Disasters
An event that occurs suddenly and causes a great loss of life and property at a particular place is called a disaster.
A natural event that occurs suddenly and causes a great loss of life and property at a particular place is called a natural disaster.
Earthquakes, volcanoes, tsunamis, cyclones, floods, droughts, etc. are all natural disasters.
Natural disasters can occur anytime and anywhere in the world. They are unavoidable and can upset the life of living beings.
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Volcano
An opening in the earth's surface through which magma, gases and ash comes out is called a volcano.
The word 'volcano' comes from the name "Vulcan" who is the Roman God of Fire.
All these things come out of the crust through a vertical hole is called a vent.
The hot magma on reaching the earth's surface is called lava.
As lava cools, it solidifies and forms rocks. Lava below the earth surface is called magma.
Types of The Volcanoes
On the basis of the frequency of eruption, there are three types of volcanoes:
1. Active volcanoes: Volcanoes that may erupt any time or have erupted in the recent past are called active volcanoes. Mount Fuji, Mount Vesuvius and Mount Etna are some famous active volcanoes.
Pacific area is Active volcanoes Area .
2. Dormant volcanoes: Volcanoes that have not erupted for a long time but may erupt in the future is called Dormant Volcanoes.
3. Extinct volcanoes: Volcanoes that have is called Extinct volcanoes.
Effects of Volcano
1. Cause of a huge loss of life and property.
2. Volcano eruption increased air pollution.
3. It increase marine temperature which kills aquatic creatures.
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Earthquakes
Sudden shaking or or motion of the earth's crust caused by vibrations occuring deep inside the It is called tremor or Earthquake.
★ The point beneath the earth's crust where the earthquake starts is called the focus.
★ The point on the surface of the earth above the focus is called epicentre. It is the most affected area.
★ The layers of the earth under the earth is called plates.
★These plates of the earth is made up of many rock. These are very hot and in molten form and move countiniously because the core below is immensely hot.
★ Some times, resulting of the sudden movements between the plates convert into the earthquakes.
Measuring an Earthquake
Earthquakes generate some special waves which travel all over the surface of the earth is called Seasmic waves.
★ The instrument that measures and records all the details of earthquakes is called a seismograph.
★ People who study earthquakes are called seismologists.
Richter Scale measures the intensity of an earthquake.
★ Richter scale was invented by Charles Richter.
★ This scale starts from magnitude 1 and goes up till magnitude 10.
★ The earthquakes of magnitude 7 or above cause massive loss of life and property.
★ Earthquakes of magnitude 3 or 4 can be felt but those of magnitude 1 or 2 can hardly be felt.
Effects of Earthquakes
1. Earthquakes can cause complete destruction of life, livestock, houses, buildings, etc.
2. Dams and bridges may be destroyed.
3. Earthquakes can give rise to other disasters like landslides, tsunamis, etc.
Earthquake at Bhuj in Gujarat
On 26 January 2001, there was a very strong and devastating earthquake at Bhuj in Gujarat. The magnitude of the earthquake was 7.1 on the Richter scale. It caused a huge loss of life and property. About 20,000 people died in that earthquake.
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Floods
When it rains heavily and continuously for several days, the rivers overflow and submerge the nearby areas. Such a condition is called flood.
Effects of Floods
1. Floods wash away people, livestock and property.
2. Many trees get uprooted and standing crops get submerged.
3. They can cause diseases like cholera, diarrhoea
4. Soil erosion, landslide, pollution of water bodies are other ill-effects of floods
Floods can be prevented by planting more and more trees, building more dams and embankments on the rivers.
Do You Know
In August 2000, there was a dangerous flood in Assam. It was in river Brahmaputra. It killed around 1000 people and left 1,00,000 people homeless.
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Test Yourself
Tick (✔) the correct word.
1. (Earthquake / Volcano) is the sudden shaking of a part of the earth's crust.
2. Soil erosion and pollution of water bodies are ill-effects of (earthquake/ floods).
3. Volcanoes that have not erupted for a long time but may erupt in future are called (active/dormant) volcanoes.
Ans. 1. Earthquake, 2. floods, 3. dormant
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Tsunami
Tsunami caused by earthquakes deep under the sea or by a severe hurricane or cyclone. Huge waves are created, causing great damage and loss of life.
Tsunami is a Japanese word. 'Tsu' means harbour and 'nami' means wave.
The waves cause destruction on the seashore within seconds. Tsunami waves can be as high as 15 metres. Such giant waves travel with a speed of 800 kilometres per hour in the sea. This causes great harm of life and property in the areas close to the seashore.
Effects of Tsunami
Tsunami can wipe out entire coastal settlements because of its high speed and big waves.
1. It can cause many diseases which may result in epidemics.
2. It can damage means of communication.
Do You Know 2
In September 2014, Jammu and Kashmir region in India suffered disastrous floods due to heavy rainfall. Almost 390 villages were completely submerged and nearly 284 people died. The loss of property worth 5000 crore to 6000 crore was estimated.
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Drought
When an area receives no or less rainfall than normal, for a long duration, that area is said to be under the spell of drought.
Hot dry winds, evaporation of moisture from soil and high temperature also bring drought like conditions.
Effects of Drought
1. There is crop failure. There is an acute shortage of food and fodder.
2. It forces people to migrate from that region to other regions.
3. People become weak physically and psychologically.
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Exercises
A. Tick (✔) the correct option.
1. This phenomena derives its name from the name of Roman God of fire.
a) volcano
b) earthquake
c) flood
d) tsunami
2. Floods can be prevented by
a) planting more trees
b) harvesting rain water
c) destroying trees
d) collecting lava
3. This is an instrument used to measure the intensity of an earthquake.
a) barometre
b) hygrometre
c) Richter scale
d) Celsius scale
4. Tsunamis are huge sea waves caused by
a) volcano
b) undersea earthquakes
c) water logging
d) both (a) and (b)
5. Hot liquid rock that comes out on the ground is called
a) magna
b) vent
c) lava
d) crust
Ans. 1. a) volcano, 2. a) planting more trees, 3. c) Richter scale, 4. d) both (a) and (b), 5. c) lava
B. Fill in the blanks.
1. When there is no rainfall for a long duration, a ………….... occurs.
2. ………….... are caused due to heavy rains.
3. People who study earthquakes are called …………....
4. Mount Vesuvius and Mount Fuji are two famous ………….... volcanoes.
5. A ………….... is an opening in the earth's surface which allows molten rock to escape.
Ans. 1. draught, 2. Flood, 3. seismologists, 4. Active, 5. volcanoes
C. Answer these questions in one or two sentences.
1. What is a disaster? Name any three natural disasters.
Ans. An event that occurs suddenly and causes a great loss of life and property at a particular place is called a disaster.
Earthquakes, volcanoes, tsunamis, cyclones, floods, droughts, etc. are all natural disasters.
2. What is seismograph?
Ans. The instrument that measures and records all the details of earthquakes is called a seismograph
3. List the conditions that can cause a drought.
Ans. When an area receives no or less rainfall than normal, for a long duration, that area is said to be under the spell of drought.
Hot dry winds, evaporation of moisture from soil and high temperature also bring drought like conditions.
4. How can floods be prevented?
Ans. Floods can be prevented by planting more and more trees, building more dams and embankments on the rivers.
D. Answer these questions in detail.
1. What is an earthquake? How is an earthquake measured?
Ans. Sudden shaking or or motion of the earth's crust caused by vibrations occuring deep inside the It is called tremor or Earthquake.
Richter Scale measures the intensity of an earthquake.
★ Richter scale was invented by Charles Richter.
★ This scale starts from magnitude 1 and goes up till magnitude 10.
★ The earthquakes of magnitude 7 or above cause massive loss of life and property.
★ Earthquakes of magnitude 3 or 4 can be felt but those of magnitude 1 or 2 can hardly be felt.
2. What is a flood? List the effects of floods.
Ans.
Floods
When it rains heavily and continuously for several days, the rivers overflow and submerge the nearby areas. Such a condition is called flood.
Effects of Floods
1. Floods wash away people, livestock and property.
2. Many trees get uprooted and standing crops get submerged.
3. They can cause diseases like cholera, diarrhoea
4. Soil erosion, landslide, pollution of water bodies are other ill-effects of floods
Floods can be prevented by planting more and more trees, building more dams and embankments on the rivers.
3. What is a tsunami? How is it harmful?
Ans.
Tsunami caused by earthquakes deep under the sea or by a severe hurricane or cyclone. Huge waves are created, causing great damage and loss of life.
The waves cause destruction on the seashore within seconds. Tsunami waves can be as high as 15 metres. Such giant waves travel with a speed of 800 kilometres per hour in the sea. This causes great harm of life and property in the areas close to the seashore.
4. What is a volcano? Explain the three types of volcanoes.
Ans.
Volcano
An opening in the earth's surface through which magma, gases and ash comes out is called a volcano.
Types of The Volcanoes
On the basis of the frequency of eruption, there are three types of volcanoes:
1. Active volcanoes: Volcanoes that may erupt any time or have erupted in the recent past are called active volcanoes. Mount Fuji, Mount Vesuvius and Mount Etna are some famous active volcanoes.
Pacific area is Active volcanoes Area .
2. Dormant volcanoes: Volcanoes that have not erupted for a long time but may erupt in the future is called Dormant Volcanoes.
3. Extinct volcanoes: Volcanoes that have is called Extinct volcanoes.
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