snowmelt can also cause flooding, especially if it occurs rapidly.
• Deforestation: Deforestation can increase the risk of flooding by reducing the amount of vegetation that can absorb water.
• Poor drainage: Poor drainage can also contribute to flooding by causing water to pool in areas where it cannot flow away.

Question 6 (f)

Mention the difference between hazards and disasters.

Answer

Answer the following questions

Question 7 (a)

Describe the two types of hazards.

Answer

The two types of hazards are natural hazards and human-made hazards:

1. Natural Hazards: These hazards are primarily associated with natural processes and phenomena. They originate from events or processes in the Earth’s environment that occur without direct human influence. Examples of natural hazards include earthquakes, hurricanes, floods, wildfires, tornadoes, volcanic eruptions, and tsunamis. Natural hazards are driven by natural forces and can have a significant impact on human and environmental systems.
2. Human-Made Hazards (Anthropogenic Hazards): Human-made hazards, also known as anthropogenic hazards, are hazards caused by human actions or inactions. These hazards result from human activities and choices. Examples of human-made hazards include industrial accidents, chemical spills, nuclear accidents, air pollution, deforestation, and climate change resulting from greenhouse gas emissions. Human-made hazards can have widespread and long-lasting effects on human health, ecosystems, and the planet. They are contrasted with natural hazards because they stem from human influence on the environment.

Question 7 (b)

Write three causes of earthquake.

Answer

The three causes of earthquake

1. Tectonic Plate Movements: The most common cause of earthquakes is the movement of tectonic plates. Earth’s outer shell is divided into several large and small plates that float on the semi-fluid asthenosphere beneath them. When these plates interact, they can collide, pull apart, or slide past each other. This movement can generate immense stress, leading to earthquakes along plate boundaries or faults.
2. Volcanic Activity: Earthquakes can occur in volcanic regions due to the movement of magma beneath the Earth’s surface. As magma rises and creates pressure, it can fracture surrounding rocks, causing volcanic earthquakes. These earthquakes are often associated with volcanic eruptions.
3. Human Activities: Some earthquakes are induced by human activities. Activities like mining, reservoir-induced seismicity (caused by the filling of large reservoirs behind dams), and hydraulic fracturing (fracking) for oil and gas can alter subsurface stress and trigger earthquakes. These are known as induced earthquakes and are typically of lower magnitude than natural tectonic earthquakes.

Question 7 (c)

What are the main causes of Tsunamis? 

Answer

The main causes of Tsunamis

1. Submarine Earthquakes: The most common cause of tsunamis is submarine earthquakes. These earthquakes occur beneath the ocean floor when there is a sudden release of energy along tectonic plate boundaries. As the seafloor shifts during these earthquakes, it displaces a large volume of water, setting off powerful tsunami waves.
2. Underwater or Coastal Landslides: Tsunamis can also result from underwater or coastal landslides. When large masses of sediment, rock, or debris slide into the ocean, they displace water and generate tsunami waves. These landslide-induced tsunamis can be triggered by various factors, including heavy rainfall, volcanic eruptions, or human activities.
3. Volcanic Eruptions: Volcanic activity, especially explosive eruptions, can lead to tsunamis. When a volcanic eruption occurs either on an island or beneath the sea, it can displace water, creating a series of waves that propagate across the ocean. These volcanic tsunamis are less common than earthquake-induced tsunamis but can be highly destructive.

Question 7 (d)

How is a cyclone generated ?

Answer

A cyclone, also known as a tropical cyclone, hurricane, or typhoon depending on its location, is generated through a specific set of meteorological conditions and processes. Here’s how it is generated:

1. Warm Ocean Waters: Cyclones form over warm tropical oceans where sea surface temperatures are typically above 26 degrees Celsius (79 degrees Fahrenheit). Warm waters provide the necessary heat and moisture to fuel the cyclone.
2. Coriolis Effect: Cyclones are characterized by their circular rotation. In the Northern Hemisphere, they rotate counterclockwise, while in the Southern Hemisphere, they rotate clockwise. This rotation is due to the Coriolis effect, caused by the Earth’s rotation.
3. Low-Pressure Center: A cyclone starts with the development of a low-pressure center over the warm ocean waters. This low-pressure area serves as the core of the cyclone.

Question 7 (e)

What is Flash flood ?

Answer

A flash flood is a sudden and rapid flooding of low-lying areas, caused by heavy rainfall, dam or levee failure, or a sudden release of water from a man-made or natural source. Flash floods are characterized by their rapid onset and often occur with little to no warning, leaving little time for evacuation or preparation.

Question 7 (f)

What are the three main types of droughts? 

Answer

There are three main types of droughts:

1. Meteorological Drought: This type of drought is based on the degree of dryness or rainfall deficit and the duration of the dry period. It focuses on the lack of precipitation over a specific area and period, leading to drier conditions.
2. Hydrological Drought: Hydrological drought is characterized by the impact of prolonged rainfall deficits on water supply systems. It considers factors such as reduced stream flow, lower reservoir and lake levels, and declining groundwater tables, which can affect water availability for various uses.
3. Agricultural Drought: Agricultural drought is linked to the deficiency of moisture in the soil, impacting crop growth and health. It focuses on the availability of soil moisture for agricultural purposes and its influence on crop production.

Question 7 (g)

What are the major causes of landslides? 

Answer

Landslides can occur due to various causes, but the major factors contributing to landslides include:

1. Heavy Rainfall: Sustained or intense rainfall can saturate the soil, reducing its stability and triggering landslides. Rainwater percolates into the ground, increasing pore water pressure and making the soil more susceptible to sliding.
2. Earthquakes: Seismic activity can shake the ground and displace soil and rock masses, leading to landslides. The vibrations from earthquakes can weaken the natural cohesion of the materials on slopes.
3. Human Activities: Activities such as deforestation, construction, mining, and excavation can alter the natural landscape, removing vegetation and changing the terrain’s stability. Improper land use and construction practices can increase landslide risk.
4. Geological Factors: The geological characteristics of an area, including rock type, fault lines, and soil composition, can influence landslide susceptibility. Weak or weathered geological formations are more prone to landslides.
5. Climate Change: Climate-related factors, such as prolonged droughts followed by heavy rainfall, can exacerbate landslide risks by affecting soil moisture levels.

Question 7 (h)

What is the difference between avalanches and blizzards?

Answer

	Avalanches	Blizzards
Definition	Rapid flow of snow or ice down a slope	Severe winter storm with blowing snow and strong winds
Cause	Steep slope, unstable snowpack, human activity	Low pressure system, cold air, moisture
Location	Mountains, steep slopes	Anywhere with snow or ice

Question 7 (i)

What are the pre-disaster management policies taken up by the Govt. of West Bengal ?

Answer

The Government of West Bengal has implemented various pre-disaster management policies and initiatives to address the challenges posed by natural calamities such as floods, cyclones, droughts, landslides, and earthquakes. While specific details of these policies may be available in official documents and manuals, here are some key elements and focus areas typically covered by disaster management policies:

1. Risk Assessment: The government conducts risk assessments to identify areas prone to different types of disasters. This includes mapping vulnerable regions and assessing the potential impact of disasters.
2. Early Warning Systems: Implementation of early warning systems to provide timely alerts to the population about impending disasters, allowing for evacuation and preparedness measures.
3. Capacity Building: Training and capacity-building programs for government officials, emergency responders, and communities to enhance their preparedness and response capabilities.

Match the following

Question 8

Column A	Column B
(1) Disaster	(e) ‘Bad or evil star’
(2) Maintenance of structure building, etc.	(d) Pre-disaster measure (short-term)
(3) Surface fire	(b) Kind of forest fire
(4) Maintenance of Law and order	(a) Post-disaster measure
(5) Circum Pacific Belt	(c) Earthquake belt.

Answer

The general nature of hazards in West Bengal includes several types of natural disasters and related risks. These hazards are influenced by the geographical and climatic conditions of the region. Here is an overview:

1. Floods: West Bengal is highly susceptible to flooding, mainly due to its low-lying deltaic terrain and the presence of several major rivers like the Ganges, Brahmaputra, and their tributaries. Monsoon rains, snowmelt from the Himalayas, and cyclonic activities in the Bay of Bengal contribute to recurrent flooding.
2. Cyclones: The state is prone to cyclones originating in the Bay of Bengal. These cyclones bring heavy rainfall, strong winds, and storm surges, causing extensive damage to coastal areas.
3. Earthquakes: Although not as seismically active as some other regions in India, West Bengal experiences occasional earthquakes. The state falls in seismic zones II, III, IV, and V, with varying degrees of seismic hazard.
4. Landslides: Hilly areas in northern West Bengal are vulnerable to landslides, especially during the monsoon season. These can disrupt transportation and pose risks to communities in hilly terrain.
5. Drought: While not as common as flooding, certain parts of West Bengal can experience drought conditions, impacting agriculture and water availability.