Q. 1. Name the major oceans of the world.
Ans. (1) The Pacific (2) The Atlantic (3) The Indian (4) The Arctic (5) Southern Ocean.
Q. 2. Name the most common features of the Oceanic land.
Ans. (1) Continental shelf (2) Submarine canyons (3) Continental slope (4) Deep sea plains. (5) Submarine ridges. (6) Ocean deeps.
Q. 3. Name some important Submarine canyons.
Ans. (1) Oceanographer Canyon. (2) Indus Canyon. (3) Berring Canyon.
Q . 4. What is Hydrosphere ?
Ans. The part of earth submerged under water.
Q. 5. Why is earth called a watery planet or ‘blue planet’ ?
Ans. Due to excess of water.
Q. 6. Which hemisphere is called water hemisphere ?
Ans. Southern Hemisphere.
Q. 7. Which instrument records the depth of oceans ?
Ans. Sonic depth record (Echo sound recording method).
Q. 8. What are economic advantages of shelves ?
Ans. These are rich fishing grounds. These are sources of oil and gas; sand and gravel.
Q. 9. What is abyssal plain ? What is its area ?
Ans. Deep sea plain. About 77% area of the oceans.
Q. 10. Name an important submarine ridge.
Ans. Mid-Atlantic ridge.
Q. 11. What is an ocean trench ?
Ans. A long, narrow, steep sided depression.
Q. 12. Name two important trenches.
Ans. Mariana trench, Kurile trench.
Q. 13. How many ocean deeps are there in the oceans ?
Ans. 57 deeps.
Q. 14. Which is the largest ocean ?
Ans. Pacific ocean.
Q. 15. What is continental Margin ?
Ans. It is the margin of each continent occupied by shallow seas and gulfs.
Q. 16. What do you understand by Hydrosphere ?
Ans. Hydrosphere: The part of the earth submerged by oceans and seas is known as Hydrosphere. The vast oceans cover an area of about 361 million sq. kms. which is 71% of the total area of the earth surface. Many scientists called the earth as a ‘Watery Planet’. Nearly 61% of the northern hemisphere and 81% of the southern hemisphere is covered by water. The southern hemisphere is known as ‘Water hemisphere’ due to excess of water. The distribution of land and water is Antipodal on the earth. The Arctic ocean surrounds the north pole and the Antarctica continent encircles the south pole.
Q. 17. What do you mean by Antipodal position ?
Ans. The distribution of land and water on the globe is antipodal. Each continent is located diametrically opposite to an ocean. If there is land in one part of the globe, there is water opposite to it on the other side of the earth. For example Arctic Ocean is opposite to Antarctica continent. Europe and Africa are antipodal to Pacific Ocean, while North America is antipodal to Indian Ocean.
Q. 18. Explain the characteristics and formation of submarine canyons.
Ans. Submarine Canyons. Narrow deep ‘V’ shaped valleys cut deep into the continental shelf and slope are called submarine canyons. These occur close to the river mouths around all the coasts of the world such as river Hudson, Mississippi, Indus, Ganges and Congo. There are about 102 submarine canyons in this world.
Types of Canyons : There are three types of canyons :
1. Small gorges found on the shelf and slope such as oceanographer canyon in new England region.
2. Canyons which begin at the mouth of the river and extend over the shelf such as the canyons of Mississippi river.
3. Deep dissected canyons such as along the coast of California.
Origin: The submarine canyons have been formed by different aerial processes and submarine processes. (1) By a rise or fall of sea level in the Pleistocene period. (2) Canyons are river-cut valleys which have been submerged due to down faulting. (3) Marine erosion has formed the canyons at great depth. (4) Erosion by Turbidity currents along the edge of the shelf has resulted in the formation of canyons.
Q. 19. What do you mean by continental shelf ?
Ans. Continental shelf is a shallow zone around a continent with an average depth of 150 to 200 metres. It is a shallow platform submerged under water. In fact, continental shelf is an extension of continents.
Q. 20. Which is the deepest place in the oceans in the world ?
Ans. The deepest place in the world lies near Guam islands in Mariana Trench. Its depth is 11022 metres. If the Mt. Everest were to be submerged in this trench, its peak will still remain 2 km below the sea level.
Q. 21. List the various direct and indirect uses of ocean to man.
Ans. Direct uses :
(i) Oceans are infinite storehouse of fish.
(ii) Oceans are storehouse of minerals.
(iii) Oceans provide the cheapest means of transportation.
Indirect uses :
(i) Oceans control the climate.
(ii) Oceans can be used to produce Tidal power and Geo-Thermal energy.
Q. 22. Why is Indian Ocean considered half ocean ?
Ans. Atlantic Ocean and Pacific Ocean open out both northward and southward. Both are balanced along the equator. But Indian Ocean is blocked on the North by Asia. In fact it extends only southward. Therefore it is considered half ocean.