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All questions of Oceanography for UPSC CSE Exam

Bay of Bengal shows low salinity of water as compared to the Arabian Sea due to
1. Huge influx of fresh water in the Bay of Bengal
2. High evaporation in the Arabian Sea as compared to the Bay of Bengal
3. Low influx of fresh water in the Arabian Sea
Choose the correct answer using the codes below:
  • a)
    2 and 3 only
  • b)
    1 only
  • c)
    1 and 3 only
  • d)
    1 and 2 only
Correct answer is option 'D'. Can you explain this answer?

Mahi Gupta answered
Explanation:

The Bay of Bengal and the Arabian Sea are two major water bodies in the Indian Ocean. They differ in terms of their salinity levels, with the Bay of Bengal showing low salinity compared to the Arabian Sea. This difference can be attributed to several factors:

1. Huge influx of fresh water in the Bay of Bengal:
- The Bay of Bengal receives a significant amount of freshwater input from various rivers, including the Ganges, Brahmaputra, and Irrawaddy.
- These rivers carry large volumes of freshwater from the Himalayas and other regions, leading to a dilution of the seawater in the Bay of Bengal.
- This freshwater influx reduces the salinity levels in the bay, making it relatively less saline compared to the Arabian Sea.

2. High evaporation in the Arabian Sea:
- The Arabian Sea experiences higher rates of evaporation compared to the Bay of Bengal.
- The warm and dry winds blowing over the Arabian Sea lead to enhanced evaporation.
- As water evaporates, the dissolved salts and minerals are left behind, increasing the salinity of the remaining seawater.
- This higher evaporation rate contributes to the higher salinity levels observed in the Arabian Sea.

3. Low influx of fresh water in the Arabian Sea:
- Unlike the Bay of Bengal, the Arabian Sea does not receive a significant influx of freshwater from major rivers.
- The rivers in the Arabian Sea region, such as the Indus, Tapi, and Narmada, have relatively smaller catchment areas and lower water discharge compared to the rivers in the Bay of Bengal region.
- The limited freshwater input in the Arabian Sea leads to a lower dilution effect on the seawater, resulting in higher salinity levels.

Therefore, the correct answer is option 'D' - all of the above factors contribute to the lower salinity levels in the Bay of Bengal compared to the Arabian Sea.
Clear all your doubts with EduRev

Concerning ocean salinity, consider the following statements:
1. In oceans, sodium chloride alone constitutes 95% of ocean salts.
2. The proportion of ocean salts vary in different parts of the ocean.
3. The salinity is constant throughout the oceans.
Which of the above is/correct?
  • a)
    1 only
  • b)
    2 only
  • c)
    3 only
  • d)
    1 and 2
Correct answer is option 'D'. Can you explain this answer?

Amit Sharma answered
1. In oceans, sodium chloride alone constitutes 95% of ocean salts.

This statement is correct. Sodium chloride, commonly known as table salt, makes up about 95% of the dissolved salts in seawater. The remaining 5% consists of other dissolved minerals such as magnesium, calcium, and potassium.

2. The proportion of ocean salts vary in different parts of the ocean.

This statement is correct. The salinity of ocean water varies depending on the location. Factors that affect salinity include evaporation, precipitation, freezing and melting of ice, and the influx of freshwater from rivers. For example, in areas where evaporation is high and precipitation is low, the salinity will be higher. Conversely, in areas with high precipitation and low evaporation, the salinity will be lower.

3. The salinity is constant throughout the oceans.

This statement is incorrect. As mentioned above, salinity varies depending on factors such as evaporation, precipitation, ice formation and melting, and river input. Additionally, ocean currents and mixing can cause variations in salinity both horizontally and vertically within the ocean. Salinity is generally higher near the surface where evaporation occurs, and lower at greater depths.

Factors that affect the formation of tides in the Ocean are
1. Alignment of Earth, Sun and Moon
2. Relative distance between the Moon, Earth and Sun
3. Shape of bays and estuaries where tides are formed
4. Local wind and weather patterns in Ocean
Select the correct answer using the codes below:
  • a)
    1 and 2 only
  • b)
    2 and 3 only
  • c)
    1 and 4 only
  • d)
    All of the above
Correct answer is option 'D'. Can you explain this answer?

Saumya Iyer answered
The correct answer is option D, which states that all of the factors mentioned affect the formation of tides in the ocean. Let's discuss each factor in detail:

1. Alignment of Earth, Sun, and Moon:
Tides are primarily caused by the gravitational pull of the Moon and, to a lesser extent, the Sun. When the Earth, Moon, and Sun are aligned in a straight line, the gravitational forces exerted by both the Moon and the Sun combine, resulting in higher high tides (spring tides) and lower low tides. This alignment occurs during a new moon and a full moon.

2. Relative distance between the Moon, Earth, and Sun:
The distance between the Moon, Earth, and Sun also affects the formation of tides. When the Moon is closer to the Earth, its gravitational pull is stronger, resulting in higher high tides and lower low tides. Conversely, when the Moon is farther away, the tidal range is smaller. Similarly, the Sun's proximity to the Earth also plays a role in the formation of tides, although its effect is less significant compared to the Moon due to its greater distance.

3. Shape of bays and estuaries where tides are formed:
The shape of bays and estuaries can influence the amplitude and timing of tides. Narrow and shallow bays tend to amplify tidal ranges, leading to higher high tides and lower low tides. Conversely, broad and shallow bays may experience smaller tidal ranges. The shape and topography of the coastline also affect the speed and direction of tidal currents.

4. Local wind and weather patterns in the ocean:
Local wind and weather patterns can influence the formation of tides in several ways. Strong onshore winds can push water towards the coast, causing higher high tides (storm surges). Conversely, offshore winds can result in lower than normal tides. Additionally, weather conditions such as low-pressure systems and tropical cyclones can generate large-scale changes in sea level, affecting the amplitude of tides.

In conclusion, the formation of tides in the ocean is influenced by multiple factors, including the alignment of the Earth, Sun, and Moon, the relative distance between them, the shape of bays and estuaries, as well as local wind and weather patterns. All of these factors contribute to the complex and dynamic nature of tidal patterns in different regions of the world's oceans.

Which of the following factors has no or negligible effect on the salinity of oceans.
  • a)
    The rate of evaporation
  • b)
    Salts released by marine volcanoes
  • c)
    The amount of freshwater added by rivers, iceberg and rainfall
  • d)
    The degree of mixing by the ocean currents
Correct answer is option 'B'. Can you explain this answer?

Anjana Chavan answered
Factors Affecting Salinity of Oceans

There are several factors that influence the salinity of oceans, which is the measure of the concentration of dissolved salts in seawater. These factors include evaporation, freshwater input, and ocean currents. However, one factor that has no or negligible effect on the salinity of oceans is the salts released by marine volcanoes.

1. The rate of evaporation
- Evaporation is a major factor contributing to the salinity of oceans.
- When water evaporates, it leaves behind the dissolved salts, increasing the salinity of the remaining water.
- The rate of evaporation is influenced by factors such as temperature, humidity, wind speed, and surface area of the ocean.
- Higher rates of evaporation lead to higher salinity levels in the ocean.

2. The amount of freshwater added by rivers, iceberg, and rainfall
- Freshwater input from various sources, such as rivers, icebergs, and rainfall, can significantly affect the salinity of oceans.
- When freshwater enters the ocean, it dilutes the concentration of salts, reducing the salinity.
- Rivers carry dissolved salts from the land to the ocean, but the volume of freshwater they contribute is much larger than the salts, resulting in lower salinity.
- Icebergs, formed from freshwater, release freshwater into the ocean as they melt, further reducing salinity.
- Rainfall also adds freshwater to the ocean, particularly in coastal regions, causing a decrease in salinity.

3. The degree of mixing by the ocean currents
- Ocean currents play a crucial role in redistributing heat and nutrients around the globe.
- These currents also mix the water masses, including high and low salinity areas, resulting in a more uniform salinity distribution.
- The degree of mixing by ocean currents can influence the overall salinity of the ocean, but it does not directly affect the salinity levels.

4. Salts released by marine volcanoes
- Marine volcanoes release various gases and solid materials, including salts, into the ocean.
- While these volcanic activities can contribute to the chemical composition of seawater, their impact on the overall salinity of the ocean is negligible.
- The amount of salts released by marine volcanoes is relatively small compared to the vast volume of the ocean, and they get dispersed and diluted quickly.

Therefore, among the given options, the salts released by marine volcanoes have no or negligible effect on the salinity of oceans.

Consider the following statements:
Assertion (A): Seamounts tend to be found on oceanic crust near mid-ocean ridges and island arcs.
Reason (R): Most seamounts are volcanic in origin.
In the context of the above, which of these is correct?
  • a)
    A is correct, and R is an appropriate explanation of A.
  • b)
    A is correct, but R is not an appropriate explanation of A.
  • c)
    A is correct, but R is incorrect.
  • d)
    Both A and R are incorrect.
Correct answer is option 'A'. Can you explain this answer?

Anjali Desai answered

Explanation:

Assertion (A) is correct:
- Seamounts are underwater mountains that rise from the ocean floor. They are often found near mid-ocean ridges and island arcs.
- Seamounts are associated with areas of volcanic and tectonic activity, which are commonly found near mid-ocean ridges and island arcs.

Reason (R) is an appropriate explanation of A:
- Most seamounts are volcanic in origin, meaning they are formed by volcanic eruptions on the ocean floor. This volcanic activity is typically concentrated near mid-ocean ridges and island arcs.
- The volcanic nature of seamounts is a key factor in why they are often found near these areas of tectonic activity.

Therefore, the correct answer is option 'A' - A is correct, and R is an appropriate explanation of A.

Increased snow cover on a water body can lead to
1. Sudden spurt in phytoplankton population which are not dependent on photosynthesis
2. Improved oxygen exchange and nutrient recycling in the lake
3. A condition of winterkill causing large scale death of fishes and organisms
Select the correct answer using the codes below:
  • a)
    1 and 2 only
  • b)
    3 only
  • c)
    1 only
  • d)
    1 and 3 only
Correct answer is option 'B'. Can you explain this answer?

Nandini Kaur answered
Increased snow cover on a water body can have various impacts on the ecosystem. The correct answer is option 'B', i.e., 3 only, which means that the increased snow cover can lead to a condition of winterkill causing large scale death of fishes and organisms. Let's understand this in detail:

Winterkill:

Winterkill is a condition that occurs when a water body becomes covered with ice and snow for an extended period. As a result, the water body becomes deprived of oxygen, and the carbon dioxide level increases, leading to the death of fishes and other organisms. The following are the reasons for winterkill:

- Reduced light penetration: The ice and snow cover reduce the amount of light that can penetrate the water body, leading to a decrease in photosynthesis by aquatic plants.

- Reduced oxygen supply: As the ice and snow cover the surface of the water, there is limited exchange of gases between the atmosphere and the water body. This leads to a decrease in oxygen supply to the aquatic organisms.

- Increased carbon dioxide level: The respiration of aquatic organisms leads to an increase in the carbon dioxide level in the water body. As there is limited exchange of gases, the carbon dioxide level can increase to toxic levels, leading to the death of fishes and other organisms.

- Nutrient accumulation: The nutrient recycling in the water body is reduced due to limited exchange of gases, leading to the accumulation of nutrients that can promote the growth of algae and other aquatic plants. The decay of these plants can further reduce the oxygen supply, leading to winterkill.

Conclusion:

Increased snow cover on a water body can lead to winterkill, causing large scale death of fishes and organisms. This happens due to reduced light penetration, reduced oxygen supply, increased carbon dioxide level, and nutrient accumulation. Therefore, it is essential to monitor the snow cover and take necessary measures to prevent winterkill.

Guyots refer to
  • a)
    These are low islands found in the tropical oceans consisting of coral reefs surrounding a central depression.
  • b)
    These are deep valleys, some comparable to the Grand Canyon of Colorado.
  • c)
    Underwater mountain in the sea
  • d)
    All of the above
Correct answer is option 'C'. Can you explain this answer?

Vikram Verma answered
  • It is a flat-topped seamount. They show evidence of gradual subsidence through stages to become flat-topped submerged mountains. It is estimated that more than 10,000 seamounts and guyots exist in the Pacific Ocean alone.

Water that rises to the surface as a result of Ocean Upwelling is typically
  • a)
    Colder and poor in nutrients
  • b)
    Warmer and poor in nutrients
  • c)
    Colder and rich in nutrients
  • d)
    Warmer and rich in nutrients
Correct answer is option 'C'. Can you explain this answer?

Vijay Kumar answered
  • Winds blowing across the ocean surface push water away. Water then rises from beneath the surface to replace the water that was pushed away. This process is known as ‘upwelling’. Upwelling occurs in the open ocean and along coastlines.
  • Water that rises to the surface as a result of upwelling is typically colder and is rich in nutrients. These nutrients ‘fertilise’ surface waters, meaning that these surface waters often have high biological productivity. Therefore, good fishing grounds typically are found where upwelling is common.

The West Wind Drift is the most important current in the Southern Ocean and the only current that flows completely around the globe. However, its circulation is circumpolar in nature due to
  • a)
    Lack of any landmass connecting with Antarctica
  • b)
    Influence of the Equatorial counter- currents
  • c)
    Guyers formed near the current
  • d)
    Thermohaline pattern on shorelines
Correct answer is option 'A'. Can you explain this answer?

Mohit Joshi answered
Understanding the West Wind Drift
The West Wind Drift, also known as the Antarctic Circumpolar Current, is crucial for the oceanic circulation in the Southern Ocean. It encircles Antarctica and plays a significant role in climate regulation and marine ecosystems.
Why is it Circumpolar?
The circumpolar nature of the West Wind Drift is primarily due to:
- Lack of Landmass
The absence of significant landmasses connecting with Antarctica allows the current to flow uninterrupted around the continent. This characteristic is vital for maintaining its circumpolar nature.
- Open Ocean Space
The Southern Ocean is largely open water, which facilitates the continuous movement of water without obstruction. This open space permits the current to gain strength and maintain its flow.
- Wind Patterns
The prevailing westerly winds in the Southern Hemisphere drive the West Wind Drift, reinforcing its uninterrupted path around Antarctica.
Significance of the Current
The West Wind Drift:
- Climate Regulation
It plays a crucial role in regulating global climate patterns by distributing heat and influencing weather systems.
- Nutrient Distribution
The current contributes to the upwelling of nutrients, supporting rich marine biodiversity in the Southern Ocean.
- Connection to Global Currents
It links with other major ocean currents, contributing to the global thermohaline circulation, which is essential for maintaining Earth's climate balance.
In summary, the lack of landmass connecting with Antarctica is the key reason for the circumpolar nature of the West Wind Drift, allowing it to flow freely and significantly impact global oceanic and climatic systems.

Which of the following factors affect the direction of movement of ocean currents?
1. Ocean Salinity
2. Ocean temperature
3. The Earth’s rotation
4. The planetary winds
Choose the correct answer using the codes below
  • a)
    1 and 2 only
  • b)
    2, 3 and 4 only
  • c)
    3 only
  • d)
    All of the above
Correct answer is option 'D'. Can you explain this answer?

Anjali Chavan answered
Factors affecting the direction of movement of ocean currents:

1. Ocean Salinity:
- Ocean currents are affected by the salinity of the water.
- Areas with high salinity water are denser and tend to sink while areas with low salinity water are less dense and tend to rise.
- This difference in density causes the movement of water in the ocean.

2. Ocean temperature:
- Temperature also affects the movement of ocean currents.
- Warm water is less dense than cold water and tends to rise, while cold water is denser and sinks.
- This movement of water due to temperature differences helps in the formation of ocean currents.

3. The Earth’s rotation:
- The rotation of the Earth affects the direction of ocean currents.
- The Coriolis effect, which is a result of the Earth's rotation, causes the currents to move in a circular pattern.
- In the Northern Hemisphere, currents move in a clockwise direction, while in the Southern Hemisphere, they move in an anti-clockwise direction.

4. The planetary winds:
- The movement of winds affects the direction of ocean currents.
- The direction of the wind determines the direction of the current.
- For example, winds blowing from the east push water towards the west, causing a current in that direction.

Conclusion:
All of the above factors - ocean salinity, ocean temperature, the Earth's rotation, and the planetary winds - affect the direction of movement of ocean currents. The combination of these factors determines the speed and direction of ocean currents, which have a significant impact on climate, marine life, and human activities.

The Chilean and Peruvian coasts are practically rainless. This is because of
  • a)
    Presence of cold ocean current along the coasts
  • b)
    Rainshadow area
  • c)
    Presence of deserts
  • d)
    None of the above
Correct answer is option 'A'. Can you explain this answer?

Anjana Chavan answered
Explanation:

The correct answer is option 'A', which states that the rainless nature of the Chilean and Peruvian coasts is due to the presence of a cold ocean current along the coasts.

Presence of Cold Ocean Current:
The Pacific Ocean off the coasts of Chile and Peru is influenced by the Humboldt Current, also known as the Peru Current. This current is a cold oceanic current that flows northward along the western coast of South America. It originates in the Southern Ocean and is driven by the South Pacific Gyre. The Humboldt Current is characterized by its low temperatures and high nutrient content.

Effect on Rainfall:
The presence of the Humboldt Current has a significant impact on the climate of the Chilean and Peruvian coasts. The cold ocean current helps to create a stable atmospheric condition known as a temperature inversion. This inversion layer prevents the formation of clouds and the vertical movement of air, leading to a lack of rainfall.

Temperature Inversion:
Temperature inversion refers to a change in the temperature profile of the atmosphere, where the temperature increases with altitude instead of decreasing. In the case of the Chilean and Peruvian coasts, the cold water of the Humboldt Current cools the air above it. This cold air is denser than the warm air above it, creating a stable layer that prevents the upward movement of warm air and the formation of clouds.

Lack of Rainfall:
As a result of the temperature inversion caused by the cold ocean current, the Chilean and Peruvian coasts experience very little rainfall. The stable atmospheric conditions prevent the lifting of warm, moist air, which is necessary for the formation of clouds and precipitation. This rainless climate has led to the development of deserts along the coasts, such as the Atacama Desert in Chile and the Sechura Desert in Peru.

Conclusion:
In conclusion, the rainless nature of the Chilean and Peruvian coasts can be attributed to the presence of the Humboldt Current, a cold ocean current that creates stable atmospheric conditions, preventing the formation of clouds and rainfall.

A lot of interest has been recently shown in seafloor hydrothermal systems on account of their
1. High concentration of-base metals
2. High biodiversity
Which of the above is/are correct?
  • a)
    1 only
  • b)
    2 only
  • c)
    Both 1 and 2
  • d)
    None of the above
Correct answer is option 'C'. Can you explain this answer?

Milan Malik answered
Seafloor hydrothermal systems are highly interesting for scientific research due to their unique characteristics and potential benefits. Two key factors that contribute to the interest in these systems are their high concentration of base metals and high biodiversity.

1. High concentration of base metals:
Seafloor hydrothermal systems are known to have high concentrations of base metals such as copper, zinc, and iron. These metals are released into the ocean water through hydrothermal vents, which are openings in the seafloor that allow hot, mineral-rich fluids to escape from the Earth's interior. The fluids that are released from these vents contain dissolved metals that precipitate out when they come into contact with the cold seawater, forming mineral deposits on the seafloor. These mineral deposits, known as hydrothermal vents or chimneys, can contain high concentrations of valuable base metals.

The presence of these high concentrations of base metals has attracted significant interest from the mining industry. Extracting these metals from seafloor hydrothermal systems could potentially provide a new source of valuable minerals, reducing the reliance on land-based mining operations. However, mining in deep-sea environments poses numerous technical and environmental challenges that need to be carefully addressed before any commercial extraction can occur.

2. High biodiversity:
Seafloor hydrothermal systems are also known for their high biodiversity. These unique ecosystems support a wide variety of organisms that have adapted to the extreme conditions found in these environments. The hydrothermal vent fluids are rich in chemicals and nutrients, providing a source of energy for the organisms living in these areas.

The most well-known organisms found in seafloor hydrothermal systems are chemosynthetic bacteria and archaea, which derive their energy from the chemicals in the hydrothermal fluids. These bacteria form the base of the food chain in these ecosystems and support a diverse community of organisms, including tubeworms, clams, crabs, and fish.

The study of these unique ecosystems and the organisms that inhabit them has provided valuable insights into the origins of life on Earth and the potential for life in extreme environments. Additionally, the enzymes and biochemical compounds produced by these organisms have potential applications in various fields, including medicine and biotechnology.

In conclusion, both the high concentration of base metals and high biodiversity make seafloor hydrothermal systems highly interesting for scientific research. The potential for mineral extraction and the understanding of unique ecosystems and their adaptations are significant factors driving the interest in these systems.

Consider the following pairs:
Trench Location
1. Tonga Pacific Ocean
2. Java Indian Ocean
3. Mindanao Deep Pacific Ocean
4. South Sandwich Atlantic Ocean
Which of the pairs given above is/are correctly matched?
  • a)
    1, 2 and 4 only
  • b)
    2, 3, and 4 only
  • c)
    1 and 3 only
  • d)
    1, 2, 3 and 4
Correct answer is option 'D'. Can you explain this answer?

Charvi Choudhary answered
Trench Locations

• Trenches are long, narrow and deep depressions on the ocean floor. They are formed by the collision of two tectonic plates.

• Some of the major trenches are located in the Pacific, Indian and Atlantic Oceans.

Pairs Correctly Matched

• Tonga Trench - Located in the Pacific Ocean, between the islands of Tonga and New Zealand.

• Java Trench - Located in the Indian Ocean, off the coast of Indonesia.

• Mindanao Deep - Located in the Pacific Ocean, near the Philippines.

• South Sandwich Trench - Located in the Atlantic Ocean, near the South Sandwich Islands.

Therefore, all the pairs given in the question are correctly matched and the correct answer is option D.

Regarding corals, consider the following statements:
1. Coral are marine invertebrate species.
2. Corals secrete calcium carbonate which forms the outer skeleton.
3. Corals grow in shallow waters to absorb sunlight for photosynthesis to produce their food.
Which of the above is/are correct?
  • a)
    1 and 2 only
  • b)
    2 and 3 only
  • c)
    1 and 3 only
  • d)
    All of the above
Correct answer is option 'A'. Can you explain this answer?

Meera Singh answered
  • Live coral is colonies of small animals embedded in calcium carbonate shells. It is a mistake to think of coral as plants or rocks. Coral heads consist of accumulations of individual animals called polyps, arranged in diverse shapes.
  • Reef-building or hermatypic corals live only in the photic zone (above 50 m), the depth to which sufficient sunlight penetrates the water, allowing photosynthesis to occur.
  • Coral polyps do not photosynthesise, but have a symbiotic relationship with zooxanthellae; these organisms live within the tissues of polyps and provide organic nutrients that nourish the polyp. Because of this relationship, coral reefs grow much faster in clear water, which admits more sunlight.

The Agulhas current acts as an oceanic convergence zone. This zone has higher primary productivity than surrounding waters. This is because
1. The zone is a meeting point of all major ocean currents of the Indian Ocean.
2. There is an upwelling of cold ocean water from the lower layers of the ocean.
Which of the above is/are correct?
  • a)
    1 only
  • b)
    2 only
  • c)
    Both 1 and 2
  • d)
    None of the above
Correct answer is option 'B'. Can you explain this answer?

Kiran Sharma answered
Explanation:

The Agulhas current flows down the east coast of Africa and around the tip of South Africa before continuing into the southern Atlantic Ocean. It is a powerful flow of warm water that acts as an oceanic convergence zone where many different ocean currents meet and mix. This convergence zone has higher primary productivity than surrounding waters, which means that there is a greater abundance of plant and animal life in this area.

The reasons for this higher primary productivity are as follows:

Upwelling of cold ocean water: The Agulhas current is a warm ocean current that flows southwards along the east coast of Africa. However, there is also an upwelling of cold ocean water from the deeper layers of the ocean that occurs in this area. This cold water is rich in nutrients that support the growth of phytoplankton, which in turn supports the entire food chain.

Incorrect option: 1 only
The statement that the zone is a meeting point of all major ocean currents of the Indian Ocean is incorrect. The Agulhas current is not a meeting point of all major ocean currents of the Indian Ocean, but rather a flow of warm water that originates in the Indian Ocean and flows into the Atlantic Ocean.

Therefore, option B - 2 only is the correct answer.

Tropical coral reefs are very productive ecosystems. Which of the following are benefits accrued from coral reefs?
1. They sustain about a quarter of the ocean’s fish population.
2. Coral reefs break the power of the waves during storms, cyclones and tsunamis.
3. Coral reefs can provide potent anti-HIV proteins.
Select the correct answer using the codes below:
  • a)
    1 and 2 only
  • b)
    2 and 3 only
  • c)
    1 only
  • d)
    All of the above
Correct answer is option 'D'. Can you explain this answer?

Meera Singh answered
  • Coral reefs are vital to the world’s fisheries. They film the nurseries for about a quarter of the ocean’s fish and thus provide revenue for local communities as well as national and international fishing fleets.
  • Coral reefs break the power of the waves during storms, hurricanes, typhoons, and even tsunamis. By helping to prevent coastal erosion, flooding, and loss of property on the shore, the reefs save billions of dollars each year in terms of reduced insurance and reconstruction costs and reduced need to build costly coastal defences.
  • A new class of proteins capable of blocking HIV from penetrating T-cells has been discovered. The proteins have been found in a coral from Australia’s northern coast. Coral reefs are also being used in the treatment of cancer.

Consider the following about the phenomenon of Upwelling in the Indian Ocean:
1. It is a seasonal phenomenon associated with the monsoon.
2. It is weakest in regions closest to the equator and strongest near subtropical latitudes.
3. It brings nutrient-rich water to the surface and enhances the biological productivity of the region.
Select the correct answer using the codes below:
  • a)
    1 and 2 only
  • b)
    2 only
  • c)
    1 and 3 only
  • d)
    1 only
Correct answer is option 'C'. Can you explain this answer?

Suyash Unni answered
Explanation:

Upwelling is a phenomenon in which cold, nutrient-rich water from the depths of the ocean rises to the surface. It occurs in various regions around the world, including the Indian Ocean. The given statements related to the phenomenon of upwelling in the Indian Ocean are as follows:

1. It is a seasonal phenomenon associated with the monsoon:
Upwelling in the Indian Ocean is indeed a seasonal phenomenon that is associated with the monsoon. During the summer monsoon season, winds blow from the southwest over the Arabian Sea, pushing the surface waters away from the coast. This creates a vacuum effect that pulls up the deeper, nutrient-rich water to the surface. This upwelling of cold water is important for the marine ecosystem as it provides nutrients to support the growth of phytoplankton and sustains the food chain.

2. It is weakest in regions closest to the equator and strongest near subtropical latitudes:
This statement is correct. Upwelling is weakest in regions closest to the equator because the Coriolis effect is weaker near the equator, resulting in weaker wind-driven currents that are responsible for upwelling. On the other hand, upwelling is strongest near subtropical latitudes where the Coriolis effect is stronger, leading to stronger wind-driven currents and more pronounced upwelling.

3. It brings nutrient-rich water to the surface and enhances the biological productivity of the region:
This statement is also correct. Upwelling brings nutrient-rich water from the deep ocean to the surface, providing essential nutrients such as nitrates and phosphates to support the growth of phytoplankton. Phytoplankton forms the base of the marine food chain and is consumed by zooplankton, which in turn are eaten by larger marine organisms. Therefore, upwelling enhances the biological productivity of the region by increasing the availability of nutrients and supporting a diverse ecosystem.

Conclusion:
Considering all the given statements, it can be concluded that upwelling in the Indian Ocean is a seasonal phenomenon associated with the monsoon, it is weakest in regions closest to the equator and strongest near subtropical latitudes, and it brings nutrient-rich water to the surface, thus enhancing the biological productivity of the region. Therefore, the correct answer is option C: 1 and 3 only.

Which of the following statements about ocean salinity is/are correct?
1. The salinity of water in the surface layer of oceans depends mainly on evaporation and precipitation.
2. Surface salinity is greatly influenced in coastal regions by the freshwater flow from rivers, and in polar regions by the processes of freezing and thawing of ice.
3. Wind also influences the salinity of an area by transferring water to other areas.
4. The ocean currents have a negligible role in affecting ocean salinity.
Select the correct answer using the codes below:
  • a)
    1,2 and 3 only
  • b)
    2, 3 and 4 only
  • c)
    3 and 4 only
  • d)
    1 and 3 only
Correct answer is option 'A'. Can you explain this answer?

Kavita Mehta answered
Factors affecting ocean salinity are mentioned below
(i) The salinity of water in the surface layer of oceans depends mainly on evaporation and precipitation.
(ii) Surface salinity is greatly influenced in coastal regions by the freshwater flow from rivers, and in polar regions by the processes of freezing and thawing of ice.
(iii) Wind also influences the salinity of an area by transferring water to other areas.
(iv) The ocean currents contribute to the salinity variations. Salinity, temperature and density of water are interrelated. Hence, any change in the temperature or density influences the salinity of an area.

Regarding continental shelf, consider the following statements:
1. In mountainous coasts, continental shelves are broad.
2. The continental shelf is an underwater landmass which extends from a continent.
3. The continental shelves are poor in fish resources as they are shallow.
Which of the above is/are incorrect?
  • a)
    1 and 2 only
  • b)
    2 and 3 only
  • c)
    1 and 3 only
  • d)
    1 only
Correct answer is option 'C'. Can you explain this answer?

Kavita Mehta answered
  • The width of the continental shelf varies considerably - it is not uncommon for an area to have virtually no shelf at all, particularly where the forward edge of an advancing oceanic plate dives beneath continental crust in an offshore subduction zone such as off the coast of Chile or the west coast of Sumatra where they are mountainous.
  • The largest shelf - the Siberian Shelf in the Arctic Ocean - stretches to 1,500 km in width. Continental shelves are the richest fishing grounds.

Hydrothermal vents in oceans are closely associated with regions of
  • a)
    Mid-oceanic ridges
  • b)
    Intersection of continental plates
  • c)
    Areas of seafloor spreading
  • d)
    All of the above
Correct answer is option 'D'. Can you explain this answer?

Anjana Chavan answered
Hydrothermal vents are common features found in the deep ocean. They are associated with various geological processes and occur in specific regions. The correct answer to the given question is option 'D', which states that hydrothermal vents are closely associated with all of the following:

a) Mid-oceanic ridges:
- Mid-oceanic ridges are underwater mountain ranges that run through the center of the ocean basins. They are formed by the divergence of tectonic plates, where new oceanic crust is created as magma rises and solidifies.
- Hydrothermal vents are commonly found along mid-oceanic ridges. This is because the tectonic activity at these ridges allows for the release of heat and the formation of cracks in the ocean crust, through which hydrothermal fluids can escape.

b) Intersection of continental plates:
- Continental plates are large pieces of the Earth's lithosphere that make up the continents. When these plates interact at their boundaries, they can form various geological features such as mountains, volcanoes, and trenches.
- In some cases, the interaction between continental plates can lead to the formation of hydrothermal vents. This can occur when one plate sinks beneath another in a process known as subduction. As the subducting plate descends into the mantle, it heats up and releases fluids that can rise back to the surface and form hydrothermal vents.

c) Areas of seafloor spreading:
- Seafloor spreading is the process by which new oceanic crust is formed at mid-oceanic ridges and spreads outward. It occurs due to the divergence of tectonic plates, where magma rises and solidifies to form new crust.
- Hydrothermal vents are closely associated with areas of seafloor spreading because the heat and cracks generated during this process provide ideal conditions for the formation of hydrothermal systems. The rising magma heats the surrounding water, which then circulates through the fractures and carries minerals from the crust. As the heated fluids rise to the surface, they mix with the cold seawater, resulting in the formation of hydrothermal vents.

In conclusion, hydrothermal vents are closely associated with mid-oceanic ridges, the intersection of continental plates, and areas of seafloor spreading. These geological processes provide the necessary conditions for the formation of hydrothermal systems, where hot fluids and minerals are released into the ocean.

Consider the following statements:
Assertion (A): In the North Indian Ocean, there is a complete reversal of the direction of ocean currents between summer and winter.
Reason (R): Monsoon winds change direction from South-west to Northeast.
In the context of the above, which of these is/are correct?
  • a)
    A is correct, and R is an appropriate explanation of A.
  • b)
    A is correct, but R is not an appropriate explanation of A.
  • c)
    A is incorrect, but R is incorrect.
  • d)
    Both A and R arc incorrect.
Correct answer is option 'A'. Can you explain this answer?

Meera Singh answered
In the North Indian Ocean, a complete reversal of direction of Monsoon Current, twice a year is observed between summer and winter because the Monsoon winds change their direction according to seasons. South-West Monsoon Current (warm).
  • In the summer season, the monsoon winds blow from south-west to north-east. Consequently, the ocean current also flows from south-west to north-east direction.
  • The main current moves in the Arabian Sea and the Bay of Bengal along the coast of India. North-East Monsoon Current (warm)
  • In the winter season, the monsoon winds blow from northeast to south-west. The ocean current also flows from northeast to south-west under the influence of these winds.

Which of these forces help in the movement or generation of ocean currents?
1. Coriolis force
2. Gravitational force
3. Solar insolation
4. Movement of wind
Select the correct answer using the codes below:
  • a)
    2 and 3 only
  • b)
    1 and 4 only
  • c)
    2, 3 and 4 only
  • d)
    All of the above
Correct answer is option 'D'. Can you explain this answer?

Deepa Iyer answered
  • Surface currents are generated largely by the wind. Their patterns are determined by wind direction, Coriolis forces from the Earth’s rotation, and the position of landforms that interact with the currents.
  • 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.
  • Solar energy makes the current warm or cold and decides their circulatory patterns.

Regarding Lakshadweep islands, consider the following statements:
1. They form the smallest Union Territories of Government of India.
2. The islands do not have any aboriginal groups.
3. Lakshadweep has no coral reefs.
Which of the above is/are correct?
  • a)
    1 and 3 only
  • b)
    1 and 2 only
  • c)
    2 and 3 only
  • d)
    All of the above
Correct answer is option 'B'. Can you explain this answer?

Ojasvi Mehta answered
Lakshadweep is an archipelago of twelve atolls, three reefs and five submerged banks, with a total of about thirty-nine islands and islets. The reefs are in fact also atolls, although mostly submerged, with only small unvegetated sand cays above the high-water mark. The submerged banks are sunken atolls.

The thermocline layer represents vertical zones of oceanic water below the first layer and is characterised by a rapid rate of decrease of temperature with increasing depth. The largest number of such layers is usually found in
  • a)
    Tropics
  • b)
    Poles
  • c)
    Temperate regions
  • d)
    Southern Ocean
Correct answer is option 'A'. Can you explain this answer?

Gauri Bajaj answered
The Thermocline Layer in Oceanic Water

The thermocline layer is a zone of oceanic water below the first layer, which is characterised by a rapid rate of decrease of temperature with increasing depth. This layer is important to understand the oceanic processes and its interaction with the atmosphere. Let's discuss this in detail.

Explanation:

Tropics have the largest number of thermocline layers:

The largest number of thermocline layers is usually found in the tropics. This is because the surface temperature of the tropical ocean water is relatively high due to the intense solar radiation. This high temperature is reduced rapidly as the water gets deeper due to the low penetration of solar radiation in the oceanic water.

Poles have less thermocline layers:

Poles are the regions with the least number of thermocline layers. This is because the surface temperature of the polar oceanic water is low due to the low solar radiation. Therefore, the temperature of the water doesn't decrease rapidly as the water gets deeper.

Temperate regions:

Temperate regions have a moderate number of thermocline layers. The surface temperature of the temperate oceanic water is moderate due to the moderate solar radiation. Therefore, the temperature of the water decreases moderately as the water gets deeper.

Southern Ocean:

The Southern Ocean is a unique oceanic region because it has the largest number of thermocline layers in the world. This is because the Southern Ocean is a circumpolar ocean, which allows the water to circulate around the globe. This circulation creates multiple thermocline layers.

Conclusion:

In conclusion, the number of thermocline layers in the oceanic water depends on the surface temperature of the water, which is mainly influenced by solar radiation. The tropics have the largest number of thermocline layers due to the high surface temperature of the water, while the poles have the least number of thermocline layers due to the low surface temperature of the water. The Southern Ocean is a unique oceanic region with the largest number of thermocline layers due to its circumpolar flow.

Regarding ocean temperatures, consider the following statements:
1. Highest temperature is observed in open seas
2. The ocean temperature decreases with depth
3. The temperature of oceans constantly reduces near the polar regions in every part of the globe
Which of the above is/are incorrect?
  • a)
    1 and 3 only
  • b)
    2 and 3 only
  • c)
    1 and 2 only
  • d)
    All of the above
Correct answer is option 'A'. Can you explain this answer?

Akshita Mukherjee answered
Ocean Temperatures

Highest Temperature in Open Seas

- This statement is incorrect as the highest ocean temperature is observed in coastal areas, where the Sun’s rays heat the water near the surface.

Ocean Temperature Decreases with Depth

- This statement is correct as the temperature of ocean water decreases with increasing depth due to several factors like pressure, density, and salinity.

Temperature of Oceans Reduces Near Polar Regions

- This statement is correct as the polar regions receive less sunlight and experience colder temperatures, leading to a reduction in ocean temperatures.

Conclusion

- Option A is the correct answer as statements 1 and 3 are incorrect while statement 2 is correct.

Sea level rise at specific locations may be more or less than the global average due to many factors. Which of these factors can create differences between local sea level and global sea level?
1. Local land subsidence
2. Ocean currents
3. Variations in land height
Select the correct answer using the codes below:
  • a)
    1 only
  • b)
    2 only
  • c)
    2 and 3 only
  • d)
    All of the above
Correct answer is option 'D'. Can you explain this answer?

Bhaskar Ghosh answered
Factors Affecting Local Sea Level Rise

Local sea level rise can vary from the global average due to several factors. These factors include:

1. Local Land Subsidence:
- Land subsidence refers to the sinking or settling of the Earth's surface. It can be caused by various factors such as groundwater extraction, natural compaction of sediments, and tectonic activity.
- When the land subsides, it effectively reduces the height of the land relative to the sea level. This can lead to an apparent increase in sea level at a specific location, making it higher than the global average.

2. Ocean Currents:
- Ocean currents play a crucial role in redistributing heat around the globe, which can affect sea level.
- Currents, such as the Gulf Stream, can transport warm water from the tropics to higher latitudes. This can result in higher sea levels in regions where the warm water accumulates.
- Conversely, currents that transport colder water away from a region can cause a decrease in sea level due to the thermal contraction of the water.

3. Variations in Land Height:
- The elevation of the land surface can also influence local sea level.
- In areas where the land is rising or uplifting, the relative sea level may appear to be falling because the land is increasing in height faster than the sea level is rising.
- Conversely, in areas where the land is sinking or subsiding, the relative sea level may appear to be rising even if the global average sea level remains constant.

Overall, a combination of these factors can lead to significant differences between local sea level and the global average. Local land subsidence, ocean currents, and variations in land height all contribute to these differences. Therefore, the correct answer is option 'D' - all of the above.

Cold currents bring cold water into warm water areas. These currents are usually found on the
1. West coast of the continents in the low and middle latitudes in both hemispheres
2. East coasts in the higher latitudes in the Northern Hemisphere
Which of the above is/are correct?
  • a)
    1 only
  • b)
    2 only
  • c)
    Both 1 and 2
  • d)
    None of the above
Correct answer is option 'C'. Can you explain this answer?

Puja Roy answered
Explanation:

West Coast of the Continents in Low and Middle Latitudes
- Cold currents are usually found on the west coast of the continents in the low and middle latitudes in both hemispheres.
- These currents bring cold water from higher latitudes towards the equator, leading to a decrease in water temperature in the warm water areas along the west coast.

East Coasts in Higher Latitudes in the Northern Hemisphere
- Cold currents are also found on the east coasts in the higher latitudes in the Northern Hemisphere.
- These currents bring cold water from polar regions towards lower latitudes, affecting the temperature of the warm water areas along the east coast.

Conclusion
Both statements are correct as they describe the typical locations where cold currents are observed and their impact on the temperature of warm water areas. Cold currents play a crucial role in regulating marine ecosystems and influencing climate patterns in these regions.

Consider the following statements:
1. Continental shelf can be rich sources of fossil fuels because of the river sediment load it carries.
2. Oceanic deeps are important for the study of plate movement as they contain several active volcanoes.
Which of these is/are correct?
  • a)
    1 only
  • b)
    2 only
  • c)
    Both 1 and 2
  • d)
    None of the above
Correct answer is option 'C'. Can you explain this answer?

Meera Kapoor answered
  • The continental shelves are shielded with sediments of variable thicknesses brought down from the land by rivers, glaciers, wind and distributed by waves and currents.
  • Massive sedimentary deposits that continental shelves have received over a long period of time serve as the source of fossil fuels. The deepest parts of the oceans are Oceanic Deeps or Trenches.

Mid-Oceanic Ridges form an interconnected chain of mountain system within the ocean. It is characterised by a central rift system at the crest. The rift system at the crest is the
  • a)
    Zone of maximum tectonic stability
  • b)
    Zone of intense volcanic activity
  • c)
    Plateau’s offshoot that has been stable over the past some time
  • d)
    Zone of Wegner’s oscillations
Correct answer is option 'B'. Can you explain this answer?

Mahi Gupta answered
Mid-Oceanic Ridges Overview
Mid-Oceanic Ridges are underwater mountain ranges formed by plate tectonics, primarily at divergent boundaries where tectonic plates are moving apart.
Rift System Characteristics
- The central rift system is the hallmark of Mid-Oceanic Ridges.
- It is a linear feature characterized by a deep valley or trough.
Zone of Intense Volcanic Activity
- The rift at the crest is indeed the Zone of Intense Volcanic Activity.
- This is where magma from the mantle rises to the surface due to the tectonic plates moving apart.
Processes Involved
- Seafloor Spreading: As the tectonic plates diverge, magma fills the gap, solidifying to form new oceanic crust.
- This process leads to frequent volcanic eruptions, creating new landforms and contributing to the ocean floor's topography.
Geological Significance
- The volcanic activity at the rift system is crucial for the creation of new oceanic crust.
- It also plays a role in the recycling of materials between the Earth's surface and the mantle.
Conclusion
Thus, the rift system at the crest of Mid-Oceanic Ridges is a dynamic and active zone characterized by significant volcanic activity, making option 'B' the correct answer. Understanding this activity is vital for grasping the processes that shape our planet's geology.

Equatorial counter-currents are unique because
  • a)
    They flow in a direction opposite to that of the surface winds.
  • b)
    They circulate from the equator the poles uninterrupted.
  • c)
    Their travel speed is not affected by ocean depth.
  • d)
    They are the only current to be sandwiched between two eastward flowing ocean currents.
Correct answer is option 'A'. Can you explain this answer?

Suyash Dasgupta answered
Equatorial counter-currents are unique because they flow in a direction opposite to that of the surface winds. This phenomenon is significant and distinguishes them from other ocean currents. Let's understand why this is the correct answer in detail:

1. Introduction:
- Briefly introduce the concept of equatorial counter-currents.
- Mention that they are distinct from other ocean currents.

2. Explanation of the surface wind direction:
- Surface winds at the equator blow from the east to the west due to the Coriolis effect.
- These winds are known as the trade winds.
- The trade winds push the surface water of the ocean towards the west, resulting in the formation of the westward-flowing equatorial currents.

3. Description of equatorial counter-currents:
- Equatorial counter-currents flow in the opposite direction to the surface winds.
- While the surface winds blow from east to west, the equatorial counter-currents flow from west to east.
- This unique characteristic makes them distinctive among ocean currents.

4. Factors influencing equatorial counter-currents:
- The equatorial counter-currents are affected by several factors such as the Earth's rotation, wind patterns, and the distribution of water temperature and salinity.
- These factors contribute to the formation and maintenance of the equatorial counter-currents.

5. Importance of equatorial counter-currents:
- Equatorial counter-currents play a crucial role in the global ocean circulation system.
- They act as a pathway for the transfer of heat and energy between the hemispheres.
- The counter-currents also influence climate patterns and weather systems in the regions they pass through.

6. Comparison with other ocean currents:
- Unlike other ocean currents, which generally flow in the same direction as the prevailing winds, equatorial counter-currents are unique because they flow in the opposite direction.
- Most ocean currents are driven by the surface winds, but equatorial counter-currents go against this trend.

7. Conclusion:
- Recap the main points discussed.
- Emphasize that the flow direction of equatorial counter-currents opposite to that of the surface winds is what makes them unique.
- Conclude by highlighting their significance in global ocean circulation and climate patterns.

Tidal energy is based on which of the following?
  • a)
    Difference in temperature of tides
  • b)
    Difference in height of tides
  • c)
    Marine upwelling
  • d)
    Difference in the height of waves
Correct answer is option 'B'. Can you explain this answer?

Meghana Roy answered
Tidal energy is based on the difference in height of tides.

Tidal energy is a form of renewable energy that harnesses the power of the ocean tides to generate electricity. It relies on the gravitational forces of the moon and the sun, which cause the tides to rise and fall. Tidal energy has the potential to provide a consistent and reliable source of power, as tides occur twice a day and are predictable.

Explanation:
Tidal energy is based on the difference in height of tides, also known as the tidal range. When the tide rises, water is stored in a reservoir, and when the tide falls, the water is released, passing through turbines to generate electricity. This process is similar to how a hydroelectric dam works, except that it uses the movement of the tides rather than the flow of a river.

Advantages of tidal energy:
1. Renewable and predictable: Tidal energy is a renewable resource as tides are caused by the gravitational pull of celestial bodies. Tides occur predictably twice a day, making tidal energy a reliable and consistent source of power.
2. Environmentally friendly: Tidal energy does not produce greenhouse gas emissions or air pollution, making it a clean energy option. It also has a minimal impact on the marine environment compared to other forms of energy generation, such as fossil fuel extraction or nuclear power.
3. High energy density: Tidal energy has a high energy density, meaning that a relatively small tidal power plant can generate a significant amount of electricity.
4. Long lifespan: Tidal power plants have a longer lifespan compared to other renewable energy technologies, such as wind turbines or solar panels. This makes tidal energy a more economically viable option in the long term.

Challenges and limitations:
1. High construction and maintenance costs: Building tidal power plants can be expensive due to the need for specialized equipment and infrastructure. Maintenance and repair costs can also be high, as the equipment is exposed to harsh marine conditions.
2. Limited availability of suitable sites: Tidal energy requires a significant tidal range, typically greater than 5 meters, to generate sufficient electricity. This limits the number of suitable locations for tidal power plants.
3. Potential environmental impacts: While tidal energy is generally considered environmentally friendly, it can have localized impacts on marine ecosystems. The construction of tidal power plants and the extraction of energy from tides can disrupt the natural flow of water and impact marine habitats and species.

Overall, tidal energy has the potential to play a significant role in the transition to a more sustainable and renewable energy future. It offers several advantages, including its predictability, reliability, and environmental benefits. However, further research and development are needed to overcome the challenges associated with this form of energy generation and to make it more economically viable on a larger scale.

Consider the following statements:
1. It is found that subsurface ocean currents once absorbed carbon dioxide from winds and released them elsewhere.
2. Ocean currents redistribute heat in the oceans.
Which of the above statements is/are correct?
  • a)
    1 only
  • b)
    2 only
  • c)
    Both 1 and 2
  • d)
    None of the above
Correct answer is option 'C'. Can you explain this answer?

Deepak Kapoor answered
Most of the debate on climate change focuses on greenhouse gases released into the atmosphere. But it has emerged that ocean circulation has an equally important role. It was believed that the severe cooling of the Earth underwent 2.7 million years ago was caused by changes in carbon dioxide (CO2) levels. But analyses of ocean sediments (2.5 million-to 3.3 million-year-old) suggest the cooling happened due to the emergence of sub-surface ocean currents. These currents absorb heat and CO2 from winds blowing close to the ocean surface in the Atlantic and release them in the Pacific.

It is the western boundary current of the southwest Indian Ocean. It acts as an oceanic convergence zone. This ocean current is
  • a)
    Labrador
  • b)
    Gulf current
  • c)
    Benguela
  • d)
    Agulhas
Correct answer is option 'D'. Can you explain this answer?

Kavita Shah answered
  • It flows down the east coast of Africa from 27°S to 40°S. It is narrow, swift and strong. It is even suggested that the Agulhas is the largest western boundary current in the world ocean. The Agulhas acts as an oceanic convergence zone.
  • Due to mass continuity, this drives surface waters down, resulting in the upwelling of cold, nutrient-rich water south of the current.

The annual range of surface temperature is much greater in the North Atlantic and North Pacific oceans than in the southern oceans. This is due to
  • a)
    High cloud formation in the northern oceans
  • b)
    Equatorial counter-currents
  • c)
    Stratospheric circulation
  • d)
    Prevailing winds from the land
Correct answer is option 'D'. Can you explain this answer?

Shalini Gupta answered
Explanation:

The correct answer is option 'D': Prevailing winds from the land.

Prevailing Winds from the Land:
- The prevailing winds refer to the dominant wind direction in a particular region. In the case of the North Atlantic and North Pacific oceans, prevailing winds blow from the land towards the oceans.
- These winds are known as continental winds or land breeze. They are influenced by the temperature differences between land and water.
- During the day, the land heats up faster than the water, causing the air above the land to rise. As a result, cooler air from the ocean rushes in to replace the rising warm air, creating a sea breeze that blows from the ocean towards the land.
- However, during the night, the land cools down faster than the water. The cooler air above the land sinks and flows towards the ocean, creating a land breeze that blows from the land towards the ocean.

Effect on Surface Temperature:
- The prevailing winds blowing from the land towards the North Atlantic and North Pacific oceans have a significant impact on the surface temperature.
- When the land breeze blows towards the ocean, it carries the cooler air from the land and lowers the surface temperature of the ocean.
- Conversely, when the sea breeze blows towards the land, it carries the warmer air from the ocean and increases the surface temperature of the land.
- This temperature exchange between the land and ocean leads to a smaller annual range of surface temperature in the southern oceans compared to the North Atlantic and North Pacific oceans.

Reasoning:
- The annual range of surface temperature refers to the difference between the highest and lowest temperatures experienced in a year.
- Due to the prevailing winds from the land, the North Atlantic and North Pacific oceans experience larger temperature fluctuations compared to the southern oceans.
- The land breeze brings cooler air from the land, causing a decrease in the surface temperature of the oceans.
- The sea breeze, on the other hand, brings warmer air from the ocean, resulting in an increase in the surface temperature of the land.
- These temperature differences between land and ocean are more pronounced in the North Atlantic and North Pacific oceans due to the prevailing winds from the land.
- In contrast, the southern oceans are not influenced by significant continental winds, leading to a smaller annual range of surface temperature.

Tides in the ocean are highest in
  • a)
    Full moon days
  • b)
    New moon days
  • c)
    First quarter of the moon
  • d)
    Both (a) and (b)
Correct answer is option 'D'. Can you explain this answer?

Anita Desai answered
  • The tides are caused by the strong gravitational pull exerted on the surface of the Earth by the Sun and the Moon. Under the influence of the gravitational force of the Moon, the Earth’s water closer to the Moon is pulled and causes high tide.
  • The Sun, the Moon and the Earth are in the same line during the full moon and the new moon days, and the highest tide called spring tides can be seen on those days.
  • But at the first and last quarters of the Moon, the ocean waters are drawn by the gravitational pull of Sun and Earth in diagonally opposite directions, resulting in low tides called neap tides.

The Rannutsav has highlighted the Rann of Kutch. This region is well known for which of these geographical features?
  • a)
    the Largest delta of India
  • b)
    Plains hosting Tropical Evergreen vegetation
  • c)
    Seasonal salt marshes
  • d)
    Deepest freshwater lakes of India
Correct answer is option 'C'. Can you explain this answer?

Suresh Reddy answered
Sunderban delta is the largest in India, so A is wrong. Rann of Kutch is one of the largest salt deserts in the world. In summer monsoon, the flat desert of salty clay and mudflats fills with standing water. Kutch is also the cultural district of Gujarat, which has been given a new identity by Rannutsav.

The meeting of the cold Labrador current and warm Gulf stream current leads to
1. Dense mist and fog
2. An Arid Climate Zone
Which of the above is/are correct?
  • a)
    1 only
  • b)
    2 only
  • c)
    Both 1 and 2
  • d)
    None of the above
Correct answer is option 'A'. Can you explain this answer?

Deepa Iyer answered
  • When cold and warm ocean current meets, the warm ocean current condenses after getting in contact with cold air and it results in fog.
  • It also leads to a high rate of precipitation in the region. The circulation in the area where the Labrador Current and Gulf Stream meet is one of the most complex and variable regions in the world.

Within the Earth’s ocean and atmosphere, Rossby waves form as a result of
  • a)
    Rotation of the planet
  • b)
    Churning of oceans
  • c)
    Tectonic movement beneath ocean plates
  • d)
    Collision of clouds
Correct answer is option 'A'. Can you explain this answer?

Amit Kumar answered
Waves in the ocean come in many different shapes and sizes. Slow-moving oceanic Rossby waves are fundamentally different from ocean surface waves.
  • Unlike waves that break along the shore, Rossby waves are huge, undulating movements of the ocean that stretch horizontally across the planet for hundreds of kilometres in a westward direction.
  • Also known as planetary waves, they naturally occur in rotating fluids.
  • They are so large and massive that they can change Earth’s climate conditions.

World’s best fishing grounds are formed where
  • a)
    Coastal areas adjoin high density of warm currents
  • b)
    Warm and cold currents meet
  • c)
    There is a severe lack of phytoplankton
  • d)
    Deep marine trenches are found
Correct answer is option 'B'. Can you explain this answer?

Amit Kumar answered
The following conditions are good for fisheries production and catch: Coastal upwelling of nutrient-rich colder water Abundance of phytoplankton Meeting of warm and cold currents Shallow continental shelves in cold regions It is exemplified by the fact that one of the world’s richest fishing grounds situated around the coast of Iceland.

The California Ocean current, which flows along the west coast of North America, is a
  • a)
    Cold current, flowing north
  • b)
    Cold current, flowing south
  • c)
    Warm current, flowing south
  • d)
    Warm current, flowing north
Correct answer is option 'B'. Can you explain this answer?

Sanjay Rana answered
  • The California Current is a Pacific Ocean current that moves southward along the western coast of North America, beginning off southern British Columbia and ending off southern Baja California Peninsula.
  • It is considered an Eastern boundary current due to the influence of the North American coastline on its course.
  • It is also one of five major coastal currents affiliated with strong upwelling zones, the others being the Humboldt Current, the Canary Current, the Benguela Current, and the Somali Current.
  • The California Current is part of the North Pacific Gyre, a large swirling current that occupies the northern basin of the Pacific.

Ocean acts as a large carbon sink on Earth due to
  • a)
    Its large geographical coverage
  • b)
    Rich population of phytoplankton and seagrass
  • c)
    Difference in the partial pressure of carbon dioxide between seawater and air
  • d)
    All of the above
Correct answer is option 'D'. Can you explain this answer?

Pooja Choudhury answered
  • Carbon dioxide readily dissolves in water and the oceans provide a huge reservoir of carbon.
  • Across the world’s oceans, there is a continual cycle of equilibration of dissolved carbon dioxide in water with carbon dioxide in the atmosphere.
  • The difference in the partial pressure of the CO2, between seawater and air, facilitate gaseous exchange. This allows atmospheric CO2 to dissolve in seawater.
  • The carbon dioxide which dissolves in our oceans occurs in three main forms. Aside from the normal carbon dioxide form, it is also found as bicarbonate and carbonate ions.

Chapter doubts & questions for Oceanography - Lucent for GK 2025 is part of UPSC CSE exam preparation. The chapters have been prepared according to the UPSC CSE exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for UPSC CSE 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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