HYDROSPHERE-2.pptx

About hydrosphere of earth

1. A hydrosphere is the total amount of water on a planet. The hydrosphere includes water that is on the surface of the planet, underground, and in the air. A hydrosphere is the total amount of water on a planet. The hydrosphere includes water that is on the surface of the planet, underground, and in the air. A planet's hydrosphere can be liquid,  vapour , or ice. On Earth, liquid water exists on the surface in the form of oceans, lakes and rivers. It also exists below ground—as groundwater, in wells and aquifers. Water vapor is most visible as clouds and fog. The frozen part of Earth's hydrosphere is made of ice: glaciers, ice caps and icebergs. The frozen part of the hydrosphere has its own name, the  cryosphere . Water moves through the hydrosphere in a cycle. Water collects in clouds, then falls to Earth in the form of  rain  or  snow . This water collects in rivers, lakes and oceans. Hydrosphere

2. Then it  evaporate s into the  atmosphere  to start the cycle all over again. This is called the  water cycle . Water is a basic necessity of life. Since 2/3 of the Earth is covered by water, the Earth is also called the blue planet and the watery planet.The hydrosphere plays an important role in the existence of the atmosphere in its present form. Oceans are important in this regard. Earth’s oceans contain 97% of the planet’s water, so just 3% is fresh water, water with low concentrations of salts. Most fresh water is trapped as ice in the vast glaciers and ice sheets of Greenland. A storage location for water such as an ocean, glacier, pond, or even the atmosphere is known as a  reservoir . A water molecule may pass through a reservoir very quickly or may remain for much longer. The amount of time a molecule stays in a reservoir is known as its residence time.

3. Tides are the periodic rise and fall of surface water caused by the gravitational force of the moon and the sun and by the rotation of the earth. As tides change, large quantities of water move toward or away from shore causing tidal currents. Introduction of Tides

4. Tides are formed by the gravitational pull of the moon and to some extend by the pull of the sun, which is very far from the earth. The moon though small is very close to the earth, it exerts a strong gravitational pull on the earth. The earth’s water is very close to the moon and is pulled by the gravitational force which is applied by the moon. The moon is directly overhead with the result of that the water piles up to the water causing an ordinary high tide there. There is piling of water on the other side of the earth. Formation of Tides

5. Tides move in a great wave around the Earth by following the movement of the moon. Tides always stripes the coast a interval of 12 hrs 26 mins . Subsequently there is a fall in the water for about 6 hrs until it resets a low tide. . Pattern of the Tides

6. DIURNAL TIDE Some areas, such as the Gulf of Mexico, have only one high and one low tide each day. This is called a diurnal tide. An area has a diurnal tidal cycle if it experiences one high and one low tide every lunar day. SEMIDIURNAL TIDE In general, most areas have two high tides and two low tides each day. When the two highs and the two lows are about the same height, the pattern is called a semi-daily or semidiurnal tide. Many areas on the eastern coast of North America experience these tidal cycles. Pattern of the Tides(cont.) MIXED SEMIDIURNAL TIDE An area has a mixed semidiurnal tidal cycle if it experiences two high and two low tides of different size every lunar day. Many areas on the western coast of North America experience these tidal cycles.

7. SPRING TIDES When the sun and the moon are in line with each other, they pull the ocean’s surface in the same direction. This causes higher high tides and lower low tides. These tides are known as “spring tides”. These are of the greatest tidal range. This occurs twice a month during full moon and new moon day. NEAP TIDES Seven days after a spring tide, the sun and moon are at right angles to each other. When this happens, the bulge of the ocean caused by the sun partially cancels out the bulge of the ocean caused by the moon. This produces moderate tides known as neap tides, meaning that high tides are a little lower and low tides are a little higher than average. Neap tides occur during the first and third quarter moon, when the moon appears "half full." Types of the Tides

8. Ocean Current INTRODUCTION An ocean current is any more or less permanent or continuous directed movement of ocean water that flows in one of the Earth’s ocean. The currents are generated from the forces acting upon the water like the earth’s rotation, the wind, the temperature and salinity differences and the gravitation of the moon.

9. An ocean current flows for great distances and together they create the global conveyor belt, which plays a dominant role in determining the climate of many earth’s regions. More specifically, ocean current influence the temperature of the regions through which they travel.

10. Circulation pattern Gyres Surface water circulates in oceans in massive circular patterns called gyres. The major surface currents (eastern boundary, western boundary, and equatorial current) in each ocean link to form a circle. Gyres are clockwise in the northern hemisphere and counter clock wise in the southern hemisphere.

11. Types of Ocean Currents The Currents of Atlantic ocean: The Gulf Stream is one of the strongest ocean currents. It is 50-150km wide, 600m deep and has a velocity of 5km/h. At 35 o N, this current is deflected eastward s under the combined effect of the Westerlies and the Coriolis force. It reaches Europe as the North Atlantic Drift, flowing at a speed of 15km/h, carrying warm Equatorial waters to the coast of Europe. Part of the waters of this current flow southwards along the Iberian coast as the cold Canaries Current. The cold Labrador Current flows between Greenland and the B affin Island to join the North Atlantic Drift at 50 o N latitude. In the South Atlantic , the currents flow anticlockwise to complete the circuit.

12. The Currents of Pacific ocean: The Kurioshio Current: The Counter Equatorial Current flows in the opposite direction of the west flowing North Equatorial Current. Its warm waters flow polewards as the North Pacific Drift, keeping the Alaskan coast ice-free in winter. The Oyashio Currents: The cold Alaskan or Bering Current flows southwards and is joined by the cold Okhotsk current and meets the warm Kuroshio or Japan Current as the cold Oyoshio , off Hokkaido. Kuroshio Current Oyashio Current The Currents of Indian ocean: In the south Indian Ocean, the Equatorial Current turns south off Malagasy as the Agulhas or Mozambique Current and merges with the West Wind Drift. The north Indian Ocean shows a reversal of flow of the currents in sync with the monsoon winds--- southwest and northwest monsoons. During summer, when the southwest monsoon predominates, the North Equatorial Current is replaced by an easterly movement of water which gives off branches into the Arabian Sea and the Bay of Bengal, producing clockwise circulation. In winter the North Equatorial Current flows westwards, south of Sri Lanka. The northeast monsoons cause a general eastward and northwards drift along the eastern shores of India and along the Arabian coast. During summer During winter

13. Effects of Ocean Currents Influence climate, by modifying the climatic conditiions of the coastal regions along which they flow, e.g. the Gulf Drift. Winds blowing over warm currents pick moisture and bring rain while those that pass over cold currents do not bring rain but make deserts colder and drier, e.g. Kalahari Desert. Currents also influence routes of cyclonic streams. The dense fogs caused by the meeting of cold and warm currents are dangerous to ships, e.g. in 1912, the Titanic struck on an iceberg due to poor visibility of the cold Labrador Current and the warm Gulf Stream Drift. Ships can sail faster if they follow the direction of the current and the opposite direction hinders speed. The mixing of cold and warm ocean currents causes plankton (fish food) to be found in abundance.