CHAPTER – 12
I Answer the following after discussing them in groups:
1. What are natural disasters?
Naturally-occurring destructive incidents resulting in loss of human life and property are called natural disasters.
2. What are the effects of cyclones?
- Cyclones are very destructive. Sometimes, the life of the people of cyclone-hit areas gets totally changed.
- They cause large scale deaths.
- Ocean tides inundate the inland water-bodies and make them salty.
- Crops get totally destroyed.
- Transport links, electricity supply and the daily life of the of people get affected badly.
- Cyclone-hit areas suffer from infectious diseases, leading to huge casualties.
3. What are floods?
Among the natural calamities faced by India every year, floods are the most dangerous. When there is heavy rainfall and excessive melting of ice, the volume of water increases in the river leading to it overflow. This is called “floods”.
4. What is Landslide?
Land mass sliding down the slopes from mountains or hills are called land slide.
5. What are Earthquakes?
Earthquakes are one of the most important natural calamities occurring on the land surface. Vibration or movement of the upper layers of the earth due to the pressure created inside is called Earthquake.
6. What are the causes of floods? Describe flood-poone areas?
- The uncertainty of monsoon rainfall sometimes gets heavy rainfall causes floods.
- Accumulation of silt in the rivers lead to overflowing of water on either side of the river, causing floods.
- Breach of dams or retention walls leads to sudden release of large quantity of water resulting in floods.
- Rivers changing their course can also cause floods.
- Heavy rainfall during cyclones can also lead to floods.
- Earthquakes in the sea are also causes floods.
- Apart from the natural causes mentioned above, man-made causes like deforestation, improperly built dams, weak retention walls, illegal encroachment of land are also important causes.
Flood-prone regions are found all over the country.
- The Ganges and its tributaries Yamuna, Gandak, Kosi and Ghagra rivers cause floods in Uttar Pradesh and Bihar.
- Damodar and Suvarnarekha rivers cause floods in Chattisgarh and West Bengal states.
- Brahmaputra and its tributaries Dibang, Dihang, Subansiri and Luhit rivers cause floods in Assam.
- Cloudburst often causes abrupt floods in the Himalayas.
- Narmada, Tapti, Sabaramathi and Mahi rivers cause floods for some days in a year in the state of Gujarat.
- Krishna, Tungabhadra, Ghataprabha, Malaprabha, Dhoni, Bennehalla etc. Cause floods during rainy season inKarnataka.
7. What is Coastal Erosion? Mention its management.
Sea waves continuously hit the coast. Because of this, the coastal land is eroded. The erosion of land by the waves in the coastal areas is called coastal erosion.
- Prohibiting sand mining in coastal areas.
- Constructing retention walls along the length of coastwherever waves are strong.
- Stocking of large rocky boulders along the coast to reduce the impact.
- The most effective method of preventing coastal erosion is by growing mangrove forests along the coast.
8. Write about the effects of earthquake and precautions to be taken.
The seventy of the earthquakes is dependent on the loss of life and destruction of property. It also leads to obstruction to transport spread of infections diseases, increased tidal activity, change in river‟s direction etc.
Precautionary measures to be taken:
- Restricting construction of multi-storied building in earthquake-prone areas.
- Using very light material for construction of houses in these areas.
- Constructing houses to ensure stability.
- Providing basic amenities to the quake-affected areas.
- Disconnecting power supply in the event of an earthquake.
9. Explain the causes and effects of Landslides.
- In the mountainous areas and coasts, constantly flowing water and tides remove soil creating slopes leading to landslides.
- When railways, roads and canals are constructed in the steep mountainous areas, the slopes become steeper leading to landslides.
- Collection of loose soil on clay soil layer can enhance steep slope formation leading to landslide.
- Landslides are common in the mining areas. Excavation of earth to reach the ore deposits deep down can cause landslides.
- Deforestation and deep tilling of the slopes can cause landslides.
Effects of Landslides:
- Flowing small rivers are checked by landslides.
- Transportation is affected.
- Streams and many plants get submerged.
- Landslides can cause loss of life and damage to property.
10. Explain the measures to control the Flood.
- To control floods, bunds should be constructed on either sideof rivers.
- Constructing dams across rivers, collecting water in reservoirs and directing the water to other places.
- Establishing centers to issue flood warnings.
- Afforestation in the river basins will prevent soil erosion, andalso reduce accumulation of silt in the rivers thereby reducing the chances of floods.
11. What are the reasons for the Earthquake ?
1. Pressure increases in the interior of the earth more earthquake are causes.
2. Earthquakes causes from the deforestation, construction of Dams, Mining activities etc.,
12. What are the preventive measues to control cyclones?
- Evacuation of people from low-lying areas.
- Ready to keeping generators, boats, helicopters and other transport facilities.
- Re-routing trains and buses from the cyclone-prone areas.
- Keeping people constantly informed about the movement of the cyclone.
- Ready to Keeping the army battalions ready.
- Ready to Keeping food, potable water and clothes ready.
- Ready to Keeping medicines and medical facilities ready.
13. What are the effects of floods?
- Floods are causes, loss of shelter, property, land and crops of the people.
- Telecommunication, electricity supply and transport facilities get affected.
- Besides washing away the fertile upper layers of soil, a lot of trees are destroyed.
- Stagnant water in the low lands leads to dangerous diseases.