Question 1

Question 1Assertion (A): Oyashio is a cold ocean current.Reason (R): The water of Oyashio current form probably the richest fishery in the world.Both A and R are true and R is the correct explanation of A.Both A and R are true and R is not the correct explanation of A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true and R is not the correct explanation of A.Explanation — The Oyashio is indeed a cold ocean current that flows along the eastern coast of Russia and Japan. It brings nutrient-rich cold water, which supports the growth of plankton and results in highly productive fishing grounds. However, the richness of the fishery is a result of the nutrients and mixing of currents, not simply because the Oyashio is cold. Therefore, while both statements are true, the reason does not directly explain the assertion.

Question 2

Question 6What is Gulf Stream famous for?

Accepted Answer

The Gulf Stream is the largest of the western boundary currents of the North Atlantic Ocean. It affects the temperature of east coast of North America and west coast of Europe. Without this warm current, UK and other places in Europe would be as cold as Canada at the same latitude.It forms one of the largest fishing area at Newfoundland where it meets Labrador current.

Question 3

Question 7Name a few minor currents of the world.

Accepted Answer

A few minor currents of the world are:Canary Current(cold)Brazil Current(warm)South Atlantic Drift(cold)Falkland Current (cold)Benguela Current (cold)Tsushima current(warm)

Question 4

Question 8What effect do the ocean currents have on the climate of a place?

Accepted Answer

Ocean currents closely affect factors, like temperature, pressure, winds and precipitation, that decide the climate of a place. Following are the effects of current on the climate of a place:Wind passing over the warm current pick up the moisture and bring rain to the adjoining areas. For example, British Columbia, British Isles and Japan get extra rain because of warm current. Eastern margins of Australia and Africa have heavy rainfall.Winds passing over cold currents do not rain. For example, Kalahari and Atacama desert are drier because of cold currents.The cold current bring elongated winter season. For example, Labrador currents bring nearly nine months of winter and bad weather in Labrador.The eastern part of ocean in lower latitudes record relatively low temperature making the climate cold and foggy.

Question 5

Question 9What are the effects of tides?

Accepted Answer

The effects of tides are:Tides help to remove the debris from the seashore.Strong tidal currents help ships to enter in shallow harbours, e.g., KolkataIn certain harbours tidal basins are constructed to store tidal water, e.g., London harbour.Tidal energy can be harnessed to generate electricity, e.g., UK and Australia.Tides help in producing salt in the coastal area as water is collected/flooded by high tide in the low lying areas.Tides govern the schedule of fishermen. They sail out and in with the tide.In cold countries, tides prevent the ports from getting frozen as they keep coastal waters in constant motion.Strong tidal waves help rivers in building their own flood plains, e.g., Thames in England.The sea creatures which are attached to rocks depend on tides to bring their food along with the tidal waters.

Question 6

Question 10What is the time difference between two tides?

Accepted Answer

The time difference between two tides is 12 hours and 26 minutes.This occurs because of the revolution of the Moon around the Earth in the same direction as Earth's rotation (West to East). If the Moon had remained stationary time difference between two tides would have been 24 hours.

Question 7

Question 11Explain by reference to actual examples the effects of ocean currents on climate, economy and fishing.

Accepted Answer

Some examples of the effects of ocean currents on climate, economy and fishing are as follows:Newfoundland where Gulf Stream and Labrador current (cold and warm currents) meet is very important fishing ground as it provides ideal temperature conditions for the life of ﬁsh.In 1912 Titanic, the largest ship of its time, off Newfoundland where Labrador Current (cold) meets Gulf Stream (warm), struck a huge iceberg and took less than 3 hours to sink. It happened due to extreme fog.Winds passing over the warm currents pick up the moisture and give extra rains to British Columbia, British Isles, Japan and Queensland. Eastern margins of Australia and Africa have heavy rainfall due to the same reason.Winds passing over cold currents do not rain at all, e.g., Kalahari and Atacama deserts are much drier because of cold currents.The cold Labrador currents bring nearly nine months of winter and bad weather conditions prevailing over the rest of the year in Labrador and Eastern Newfoundland.North Atlantic drift (warm current) has moderating effect on climate of western Europe.Warm water of Tsushima current keeps the west coast of Japan warm.Kuroshio current keeps the eastern coast of Japan warm.Oyashio current has impact on the climate of the Russia Far East i.e. Kamchatka and Chukotka. It also forms one of the richest fishery in the world.

Question 8

Question 12How are tides caused?

Accepted Answer

Following are the causes of tides:Gravitational Force — The gravitational pull of Moon and the Sun cause the tides. The influence of moon is more due to its proximity to earth.Influence of the Moon — The Earth is pulled towards the Moon more than the water on the other side of earth therefore, water lags behind and rises up on the side facing the moon, forming high tide.The rotation of the Earth — It results in every meridian coming into the position of two high tides and two low tides nearly every 24 hours. Since Moon travels in its orbits in the same direction as the Earth is rotating it takes about 24 hours and 52 minutes or one lunar day for the sequence of two high and two low tides to be completed.

Question 9

Question 13Name the two movements in the ocean.

Accepted Answer

The two movements in the Ocean are:Horizontal (ocean current)Vertical (the rising and sinking of water)

Question 10

Question 14Name any two warm currents of the Atlantic Ocean.

Accepted Answer

Two warm currents of the Atlantic Ocean are:Brazil CurrentGulf Stream Current

Question 11

Question 5The time difference between two tides is approximately 12 hours 26 minutes.

Accepted Answer

The time difference between two tides is approximately 12 hours 26 minutes because the revolution of the Moon around the Earth is in the same direction as Earth's rotation, i.e., from West to East. If the Moon had remained stationary then each place on Earth's surface would have come under its influence after 24 hours and each tide would have occurred at the interval of 24 hours.

Question 12

Question 2Neap Tide

Accepted Answer

When the Sun, Earth and Moon are not in a straight line, the Sun and Moon are not exerting combined force, i.e., they are not ‘pulling’ together and the gravitational pull is much less. At half moon, that is, when the Sun and Moon are ‘pulling’ at right angles, the force exerted is at its least and the difference between high and low tide is not large. These tides are called Neap Tides.

Question 13

Question 3Gulf Stream

Accepted Answer

The Gulf Stream is the largest of the western boundary currents of the North Atlantic Ocean. This is a warm water current which originates in the Gulf of Mexico around 20° N and moves in a north- easterly direction along the eastern coast of North America. It influences the climate of eastern coast of North America. Water within the current is usually warm and blue, often depleted of nutrients and incapable of supporting much life.

Question 14

Question 4Labrador Current

Accepted Answer

The Labrador, an important cold water current of the North Atlantic Ocean, has its origin in the Arctic Ocean which flows from North to South between the Greenland and the Baffin Islands (Davis Strait). Passing southward, it merges with the Gulf Stream near Newfoundland. The average speed of the current is about 28 km per day. It brings down huge icebergs from the Arctic Ocean to the eastern coast of Canada which are hazardous to navigation.

Tides and Ocean Currents

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