Chapter - 14
Ocean Water Movement
️ Introduction :-
The water of the ocean never remains calm, that is, it is always in motion, due to which the water keeps on stirring.
The movement of water leads to the formation of waves, currents, tides. Human life is affected by them in different ways, in this chapter we will study these facts.
️ Sea Waves :-
Sea waves are actually that state of water in which water keeps moving up and down at one place, but does not leave its place and does not go to any other place, only energy flows from one place to another.
️ Characteristics of Waves :-
Waves have the following characteristics.
Wave Crest and Trough :- The highest and lowest points of a wave are called peak and trough respectively.
Wave Height: - It is the vertical distance of the trough and peak of the wave.
Wave Amplitude : - It is half of the height of the wave.
Wave Period:- Wave period is the time interval between two successive wave peaks or troughs passing through a fixed point.
Wave Length :- It is the horizontal distance between two consecutive peaks or troughs.
Wave Speed: The rate of movement of a wave through water is called wave speed. This is measured in knots.
️ Tide - Eruption :-
The water level of the sea does not always remain the same. It regularly rises and descends twice a day. The rise of sea level is called tide and the fall is called ebb. ( Tides are the rhythmic rise and fall of the water in the ocean ) ! The height of the tides of Purna Masi and Amavasya is 20% higher than that of other days. It happens twice a month.
Type Type of tides: -
The tides can be classified on the basis of their frequency and height.
On the basis of frequency ( TidesBased on Frequency ) :-
- Semi-daily tide (Semidiurmaltide)
- Diurmal Tide
- Mixed Tide
Tides Based onHeights :-
- High or large spring tide
- Low or low tide - Neap Tide
️ Importance of the tides :-
Sea ships can easily enter on the rivers. Like the Hooghly river in Kolkata.
Fishing sailors go into the sea with the rent and come out with the tide.
The filth and pollution of the coastal cities are cleared by the tides.
We get very valuable things on the seashore by tides like conch shells, oysters, snails etc.
Due to the tides, the sea water remains in motion, due to which the water does not freeze in the cold regions.
Electricity generation is also done from tides. This type of energy is being obtained in many areas.
️ Ocean currents :-
The continuous flow of water from one part of the oceans to another in a particular direction is called ocean current.
️ Due to the origin of ocean currents :-
Causes of Origin of Currents :-
Causes of Earth's rotation, intra-oceanic and oceanic factors like-
- Variation of temperature
- sea level
- Density Variation
External factors :-
- air pressure and wind direction
- evaporation and precipitation
Factors causing change in the direction and form of currents :-
- coast direction and size
- shape of ocean floor
- seasonal change
- prevailing persistent winds
Classification of ocean currents on the basis of depth and temperature :-
Classification of ocean currents on the basis of depth :-
Surface Current or Upper Current Surface Currents: - 10 percent of the ocean water is in the form of surface water current, these currents are 400 meters in the oceans. are present in depth.
Deep Current Deep Currents :- 90% of the ocean water is in the form of deep water current. These currents flow due to the difference in density and gravity of the oceans.
️ Ocean currents based on temperature :-
Warm Currents Warm Currents: - The currents which move from warm areas to colder areas are called hot currents, they often move from the equator to the poles. The temperature of their water is higher than the temperature of the water coming in the way. Therefore, the temperature of the areas where these currents move increases. The Galk Stream is an example of this.
Cold Currents Cold Currents :- The currents which move from cold areas to warm areas are called cold currents. They often move from the poles to the equator, the temperature of their water is less than the temperature of the water coming in the way, so the temperature of the areas where these currents move decreases. The Labrador cold current is an example of this.
Effects of ocean currents :-
These currents affect the temperature and temperature difference of the land areas around them. Cold currents lower the temperature of land areas and warm currents increase the temperature of land areas.
Ocean currents can also cause other climatic changes such as the generation of fog, increased humidity and mildness.
In place of the meeting of cold and warm currents, there is an increase in plankton, due to which fish are found in abundance in these areas. Major fishing areas of the world are found in these places.
️ Tidal current :-
When a bay is connected to the open ocean by a narrow mouth, the water of the sea enters the bay at the time of tide and exits the bay at the time of ebb. This flow of water in and out of the bay is called tidal current.
️ Sargasso Sea :-
The area of calm water located between the Gulf Stream, Canary and North Equatorial currents in the North Atlantic is called Sargasso Sea. Thick sea grass floats on its shore. The grass is called Sargasam in Portuguese language, after which it is named Sargasso Sea. Its area is about 11,000 sq. m. Is .
️ Difference between waves and currents :-
Waves :-
- The water of the waves moves up and down and back and forth.
- He does not move forward leaving his place.
- Waves are confined to the water level only.
- The velocity of the waves depends on the movement of the air.
- The size of the waves depends on the depth of the water.
- Waves are permanent and are always created and deteriorating.
Sections :-
- The water moves forward leaving its place in the streams.
- The currents are effective up to a sufficient depth.
- The currents move under the influence of permanent winds and heat the cold coasts.
- Currents are always of huge size.
- The areas where they meet are full of fish.
- Currents are always permanent and flow continuously in a definite direction.
️ Agulhas hot water stream :-
In the south of the island of Madagascar, the Mozambique Current and the Madagascar Current join together, this combined current is known as the Agulhas Hot Current.
