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C) Deep sea plain

B) Arctic ocean

Continental shelf: The border zone between land and sea with depth up to 200 m is called the continental shelf.

1. The continental shelf with depth up to 200 mts occupied about 7.6% of the oceans area. 

2. It is the border zone between land and sea. 

3. Continental shelf is most important to 

a) Fish wealth is more in this region. 

b) Rock petroleum, natural gas are found here. 

c) Building sea port is possible here.

(A) Both A and R are correct and R explains A.

Continental Shelf:

1. A shallow and gently sloping platform extending out from the adjoining continental land mass into the sea is called Continental Shelf.

2. It is almost a uniform zone of sea bed with a gentle gradient.

3. They are shallower, thus enables sunlight to penetrate through the water. This encourages abundant growth of grass, sea weeds and plankton. Hence these zones become the richest . fishing grounds in the world,

e.g. The Grand Banks of Newfoundland. 

4. The continental shelves have extensive deposits of minerals and mineral fuels. Hence, this zone becomes accessible for oil drilling and mining activities.

e.g. Mumbai High in Arabian Sea.

Continental Slope: 

1. A steep slope which descends from the edge of the continental shelf to the deep ocean- bed is called continental slope. 

2. It forms a boundary between the Continental Crust and the oceanic crust.

3. This zone is free from deposits as they are steep. The most important characteristic of . continental slope is the presence of deep canyons and trenches.

4. Due to the low penetration of sunlight, the slope has nearly freezing temperature. Hence aquatic life has very slow rate of metabolism.

An arc-shaped depression in the deep ocean floor is called ocean deep or trench. These are the deepest parts of the ocean floor. Ocean trenches are produced by the subduction of oceanic crust under continental crust. They resemble step sided valleys or canyons on the land. Trenches or deeps are generally parallel of the coasts facing mountains and along the islands. Great earthquakes and tsunamis generally take birth in this region.

World’s deepest trench is Mariana

The challenger deep in the Marina trench near the Philippine Islands in the Pacific Ocean is the deepest part of the Ocean floor (10,898 meters).

Stream: The ocean current that flows speedily is called a stream.

Correct Answer is : (d) Ocean trenches.

Transpiration: A considerable proportion of water vapor is released into the atmosphere by plants, through a process called ‘Transpiration’.

Salinity is the amount of sodium in the oceanic water. It is 35%.

1. Most of the deepest trenches are located close to the continents.
2. A line joining points on the sea bed at an equal vertical distance beneath the surface is called ‘Isobath’ or ‘Depth contour’.
3. Over millions of years rain, rivers and streams have washed over rocks containing the compound Sodium Chloride (NaCl) and carried them into the sea.
4. The total content of dissolved salts in seawater is called salinity.
5. Salinity is usually expressed as parts per thousand or ppt.

(a) Continental shelf-Continental slope-Sea plainSea trench.

Hydrological cycle: Water undergoes a cycle from oceans to land and then from land to the oceans. This cyclic process is called the hydrological cycle.

The cyclic process in which water undergoing a cycle from oceans to land and land to oceans is called the hydrological cycle.

Oceanic Deeps (or) Trenches: The large narrow trenches that plunge as great ocean deeps to a depth of 6000 m are called oceanic depths or trenches.

a) Ocean trenches are the deepest parts of the ocean floor. 

b) Relief features of the oceans are Trenches, Deep sea plains and Ridges. 

c) True. 

d) Temperature of ocean water varies from place to place across the globe.

There are six stages of water cycle. 

They are – 

a) Evaporation : The process by which water changes from liquid to gas by using sun’s energy is called evaporation. Land, lakes, rivers and oceans send up a steady of water vapour and plants lose water to the air through transpiration. 

b) Transportation : The movement of water through the atmosphere specifically from over the ocean to land in the form of clouds is transportation. Clouds are propelled from one place to another by either the jet stream, surfaces based circulations like land and sea breezes or other mechanisms. 

c) Condensation : The transported water vapour eventually condenses forming tiny droplets and clouds. 

d) Precipitation :

• The primary mechanism for transporting water from the atmosphere to the surface of the earth is precipitation. 
• When the clouds meet cool air over land precipitation is triggered in the form of rain, sleet or snow and thus water reaches the ground. 

e) Run off:

• Most of the water which returns to land flows down hills as run off. 
• Some of it penetrates into the land and charges ground water while the rest, as river flow, returns to the oceans where it evaporates.

f) Groundwater : Under special circumstances, groundwater can even flow upward in artesian wells.

The highest temperature is recorded in the Inland Seas. The temperature is the highest in the Red Sea, i.e., 38°C.

Transportation: The movement of water through the atmosphere specifically from over the ocean to land in the form of clouds is called transportation.

The four major parts of the ocean floor are :

1. The Continental Shelf 

2. The Continental slope 

3. The Deep sea plain and 

4. The Ocean deep.

The ocean basins are characterised by the following major relief features: 

• Continental shelf
• Continental slope
• Continental rise
• Deep sea plain or Abyssal plain 
• Oceanic deep
• Oceanic ridge.

(B) both A and R are correct but R does not explain A.

The major submarine relief features are 

1. The Continental slope 

2. The Continental Slope 

3. The Deep Sea Plains 

4. The Ocean Deep.

• Contrary to our expectations, most of the deepest trenches are not located in the midst of oceans. 
• They are found more close to the continents. 
• They are very significant in the study of plate movements.

• Yes. I think the rain we get is related to hydrological cycle. 
• It is a part of precipitation, which constitutes in hydrological cycle. 
• It is the fourth stage of the six stages in hydrological cycle.

• Continental shelf of ocean floor is suitable for building seaport. 
• The continental shelf with depth upto 200 m.
• It is the border zone between land and sea.
• It will be useful in anchoring the ships.

(b) Survival

Water table is a level below the ground, where water is found collected beneath the Earth’s surface

The biotic and abiotic resources found in the oceanic water and at the bottoms are called marine resources. The ocean’s resources play a vital role in sustaining the needs of society. A diverse array of marine organisms is used for food, medicine, cosmetics, and a wealth of • industrial applications. The world’s demand for energy, minerals and water have become increasingly dependent on non-living marine resources.

(c) Hydrosphere

The Earth is called the Blue Planet.

There are five oceans on the earth.

They are:

1. The Pacific Ocean

2. The Atlantic Ocean

3. The Indian Ocean

4. The Southern Ocean and

5. The Arctic Ocean.

There are two types current of the North Atlantic Ocean.

1. Warm current: Antilles current, Florida current Gulf stream Norwegian current. 

2. Cold currents: There are three cold currents, canary current, East Greenland Current and Labrador Current.

• Oceans are international highways hence facilitate imports and exports among different countries. 
• Oceans are sources of rainfall. Much of the evaporation takes place from oceans and comes to earth in the form of rainfall. 
• They are the source of sea food which is staple food for some people. 
• Oceans are warehouses of minerals like Petroleum, Natural Gas, Manganese etc., which are necessary for industrial development.

Hence life of the man is impossible without oceans.

1. The general movement of a mass of water in a fairly defined direction over great distance is called ocean current.

2.Causes that lead to the formation of ocean currents are : 

a) Centrifuge! Force : 

The centrifugal force at the equator is greater than that at the poles. The variation of these forces makes the equatorial water to move towards the poles. 

b) Effect of Winds : 

The stresses due to wind and the wind movement modifies the the theoretical direction of currents. Due to the frictional gliding of winds water is dragged along the wind direction. Thus a 50 miles per hour wind will produce a current whose velocity is 0.75 miles per hour.

c) Effect of Precipitation :

Since the level of sea is higher water moves north and south from the equator. 

d) Effect of Solar Energy :

Heating by solar energy causes the water to expand near the equator. Hence near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope. 

e) Salinity, density differences, melting of ice also affect the ocean currents

Throughout the history man is directly or indirectly influenced by the oceans. Oceans have many uses for man. 

1. Since early times man depended on oceans for food. Oceans are store houses for fish.

2. Ocean is a source of valuable minerals. Chlorine, Fluorine, Bromine and Iodine are found in oceans. 

3. Rock petroleum, Natural gas are extracted under oceans. 

4. Oceans are mined for mineral salt, sand, gravel manganese, copper, nickel etc. 

5. Some biological products of oceans are also commercially used. For example, pearls taken from oysters are used in jewellery. 

6. Shells and corals have been widely used as source of building material. 

7. Tides and waves are renewable energy sources. 

8. Oceans are sources of rainfall. 

9. Oceans act as international highways. 

10. Many great civilizations such as Greek civilization, Rome civilization all flourished on the banks of rivers and oceans.

There are many more uses for man from oceans. Hence we can say without oceans life of man is impossible.

The Earth is also called the Blue planet, as it holds water in abundance and thus stands unique among all other planets.

(a) Labrador Current originates from the Arctic ocean along the coast of Labrador and passes touching Newfoundland continuing southwards along the coast of Nova Scotia. It is joined by West Greenland and Baffin Island Current. It meets the warm Gulf Stream Current at the Grand Banks, making this region the famous fishing bank. 

(b) The Kuroshio current – is a strong western boundary current in the western north Pacific Ocean. It begins off the east coast of Taiwan and flows north-eastward past Japan, where it merges with the easterly drift of the North Pacific Current. It is analogous to the Gulf Stream in the Atlantic Ocean, transporting warm, tropical water northward towards the polar region. It is also sometimes known as the Black Stream — the English translation of Kuroshio, and an allusion to the deep blue of its water — and also as the Japan Current.

(c) Oyashio Current is a cold current colliding with warm Kuroshio current along the eastern coast of Japan. It originates in the Arctic ocean and passes through the Bering strait proceeding towards south. 

(d) The North Atlantic Drift : It is the eastern extension of Gulf Stream to Europe as a warm current.

Temperature of ocean water has much importance. If affects the climate of coastal areas and it is important for marine plans and animals.The average range of the temperature of ocean water is 12’C. But it is varies from place to place and from time to time. This is due to the regional variation of solar energy, prevailing winds, location of their extent etc.

The distribution of temperature in the oceans varies much owing to the latitude, depth and salinity. It is also much influenced by the prevailing winds, currents and nearness to land masses. The main source of heat for ocean water is the sun. The mechanism of heating and cooling ocean water is quite different from that of land. Ocean water warms up and cools down more slowly the diurnal range and annual range of temperature of ocean water is not significant. The temperature of the ocean water varies from place to place. 

Distribution of temperature of Ocean water:

The distribution of temperature of ocean water is of two types. They are:

1. Horizontal distribution of temperature of ocean water. 

2. Vertical distribution of temperature of ocean water.

a. Horizontal distribution of temperature of Ocean water: The temperature of ocean water decreases from the equator towards the poles. This is known as horizontal distribution of temperature. 

b. Vertical Distribution of Temperature: The decrease in temperature from the ocean surface with increasing depth is known as vertical distribution of temperature.

The distribution of temperature of ocean water is of two types. They are:

1. Horizontal distribution of temperature of ocean water. 

2. Vertical distribution of temperature of ocean water.

The Indian Monsoon current refers to the seasonally varying ocean current regime found in the tropical regions of the nothern Indian ocean. The seasonally reversing open ocean currents that pass through south of India are referred to as the winter monsoon current and the summer monsoon current, alternately the north-east monsoon current and the southwest monsoon current. India receives rainfall due to these currents.

1. Ocean currents may be classified on the basis of temperature as – 

(a) Cold Currents 

(b) Warm Currents 

2. Ocean currents may be classified on the basis of speed as – 

(a) a stream 

(b) a drift

Most of the Creek area gets submerged due to high tide and at times of low tide, the creek emerges out along with poisonous creatures like snakes, scorpions.

The continents and oceans are however, not evenly distributed in the northern and the southern hemispheres. The northern hemisphere holds 61% of land whereas the southern hemisphere holds 81% of water. It is because of this pattern of land and water distribution, the northern hemisphere is called as the land hemisphere and the southern hemisphere is called the water hemisphere.