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NIOS Class 12 Geography Chapter 8 Ocean: Submarine Relief And Water Circulation
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Ocean: Submarine Relief And Water Circulation
TEXTUAL QUESTION & ANSWER
INTEXT QUESTION 8.1
Q.1. Fill in the blanks:
(i) The four oceans are:
Ans. (a) Pacific Ocean.
(b) Atlantic Ocean.
(c) Indian Ocean.
(d) Arctic Ocean.
(ii) The four major subdivisions of ocean basins are:
Ans. (a) Continental shelf.
(b) Continental slope.
(c) Abyssal plains.
(d) Ocean deeps.
(iii) The submerged portion of the continent is called.
Ans. The continental shelf.
(iv) The two main types of sediments deposited in the abyssal plains are.
Ans. (a) Oozes.
(b) Red clay.
(v) A long narrow steep-sided depression on the ocean floor is called:
Ans. Submarine trench.
(vi) A submerged volcano with sharp top is called.
(vii) ________trench in the Pacific Ocean is the deepest known part of the ocean.
Ans. The Mariana.
Q.2. Tick (✓) the correct ending:
(i) The boundary between the continental shelf and ocean floor is always marked by:
(a) continental slope.
(b) abyssal plain.
Ans. (a) continental slope.
(ii) The best fishing grounds in the world are located in:
(a) continental shelves.
(b) abyssal plains.
(c) Submarine trenches.
(d) Ocean deeps.
Ans. (a) continental shelves.
Q.3. Write true against the correct statements and false against the wrong.
(i) A submerged volcano with a flat top is called seamount.
(ii) Oozes are formed by non-living things.
(iii) Submarine ridge is continuous chain of mountains.
Ans. (iii) True.
INTEXT QUESTIONS 8.2
Q.1. Define the term salinity.
Ans. Salinity is the weight in grams of solid material left after the evaporation of 1000 grams of sea water.
Q.2. When 1000 gm. of water from the Great Salt Lake is evaporated, 250 gm. of salt remains. What is the salinity of Great Salt Lake?
Q.3. Fill in the blanks:
(a) Solar radiation is ________in quatorial region on in the polar region.
Ans. maximum, minimum.
(b) The average salinity of sea water is _________.
(c) Enclosed seas are the areas of _________ salinity.
INTEXT QUESTIONS 8.3
Q.1. Choose the correct alternative for the following statements:
(i) The source of most waves on the sea surface is ________.
(d) density difference.
Ans. (a) winds.
(ii) The length of time for one crest of a wave to follow another crest past is called the wave_______.
Ans. (c) period.
(iii) The time between a high tide and a low tide is about __________.
(a) 6 hrs, 13 minutes.
(b) 12 hrs.
(c) 24 hrs.
(d) 24 hrs. 50 minute.
Ans. (a) 6 hrs. 13 minutes.
Q.2. Define tide.
Ans. Periodic change in the elevation of the ocean surface at a particular place.
Q.3. Define wave length.
Ans. The horizontal distance between two crests and two throughs.
Q.4. If the first high tide occurred at 9.00 a.m. on the day, when will the first high tide most likely to occur the next day?
Ans. 9.51 A.M.
INTEXT QUESTIONS 8.4
Q.1. Study the map given below. Each current in the map is shown by a number. Write the name of the corresponding ocean current against the number given below. Also complete the key of the map by writing appropriate words.
Ans. Warm Currents: 1. Okhotsk, 3. Californian Current, 5. Counter Equatorial Current, 7. East Australia Current, 9. Peru Current, 11. West Wind Drift, 13. Benguela Current, 15. Canaries Current, 17. East Green Land Current, 19. Agulhas Current.
Cold Currents: 2. North Pacific Current, 4. North Equatorial Current, 6. South Equatorial Current, 8. West Wind Drift, 10. Falkland Current, 12. Brazil Current, 14. North Equatorial Current, 16. Norwegian Current, 18. Labrador Current, 20. West Australian Current.
Q.2. The warm current which flows off the east coast of South East Africa is called the:
(i) Benguela Current.
(ii) Mozambique Current.
(iii) Canaries Current.
(iv) West Wind Drift.
Ans. (ii) Mozambique Current.
Q.3. Which one of the following statements is not true:
(i) Ocean currents sometime caused fog.
(ii) The distribution of fishes is often influenced by ocean currents.
(iii) Ocean current can influence coastal temperature.
(iv) Warm water wells up along a coast from which an ocean current moves.
Ans. (iv) Warm water wells up along a coast from which an ocean current moves.
INTEXT QUESTIOS 8.5
Q.1. Which one of the following statements is not true?
(a) Oceans control the distribution of pressure in the upper atmosphere.
(b) Oceans receive large amount of solar energy in seasons of excessive insolation and pay them back in season of short supply.
(c) Ocean currents help to redistribute heat over thousands of kilometres.
(d) Oceans provide natural highways but are a big hindrance to international trade.
(e) Energy due to the rise and fall of sea water is called geothermal energy.
Ans. (a), (d) and (e).