1. NAME SINDHU.M.P SUBJECT SOCIAL STUDIES

2. HYDROSPHERE The hydrosphere ] in physical geography describes the combined mass of water found on, under, and over the surface of a planet. ]physical geographywaterplanet The total mass of the Earth's hydrosphere is about 1.4 × 10 18 tonnes, which is about 0.023% of the Earth's total mass. About 20 × 10 12 tonnes of this is in the Earth's atmosphere (the volume of one tonne of water is approximately 1 cubic metre). Approximately 75% of the Earth's surface, an area of some 361 million square kilometers (139.5 million square miles), is covered by ocean. The average salinity of the Earth's oceans is about 35 grams of salt per kilogram of sea water (3.5%) [3]Earth tonnes Earth's atmospheresurfaceoceansalinitysalt [3]

3. A hydrosphere in physical geography describes the combined mass of water found on, under, and over the surface of a planet. The total mass of the Earth’s hydrosphere is about 1.4 × 10 24 grams, which is about 0.023% of the Earth’s total mass. Around 2 × 10 19 grams of this is the Earth’s atmosphere. In addition, 71% of the Earth’s surface, an area of 361 million square kilometers, is covered by ocean.mass of the Earth

4. Having liquid water makes the Earth a special place. Our planet has a very nice temperature range that allows water to remain in its liquid state. If we were a colder object like Pluto, it would not matter how much water there was on the planet; it would all be frozen. On the other hand, if we were on a very hot planet, all of the water would be in a gaseous state. Water vapor and solid water are useless to the living organisms found on Earth.

7. TIDES Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. MoonSun Some shorelines experience two almost equal high tides and two low tides each day, called a semi-diurnal tide. Some locations experience only one high and one low tide each day, called a diurnal tide. Some locations experience two uneven tides a day, or sometimes one high and one low each day; this is called a mixed tide. The times and amplitude of the tides at a locale are influenced by the alignment of the Sun and Moon, by the pattern of tides in the deep ocean, by the amphidromic systems of the oceans, and by the shape of the coastline and near-shore bathymetry (see Timing). [1][2][3]semi-diurnaldiurnalpattern of tides in the deep oceanamphidromic bathymetryTiming [1][2][3]

8. Tides Tides vary on timescales ranging from hours to years due to numerous influences. To make accurate records, tide gauges at fixed stations measure the water level over time. Gauges ignore variations caused by waves with periods shorter than minutes. These data are compared to the reference (or datum) level usually called mean sea level. [4]tide gaugesmean sea level [4] While tides are usually the largest source of short-term sea-level fluctuations, sea levels are also subject to forces such as wind and barometric pressure changes, resulting in storm surges, especially in shallow seas and near coasts.storm surges Tidal phenomena are not limited to the oceans, but can occur in other systems whenever a gravitational field that varies in time and space is present. For example, the solid part of the Earth is affected by tides, though this is not as easily seen as the water tidal movements.

10. OCEAN CURRENTS An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun. Depth contours, shoreline configurations and interaction with other currents influence a current's direction and strength.ocean watermean flowbreaking waveswindCoriolis effectcabbelingtemperaturesalinitytidesMoonSunDepth contoursshoreline Ocean currents can flow for great distances, and together they create the great flow of the global conveyor belt which plays a dominant part in determining the climate of many of the Earth’s regions. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude. Another example is Lima, Peru, where the climate is cooler (sub-tropical) than the tropical latitudes in which the area is located, due to the effect of the Humboldt Current.climateEarthGulf Streamnorthwest Europetemperate latitudeLima, PeruHumboldt Current