Class 9 Social Science II Chapter 02 The Signature of Time - Questions and Answers

Study Notes for Class 9th Social Science II (English Medium) കാലത്തിന്റെ കൈയ്യൊപ്പുകൾ | Text Books Solution Geography (English Medium) Geography: Chapter 02 The Signature of Time

ഈ അദ്ധ്യായം Malayalam Medium Notes Click here
Social Science II Questions and Answers in English

The Signature of Time -Textual Questions and Answers & Model Questions
1. You have recognized from the below map that the earthquake zones, volcanoes, and mountain ranges overlap. Why is this so?
- The Earth surface is composed of many individual plates (lithospheric plates) that move and interact, constantly changing and reshaping Earth's outer layer.
- Earthquake zones, volcanoes and distribution of mountains occur because of the movement of lithospheric plates at the plate boundaries.
- That is why the earthquake zones, volcanoes, and mountain ranges overlap

 2. What is the difference between the seismograph and the Richter scale?
- Seismograph -Instrument used to record the seismic waves
- Richter Scale -The scale used to measure the intensity of earthquakes

3. What is the lithosphere?
- The outermost layer of the earth, the crust, together with the upper part of the mantle is known as the lithosphere

4. What is the average thickness of the lithosphere?
- 100 KM

5. Define lithospheric plates
- The portions of the lithosphere which are several thousand kilometres wide and roughly 100 kilometres thick are called lithospheric plates

6. What is the asthenosphere?
- The part beneath the lithosphere, where the materials exist in a partially
molten state is known as the asthenosphere.

7. Make a table about the different lithospheric plates.
8. Define Magma
*Magma is a part of the mantle which remain molten due to the high
temperature at the earth’s interior and undergoes continuous convection.
This causes the movement of lithospheric plates

9. Who put forward the idea of continental drift?
- Alfred Wegener

10. Prepare a flow chart about plate margins and created landforms.


11. Which is the largest lithospheric plate?
- The Pacific plate

12.  Name the lithospheric plate which involves oceanic parts alone.
- The Pacific plate

13. Explain the difference between the Convergent margin and the Transform margins with an example.
* Convergent margin - Plates move towards each other. 
- Fold mountains and Ocean trenches are formed along the convergent margins.  
- Himalaya Mountain and Challenger Deep.
* Transform margins - Plates slide past each other
- The plate margins are fault zones. 
- The San Andreas Fault Zone in North America is an example

14. Divergent margin.
* Divergent margin - Plates move away from each other- causing the formation of Mid Oceanic ridges.
- Example -Mid-Atlantic Ridge

15. Write an example for the Fold mountain range. How it is formed?
- The Himalayas. It is formed along the convergent margins between the Indian Plate and the Eurasian Plate.

16. Identify the plate margins where the world's major fold mountains are
formed?

17. What are called subduction zones?
- If there is any difference in density between the plates along a convergent margin, the denser plate will submerge under the lighter one.
These zones are called subduction zones.
18. Write an example for the Ocean trenches that are developed in subduction zones. Identify the plates responsible for this
- The Challenger Deep in the Pacific Ocean
- Philippine plates are responsible for Challenger deep in the Pacific Ocean
where the Pacific plate is subducting beneath the Philippine plate.

19. How the Mid-Atlantic Ridge formed?
- The Mid-Atlantic Ridge has been formed as a result of the divergence of
the plate margin between the African Plate and the South American
plate.

20. What are Mid-Oceanic ridges?
- Magma comes out through the gap formed due to the divergence of plates and solidifies to form mountains. These types of mountains are known as Mid-Oceanic ridges.

21. How fault zones are formed? Write an example
- Landforms are not generally created along the margins where the plates slide past each other. But such margins are fault zones.
- The San Andreas Fault Zone in North America

22. The plate margins are generally vulnerable to earthquakes, volcanoes,
and faults. Why?
- Because the plate margins are weaker than other areas

23. How did the Challenger Deep, the deepest part of the Earth's surface, form?
- If there is any difference in density between the plates along a convergent margin, the denser plate submerges under the lighter one. 
- Subduction zones are formed in regions where the denser plate will submerge under the lighter one. 
- The Challenger Deep in the Pacific Ocean is an example of Ocean trenches developed in Subduction zones

24. Make a flow chart related to Earth Movements

25. What is an earthquake?/How do earthquakes occur?
- Rocks in the deeper part of the earth undergo displacement and faults due to plate movements and other causes.
- Under such situations, severe pressure is exerted on the earth's lithosphere.
- Seismic waves are generated
- These waves create tremors on the earth's surface. 
- These tremors are experienced by us as an earthquake.

26. What is the difference between uplift and subsidence?
- As a result of the earth's movements, some regions on the earth's crust are either raised or lowered.
- Raising of the crustal portions are called uplift and lowering of the crust are called subsidence.

27. What are the reasons for the occurrence of earthquakes?
- Plate movements
- Faulting
- Collapse of the roofs of mines
- Pressure in reservoirs
- Volcanic eruptions

28. Define the Focus and Epicentre of an earthquake
- The deep points inside the earth where the earthquake occurs are known as focus.
- The point vertically above it on the earth's surface is known as epicentre.

29. What are the different types of seismic waves?
- Primary waves, secondary waves and surface waves.

30. Which one of the seismic waves causes maximum destruction on the earth's surface?
- The surface waves

31. What is the scale used to measure the intensity of earthquakes?
- The Richter scale

32. Which is an instrument used for recording seismic waves?
- Seismograph

33. What are tsunamis?
- Tremor waves originating due to earthquakes, volcanic eruptions, meteor impact. etc. in the ocean floor generates huge sea waves rising to several metres. Such waves are called Tsunamis

34. What is the term meaning of the Japanese word ‘Tsunami’?
- Harbour waves

35. Write the impact of the Tsunami.
- The coastal regions are mainly affected by the disastrous effects of Tsunamis.
- The visible impact of a Tsunami is the damage and destruction to life
and property caused by it

36. Kerala coast was also affected by Tsunami on 26 December 2004. What
was the reason for that?
- It was caused by the intense earthquake waves that originated from Sumatra in the Indian Ocean

37. What is the use of Tsunami surveillance and warning systems?
- Aims to identify the areas prone to Tsunami
- To extend the warning to the coastal areas so as to prevent loss of life.
38. Name the real-time Tsunami monitoring system introduced by NOAA.
- Dart (Deep-ocean Assessment and Reporting of Tsunami)

39. Write the full form of NOAA
- National Oceanic and Atmospheric Administration

40. What measures can we take to mitigate the impact of Tsunamis?
- Recession in sea level may be an indicator of a Tsunami. If so, move on to
safer locations.
- Take official warnings seriously.
- Don’t arrive at the self-conclusion that the dangerous situation is over, wait for an official declaration.
- Once trapped by Tsunami waves try to escape by holding any floating materials firmly.

41.  How volcanoes are formed?
- Volcanoes are formed by molten rock material coming out through the fissures along the plate margins.

42. What do you mean by 'the Pacific Ring of Fire?
- Nearly 80% of the world's volcanoes are situated around the Pacific Ocean. This zone containing more than 452 volcanoes is known as 'the Pacific Ring of Fire.

43. How are volcanoes beneficial to mankind?
- The soil formed by the weathering of lava rocks is fertile.
Example: the black soil of the Deccan plateau.
- Volcanic ash is good manure.
- Geysers are formed in many volcanic regions. Such regions are being developed as tourist centres.
Example: The Old Faithful Geyser, Yellow Stone National Park - North
America.

44. Is there any chance of Volcanic eruptions in Kerala?
- Located at the extreme southern tip of the Indian subcontinent, Kerala lies near the centre of the Indian Plate;  the state is subject to comparatively little seismic or volcanic activity.
 
Practice Questions and Answers
45. Prepare a note on plate movement based on the following indicators.
i. The force that causes the plate movement.
ii. The speed of the lithospheric plate movement.
Answer:
 - The lithospheric plates are situated above the asthenosphere.
- Magma, which is a part of the mantle remain molten due to the high temperature at the earth’s interior and undergoes continuous convection.
- The plates move at a speed of 2 centimetres to 12 centimetres a year. The speed of this movement has not always been uniform. 580 million years ago, the speed of motion was 30 cm per year.
(For any 2 factor that influences the speed )

46. Identify the false statement
1. The Mid Oceanic ridges are formed in divergent margins.
2. Fault zones are formed in Transform margins.
3. Ocean trenches are formed in convergent margins.
4. Fold mountains are formed along divergent margins.
Answer:
Fold mountains are formed along the divergent margin.

47. Which of the following is a landform that develops due to the submergence of plates under the lighter ones?
(Fold mountains, Ocean trenches, Mid Oceanic ridges, Fault zones)
- Ocean trenches
48. Which of the following is an incorrect statement regarding lithospheric plates?
1. Situated above the asthenosphere which is in a semi-plastic state.
2. The maximum thickness is 100 km.
3. Contains both oceanic crust and continental crust.
4. Philippine plate is an example of a major plate.
Answer: Philippine plate is an example of a major plate.

49. Which of the following mountain is situated in the western boundaries of the North American plate?
(Alps, Atlas, Anties, Rockies)
- The Rockies 

50. Write any three characteristics of the lithospheric plates.
- Contains both oceanic crust and continental crust.
- It is divided into major plates and minor plates.
- The lithospheric plates are situated above the asthenosphere in a semi-plastic state.
- The plates move.

51. What is the reason for the formation of the Mid- Atlantic ridge?
- Magma comes out through the gap formed due to the divergence of the African Plate and the South American plate solidifies to form mountains. These mountains are known as the Mid-Atlantic Ridge.

52. Answer the following questions related to earthquakes:
(i) Where do earthquakes occur? 
(ii) What are the different types of seismic waves? 
(iii) Which is the most destructive seismic wave? 
Answer:
(I) Focus 
(ii) Three types – primary waves, secondary waves, and surface waves
(iii) Surface waves 

53. Answer the following questions related to the movement of plate margins.
i. Name the plate margin where plates move towards each other.
ii. Mention a landform formed in the plate margins, where plates move towards each other.
iii. Write two examples for such landforms.
Answer:
i. Convergent margins
ii. Fold mountains and Ocean trenches 
iii. The Himalaya and The Challenger Deep 

54. Select 'B' and 'C' columns, which correspond to column A.



👉Social Science II Textbook (pdf) - Click here 

ഈ ബ്ലോഗിലെ എല്ലാ പോസ്റ്റുകളും ഒരുമിച്ച് കാണാനും ആവശ്യമുള്ളവ എളുപ്പത്തിൽ തിരഞ്ഞെടുക്കാനും ഇവിടെ ക്ലിക്കുക.

PSC Solved Question Papers ---> Click here 
PSC TODAY's EXAM RESULTS ---> Click here
PSC EXAM PROGRAMME -> Click here
CURRENT AFFAIRS QUESTIONS -> Click here
PSC Degree Level Questions & Answers - Click here
PSC 10th, +2 Level Questions & Answers - Click here
PSC SHORTLISTS -> Click here
PSC RANK LISTS -> Click here
TEACHING APTITUDE TEST (K-TET, C-TET,, etc.) ---> Click here