Q. 1. Name the different Natural Disasters occurring in India.
Ans. Floods, Droughts, Cyclones, Landslides and Earthquakes.
Q. 2. What is the main cause of Natural disasters?
Ans. Sudden tectonic movements.
Q. 3. Name the recent devastating Earthquake which occurred in India.
Ans. Bhuj (Gujarat) — 26 January, 2001.
Q. 4. Name the different Earth- quake waves.
Ans. P-Waves, S-Waves, L-Waves.
Q. 5. Which instrument measures the seismic waves?
Q. 6. On which scale, is the intensity of Earthquakes measured?
Ans. Richter Scale.
Q. 7. What was the main cause of lattur Earthquakes?
Ans. Northward drifting of Indian Plate.
Q. 8. To which theory are Earthquakes related?
Ans. Plate tectonics.
Q. 9. How many divisions are there on Richter Scale?
Ans. From 1 to 9.
Q. 10. What was the cause of Koyna Earthquake?
Ans. Hydraulic Pressure in Koyna reservoir.
Q. 11. What is a drought?
Ans. Drought means widespread and extreme scarcity of food.
Q. 12. What is the main cause of droughts?
Ans. Uncertain, variable rainfall and high temperatures.
Q. 13. How much area is affected by droughts and floods?
Ans. 10% by droughts and 12% by floods.
Q. 14. What is the cause of floods?
Ans. Heavy rainfall and cyclones.
Q. 15. Why do major floods not occur in Southern Peninsula?
Ans. The rivers are seasonal.
Q. 16. What is a Landslide?
Ans. When a mass of earth saturated with water slides down a hill slope.
Q. 17. Name different units of Landslides.
Ans. Slumps, Rockslides, Rockfall.
Q. 18. Name three states which are affected by cyclones.
Ans. Odisha, Andhra Pradesh, Tamil Nadu.
Q. 19. What are the major natural hazards occurring in India?
Ans. Natural disasters or Hazards are the result of sudden earth movement's which change the face of earth in a short period causing a lot of loss of life and property. Droughts, Floods, Cyclones, Land slides, and Earthquakes and some of the major hazards.
Q. 20. Describe the loss and life and property caused due to natural hazards.
Ans. Natural disasters kill an average 1 lakh persons and cause property damage of '20,000 crores world wide every year. These disasters are a serious impediment to human development. U.N.O. declared 1990-99 on the international decaded for natural disaster Redvilon. India is one of the top 10 hazardprone countries in the world. 60 million Indians are affected every year. About 50% of natural hazards occur in India. Over the years, India has developed an extensive hazard detection network of seismological stations, cyclones, flood tracking satellites and randan, and rheam flow measuring stations.
Q. 21. What are Landslides? Explain their effects.
Ans. Landslides. Ground water increases the weight of the rock or the soil which contains it.Sometimes a mass of earth saturated with water slides down a hill slope causing landslides. There are many varieties of landslides depending on the mass slided and the distance traversed. Those which move only through short distances are called slumps. When millions of cubic feet of material moves through thousands of feet distance they are known as rockslides (debris slides). When under gravity rock material falls down a high cliff debris fall or rockfall occurs.
Causes. One or more causes such as lubrication by rains or melting snow, steep slopes and unusual structures, earthquakes, removal of support or gravity may produce landslides. Lubrication of rocks takes place by means of rains or melting snows as in many parts of Himalayas. Rocks become slippery and slide down. Steep slopes may be caused by sliding of rock strata through faulting or by quarries made by man. The sides of these may collapse on account of other factors. These include unusual structures in which beds of rocks may have steep slopes. Earthquakes cause earth shaking which makes the rock mass of the roofs of mines and caverns unstable causing land slips. Volcanic explosions also are the causes of the tremors. Removal of support takes place in this way.
Effects of Landslides. Landslides produce great scares, on the sides of mountains, and sometimes give a rippled shape to the hill-side on account of mixed rock slumps on back slopes. These may form backward rotation when their base slips thus creating a terrace-like structure. Landslides and rock slides are of frequent occurrence in many mountains. In 1957, such a huge land slides came down in Kashmir. It washed out the National highway. The traffic was suspended. Recently a land slide in Tehri-Garhwal region occurred due to cloud burst.
Q. 22. Write a note on Tropical cyclones in India.
Ans. Tropical cyclones originate in Bay of Bengal and Arabian Seas during the season of retreating monsoons. These mostly occur in the months of October-November. Their direction is variable. These move in a west or North-West and North-East direction. These effect the coastal areas of Tamil Nadu, Andhra Pradesh, Odisha. Most of these cyclones recurve in North East direction.
These cyclones bring strong winds, dense clouds, and heavy rainfall. On an average, 50 cms. of rainfall occurs in a day. These cyclones cause a large scale damage and destruction to lives and property. The low pressure of N.W. India shifts to Bay of Bengal. It results in the occurrence of Cyclones over Bay of Bengal. These manage to cross the southern Peninsula and cause heavy rains and arid destructive.
The deltas of Godawari, Krishna and Cauvery are the main targets. Sunderbans Delta and Bangladesh also suffer from these cyclones.
Q. 23. What are Natural Hazards and Disasters?
Ans. Due to tectonic movements, the earth is undergoing various types of changes—slow and catastrophic changes that affect humans adversely are called natural hazards. Sometimes natural hazards are called disasters–(French word des meaning Bad and aster meaning 'Star'). Disaster is a calamity or tragedy or a consequence of a hazard that causes great loss to human life and Economy.
Q. 24. Name the important disasters which occurred during last 60 years.
Ans. 12 serious disasters occurred during last 60 years. It has resulted in loss of life and property. UNO organised a disaster management conference in 1994 at Yokohama (Japan).