NCERT Solutions Class-11 Geography Chapter-12: Water (Oceans)
Exercises Page No. 106
Que 1. Multiple choice questions.
(i) Identify the element which is not a part of the hydrological cycle
(a) Evaporation (c) Precipitation
(b) Hydration (d) Condensation
Answer:
(b) Hydration
(ii) The average depth of continental slope varies between
(a) 2–20m (c) 20–200m
(b) 200–2,000m (d) 2,000–20,000m
Answer:
(b) 200-2,000m
(iii) Which one of the following is not a minor relief feature in the oceans:
(a) Seamount (c) Oceanic Deep
(b) Atoll (d) Guyot
Answer:
(b) Atoll
(iv) Salinity is expressed as the amount of salt in grams dissolved in sea water per
(a) 10 gm (c) 100 gm
(b) 1,000 gm (d) 10,000 gm
Answer:
(b) 1,000 gm
(v) Which one of the following is the smallest ocean:
(a) Indian Ocean (c) Atlantic Ocean
(b) Arctic Ocean (d) Pacific Ocean
Answer:
(b) Arctic Ocean
2. Answer the following questions in about 30 words.
(i) Why do we call the earth a Blue Planet?
Answer:
Earth is called the Blue Planet because about 71% of its surface is covered by water, giving it a blue appearance when seen from space.
(ii) What is a continental margin?
Answer:
A continental margin is the zone where continents meet oceans, consisting of the continental shelf, slope, and rise.
(iii) List out the deepest trenches of various oceans.
Answer:
Deepest trenches include the Mariana Trench (Pacific), Tonga Trench (Pacific), Puerto Rico Trench (Atlantic), Java Trench (Indian), and South Sandwich Trench (Southern).
(iv) What is a thermocline?
Answer:
The thermocline is a boundary layer in the ocean characterized by a rapid decrease in temperature with increasing depth. It lies below the surface layer and marks the transition between the warmer upper layer and the colder deeper layer of the ocean. This temperature gradient within the thermocline is essential for understanding ocean circulation patterns and the distribution of marine life.
(v) When you move into the ocean what thermal layers would you encounter? Why the temperature varies with depth?
Answer: As you move into the ocean, you would encounter different thermal layers:
- Epipelagic Zone (Surface Layer): This is the top layer of the ocean, extending from the surface down to about 200 meters. It is warmed by sunlight and experiences the most temperature variation. Temperatures typically range from 20°C to 25°C in this layer.
- Mesopelagic Zone (Twilight Zone): Below the epipelagic zone lies the mesopelagic zone, which extends from about 200 meters to 1,000 meters deep. Temperatures gradually decrease with depth in this layer.
- Bathypelagic Zone (Midnight Zone): Deeper still is the bathypelagic zone, reaching from about 1,000 meters to 4,000 meters deep. Here, temperatures continue to decrease, and it becomes progressively colder as you descend into the ocean depths.
(vi) What is salinity of sea water?
Answer:
Salinity refers to the concentration of dissolved salts in seawater, typically measured in parts per thousand (ppt) or grams of salt per kilogram of seawater (g/kg). Salinity is influenced by factors such as evaporation, which increases salinity by leaving behind salts, and precipitation, which dilutes seawater by adding freshwater. It also varies based on inputs from rivers, melting ice, and underwater volcanic activity. Salinity plays a crucial role in determining the density and buoyancy of seawater, affecting ocean circulation patterns and marine life distribution.
3. Answer the following questions in about 150 words.
(i) How are various elements of the hydrological cycle interrelated?
Answer:
The various elements of the hydrological cycle, such as evaporation, condensation, precipitation, runoff, and groundwater flow, are interconnected in a continuous cycle. For instance, water evaporates from the surface of oceans and other water bodies, forming clouds through condensation.
These clouds release precipitation, which replenishes water sources on land and infiltrates into the ground, contributing to groundwater recharge. Surface runoff transports water back to oceans and rivers, completing the cycle. This interdependence ensures the continuous movement and distribution of water on Earth, sustaining life and ecosystems.
(ii) Examine the factors that influence the temperature distribution of the oceans.
Answer:
The temperature distribution of oceans is influenced by several factors.
(i) Latitude: Surface water temperature decreases from the equator towards the poles due to varying amounts of sunlight received at different latitudes.
(ii) Unequal Distribution of Land and Water: Oceans in the northern hemisphere receive more heat because they are more surrounded by land compared to oceans in the southern hemisphere.
(iii) Prevailing Winds: Winds blowing from land to oceans push warm surface water away from the coast, leading to upwelling of cold water from below, which affects temperature. Conversely, onshore winds can pile up warm water near the coast, increasing temperature.
(iv) Ocean Currents: Warm ocean currents raise temperatures in colder areas, while cold currents lower temperatures in warmer areas. For example, the Gulf Stream warms the eastern coast of North America and the West Coast of Europe, while the Labrador current cools the northeast coast of North America.
NCERT Solutions Class-11 Geography Chapter-12: Water (Oceans)
NCERT Solutions Class-11 Geography Chapter-12 Water (Oceans): NCERT Solutions for Class 11 Geography provides solutions that are easy to understand. The Class-11 NCERT solutions for Geography provided by our expert team can help you to build a deeper understanding of concepts like Hydrological Cycle, Temperature Of Ocean Waters, Salinity Of Ocean Water, etc.
These Class-11 NCERT Geography solution exercises are compiled and created by certified professionals who guarantee that students will build a strong foundation in Geography.