Water (Ocean)| Class 11 Chapter 12 Geography Notes

The Ocean Water is the salty water that makes the whole ocean and sea. It is the primary component of the Earth’s hydrosphere which accounts for almost 97% of the Earth’s water. The ocean and sea are the important habitats for so many species of the Earth. It is a complex mixture of 96.5 percent water and 2.5 percent salts. Some smaller amounts of other substances, including dissolved inorganic and organic materials, particulates, and a few atmospheric gases are also present in the Ocean Water.

In this article, we are going to discuss the Water of the Ocean in detail.

Water (Ocean)| Class 11 Chapter 12 Geography Notes

Hydrological Cycle  – Water (Ocean)

The hydrological cycle is also known as the water cycle. It is s continuous movement of water between the Earth’s land, ocean, and atmosphere. The cycle consists with many processes including evaporation, condensation, precipitation, infiltration, and surface runoff.

The sun’s heat provides energy to evaporate the water of the earth’s surface. This water moves through the air, from the oceans to the land. Eventually, it gets absorbed into the atmosphere and comes back down to Earth as rain. The hydrological cycle is really important to sustain the functionality of the Earth. It plays a major role in the cycling of solar energy, sediments, and chemical elements that are really vital for our life. The cycle is also linked to the changes in the atmospheric temperature and to maintaining the radiation balance of it. Here are some major facts about the Hydrological Cycle of ocean water as mentioned below.

• Water distribution varies across the Earth, with some places having plenty while others face scarcity.
• 71% of Earth’s water is in oceans. On the other side, the rest is in lakes, glaciers, groundwater, and living organisms.
• About 59% of water reaching land evaporates back into the air. The rest either stays on the surface, goes underground, or forms glaciers.
• Despite continuous demand, the amount of renewable water remains unchanged and it leads to ongoing or occasional water shortages in different regions.
• Around 70.8 % of the area of the earth is covered by water and 29.2% of its area is covered by land.
• About 96.5% of the Earth water is salty that is found in seas and oceans.
• Fresh water occupies only 2.5%. Saline ground water and the saline lakes together consists with 1% of total water.

Relief of the Ocean Floor

The oceans occupy the depressions of the Earth’s outer layer, and their topography is complex and varied. Geographers have divided the oceanic part of the Earth into five oceans: the Pacific, Atlantic, Indian, Southern, and Arctic oceans, along with various seas, bays, gulfs, and inlets. The ocean floor, situated between 3-6 km below sea level, displays diverse features similar to those on land, including mountain ranges, trenches, and plains, shaped by tectonic, volcanic, and depositional processes.

The ocean floors can be categorized into four major divisions: the Continental Shelf, the Continental Slope, the Deep Sea Plain, and the Oceanic Deeps. Additionally, there are various relief features such as ridges, hills, seamounts, guyots, trenches, canyons, and atolls.

• The Continental Shelf: This is the shallowest part of the ocean, extending from each continent and typically ending at a steep slope known as the shelf break. It varies in width and depth, covered with sediments that accumulate over time and become a source of fossil fuels.
• The Continental Slope: Connecting the continental shelf to the ocean basins, the continental slope is a steep region with varying gradients and depths, featuring canyons and trenches.
• Deep Sea Plain: These are gently sloping areas of the ocean basins, characterized by fine-grained sediments like clay and silt, and depths ranging from 3,000 to 6,000 meters.
• Oceanic Deeps or Trenches: These are the deepest parts of the oceans, occurring at the bases of continental slopes and associated with active volcanoes and strong earthquakes. They play a significant role in the study of plate movements.

In addition to these major divisions, there are minor relief features like mid-oceanic ridges, seamounts, submarine canyons, guyots, and atolls. These features contribute to the diverse and dynamic nature of the ocean floor.

Temperature Of Ocean Waters

The temperature of ocean water may vary from -2°C near the poles to 30°C in the tropic regions. The average temperature of the ocean surface is around 20°C. The ocean surface is warmer in low latitude regions and the surface water at the poles is much colder. Deep ocean water are really cold in nature.

Factors Affects The Temperature Of Ocean Waters

Here are some major factors that affects the temperature of ocean waters as mentioned below.

• Latitude is a major factor the affects the temperature of ocean waters. Temperature decreases from the equator to the poles due to less sunlight reaching higher latitudes.
• Northern hemisphere oceans receive more heat due to more land contact. As a result in higher surface water temperatures become so hot.
• Prevailing winds also affects the temperature of ocean waters.
• Offshore winds push warm surface water away from the coast, causing cold water upwelling.
• Onshore winds pile up warm water near the coast, raising temperatures of ocean waters.
• Ocean currents are the major contributors to the temperature of ocean waters. Warm currents increase temperatures. Like the Gulf Stream warming eastern North America and Europe is really warm.
• Cool currents lower temperatures. Such as the Labrador and Kurile currents cooling northeastern North America and eastern Siberia respectively have the lower temperature.

Intresting Facts:
Water is essential for life and is scarce in our solar system.
Earth is known as the 'Blue Planet' because it has lots of water on its surface.

Major Oceans

Here are the major oceans of the Earth with their specifications as mentioned below.

Ocean	Specifications
Pacific Ocean	Largest ocean in this worls that covers one third of the Earth’s surface. Separates the North and South America from Asia and Australia. Named ‘Pacific’ for its calmness by Ferdinand Magellan. Deepest trench: Mariana Trench (deepest in the world). Average depth: 4280 meters.
Atlantic Ocean	Second-largest ocean, covering about 20% of Earth’s surface. Named after Greek mythology, “Sea of Atlas”. Deepest trench: Puerto Rico Trench. Formation linked to Pangaea and Gondwanaland. Largest island: Greenland. – Sargasso Sea.
Indian Ocean	Third-largest ocean, named after India. Warmest ocean, mostly in the eastern hemisphere. Deepest trench: Sunda Trench. Marginal seas vital for global trade routes. Largest island: Madagascar.
Southern Ocean	Also called Antarctic or Austral Ocean. Encircles Antarctica, known for turbulent waters. Drained by the Drake Passage. Shares borders with Atlantic, Indian, and Pacific Oceans.
Arctic Ocean	Smallest and shallowest ocean that lies within the Arctic Circle. Frozen in winter, lowest average salinity. Deepest point: Molloy Deep. Connected to the Atlantic and Pacific via various seas and straits.

Horizontal and Vertical Distribution of Temperature in Oceans

The vertical distribution of temperature in oceans is not uniform in nature. The maximum temperature is found at the surface because it directly absorbs the sunlight. The horizontal distribution of temperature in oceans is the distribution process of temperature across the latitudes over the ocean surface. The average temperature of the ocean surface water is about 27°C. Here are the major differences between Horizontal and Vertical Distribution of Temperature in Oceans as mentioned below.

Aspects	Horizontal Distribution of Temperature	Vertical Distribution of Temperature
Description	How temperature changes across the ocean’s surface.	How temperature changes with depth within the ocean.
Factors affecting	Influenced by location, wind patterns, ocean currents, and land areas.	Affected by sunlight reaching depths, ocean currents, and water circulation.
Impact on climate	Affects regional weather patterns and climate systems.	Crucial for regulating global climate and ocean environments.
Measurement methods	Data collected from satellites, buoys, and ships.	Data gathered using temperature sensors, floats, and deep-sea probes.
Variability	Temperature can vary widely based on location and season.	Generally, temperature decreases gradually with depth.
Importance for ecology	Influences distribution of marine life and habitats.	Determines nutrient distribution and supports marine ecosystems.

Salinity Of Ocean Waters

Salinity is the specific amount of the dissolved salts in seawater. It is evaluated as the number of grams of salts per kilogram of seawater or parts per thousand (ppt). Here are the major facts about the Salinity Of Ocean Waters as mentioned below.

• The average saltiness of ocean water is 35 parts per thousand (ppt), or 35,000 parts per million (ppm), which means that about 3.5% of seawater’s weight comes from dissolved salts.
• This is expressed as a ratio of salt (in grams) to liter of water.
• In seawater, there is typically close to 35 grams of dissolved salts in each liter (35ppt), but ranges between 33-37 grams per liter (33ppt – 37ppt).

FAQs – Class 11 Chapter 12 Water (Ocean)

What is an ocean short answer?

An ocean is a continuous body of salt water that is contained in an enormous basin on Earth’s surface. The major oceans and their marginal seas cover nearly 71 percent of Earth’s surface, with an average depth around of 3,688 metres (12,100 feet).

What are ocean currents class 11?

Ocean currents are channels of water moving in a particular direction in the oceans. The ocean currents are of two types – the warm currents and the cold currents. The warm currents flow from the equatorial region towards the poles. The cold currents flow from the poles to towards the equatorial regions.

What is a short note on variation in salinity Class 11?

There are 35 parts per thousand of salinity on average in the oceans and seas, but this varies with spatial and temporal variations among the oceans, seas, and lakes. Salinity varies horizontally as well as vertically.

What are the movements of ocean water Class 11?

The horizontal and vertical motions are common in ocean water bodies. The horizontal motion refers to the ocean currents and waves. The vertical motion refers to tides. Ocean currents are the continuous flow of huge amount of water in a definite direction while the waves are the horizontal motion of water.

What are the 5 lines of the ocean?

Ocean is a huge body of salt water. Oceans cover nearly 71 percent of Earth’s surface. They contain almost 98 percent of all the water on Earth. There is one world ocean, but it is divided into five main areas: the Pacific, the Atlantic, the Indian, the Arctic, and the Southern, or Antarctic.

What are two types of ocean currents?

There are two distinct current systems in the ocean—surface circulation, which stirs a relatively thin upper layer of the sea, and deep circulation, which sweeps along the deep-sea floor.

Why is the ocean so important?

The ocean affects us all in positive ways, no matter if you live on the coastline or in the desert. It provides climate regulation, food, jobs, livelihoods, and economic progress. Thus, we must work together to protect and save the ocean for the sake of our future survival on this planet.