15- Some Natural Phenomena | Part 2 | Science | NCERT | Class 8

Hello students, in this blog you can find important summary notes from the Chapter 15, Science , NCERT Book of Class 8. These notes can be used for preparation of various school Competitive Exams, Olympiads and also developing strong Fundamentals.

23. Lightning can strike telephone cords, electrical wires and metal pipes and hence we should stay away from these items.

24. Bathing should be avoided during thunderstorms to avoid contact with
running water.

25. Electrical appliances like computers, TVs, etc., should be unplugged.

26. Lightning Conductor is a device used to protect buildings from the effect of lightning. It provides easy route for the transfer of electric charge to the ground.

27. If a thunderstorm occurs there is always a possibility of lightning and cyclones accompanying it.

28. Earthquake is one of the natural phenomenas which cannot be predicted accurately.

29. Two major earthquakes occurred in India:
• on 8 October 2005 in Uri and Tangdhar towns of North Kashmir.
• on 26 January 2001 in Bhuj district of Gujarat.

30. Earthquake : An earthquake is a sudden shaking or trembling of the earth which lasts for a very short time. It is caused by a disturbance deep inside the earth’s crust.

31. Earthquakes can cause floods, landslides and tsunamis.

32. A major tsunami occurred in the Indian Ocean on 26 December 2004.

33. Crust : The tremors are caused by the disturbance deep down inside the uppermost layer of the earth called the crust.

34. Plate : The outermost layer of the earth is not in one piece, but fragmented. Each fragment is called a plate.

35. When the plates brush past one another, or a plate goes under another due to collision, they cause disturbance in the earth’s crust. It is this disturbance that shows up as an earthquake on its surface.

36. Tremors on the earth can also be caused when :
• a volcano erupts
meteor hits the earth
• underground nuclear explosion is carried out

37. Seismic or Fault zones : As earthquakes are caused by the movement of plates, the boundaries of the plates are the weak zones
where earthquakes are more likely to occur. The weak zones are also known as seismic or fault zones.

38. In India, the areas most threatened for earthquake are :
Kashmir
Western and Central Himalayas
whole of North-East
Rann of Kutch
Rajasthan
the Indo–Gangetic Plane some areas of South India

39. Richter scale : The power of an earthquake is expressed in terms of a magnitude on a scale called the Richter scale.

40. Really destructive earthquakes have magnitudes higher than 7 on the Richter scale.

41. Seismic waves : The tremors produce waves on the surface of the earth, called seismic waves.

42. Seismograph : The seismic waves are recorded by an instrument called the seismograph.

43. Richter scale is not linear, it means an earthquake of magnitude 6 has thousand times more destructive energy than an earthquake of magnitude 4.

44. The buildings in seismic zones should be so designed that they can withstand major tremors.

45. In highly seismic areas, the use of light materials like mud or timber is better than using heavy construction material.

46. Be careful with objects (like cupboards, shelves) so that in the event of an earthquake, they do not fall on people.

47. Some buildings may catch fire due to an earthquake, hence it is necessary that all buildings and especially tall buildings, have ready to use fire fighting equipment.

48. In the event that an earthquake does strike, take the following steps to protect yourself.
(a) Indoors
• Take shelter under a table and stay until the shaking stops.
• Stay away from tall and heavy objects as it may fall on you.
• If you are in bed, do not get up and protect your head with a pillow.
(b) Outdoors
• Find a clear spot, away from buildings, trees and overhead power lines and drop to the ground.
• If you are in a car or a bus, do not come out. Drive slowly to a clear spot and do not come out till the tremors stop.

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To Read Part 1 : Click Here

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