All questions of Natural Calamities for Class 5 Exam

Option A is the correct answer

Understanding Excessive Rainfall
Excessive rainfall refers to an unusually high amount of rain falling over a short period of time. This phenomenon can lead to various environmental impacts, with floods being the most significant consequence.
How Excessive Rainfall Causes Floods
- Water Accumulation: When rain falls excessively, the ground and water bodies cannot absorb all the water, leading to accumulation.
- Overflowing Rivers and Streams: The excess water can cause rivers and streams to overflow, spilling into surrounding areas and causing flooding.
- Urban Areas: In cities with impermeable surfaces, such as concrete, rainwater cannot seep into the ground. This leads to surface runoff, contributing to urban flooding.
- Soil Saturation: When soil becomes saturated, it cannot absorb more water, leading to surface runoff and potential flooding.
Different Types of Floods
- Flash Floods: These occur suddenly and can be extremely dangerous, often as a result of intense rainfall in a short period.
- River Floods: These happen when riverbanks overflow due to prolonged rainfall.
- Coastal Floods: Excessive rainfall can also lead to coastal floods, especially during storms.
Impact of Floods
- Property Damage: Floods can cause significant damage to homes, infrastructure, and businesses.
- Displacement: Communities may be forced to evacuate, leading to temporary or permanent displacement.
- Health Hazards: Floodwaters can lead to waterborne diseases and other health risks.
In summary, excessive rainfall is a primary cause of floods, resulting in severe consequences for the environment and human life. Understanding this relationship helps in planning and disaster management.

Understanding Extinct Volcanoes
Volcanoes are fascinating geological structures, and they can be categorized based on their activity. One such category is "extinct volcanoes."
What Are Extinct Volcanoes?
Extinct volcanoes have not erupted in thousands of years and show no signs of future activity. They are considered "dead" in the sense that they are unlikely to erupt again. Here are some key points about extinct volcanoes:

• Long Dormancy: Extinct volcanoes have been dormant for a very long time, often millions of years.
• Geological Changes: Over time, geological processes, such as erosion and sedimentation, can significantly alter the structure of these volcanoes.
• Formation: Many extinct volcanoes formed from repeated eruptions in the past, but eventually, the magma supply is depleted.
• Examples: Famous examples of extinct volcanoes include Mount Kilimanjaro in Tanzania and the Scottish volcanoes on the Isle of Skye.

Why Are They Important?
Understanding extinct volcanoes helps scientists learn about the Earth's geological history and the processes that lead to volcanic activity. They also provide insight into past climates and ecosystems.
Conclusion
In summary, the correct answer to the question is "D) Extinct Volcanoes." These geological formations illustrate the dynamic nature of the Earth and remind us that not all volcanoes are active or pose a threat.

Understanding Icebergs
An iceberg is a large mass of ice that has broken off from a glacier and fallen into the sea. Here’s a detailed explanation:
Formation of Icebergs
- Icebergs are formed when chunks of ice from glaciers calve, or break off.
- This process often occurs in polar regions, where glaciers meet the ocean.
Characteristics of Icebergs
- Icebergs can vary in size, with some being small and others as large as buildings.
- Approximately 90% of an iceberg's mass is submerged underwater, making them difficult to see and navigate around.
Importance of Icebergs
- Icebergs play a crucial role in Earth's climate and oceanic systems.
- They help regulate ocean temperatures and contribute to the salinity of ocean waters.
Differences from Other Natural Phenomena
- Unlike earthquakes (a sudden shaking of the ground) and tsunamis (large ocean waves usually caused by underwater earthquakes), icebergs are related to glacial activity.
- Tornadoes are violent windstorms and are not related to ice or glaciers.
In summary, icebergs are fascinating natural formations resulting from the dynamic processes of glaciers. They are distinct from other natural occurrences, making "iceberg" the correct answer to the question posed.

Understanding Tsunamis
Tsunamis are large ocean waves caused primarily by underwater disturbances. The most common cause of tsunamis is underwater earthquakes.
How Underwater Earthquakes Create Tsunamis
- Seafloor Displacement: When an earthquake occurs beneath the ocean, it can cause the seafloor to suddenly rise or fall. This displacement of the seafloor pushes the water above it, generating powerful waves.
- Wave Propagation: These waves travel across the ocean at high speeds. In deep water, they may not be noticeable, but as they approach shallower coastal areas, their height increases dramatically.
Other Causes of Tsunamis
- Volcanic Eruptions: Underwater volcanic eruptions can also create tsunamis. Similar to earthquakes, the sudden release of energy can displace water.
- Landslides: If a large amount of debris falls into the ocean from a coastal landslide, it can displace water and create waves.
Why Not Cyclones and Droughts?
- Cyclones: While cyclones can produce storm surges and high waves, they do not create tsunamis. Tsunamis are specifically associated with seismic activities.
- Droughts: Droughts, which are prolonged periods of abnormally low rainfall, have no direct impact on ocean water levels or wave formation.
In conclusion, the correct answer to why tsunamis occur is option 'A' - underwater earthquakes, as they are the primary cause of these powerful ocean waves.

Volcanic eruption is a natural calamity caused by volcanic activity. When a volcano erupts, it releases hot lava, volcanic ash, and gases into the environment. This can result in various destructive effects on the surrounding areas.

Causes of Volcanic Eruption:
- Volcanic eruptions occur due to the movement of tectonic plates beneath the Earth's surface. These plates are constantly shifting and when they collide or separate, it can cause magma to rise towards the surface.
- Magma is a molten rock that forms beneath the Earth's crust. When it reaches the surface, it is called lava.

Effects of Volcanic Eruption:
1. Lava Flow: During a volcanic eruption, lava flows out of the volcano and spreads over the surrounding areas. Lava flows can destroy everything in their path, including buildings, vegetation, and infrastructure.

2. Pyroclastic Flow: This is a fast-moving mixture of hot gas, ash, and volcanic rocks that rushes down the sides of a volcano. Pyroclastic flows can cause severe damage and can be deadly to living organisms.

3. Ashfall: Volcanic eruptions release large amounts of volcanic ash into the atmosphere. Ashfall can cover vast areas, blocking sunlight and causing respiratory problems for humans and animals. It can also contaminate water sources and disrupt transportation systems.

4. Volcanic Gas: Volcanoes emit various gases during an eruption, including sulfur dioxide, carbon dioxide, and hydrogen sulfide. These gases can have harmful effects on the environment and human health.

5. Volcanic Explosions: Some volcanic eruptions can be explosive, resulting in the ejection of rocks, ash, and gases into the air. These explosions can cause significant damage to the surrounding areas, including destruction of buildings and infrastructure.

Conclusion:
Volcanic eruptions are natural calamities caused by volcanic activity. They can have devastating effects on the environment and human populations. It is important for communities living near active volcanoes to be prepared for such events and have evacuation plans in place to ensure their safety.

Understanding Landslides and Their Effects
Landslides can have severe consequences for the environment and surrounding areas. One of the significant outcomes of landslides is their role in causing floods.
How Landslides Cause Floods
- Displacement of Soil and Debris: When a landslide occurs, it displaces large amounts of soil and debris. This sudden movement can block rivers and streams, creating temporary dams.
- Water Accumulation: If the blockage is significant, water can accumulate behind the debris. This buildup can lead to an overflow when the dam breaks, causing floods in the downstream areas.
- Reduced Drainage: The soil and rocks from the landslide can fill in natural drainage paths. This alters the landscape and prevents water from flowing away, leading to localized flooding.
Additional Consequences of Floods
- Erosion: Floodwaters can lead to increased soil erosion, further destabilizing the area and potentially causing more landslides.
- Damage to Infrastructure: Flooding can damage roads, bridges, and homes, leading to costly repairs and displacement of residents.
- Impact on Ecosystems: Floods can disrupt local ecosystems, affecting plants and animals that rely on stable habitats.
Conclusion
In conclusion, landslides can indeed lead to floods by blocking waterways and altering the natural flow of water. Understanding this relationship helps in preparing for the risks associated with landslides and floods, ensuring better safety measures for communities at risk.

Explanation:
Earthquakes are natural calamities that are caused by the movement of the Earth's tectonic plates. These plates are massive slabs of rock that float on the semi-fluid mantle layer beneath them. The Earth's lithosphere, which includes these tectonic plates, is divided into several large and small pieces that constantly move and interact with each other.

What are tectonic plates?
Tectonic plates are pieces of the Earth's lithosphere that fit together like a jigsaw puzzle. There are several major tectonic plates, such as the Pacific Plate, the Eurasian Plate, the African Plate, and the North American Plate, among others. These plates are constantly moving, albeit very slowly, due to convection currents in the mantle beneath them.

How do earthquakes occur?
When tectonic plates interact, they can either move apart, move towards each other, or slide past each other. It is at the boundaries of these plates where most earthquakes occur. There are three types of plate boundaries:

1. Divergent boundaries: At divergent boundaries, plates move apart from each other. This movement creates a gap, and magma from the mantle rises to fill the space, creating new crust. Earthquakes can occur when the newly formed crust fractures and moves.

2. Convergent boundaries: At convergent boundaries, plates move towards each other. When two plates collide, one can be forced beneath the other, creating a subduction zone. The intense pressure and friction at the subduction zone can cause earthquakes.

3. Transform boundaries: At transform boundaries, plates slide past each other horizontally. The friction between the plates can cause them to lock together, and when the stress becomes too great, they suddenly slip, releasing energy in the form of an earthquake.

Impact of earthquakes:
Earthquakes can have devastating impacts. They can cause buildings and infrastructure to collapse, leading to loss of life and property. They can trigger landslides, tsunamis, and in some cases, volcanic eruptions. The severity of an earthquake is measured using the Richter scale.

In conclusion, earthquakes are natural calamities caused by the movement of the Earth's tectonic plates. Understanding the causes and effects of earthquakes is important for scientists and engineers to mitigate their impact and improve the safety of communities living in seismically active areas.

Active volcanoes eruption frequency:

Regular eruptions:
- Active volcanoes erupt frequently compared to dormant or extinct volcanoes.
- The frequency of eruptions can vary from several times a year to once every few years.

Reasons for frequent eruptions:
- Active volcanoes are located on tectonic plate boundaries where magma can easily rise to the surface.
- The presence of magma chambers beneath active volcanoes increases the likelihood of eruptions.
- Volcanic activity is also influenced by factors such as the composition of the magma, gas content, and external triggers like earthquakes.

Impact of frequent eruptions:
- Frequent eruptions can have significant impacts on the surrounding environment, including the release of ash, gases, and lava flows.
- Volcanic eruptions can also pose risks to nearby communities, infrastructure, and ecosystems.
- Monitoring and studying active volcanoes is essential to understand their behavior and mitigate potential hazards.

Conclusion:
Active volcanoes exhibit frequent eruptions due to their location, geological characteristics, and other influencing factors. Understanding the frequency of eruptions is crucial for managing the risks associated with volcanic activity.