Go through these RBSE Class 11 Geography Notes Chapter 18 Movements of Ocean Water contain important concepts so that students can score better marks in the exam.
Rajasthan Board RBSE Class 11 Geography Notes Chapter 18 Movements of Ocean Water
→ Ocean water never stays stable, but it always keeps moving.
→ Ripples and waves are produced by the friction of ocean water and air.
→ There are three major types of motion in the oceans – Waves, Tides and Currents.
Ocean Currents and Waves
- The waves continuously rise and fall on the surface of the ocean water. This is the most extensive and ubiquitous motion of the ocean water. A scholar named Richard considered these as the turbulence for the liquid surface of the ocean.
- There are two main causes of the origin of ocean waves : (i) by blowing of winds (ii) when water surface becomes wavy by the motion in the earth’s crust.
- Waves are the rocking motion on the ocean surface.
- On the basis of the structure of waves, they have Wave Crest, Wave Trough and Wave Length.
- Wave velocity is related to its length and frequency.
- Waves occur due to the friction and pressure of winds.
- The size and strength of waves depends on the wind velocity, period of blowing of wind and the distance of uninterrupted blow of wind.
- There are three types of waves caused by the winds – See, Swale and Surf.
- In addition to the waves caused by winds, there are also other types of sea waves, in which Tsunami, Stormy Waves and Internal Waves are the major ones. They originate due to earthquakes, volcanoes and oceanic landslides.
- Tide is an important process in the motions of the sea water, which is the result of the gravitational force of the sun and the moon.
- Rising up of the sea water level is called Tide and its falling down is called Ebb.
- Gravity pulls the whole earth towards the sun and the moon, but its impact is more on water than on land.
- Due to uninterrupted flow of water in the open seas and oceans, lesser high tide is produced.
- The difference of ocean surface between the tide and the ebb is called Tidal Range.
- The tidal range is less in the open seas, while it is found more in the shallow seas and bays.
- Coast line has an impact on the height of the tide, and the time of tide varies from place to place.
- At every place, tide occurs after the interval of 12 hours and 26 minutes.
- The position of lesser distance of the moon from the earth is called Perigee, and the position of greater distance is called Apogee.
- There are two types of tides – Spring Tide and Neap Tide.
- The condition of spring tide occurs on the days of the Full Moon and the New Moon, when the sun, the moon and earth, all three are in a straight line. This situation is called Syzygy.
- When both, the sun and the moon, are on one side of the earth, then this situation is called Conjunction. This situation occurs on the day of the New Moon. When the earth comes between the sun and the moon, this situation is called Opposition. This situation occurs on the day of the Full Moon.
- Neap Tides originate on the Saptami and the Ashtami dates of the Shukla-paksha and the Krishna-paksha of every lunar month, which are lesser in height than the ordinary tide.
- Tides are the source of energy from which the tidal energy is generated in form of electricity and the oceanic resources are exploited.
- An ocean current is a continuous flow of ocean water in a particular direction from one place of the ocean to another place.
- In the currents, water moves not only on the surface, but also in the depths.
- On the basis of temperature, currents are classified into warm current and cold current.
- Warm currents flow from the hot regions towards the cold regions. Cold currents flow from the cold regions towards the hot regions.
- Ocean currents originate due to the processes of gravitational force of earth, rotation, atmospheric pressure and winds, evaporation, rainfall, temperature, salinity, density and snow-melting.
Currents of Atlantic Ocean
- Cold and warm ocean currents are found in the Atlantic Ocean.
- North Equatorial Current, Antilles Current, Florida Current, North Atlantic Current, Gulf Stream, Canary Current, Labrador Current and Sargasso Sea Current are included in the ocean currents of the North Atlantic Ocean.
- South Equatorial Warm Current, Brazil Current, Falkland Current, Benguela Current and South Atlantic Drift are included in the ocean currents of the South Atlantic Ocean.
Currents of Pacific Ocean
- The water currents of the Pacific Ocean are classified into the North Pacific Ocean Current and the South Pacific Ocean Current.
- North Equatorial Current, Kuroshio Current, North Pacific Warm Current, California Current, Alaska Current, Oyashio Current, Okhotsk or Kurile Current are included in the ocean currents of the North Pacific Ocean.
- South Equatorial Current, South Pacific Current, East Australian Current and Peru Cold Current are included in the ocean currents of the South Pacific Ocean.
Currents of Indian Ocean
- Indian Ocean is an semi-ocean. The currents of this ocean are classified into two parts.
- North East Monsoon Drift and Counter Equatorial Current are included in the ocean currents of the North Indian Ocean.
- South Equatorial Current, Madagascar Current, Mozambique Current, Agulhas Current, West Winds Drift and West Australian Cold Current are included in the ocean currents of the South Indian Ocean.
Movements of Ocean Water Notes Important Terms
→ Ripple: A small wave or series of waves on the surface of water, especially caused by a slight breeze or an object dropping into it.
→ Tides: Tides refer to the rise and fall of sea levels caused by the joint effects of the gravitational forces exerted by the moon and the sun and the rotation of earth.
→ Turbulence or Disturbance: Violent and unsteady flow or motion of air or water, in which minor swirls are produced.
→ Wave Crest: The crest of a wave is the point on the medium that exhibits the maximum amount of positive or upward displacement from the rest position.
→ Wave Trough: The trough of a wave is the point on the medium that exhibits the maximum amount of negative or downward displacement from the rest position.
→ Wave Length: The distance between two successive crests of a wave is called the wavelength.
→ Friction: The force generated by rubbing of one object or surface against another is called friction.
→ See: Whenever waves with different wavelengths or directions originate in the sea simultaneously, an irregular wave format is formed, which is called See.
→ Swale: When the waves move away from the influence of those winds that have created them, the waves sustain a uniform height and periodicity. This is called Swale.
→ Surf: When the waves reach near the seashore, their slopes become steep and their height increases. After reaching the shore, they proceed back to the sea. In the coastal areas, these breaking waves are called surf.
→ Tsunami: Huge waves arising in oceans formed due to the effect of the oceanic earthquake, whose height is the highest on reaching the shallow part near the coast.
→ Tide: The rise and fall in the oceanic water taking place on the earth by the gravitational force of the sun and the moon, in which high waves occur.
→ Tour: A journey made with the objective of pleasure, income, business, education, health-benefit, inspection, etc. in which the tourists return to their original place at the end of their journey.
→ Aphelion: The position of the earth when it is at the greatest distance from the sun in its orbit.
→ Perihelion: The position of the earth when it is at the nearest distance from the sun in its orbit.
→ Perigee: The point in the orbit of the moon or a planet or in the virtual orbit of the sun, which is nearest to the earth.
→ Apogee: The position of the moon or a planet when it is at the greatest distance from the earth in its orbit.
→ Spring Tide: When the sun, the moon and the earth are in a straight line, by the combined effect of the gravitational forces of the sun and the moon, the highest altitude tides are produced in the oceans on the earth. This is called Spring Tide.
→ Neap Tide: Tides originated on the Saptami and the Ashtami dates of the Shukla-paksha and the Krishna-paksha of every lunar month which are less in height than the normal tide are called the Neap Tide.
→ Conjunction: When both, the sun and the moon, are on one side of the earth, then this situation is called Conjunction. This situation occurs on the day of the New Moon.
→ Opposition: When the earth comes between the. sun and the moon, this situation is called Opposition. This situation occurs on the day of the Full Moon.
→ Syzygy: When the sun, the moon and the earth, all three are in a straight line, this situation is called Syzygy.
→ Tidal Energy: Energy generated by the oceanic waves which is used to make electricity.
→ Salinity: The amount of salt dissolved in the water of a reservoir (ocean, sea, lake, river) which is usually expressed in the form of per thousand grams of the total water.
→ Strait: A narrow passage of water connecting two seas or two other large areas of water. Strait of Gibraltar and Bering Strait are excellent examples of this.
→ Sargasso Sea: Mostly calm and sedentary water area located in the intermediate part of the North Atlantic Ocean, which is surrounded by the regular and uninterrupted flow order of the North Equatorial Current, Gulf Stream and Canary Current.
→ Mist: Amount of small water droplets formed by the condensation of water vapour located in the lower layers of the atmosphere which leads to slight reduction in visibility.
→ Peninsula: A peninsula is a piece of land that is bordered by water on three sides, while being connected to a mainland on one side from which it extends.