Class 11 Geography (Fundamental of Physical Geography) Chapter 12 Water (Oceans)

Key Concept: Basic Components

b) Evaporation

[Solution Description] The process that involves water changing from a liquid to a gas and moving into the atmosphere is called evaporation.

Key Concept: Basic Definition

b) A steep drop-off connecting the continental shelf and ocean basins

[Solution Description] The continental slope is a geographical feature that connects the continental shelf to the ocean basins. It acts as a transition zone between these two regions.

Key Concept: Definition Recall

b) A mountain with pointed summits rising from the seafloor

[Solution Description] A seamount is defined as a mountain with pointed summits that rise from the seafloor but do not reach the ocean surface.

Key Concept: Depth Comparison

b) 3-5 km

[Solution Description] Oceanic trenches are typically 3-5 km deeper than the surrounding ocean floor.

Key Concept: Salinity Definition

b) parts per thousand

[Solution Description] Salinity measures the total content of dissolved salts and is typically expressed in parts per thousand (ppt).

Key Concept: Basic Definition

c) A chain of mountains with a large depression

[Solution Description] A mid-oceanic ridge is composed of two chains of mountains separated by a large depression, formed due to tectonic activity.

Key Concept: Basic Definition

c) Waves and currents

[Solution Description] The process responsible for the movement and deposition of sediments on continental shelves is primarily caused by waves and currents. These forces can transport sediment particles over long distances and deposit them in new locations on the ocean floor.

Key Concept: Basic Concept

c) Photosynthesis

[Solution Description] The hydrological cycle consists of processes like evaporation, condensation, and precipitation. Photosynthesis is a biological process, not part of the hydrological cycle.

Key Concept: Depth Range

c) 3000-6000m

[Solution Description] Deep sea plains are described as some of the flattest regions in ocean basins, generally found at depths ranging from 3000 meters to 6000 meters. Therefore, referring to the syllabus, we conclude that their depth range is 3000-6000m.

Key Concept: Location Recall

c) Pacific Ocean

[Solution Description] The Pacific Ocean contains more than 10,000 seamounts and guyots, making it the largest collection of these features in any ocean.

Key Concept: Surface Temperature

c) 26°C to 28°C

[Solution Description] The surface temperature of ocean waters near the equator typically ranges from about 26°C to 28°C due to direct sunlight and less variation caused by seasonal changes.

Key Concept: Salinity Variation

b) Halocline

[Solution Description] The halocline is the layer in the ocean where there is a distinct change in salinity with depth. It usually refers to the part of the water column where salinity increases rapidly with increasing depth.

Key Concept: Basic Concept

b) Decrease temperature

[Solution Description] Offshore winds blow from the land toward the sea, often causing upwelling of cold water. This process brings cooler water to the surface near the coast, thereby lowering coastal temperatures.

Key Concept: Location

b) Tropical Oceans

[Solution Description] Atolls are typically located in tropical oceans, where the temperature and environmental conditions support the formation of coral reefs.

Key Concept: Mid-Oceanic Ridge Features

b) Broad, raised volcanic ridges

[Solution Description] Mid-oceanic ridges are characterized by volcanic activity and are often found at divergent tectonic plate boundaries. These ridges have peaks that can rise above the ocean’s surface but typically don’t form flat-topped summits.

Key Concept: Basic Facts

c) 71%

[Solution Description] Oceans cover about 71% of Earth’s surface. This is a basic fact about the coverage of oceans on Earth.

Key Concept: Hemisphere Temperature

a) Northern Hemisphere

[Solution Description] Oceans in the northern hemisphere record relatively higher temperatures than oceans in the southern hemisphere, according to the syllabus information.

Key Concept: Scenario Application

c) Increase due to higher salinity

[Solution Description] Increased ocean temperature can decrease water density, while higher salinity increases it. The interplay between these factors typically leads to more dynamic water conditions that can enhance wave formation, resulting in an increase in wave size.

Key Concept: Equatorial Temperature

d) Due to land-water distribution

[Solution Description] The highest ocean temperatures are recorded slightly north of the equator due to land-water distribution. The large landmass in the northern hemisphere absorbs more solar heat, leading to a higher temperature than directly on the equator.

Key Concept: Influence of Ocean Currents, Factors Affecting Temperature Distribution

b) Milder winters and cooler summers in western Europe due to the Gulf Stream’s warmth.

[Solution Description] Ocean currents can have significant effects on regional climates. The Gulf Stream, a warm Atlantic Ocean current originating in the Gulf of Mexico, flows northwards along the east coast of the United States before crossing the Atlantic Ocean towards Europe.

This warm current transfers heat from lower latitudes to higher latitudes, leading to milder winters in western Europe compared to eastern North America, despite being at similar latitudes. Thus, the warming effect of the Gulf Stream raises the temperature of Western Europe’s coastal areas.

Hence, the correct choice explains this phenomenon accurately.

Key Concept: Measurement Units

c) 1,000 gm

[Solution Description] Salinity is commonly measured in parts per thousand, which means the amount of salt in grams per 1,000 grams of seawater.

Key Concept: Measurement Units

c) 1,000 gm

[Solution Description] Salinity is measured in parts per thousand (o/oo), which denotes the number of grams of salt per 1,000 grams or kilograms of seawater.

Key Concept: Water Distribution

a) Glaciers and ice caps

[Solution Description] The largest amount of Earth’s freshwater is stored in glaciers and ice caps. Approximately 68.7% of all freshwater on Earth is found in these forms, making them the primary reservoir of freshwater.

Key Concept: Basic Definition

c) Gravitational pull of the moon and the sun

[Solution Description]

Tides are primarily caused by the gravitational pull exerted by the moon and the sun on Earth’s oceans. This gravitational force leads to the rising and falling of sea levels, known as tides.

Key Concept: Temperature Influence

d) Gulf Stream

[Solution Description]

The Gulf Stream is a powerful, warm Atlantic Ocean current that originates in the Gulf of Mexico and flows into the Atlantic at the tip of Florida, accelerating along the eastern coastlines of the United States and Newfoundland. This current then crosses the Atlantic Ocean toward Western Europe. It significantly affects the climate by warming the waters, ultimately influencing the climate of Western Europe, making it milder than other regions at the same latitude.

Key Concept: Wind Impact

b) Onshore winds

[Solution Description] Downwelling is typically caused by onshore winds that push water towards the coast, resulting in the sinking of water.

Key Concept: Definition Recall

d) A deep valley on the ocean floor

[Solution Description] A submarine canyon is a deep, steep-sided valley found on the ocean floor, typically cutting across continental shelves and slopes.

Key Concept: Warm Currents

d) Gulf Stream

[Solution Description] The Gulf Stream is a warm ocean current known for raising temperatures on the eastern coast of North America and also affecting the West Coast of Europe.

Key Concept: Basic Definition

b) 71%

[Solution Description] According to the syllabus, the oceans contain 71% of the planetary water, which plays a crucial role in climate regulation.

Key Concept: Ocean Floor Features

b) Seamount

[Solution Description] The features of the ocean floor include ridges, hills, seamounts, guyots, trenches, and canyons. Among these, seamounts are recognized as prominent underwater mountains or volcanic peaks on the ocean floor.

Key Concept: Ocean Distribution

c) 71%

[Solution Description] According to the syllabus, 71% of Earth’s water is stored in the oceans.

Key Concept: Ocean Floor Processes

b) Tectonic subduction

[Solution Description] Oceanic trenches are primarily formed by tectonic processes, specifically at convergent boundaries where one tectonic plate is forced under another in a process known as subduction.

Key Concept: Basic Concept

d) It supports life by recycling Earth’s water resources

[Solution Description] The primary significance of the hydrological cycle is its role in maintaining life on Earth. It is responsible for the continuous movement of water, which is crucial for weather patterns, supporting ecosystems, and supplying fresh water for human needs.

Key Concept: Ocean Relief Features

b) Continental shelf

[Solution Description] Major oceanic relief features include continental shelves, slopes, and deep sea plains. Seamounts are typically considered minor relief features.

Key Concept: Vertical Distribution

b) Increases

[Solution Description] The salinity in an ocean generally increases with depth until it reaches a zone known as the halocline, where this increase is sharp and distinct.

Key Concept: Basic Concept

c) Moon

[Solution Description] The gravitational pull of the moon is the primary cause of tides on Earth. Although the sun also exerts a gravitational force, the moon’s proximity to Earth makes its gravitational influence stronger in this context.

Key Concept: Ocean Floor Divisions

c) Continental Shelf

[Solution Description]

The major divisions of the ocean floor include the Continental Shelf, Continental Slope, Deep Sea Plain, and Oceanic Deeps.

Therefore, one of these should be the correct answer for this question.

Key Concept: Direct Application

c) High energy

[Solution Description] A high crest indicates that the wave carries more energy. Higher crests correspond to larger amplitudes, which means more energy.

Key Concept: Basic Identification

d) They have steep sides and narrow basins.

[Solution Description] Oceanic trenches are characterized by steep sides and narrow basins, making them distinct from other features on the ocean floor.

Key Concept: Basic Definitions

a) 1°

[Solution Description] The continental shelf is described as having an average gradient of 1°. This is a key characteristic used to differentiate it from other ocean floor features.

Key Concept: Process Identification

b) Condensation

[Solution Description] The transformation of water vapor into liquid water droplets is called condensation. This process occurs when water vapor in the air cools down and changes back into a liquid form, often forming clouds or dew.

Key Concept: Basic Definitions

b) 2° – 5°

[Solution Description] The continental slope connects the continental shelf and ocean basins. According to the syllabus, its gradient typically ranges from 2° to 5°.

Key Concept: Salinity Measurement

c) 1,000 gm

[Solution Description] Salinity in ocean water is typically measured as the amount of salt in grams dissolved in 1,000 grams of seawater. This measurement is commonly referred to as parts per thousand (permil).

Key Concept: Ocean Currents

b) Gulf Stream

[Solution Description] The Gulf Stream is a warm ocean current that flows from the Gulf of Mexico along the eastern coast of the United States to Europe. It significantly affects the climate of the eastern coast of North America by raising temperatures.

Key Concept: Definition Recall

d) A mountain with pointed summits rising from the seafloor that does not reach the ocean surface

[Solution Description] A seamount is a mountain with pointed summits rising from the seafloor, volcanic in origin, typically between 3,000 and 4,500 meters tall. It does not reach the ocean surface.

Key Concept: Layer Characteristics

c) Rapid decrease in temperature

[Solution Description] The thermocline is characterized by a rapid decrease in temperature. It serves as a boundary where the warm surface water separates from the colder deep ocean water. This layer typically lies between 100 m to 400 m below the ocean’s surface.

Key Concept: Impact of Overfishing

c) A decline in fish populations

[Solution Description] Overfishing can lead to a decline in fish populations, which disrupts the food chain and affects biodiversity.

Key Concept: Salinity and River Influx

c) Baltic Sea

[Solution Description]

The Baltic Sea has a relatively low salinity because it receives a significant amount of fresh water from rivers, which dilutes the salt content in the sea.

Key Concept: Salinity Factors

d) Evaporation and precipitation

[Solution Description] Salinity is mainly influenced by evaporation and precipitation. High evaporation rates increase salinity, while significant precipitation decreases it.

Key Concept: Basic Definition

b) Movement of water

[Solution Description] The hydrological cycle describes the movement of water on, in, and above the Earth. It involves the circulation of water within the Earth’s hydrosphere.

Key Concept: Definition Recall

d) Salinity

[Solution Description] The term used to describe the total content of dissolved salts in seawater is “Salinity”. Salinity measures the concentration of salts in water and is expressed in parts per thousand (o/oo).

Key Concept: Basic Definition

b) Shallow waters with gentle slopes

[Solution Description] The continental shelf is a submerged border that surrounds continents, featuring shallow water depths and a gentle slope.

Key Concept: Temperature Distribution

b) Sunlight Penetration

[Solution Description] The thermocline is a layer in the ocean where the temperature decreases rapidly with depth. This phenomenon occurs due to the lack of sunlight penetration at greater depths. As sunlight cannot reach deeper layers, the surface water remains warm while the deeper water stays cold. Therefore, the boundary between these layers results in a sharp temperature gradient, which characterizes the thermocline.

Key Concept: Ocean Features

d) Deep Sea Plain

[Solution Description] Minor relief features of the ocean floor include ridges, seamounts, guyots, and trenches. These are smaller-scale formations compared to the major divisions like continental shelves or slopes.

Key Concept: Temperature Layers

b) Thermocline

[Solution Description] The thermocline is a distinct layer in the ocean where there is a rapid change in temperature with depth. It acts as a boundary between warmer surface water and colder deep water.

Key Concept: Latitude Effect

b) It decreases

[Solution Description] The temperature of the ocean surface decreases as one moves from the equator toward the poles because the insolation, or solar energy received per unit area, decreases with increasing latitude.

Key Concept: Basic Definition

c) 3,000-6,000 meters

[Solution Description] Deep sea plains, also known as abyssal plains, are gently sloping areas of the ocean floor. According to the syllabus, these plains have depths ranging between 3,000 meters and 6,000 meters.