Hydrosphere

Choose the correct option

Question 1

Hydrosphere refers to the combined mass of water :

1. in the oceans
2. rivers, streams and lakes
3. in the atmosphere
4. All of the above.

Answer

All of the above

Question 2

Ocean : 97% :: Fresh water : ...............

1. 3%
2. 2.3%
3. 0.7%
4. 0.66%

Answer

0.7%

Question 3

Underground water is found in:

1. soil
2. subsoil
3. underground streams
4. All of the above.

Answer

All of the above

Question 4

Name the oscillatory movements in water, manifested by an alternate rise and fall of the sea surface.

1. Tides
2. Waves
3. Spheres
4. Oscillations

Answer

Waves

Question 5

Apogee : Earth-moon distance ............... :: Perigee : Earth-moon distance ...............

1. maximum, minimum
2. minimum, maximum
3. equal, equal
4. All of the above.

Answer

maximum, minimum

Question 6

............... flow from the lower latitudes towards the higher latitudes.

1. Warm currents
2. Cold currents
3. Surface currents
4. Deep water currents

Answer

Warm currents

Question 7

Which amongst the following is NOT one of the causes of Ocean Currents?

1. Level of Salinity
2. Temperature
3. The Earth's Revolution
4. Planetary Winds

Answer

The Earth's Revolution

Question 8

Name the winds that blow between the Equator and the Tropics.

1. Westerlies
2. Trade Winds
3. Monsoon Winds
4. Summer Winds

Answer

Trade Winds

Question 9

What is the direction of air circulation over the oceans in the middle latitudes?

1. Cyclonic
2. Hemispherical
3. Spherical
4. Anticyclonic

Answer

Anticyclonic

Question 10

Name the warm Atlantic Ocean Current which flows from North America to Western Europe.

1. The West Atlantic Drift
2. The East Atlantic Drift
3. The North Atlantic Drift
4. The South Atlantic Drift

Answer

The North Atlantic Drift

Question 11

Which current is also known as the 'Black Stream'?

1. Atlantic current
2. Kuroshio current
3. Oyashio current
4. Newfoundland current

Answer

Kuroshio current

Question 12

Name the current that keeps ports of Europe ice-free in winters

1. North Atlantic drift
2. Labrador current
3. Canaries current
4. Florida current

Answer

North Atlantic drift

Question 13

Which currents have created one of the world's richest fishing grounds?

1. Labrador current and Gulf stream
2. Labrador current and Irminger current
3. Oyashio current and Kuroshio current
4. Both (a) and (c).

Answer

Both (a) and (c)

Question 14

Currents influence:

1. temperature
2. rainfall
3. fish population
4. all of the above.

Answer

all of the above

Short Answer Questions

Question 1

Name any two ways in which movement of ocean water takes place.

Answer

Two ways in which movement of ocean water takes place are-

1. Waves
2. Currents

Question 2

What are tides? Name one factor that causes tides.

Answer

The rise and fall of sea water due to gravitational forces of the sun and the moon are called tides.

Tides are caused by the gravitational forces of the sun and moon.

Question 3

What is the time interval between tides? Name the factors responsible for this time interval.

Answer

A particular tide centre takes 24 hours 52 minutes to come under the moon but by the time there is another tide at the opposite side of the referred tide centre and this happens after 12 hours 26 minutes.

The factors responsible for this time interval are the rotation of the earth and the rotation and revolution of the moon.

Question 4

What are Spring and Neap tides?

Answer

Very high tide is caused when the sun, the moon and the earth are almost in the same line. Such high tides are called spring tides.

On the seventh or eighth day of every fortnight of a month, the sun, the earth and the moon come in the position of quadrature. The tide producing forces of the sun and the moon work in opposite direction, with the result, a low tide occurs. Such a tide, which is lower in height than that of a normal tide, is called neap tide.

Question 5

Name two types of ocean currents based on their temperature. Give an example of each.

Answer

Two types of ocean currents based on their temperature are-

1. The Warm Currents, e.g. Gulf Stream
2. The Cold Currents, e.g. Labrador current

Question 6

For what is the Gulf Stream famous?

Answer

The Gulf Stream is a powerful warm ocean current affecting the climate of east coast of North America and west coast of Europe. It is also a potential source of renewable power generation.

Question 7

What happens when warm and cold currents meet?

Answer

The combination of warm and cold currents produces heavy fogs and creates rich fishing grounds.

Structured Questions

Question 1(a)

How are tides formed?

Answer

The tides have their origin in the gravitational forces of the sun and the moon.

When the sun, the earth and the moon are in the same line, their gravitational forces work together and high tides are formed.

When the sun and the moon are at the position of right angle with reference to the earth, the gravitational forces of the sun and the moon work against each other and hence, low tides are formed.

Question 1(b)

Differentiate between High Tides and Low Tides.

Answer

Question 1(c)

Give a reason for each of the following:

(i) There are two high and two low tides in a day.

(ii) Each day a tide is delayed by 26 minutes.

(iii) The tidal range differs from one water body to the other.

Answer

(i) Because the Earth rotates through two tidal bulges every lunar day, coastal areas experience two high and two low tides every 24 hours and 52 minutes. This occurs because the moon is revolving around the Earth in the same direction as the Earth is rotating on its axis.

(ii) Each day a tide is delayed by 26 minutes because the moon also rotates on its axis while revolving around the earth. Since the earth rotates from west to east the tide centre shifts westwards. When the tide centre completes one round, the moon's position is ahead of the tide centre by that time. This delays the tide by 26 minutes each day.

(iii) The tidal range differs from one water body to the other as tidal range is not constant but changes depending on the locations of the moon and the sun.

Question 1(d)

Draw a well labelled diagram showing the formation of spring and neap tides.

Answer

Below diagram shows the formation of spring and neap tides:

Question 2(a)

Describe the two types of ocean currents based on their temperature.

Answer

The two types of ocean currents based on their temperature are-

1. The Warm Current — These are those currents which flow from the low latitudes in Tropical Zones towards the high latitudes in the Temperate and sub-polar zones. They bring warm water into cold water areas. For example, Gulf Stream.

2. The Cold Current — These currents have a lower surface temperature and bring cold water into warm water areas. These currents flow in the high latitudes from the Polar regions towards the low latitudes in the warm Equator region. For example, Labrador current.

Question 2(b)

State any two factors responsible for causing the currents.

Answer

Two factors responsible for causing the currents are-

1. Level of Salinity
2. Temperature

Question 2(c)

Give a reason for each of the following:

(i) Warm currents produce a milder climate.

(ii) The eastern coasts of USA are comparatively cold.

(iii) The coasts of Norway are not frozen in winter whereas its adjoining coasts are frozen for most parts of the year.

Answer

(i) Warm currents produce a milder climate because warm currents tend to raise the temperature of the places where they flow.

(ii)The eastern coast of US is comparatively cold because of the cold Labrador Current.

(iii) The coasts of Norway are not frozen in winter whereas its adjoining coasts are frozen for most parts of the year on account of the influence of the warm North Atlantic Drift.

Question 2(d)

Describe one effect of each of the following three ocean currents.

(i) Labrador Current of the Atlantic Ocean.

(ii) The Kuroshio current

(iii) Oyashio Current of the Pacific Ocean.

Answer

(i) The waters of the Labrador current have a cooling effect on the Canadian Atlantic provinces and coastal New England.

(ii) The warm waters of the Kuroshio current sustain the coral reefs in the world.

(iii) Oyashio current has an important impact on the climate of the Russian Far East, mainly in Kamchatka and Chukotka.

Question 3(a)

State the origin and flow of the Gulf Stream.

Answer

Gulf Stream originates in the gulf of Mexico, exits through the Strait of Florida, and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean. At about 30°W, 40°N, it splits in two, with the northern stream crossing to northern Europe and the southern stream recirculating off West Africa.

Question 3(b)

What is the effect of Gulf Stream on the coasts of North America and Western Europe?

Answer

The Gulf Stream influences the climate of the east coast of North America from FLorida to Newfoundland, and the west coast of Europe. The current keeps these regions warm in winter.

Question 3(c)

Give a reason for each of the following:

(i) The waters of the Oyashio Current form the richest fishing grounds in the world.

(ii) There is heavy rainfall in Queensland but the Atacama desert is arid.

(iii) Rich fishing grounds are located on the Pacific coast of North America.

Answer

(i) The waters of the Oyashio Current form the richest fishing grounds in the world owing to the extremely high nutrient content of the cold water and the very high tides in some areas, which further enhances the availability of nutrients.

(ii) Warm currents flow towards Queensland which make the air warm and enable it to acquire greater moisture. Thus, the winds increase the amount of precipitation in Queensland while Atacama desert owe their existence to some extent to Benguela and Peru currents which are cold and keep the air dry and devoid of moisture.

(iii) Rich fishing grounds are located on the Pacific coast of North America due to the convergence of warm and cold currents.

Question 3(d)

Describe three major effects of currents.

Answer

Three major effects of currents are-

1. Effect on Climate — The climate of the coasts becomes warm or cool according to the current washing the coast which may be warm or cool.

2. Effect on Marine life — Ocean currents move organic material off the coast which is the food of planktons. The more the planktons, higher the concentration of fish.

3. Effect on commerce — On account of influence of warm currents, harbours are kept open in winter, facilitating trade throughout the year.

Thinking Skills

Question 1

You are watching the sea waves from the balcony of a seaside resort in Mumbai on a New Moon Day. Suddenly you noticed rise of sea water and its movement towards the coast. What was this wave and after how much time will it be repeated?

Answer

It was a tidal wave which I observed where the sea water rises and moves towards the coast. Tidal waves occur due to the gravitational pull of the moon and the sun on the Earth's oceans.

Tidal waves are most prominent during the occurrence of spring tides. Spring tides happen during the new moon and full moon phases when the gravitational forces of the moon and the sun align.

The interval between two consecutive tidal waves is approximately 12 hours and 26 minutes. Thus, I can expect to witness another tidal wave approximately 12 hours and 26 minutes after observing the previous one.

Question 2

Imagine that the Ocean Currents stop flowing. What would be its consequences for the human beings?

Answer

The consequences of ocean currents ceasing would have significant effects on human beings:

1. Climate Disruption — Ocean currents redistribute heat energy from the equator to the poles, maintaining a balance in temperature. The absence of ocean currents would disrupt heat distribution, causing extreme climate changes and irregular weather patterns.
2. Altered Weather Patterns — Ocean currents influence weather patterns on a regional scale. Without the currents, the regular weather patterns would be disrupted, potentially leading to irregular rainfall, storms, and even the formation of new climate zones.
3. Impact on Marine Ecosystems — Without currents, nutrient supply would be disrupted, leading to biodiversity loss, affecting fisheries and coastal communities.
4. Sea Level Changes — The disruption of ocean currents would result in altered sea levels, leading to coastal erosion and changes in sea level rise patterns.
5. Disrupted Oceanic Carbon Cycle — The absorption of carbon dioxide by the oceans would decrease, potentially increasing atmospheric carbon dioxide levels and exacerbating climate change.
6. Economic Implications — Industries such as fishing and tourism would suffer, shipping routes and trade patterns could be disrupted, and the global economy would be affected.

Thus, the consequences would be far-reaching and detrimental for human beings and the environment.