Hydrosphere

All of the above

All of the above.

All of the above

Both A and R are true and R is the correct explanation of A.

Explanation — Waves are oscillatory movements in water, manifested by an alternate rise and fall of the sea surface. These moving ridge-like curves on the surface of the sea are mainly produced by winds on the surface of the oceans.

Tides

Tidal range

maximum, minimum

A: High tide B: Low tide

A is true but R is false.

Explanation — While tidal range does get influenced by Earth's rotation on its axis, the main reason for variation in tidal range is due to changes in the locations of the Moon and Sun.

(A) (B) (C) (D)

Warm currents

The Earth's Revolution

The latter is more saline.

Trade Winds

Anticyclonic

Both A and R are true and R is the correct explanation of A.

Explanation — Since the speed of rotation of the earth is maximum at the Equator, all moving bodies (winds and ocean currents) move in a clockwise direction in the Northern Hemisphere and anticlockwise direction in the Southern Hemisphere. This is why Gulf stream flows in a clockwise direction.

The North Atlantic Drift

Both A and R are true and R is the correct explanation of A.

Explanation — The Labrador Current remains frozen for nine months on account of the influence of the cold Arctic Current.

Gulf Stream — North Atlantic Drift

North Atlantic Drift

Both A and R are true but R does not explain A.

Explanation — The water from precipitation, that is from rain or snow flows on the surface. Some of the water evaporates and the rest sinks into the soil. The water which gets collected under the surface of the land, known as underground water, remains in soil, sub-soil or bedrock.

A is false but R is true.

Explanation — On the seventh or eighth day of every fortnight a neap tide, which is lower in height than a normal tide, occurs. The height of neap tides is generally 20 per cent lower than that of the normal tides.

Kuroshio current

Gulf Stream

Both (1) and (3)

Both A and R are true and R is the correct explanation of A.

Explanation — Warm currents 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, influencing climate and marine life.

Both A and R are true and R is the correct explanation of A.

Explanation — Ocean currents are greatly influenced by the stresses exerted by the prevailing winds and Coriolis force. The oceanic circulation pattern roughly corresponds to the Earth's atmospheric circulation pattern. The air circulation over the oceans in the middle latitudes is mainly anticyclonic. Hence, the oceanic circulation pattern also corresponds with the circulation of air.

all of the above

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

1. Waves
2. Currents

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.

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.

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.

The phenomenon that Mona observed is called a Low Tide.

Tides are the regular rise and fall of sea levels caused by the gravitational pull of the moon and the sun on the Earth's oceans. During low tide, the water level recedes from the shore, exposing more of the seabed and causing boats at a jetty or dock to appear lower than usual. This can make gangways steep or even vertical, as Mona noticed.

So, what she saw was the effect of low tide, a natural and periodic event that occurs twice a day in most coastal areas.

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

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.

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

Tara said that the heavy fog in the seaside of Newfoundland is caused by the meeting of two ocean currents — the cold Labrador current and the warm Gulf Stream. Tara explained to them that when the warm, moist air of the Gulf Stream meets the cold air from the Labrador Current, the moisture in the warm air condenses rapidly, forming thick fog.

Due to the rich fishing grounds created by the mixing of these currents, the main occupation of the people in Newfoundland is fishing.

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.

(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.

Below diagram shows the formation of spring and neap tides:

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.

Two factors responsible for causing the currents are-

1. Level of Salinity
2. Temperature

(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.

(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.

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.

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.

(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.

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.

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.

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.