Movement of Ocean water

OCEANS:SALINITY,TEMEPRATURE,WAVES,TIDES,OCEAN CURRENTS,RELIEF OF OCEAN FLOOR ETC.

1. OCEANS-TEMPERATURE

2. INTRODUCTION Oceanography is the branch of Physical Geography which studies about the distribution of oceans in world. 71% of earth surface is covered by water and 29% is by land. As a maximum of earth surface is covered by water, it is called a Blue Planet. Distribution of oceans is more in southern hemisphere as maximum portion of northern hemisphere by land. There are five oceans i.e. Pacific Ocean, Atlantic Ocean, Indian ocean, Arctic Ocean and Antarctica. The largest ocean among all this Pacific Ocean.

3. Hydrological Cycle Water moves in a continuous cycle and changes from one form to another. Water from the surface of earth evaporates on heating ad changes from liquid to gas. This process of change of water vapour from liquid to gas is called evaporation. Water vapour is carried by the air to a particular height where condensation of water vapour takes place and result in forming clouds. This process of change of water vapour from gas to solid is called Condensation. When the cloud is not able to hold the condensed water vapours , they fall on the surface of Earth in form of rain, snow etc. This process of falling of water vapour on surface of earth in form of rain or snow is called precipitation. This continuous interchange of forms of water on surface of earth is called Hydrological Cycle.

4. Temperature of Ocean water Ocean water temperature increases when it receives insolation from sun. Temperature of ocean water is not same rather it varies from place to place and time to time. Various factors affecting ocean water temperature are: 1. Latitude: temperature of ocean water is more near to equator and less at poles. It is because of more heat received by the sun near equator as compared to poles.

5. 2.Winds: In difference in temperature and pressure conditions result in movement of wind from one area to another. Warm winds increases the temperature of the region it passes and and cold wind decreases the temperature of the region it passes. 3.Ocean currrent : Movement of water by wind in a particular direction is called ocean current. Warm ocean current increases the temperature of the region it passes like Gulf Stream and Cold current like Labrador current near Greenland decreases the temperature of the region it passes .

6. 4. Unequal distribution of Land and Sea: Distribution of land is more in northern hemisphere as compared to southern hemisphere. Therefore oceans in the northern hemisphere like Pacific Ocean are warmer as compared to oceans in southern hemisphere like Antarctica.

7. 5. Icebergs : Icebergs decrease the temperature of the ocean water of which they are present. 6.Salinity: Oceans with high salinity like tropical areas have more temperature as compared to oceans near poles like Arctic Ocean.

8. Vertical Distribution of Temperature I Oceans Temperature of oceans is maximum at surface because of heat received by the sun. As we go down the ocean surface, temperature starts decreasing. The region from where there is certain decrease in temperature is called Thermocline . 90% of total volume of water is present below thermocline .

9. The first layer of Thermocline ranges between 0-500 metres with temperature ranging between 20-25°C. it is present near tropical areas. The second layer of Thermocline ranges between 500-1000 metres with temperature ranging between 8-16°C. it is present near temperate areas. The third layer of Thermocline is very cold and extends upto the depth of ocean floor.the temperature ranges between 0-4°C. it is present near polar areas.

10. Horizontal Distribution of Temperature in Oceans. Horizontal Distribution of temperature in oceans is studied with the help of distribution of land and sea. In northern hemisphere distribution of land is more as compared to southern hemisphere. Oceans in northern hemisphere have a higher temperature like Pacific Ocean as compared to Southern hemipshere like Antartica . Temperature in oceans of tropical zone is 27°C, 14°c in temperate lattitudes and 0°c near poles. The rate of decrease of temperature is 0.5°c per lattitude in oceans. The average temperature for all oceans is 17.2°C.

11. OCEANS-SALINITY

12. Introduction Salinity refers to presence of dissolved salts in sea water. It is calculated as ppt or parts per thousand grams of sea water. The average salinity of sea water is 35 per thousand grams of sea water. Salts Ppt Chlorine (Cl 2 ) 19 Sodium(Na) 10 Sulphate (SO 4 ) 3

13. Factors Affecting Salinity 1.Temperature: Areas which are near to equator have high temperature which result in high evaporation and adding salts on ocean surface. 2. Fresh Water : Areas which receive fresh water from rivers have low salinity. Fresh water mixes with the water with salts and thus reduces its salinity. 3 . Ocean Currents: Warm Ocean currents carry high saline water to the area they move and cold currents carry less saline water to area they move.

14. HORIZONTAL DISTRIBUTION OF SALINITY 1. Salinity in Open Seas: Open seas are the seas which have access to fresh water. If open seas are located near to Equator they will have less salinity because heavy rainfall will increase the fresh water and decrease the salinity. Salinity is also less in polar areas because melting of ice adds fresh water and help in decreasing the salinity.

15. 2 Salinity in partially enclosed seas: Partially enclosed seas are the seas which are partially covered by land and other by sea like Mediterranean Sea, Red sea and Baltic Sea. Mediterranean Sea have high salinity because of its location in high temperature area which increases the evaporation rate and absence of large rivers helps in increasing the salinity in the area.

16. Salinity of Enclosed Seas: Enclosed seas are the seas which are covered from all sides. Lake Van in Turkey have 330 ppt as the salinity, Dead Sea have 24 pt salinity and Great Salt Lake have 220 ppt salinity.

17. Vertical Distribution of Salinity On the sea surface salinity is increased by high evaporation and is reduced by the addition of fresh water. More salinity will add more salts to water, make water more dense. With the increasing depth the salts keep on depositing and salinity increases with increasing depth. Halocline is the line which help in reflecting the amount of salinity in the area.

18. Relief of Ocean Floor or Features of Ocean Floor

19. Introduction The ocean floor is not plain as believed. Floor of various oceans have complex mountain ranges, trenches etc. Tectonic plates movement, volcanic erruptions inside oceans, depositional or erosion of material by sea waves has resulted in its formation. The various features of ocean floor are: 1. Continental Shelf 2.Continetal Slope 3.Oceanic Deeps or Trenches 4.Abyssal Plains 5. Submarine Ridges 6.Abyssal Hills

20. 1.Continental Shelf: It is the gentle seaward sloping surface extending from coast towards open sea. It is formed by sediments brought down by rivers, wind, waves etc. It covers 7.5% of total area of worlds ocean. It have a gentle slope 1°C and depth is normally 200 mts .

21. Importance of Continental Shelf: Sun’s rays can’t penetrate upto Continental Shelf which encourages growth and reproduction of marine organisms. Marine food comes from this part of ocean floor. Provides richest fishing grounds. Storehouse of various minerals like petroleum and natural gas. It is also storehouse of sand , gravel etc.

22. 2.Continental Slope: It is the steep slope separating a continental shelf and a deep ocean basin. The gradient of slope varies between 2-5° The depth of the slope is between 200-3600 mts .

23. 3.Oceanic Deeps or Trenches These are deepest part of the oceans. They occur at the base of continental slope. They are long, narrow and deep in nature. They extend upto 5500 mts They are formed by the folding and faulting of the Earth’s Crust. Mariana trench is the deepest trench of the Pacific Ocean.

24. 4. Abyssal Plains These are also called as Deep Sea Plains. They are flat and smooth in nature. These plains are covered with fine sediments like clay, silt etc. They are cover 40% of the ocean floor. they depth vary between 3000-6000 mts They are present in all major oceans and seas in world.

25. 5.Submarine Ridges:. It consist of various underwater mountain ranges in sea. It is spread over thousand kilometers longs It is formed by converging or diverging of the plates. They form the longest mountain system under the Earth. Mid Atlantic ridge in Atlantic Ocean is the example of Submarine Ridge.

26. 6.Abbysal Hills: There are thousand hills inside the ocean floor. Various hills are Sea Mount and Guyots . A)Sea Mount: It is the mountain peak which is rising from the ocean floor but they are not reaching the ocean surface. They are of volcanic origin. They can be 3000mts to 4500 mts . Example Hawaiian Islands in Pacific Ocean in Japan

27. B) Guyots : The flat bottomed sea mount is called Guyot . It is volcanic origin. Erosion of sea mount by various agents like water, waves give this feature. Example: Hawaiian Sea Guyot in Japan.

28. OCEAN -WAVES

29. Introduction Ocean water is never static but keeps on moving horizontally or vertically. The horizontal motion refers to ocean waves and currents and vertical motion is called tides.

30. OCEAN WAVES The movement of water due to energy produced by wind is called Wave. A thing is floating up and down but it is carried by the wind in a particular direction. As wave approaches the beach, it slows down. This is due to friction between water and surface.

31. The size of waves depend upon following factors: 1. Velocity of Wind: More the velocity of wind, more will high will be the wave. 2.Duration of Wind : if wind moves a longer duration of time, more waves will be formed. 3.Distance (Area) over which wave is moving: If wave is moving over an area with more speed, long time, and over an area which does not stops it then more high wave will be formed.

32. Terms associated with Waves: Crest: The upper part of the wave is called Crest. Trough: the lower part of the wave is called trough. Wavelength: The distance between Crest and Trough is called Wavelength. Waveheight : vertical distance between Crest and Trough is called Wave height Wave amplitude : Half of the wave height is called Wave amplitude. Wave frequency : the number of waves passing a given point during one second time interval is called wave frequency.

33. OCEAN -TIDES

34. OCEAN-TIDES The periodic rise and fall of sea level due to gravitational attraction of sun and moon acting on Earth is called tides. It occurs twice a day after 12 hours 26 minutes. The rise of sea level is called high tide or flood tide and fall is called low tide or ebb tide.

35. ORIGIN OF TIDES 1.Gravitational pull of Sun and Moon Water of Earth is held in position by its own gravity but gravitational pull of moon and sun acts on it. Due to large size of the sun, sun is attracting more but at large distance it is not able to have more gravitational force. Moon’s size is low but its near to Earth so gravitational pull is more

36. 2. Centrifugal Force: It is force applied moving in circular orbit. It moves from centre to outside. 3. Tide Generating Force: Difference between centrifugal and gravitational pull of moon.

37. Types of Tides 1.On basis of frequency: 1.Semi-diurnal Tide: When there are two high and two low tides in a day. But tides are of same height. 2.Diurnal Tide: There is one high tide and low tide but the tides are of same height. 3. Mixed Tide: Tide having variations in high and low tide is called Mixed tide.

38. 2. On basis of Position of Earth, Moon and Sun. 1. Spring Tide: When Sun, Moon and Earth are in straight line, they exert combined gravitational pull on Earth. Therefore on both days tides are high.

39. 2. Neap Tide: When Sun, Moon, Earth are at right angle it is called Neap tide. Attraction of Sun and Moon tide to balance each other as a result of which low tide is formed.

40. When moon orbit is near to Earth it is called Perigee and when moon is farthest from Earth it is called Apogee.

41. Importance of Tides 1.Tidal force can be used for generating electricity. Example in India, Gujarat Gulf of Kuchch and Khambat have high potential. 2. Tides keep sea water in motion and avoids its freezing. 3.tides leave shells and other sea products on shore. 4. Fishermen go to open sea for catching fish on high tide and come back on low tide. 5. Tides help in making river water navigable.

42. OCEAN CURRENTS

43. Meaning of Ocean Currents Regular movement of water in a particular direction is called ocean currents.

44. Factors responsible for origin of currents : 1. Temperature difference: At the Equator, temperature is high and the water also becomes light on heating. At the poles, the temperature is low and water becomes dense. Difference in temperature is also one the cause of movement of water from polar areas to equator. 2. Prevailing Winds: Winds move in area due to indifference in temperature conditions. When winds blow in a particular direction and take the water along is called ocean currents.

45. 3.Evaporation: More evaporation reduces the level of water and water moves from surrounding area to balance the level of water. 4. Rotation of Earth: Due to rotation of Earth, coriolis force becomes active because of which winds move right in northern hemisphere and left in southern hemisphere. Winds carry the water also in its direction and give birth to currents. 5.Salinity differences : Water having high salinity is denser and thus moves down. Light water with less salinity moves toward it and a current is formed. Example : Mediterrenean Sea have highest salinity which thus causes to water move from Atlantic Ocean.

46. TYPES OF OCEAN CURRENTS 1.ON THE BASIS OF DEPTH 1.SURFACE CURRENTS: The currents which are prevalent over the surface of water. They constitute over 10% of all water in the ocean. 2.DEEP WATER CURRENTS: When the water is carried by wind due to various differences like salinity, density deep in the oceans is called DEEP WATER CURRENTS. They constitute 90% of total ocean water.

47. 2. ON THE BASIS OF TEMPERATURE 1.WARM CURRENTS : The currents which move from warm areas of tropics to cold areas of polar latitudes is called warm currents. They increase the temperature of the area to which they go. Example: Gulf Stream is a warm current in Atlantic Ocean. 2. COLD CURRENTS: The currents which move from cold areas to warm areas is called Cold Currents. There temperature is lower so they decrease the temperature of the area they go. Example: Canaries current is a cold current.