CBSE Class 11 Fundamental of Physical Geography: Chapter 13 Water Oceans NCERT Solutions

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NCERT Solutions PDF Class 11 PDF

This chapter delves into the fundamental aspects of physical geography related to Earth's oceans. It covers the hydrological cycle, explaining its key components and processes. The solutions detail the various features of the ocean floor, including continental margins, slopes, and minor relief features like seamounts and atolls, while distinguishing them from major features like oceanic trenches. The chapter also addresses the concept of salinity, its measurement, and factors influencing it. Furthermore, it explores the thermal structure of the oceans, defining thermocline and explaining how temperature changes with depth. These NCERT Solutions provide clear, step-by-step explanations and answers to help students grasp complex oceanographic concepts, aiding in effective exam preparation and revision.

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Quick info

BoardCBSE
ClassClass 11
SubjectFundamental of Physical Geography
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 13

Chapter summary

Chapter 13, 'Water Oceans,' focuses on the physical characteristics and processes of the world's oceans. The NCERT Solutions cover the hydrological cycle, ocean floor topography including continental margins and minor relief features, and the concept of salinity. It also explains the thermal stratification of oceans and the thermocline. These solutions are designed to clarify the key concepts and provide accurate answers to the chapter's questions, facilitating a deeper understanding of oceanography.

Learning outcomes

  • Understand the components of the hydrological cycle.
  • Identify and differentiate between major and minor ocean relief features.
  • Define and explain ocean salinity and its measurement.
  • Describe the thermal layers of the ocean and the concept of thermocline.
  • Explain the variation of ocean temperature with depth.

Topics covered

Paper topics

  • Hydrological Cycle
  • Continental Margin
  • Continental Slope
  • Ocean Floor Relief Features
  • Seamount
  • Atoll
  • Oceanic Deep
  • Guyot
  • Salinity
  • Thermocline
  • Ocean Temperature Variation
  • Blue Planet

Important topics

  • Hydrological Cycle components
  • Major vs. Minor Ocean Relief Features
  • Definition and Measurement of Salinity
  • Thermal Layers and Thermocline
  • Continental Margin and Slope

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Questions and Solutions

Multiple choice questions

1. Identify the element, which is not a part of the hydrological cycle
  1. Evaporation
  2. Hydration
  3. Precipitation
  4. Condensation
Solution: The hydrological cycle, also known as the water cycle, describes the continuous movement of water on, above, and below the surface of the Earth. The main processes involved are evaporation, transpiration, condensation, precipitation, and collection. Hydration, in a geological context, refers to the chemical addition of water to a mineral. Therefore, hydration is not considered a part of the hydrological cycle.

Answer: (b) Hydration

2. The average depth of continental slope varies between
  1. 2-20m
  2. 200-2,000m
  3. 20-200m
  4. 2,000-20,000m
Solution: The continental slope is the steep gradient that descends from the edge of the continental shelf to the deep ocean floor. It represents the actual edge of the continent. The average depth of the continental slope typically ranges from 200 meters to 2,000 meters.

Answer: (b) 200-2,000m

3. Which one of the following is not a minor relief feature in the oceans:
  1. Seamount
  2. Atoll
  3. Oceanic Deep
  4. Guyot
Solution: Ocean floor relief features are broadly classified into major and minor categories. Major features include continental shelves, continental slopes, continental rises, abyssal plains, mid-oceanic ridges, trenches, and oceanic deeps. Minor relief features are smaller formations like seamounts, guyots, atolls, submarine canyons, and volcanic islands. An oceanic deep, such as a trench, is a significant and extensive feature, not a minor one.

Answer: (c) Oceanic Deep

4. Salinity is expressed as the amount of salt in grams dissolved in sea water per
  1. 10 gm
  2. 1,000 gm
  3. 100 gm
  4. 10,000 gm
Solution: Salinity refers to the total concentration of all dissolved salts in seawater. It is conventionally expressed as the number of grams of salt dissolved in 1,000 grams (or 1 kilogram) of seawater. This unit is often referred to as 'per mille' (‰).

Answer: (b) 1,000 gm

5. Which one of the following is the smallest ocean:
  1. Indian Ocean
  2. Arctic Ocean
  3. Atlantic Ocean
  4. Pacific Ocean
Solution: The world's oceans, listed by size from largest to smallest, are the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean. The Arctic Ocean is the smallest and shallowest of the five major oceans.

Answer: (b) Arctic Ocean

2. Answer the following questions in about 30 words

(i) Why do we call the earth a Blue Planet?

Why do we call the earth a Blue Planet?
Solution: The Earth is referred to as the 'Blue Planet' because a vast majority of its surface, approximately 71 percent, is covered by water bodies like oceans, seas, and lakes. This extensive water coverage gives the planet a distinct blue hue when viewed from space.

(ii) What is a continental margin?

What is a continental margin?
Solution: A continental margin is the underwater region where the continental crust transitions into the oceanic crust. It comprises the continental shelf (a gently sloping submerged plain), the continental slope (a steeper descent), and the continental rise (a gently sloping accumulation of sediments at the base of the slope).

(iii) List out the deepest trenches of various oceans.

List out the deepest trenches of various oceans.
Solution: The deepest trenches in the world's oceans are significant geological features. The Mariana Trench in the Pacific Ocean is the deepest, reaching approximately 10,994 meters. In the Atlantic Ocean, the Puerto Rico Trench is the deepest at about 8,648 meters. The Indian Ocean's deepest point is the Sunda (or Java) Trench, with a depth of around 7,725 meters. The deepest point in the Southern Ocean is the South Sandwich Trench at approximately 7,235 meters, and in the Arctic Ocean, it is the Litke Deep at about 5,450 meters.

(iv) What is a thermocline?

What is a thermocline?
Solution: A thermocline is a distinct layer within a body of water, such as an ocean or a lake, where the temperature changes more rapidly with depth than it does in the layers above or below. It acts as a boundary between the warmer surface waters and the colder deep waters.

(v) When you move into the ocean what thermal layers would you encounter? Why the temperature varies with depth?

When you move into the ocean what thermal layers would you encounter? Why the temperature varies with depth?
Solution: As one moves from the ocean surface downwards, three main thermal layers are encountered: the mixed layer (surface layer), the thermocline, and the deep cold layer. The temperature varies with depth primarily due to solar radiation, which heats the surface waters. The mixed layer is relatively warm and uniform due to wind and wave action. Below this lies the thermocline, where temperature drops significantly over a short distance. Finally, the deep cold layer extends to the ocean floor, where temperatures are consistently low (around 2-4°C) as sunlight does not penetrate these depths.

Common mistakes

  • Confusing minor ocean relief features with major ones.
  • Incorrectly recalling the definition or measurement of salinity.
  • Misunderstanding the concept of continental margins and slopes.
  • Difficulty in explaining the thermal layers and temperature variations in oceans.

Revision tips

  • Draw diagrams to illustrate ocean floor features and thermal layers.
  • Memorize the key terms like 'hydrological cycle', 'salinity', and 'thermocline'.
  • Practice identifying which elements are part of the hydrological cycle.
  • Review the depths of major ocean trenches and their locations.

Practice MCQs

Q1. Which of the following is NOT a part of the hydrological cycle?

Q2. The continental slope typically has a depth range of:

Q3. Which of the following is considered a major ocean relief feature, not a minor one?

Q4. Salinity is measured as the amount of salt in grams per:

Q5. Which is the smallest ocean on Earth?

Frequently asked questions

What is the significance of the Earth being called the 'Blue Planet'?

The Earth is called the 'Blue Planet' because approximately 71% of its surface area is covered by water, giving it a distinct blue appearance from space and indicating an abundant supply of water.

What constitutes the continental margin?

The continental margin is the underwater zone that separates the continental crust from the oceanic crust. It includes the continental shelf, continental slope, and continental rise.

What are the deepest trenches in the world's oceans?

The deepest trenches include the Mariana Trench (Pacific Ocean, ~10,994m), Puerto Rico Trench (Atlantic Ocean, ~8,648m), Sunda/Java Trench (Indian Ocean, ~7,725m), and South Sandwich Trench (Southern Ocean, ~7,235m).

How is salinity measured in oceans?

Salinity is typically measured as the amount of salt in grams dissolved in 1,000 grams of seawater.

What is a thermocline and why is it important?

A thermocline is a transitional layer in the ocean where water temperature decreases rapidly with depth. It separates the warmer surface waters from the colder deep waters and influences marine ecosystems.

How does ocean temperature change with depth?

Ocean temperature generally decreases with depth. Surface waters are warmer due to solar radiation, while deeper waters are colder. The thermocline marks a significant drop in temperature between these layers.

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