Class 5 EVS Chapter 20 Natural Calamities Notes & Exercise Answers
Complete solved exercises and revision notes for Class 5 EVS Chapter 20 Natural Calamities. Includes NCERT/EVS question answers, fill in the blanks.
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Earthquakes
- Definition: Sudden movements or shaking of the ground caused by vibrations deep below the Earth’s surface.
- Cause: The Earth’s outer layer (crust) is made up of moving tectonic plates. When these plates slide against each other and get stuck, pressure builds up. When released suddenly, it causes the Earth to shake violently.
- Epicentre: The point on the Earth’s surface directly above the place where the earthquake originates is called the epicentre.
- Measurement: Measured using an instrument called a Seismograph on the Richter Scale (invented by Charles Richter in 1935). Readings above 5 cause severe destruction.
- Precautions: If indoors, drop, cover, and hold on under a sturdy table or desk. Stay away from glass windows, tall cabinets, and light fixtures. If outdoors, move to an open area away from buildings, trees, and power lines.
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Floods
- Definition: An overflow of a large amount of water beyond its normal limits, submerging normally dry land.
- Causes: Heavy rains, melting of snow on mountains, cyclones, or bursting of dams.
- Effects: Destruction of crops, damage to houses, loss of livestock, contamination of drinking water leading to waterborne diseases like cholera, typhoid, and malaria.
- Prevention: Construct raised embankments (bunds) near rivers, build dams, avoid deforestation near riverbanks, and move to higher ground during alerts.
- Droughts
- Definition: A prolonged period of abnormally low rainfall, leading to a severe shortage of water.
- Causes: Lack of rainfall over a long period, excessive deforestation, and global temperature rise.
- Effects: Crop failure, acute shortage of food and drinking water, famine, and death of livestock.
- Prevention: Plant more trees (afforestation), practice rainwater harvesting, and construct reservoirs/check dams.
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Volcanic Eruptions
- Definition: An opening (vent) in the Earth’s crust through which molten rock (magma), ash, and hot gases erupt.
- Lava: When magma rises to the surface and erupts out of a volcano, it is called lava.
- Active Volcanoes: Erupt regularly (e.g., Mount Etna, Mount Vesuvius, Barren Island in Andaman & Nicobar).
- Dormant Volcanoes: Have not erupted in a long time but may erupt in the future (e.g., Four Peaked Mountain in Alaska).
- Extinct Volcanoes: Have stopped erupting permanently with no record of historical activity (e.g., Edinburgh Castle rock in Scotland).
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Cyclones & Typhoons
- Overview: Violent, rotating wind storms accompanied by heavy rain that form over warm ocean waters. In coastal regions, they cause massive destruction and storm surges.
- Eye of Storm: The calm, low-pressure centre of a typhoon or cyclone is called the ‘eye’.
- Precautions: Listen to weather forecasts on radio/TV, move to cyclone shelters, and keep an emergency kit ready.
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Tsunamis
- Definition: A series of massive ocean waves caused by underwater earthquakes, volcanic eruptions, or landslides.
- Impact: These waves travel across the ocean at speeds up to 800 km/h and flood coastal cities within minutes, causing extreme devastation (e.g., 2004 Indian Ocean Tsunami).
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Disaster Management & Role of Agencies
- Government Role: The government provides medical assistance, financial support, evacuation, and army/air force airlifts for rescue operations.
- NGOs & International Bodies: Provide immediate emergency food, medical supplies, and shelter.
- UNICEF: Provides aid, clean water, and food for children.
- WHO: Provides emergency medical treatment and prevents epidemics.
- UNDMT: Coordinates disaster relief and risk management.
- Red Cross Society: Provides voluntary medical aid, blood supplies, and relief equipment.
- Community Role: Local citizens, police, and fire personnel act as first responders to rescue victims, clear debris, and maintain law and order.
SECTION 2: SOLVED SCHOLASTIC ASSESSMENT EXERCISES
Tick (✓) the right answer:
- Floods in coastal regions are caused due to: Answer: (b) typhoons
- Earthquake is measured on the ________ scale. Answer: (c) Richter
- Drought is common in areas of ________. Answer: (b) less rain
- The only active volcano in Indian sub-continent is: Answer: (a) Barren Island
- WHO provides ________ to the affected people. Answer: (c) medical help
Answer the following questions:
What is earthquake? When did it strike in Gujarat severely?
Answer:
An earthquake is a sudden shaking of the Earth’s surface caused by vibrations deep inside the crust due to the movement of tectonic plates. A severe earthquake struck Gujarat on 26th January 2001 in the Bhuj district.
- Explain three types of volcanoes with examples. Name some active volcanoes on the earth.
Answer:
The three types of volcanoes are:
• Active Volcanoes: Volcanoes that erupt frequently (e.g., Mount Etna in Italy, Mount Vesuvius, Mount Fuji, and Barren Island in India).
• Dormant Volcanoes: Volcanoes that have not erupted recently but can erupt in the future (e.g., Four Peaked Mountain in Alaska).
• Extinct Volcanoes: Volcanoes that have stopped erupting completely and will not erupt again (e.g., Edinburgh Castle in Scotland).
- What is flood? What are its effects?
Answer:
A flood is the overflowing of a large amount of water onto dry land, usually from rivers or coastal waters.
Effects of Floods:
• Submerges houses, roads, and railway tracks.
• Destroys agricultural crops and leads to livestock loss.
• Contaminates drinking water sources.
• Spreads waterborne and mosquito-borne diseases like malaria, dengue, and cholera.
- What precautions should be followed during earthquake?
Answer:
Precautions during an earthquake:
• Move out to an open field away from tall buildings, trees, and power lines.
• If indoors, take shelter under a strong table, desk, or bed.
• Stay away from glass windows, mirrors, and wall hangings.
• Do not use elevators during an earthquake.
- Explain the term ‘Tsunami’. How is it caused?
Answer:
A Tsunami is a series of massive ocean waves that move at high speeds across the sea and flood land. It is caused by underwater earthquakes, submarine volcanic eruptions, or underwater landslides.
- What are the effects of drought on people?
Answer:
Effects of drought on people:
• Severe scarcity of drinking water and food.
• Failure of agricultural crops, causing financial hardship and famine for farmers.
• Death of cattle and livestock due to lack of fodder and water.
• Forced migration of people to cities in search of food and work.
- What role does community institutions play in disaster management?
Answer:
Community institutions, such as local police, fire departments, schools, and NGOs, play a crucial role in disaster management by:
• Providing immediate rescue and relief operations.
• Setting up shelter camps and community kitchens.
• Distributing emergency medicines, food, and clothes.
• Spreading awareness and conducting safety drills.
Fill in the blanks with appropriate words:
- The shaking of the earth is called an earthquake.
- A cyclone / typhoon destroyed thousands of villages in Odisha.
- Tsunamis are huge sea waves.
- The full form of WHO is World Health Organization.
- Flow of water over the banks of river filling in nearby area is called flood.
Write ‘T’ for true and ‘F’ for false statements:
- When a river overflows the banks, earthquake is caused. — False (It causes a flood)
- Excessive cutting of trees affects the rainfall. — True
- A typhoon is also called cyclone. — True
- The farmers get most affected by droughts. — True
- Seismograph is used to measure Tsunami. — False (It is used to measure Earthquakes)
Match the following:
| Column A | Column B | Correct Match |
| 1. Richter Scale | (a) No rainfall | 1 — (d) Seismology / Richter Scale |
| 2. Tsunami | (b) Volcano | 2 — (c) Ocean |
| 3. Magma | (c) Ocean | 3 — (b) Volcano |
| 4. Drought | (d) Seismology | 4 — (a) No rainfall |