Water (Oceans)Class 11 Fundamentals of Physical Geography NCERT Solutions
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Q11. Multiple choice questions.
(i) Identify the element which is not a part of the hydrological cycle
(a)
Evaporation
(b)
Hydration
(c)
Precipitation
(d)
Condensation
Solution
(b) Hydration
The hydrological cycle describes the movement of water and includes processes like evaporation, condensation, and precipitation, as mentioned in the chapter. Hydration, which is a chemical process of adding water to a substance, is not a part of this large-scale natural cycle.
Q21. Multiple choice questions.
(ii) The average depth of continental slope varies between
(a)
2-20 m
(b)
200-2,000 m
(c)
20-200 m
(d)
2,000-20,000 m
Solution
(b) 200-2,000 m
According to the chapter, the continental slope connects the continental shelf and the ocean basins. The text states that "The depth of the slope region varies between 200 and 3,000 m." The option 200-2,000 m is the closest range provided.
Q31. Multiple choice questions.
(iii) Which one of the following is not a minor relief feature in the oceans:
(a)
Seamount
(b)
Atoll
(c)
Oceanic Deep
(d)
Guyot
Solution
(c) Oceanic Deep
The chapter classifies the ocean floor into four major divisions: the Continental Shelf, the Continental Slope, the Deep Sea Plain, and the Oceanic Deeps. Features like seamounts, guyots, and atolls are listed under the category of 'Minor Relief Features'. Therefore, an Oceanic Deep is a major, not a minor, relief feature.
Q41. Multiple choice questions.
(iv) Salinity is expressed as the amount of salt in grams dissolved in sea water per
(a)
10 gm
(b)
1,000 gm
(c)
100 gm
(d)
10,000 gm
Solution
(b) 1,000 gm
The text defines salinity as "the total content of dissolved salts in sea water." It further clarifies that "It is calculated as the amount of salt (in gm) dissolved in 1,000 gm (1 kg) of seawater."
Q51. Multiple choice questions.
(v) Which one of the following is the smallest ocean:
(a)
Indian Ocean
(b)
Arctic Ocean
(c)
Atlantic Ocean
(d)
Pacific Ocean
Solution
(b) Arctic Ocean
The chapter lists the five major oceans as the Pacific, the Atlantic, the Indian, the Southern, and the Arctic. Among these, the Arctic Ocean is the smallest in terms of area.
Q12. Answer the following questions in about 30 words.
(i) Why do we call the earth a Blue Planet?
Solution
The earth is called the 'Blue Planet' because of its abundant supply of water. Approximately 71 percent of the planet's surface is covered by water, primarily in the oceans, giving it a distinct blue appearance from space.
Q22. Answer the following questions in about 30 words.
(ii) What is a continental margin?
Solution
A continental margin is the extended edge of a continent that is submerged under the ocean. It consists of the continental shelf, which is the shallow, extended part of the landmass, and the continental slope, where the seafloor drops steeply to the deep ocean basin.
Q32. Answer the following questions in about 30 words.
(iii) List out the deepest trenches of various oceans.
Solution
The deepest trenches are areas of significant depth in the ocean floor. While the text notes that 32 trenches are in the Pacific, 19 in the Atlantic, and 6 in the Indian Ocean, it does not name them. The deepest known trenches are:
- Pacific Ocean: Mariana Trench
- Atlantic Ocean: Puerto Rico Trench
- Indian Ocean: Java Trench (Sunda Trench)
Q42. Answer the following questions in about 30 words.
(iv) What is a thermocline?
Solution
A thermocline is a boundary region in the ocean, typically found below the surface layer, where there is a rapid decrease in water temperature with increasing depth. It separates the warmer upper layer of the ocean from the colder, deeper water below.
Q52. Answer the following questions in about 30 words.
(v) When you move into the ocean what thermal layers would you encounter? Why the temperature varies with depth?
Solution
Moving down into the ocean in middle and low latitudes, one encounters three thermal layers: a warm top layer, a thermocline layer where temperature drops rapidly, and a very cold deep layer. Temperature varies with depth because the sun's heat only penetrates the surface layers, and this heat is transferred slowly to deeper sections through convection.
Q62. Answer the following questions in about 30 words.
(vi) What is salinity of sea water?
Solution
Salinity is the term used to define the total amount of dissolved mineral salts in seawater. It is typically expressed as parts per thousand (‰) and is calculated as the amount of salt in grams dissolved in 1,000 grams (1 kg) of seawater.
Q13. Answer the following questions in about 150 words.
(i) How are various elements of the hydrological cycle interrelated?
Solution
The various elements of the hydrological cycle are deeply interrelated, forming a continuous, circular movement of water on, above, and below the Earth's surface. The cycle is driven by solar energy.
It begins with evaporation from water bodies like oceans, where liquid water turns into water vapor and enters the atmosphere. Plants also release water vapor through transpiration. This water vapor in the atmosphere undergoes condensation, forming clouds. When the water droplets in clouds become heavy enough, they fall back to the Earth's surface as precipitation (rain, snow, etc.).
Once on the surface, water can follow several paths. It can collect as surface runoff in streams and rivers, which flow back to the oceans. It can also infiltrate the ground and become part of the groundwater storage. Water stored in ice and snow can melt and also contribute to runoff. All these paths eventually lead the water back to the oceans, where the cycle of evaporation begins again. Each process is a crucial step that transfers water from one storage component (e.g., oceans, atmosphere, groundwater) to another, making the entire cycle interconnected.
Q23. Answer the following questions in about 150 words.
(ii) Examine the factors that influence the temperature distribution of the oceans.
Solution
The temperature distribution of the oceans is influenced by several key factors that operate both globally and locally. These factors are:
-
Latitude: The primary factor is latitude. Since the amount of solar insolation decreases from the equator towards the poles, the surface water temperature of the oceans is highest near the equator and gradually decreases with increasing latitude.
-
Unequal Distribution of Land and Water: The oceans in the northern hemisphere are in contact with a larger extent of land compared to the southern hemisphere. Land heats up and cools down faster than water. This contact results in the oceans of the northern hemisphere receiving more heat and recording a relatively higher average temperature than those in the southern hemisphere.
-
Prevailing Winds: Winds blowing over the ocean surface influence temperature. Offshore winds push the warm surface water away from the coast, causing an upwelling of cold, deep water, which lowers the surface temperature. Conversely, onshore winds tend to pile up warm surface water near the coast, raising the temperature.
-
Ocean Currents: Ocean currents act like large rivers, transporting water across vast distances. Warm currents, such as the Gulf Stream, carry warm water to colder regions, raising the local temperature. Cold currents, like the Labrador Current, bring cold water to warmer areas, thereby lowering the temperature.
Q1Project Work
(i) Consult the atlas and show ocean floor relief on the outline of the world map.
Solution
To complete this task, you would need an outline map of the world and an atlas with physical or bathymetric maps of the oceans.
- Continental Shelf: Lightly shade the shallow areas immediately adjacent to the continents. These are extensive in some areas, like the Siberian Shelf in the Arctic Ocean, and narrow in others, like off the coast of Chile.
- Continental Slope: Draw a line or a more densely shaded area just outside the continental shelf to represent the steep drop-off to the deep ocean floor.
- Mid-Oceanic Ridges: Locate and draw the major underwater mountain ranges. Key examples include the Mid-Atlantic Ridge in the Atlantic Ocean, and the East Pacific Rise in the Pacific Ocean.
- Oceanic Deeps (Trenches): Identify and mark the deepest parts of the oceans with thick, dark lines. Notable trenches to include are the Mariana Trench in the Pacific Ocean, the Puerto Rico Trench in the Atlantic, and the Java Trench in the Indian Ocean.
- Deep Sea Plains (Abyssal Plains): The vast, flat areas of the deep ocean floor between the ridges and trenches can be left largely unmarked or lightly labelled to represent their flat, featureless nature.
Q2Project Work
(ii) Identify the areas of mid oceanic ridges from the Indian Ocean.
Solution
Using an atlas, one can identify the interconnected system of mid-oceanic ridges in the Indian Ocean. The main ridges form an inverted 'Y' shape:
- The Central Indian Ridge: This ridge runs in a north-south direction in the central Indian Ocean, separating the African Plate from the Indo-Australian Plate.
- The Southwest Indian Ridge: This ridge branches off from the Central Indian Ridge and extends southwestward, separating the African Plate from the Antarctic Plate.
- The Southeast Indian Ridge: This is the third branch, extending southeastward from the central junction point. It separates the Indo-Australian Plate from the Antarctic Plate. These ridges are active tectonic zones characterized by volcanic and seismic activity.