Ocean water movement - class-VIII

Neap tides occur when the sun and moon are at right angles relative to the earth, causing their gravitational forces to partially cancel each other out, resulting in lower high tides.

Tides are the periodic rise and fall of sea levels caused by the gravitational forces exerted by the moon and the sun, and the rotation of the earth.

Ocean currents significantly influence the climate of coastal regions by transporting warm or cold water, which affects air temperature and humidity.

Ocean currents have a profound effect on coastal rainfall; for example, warm currents often increase moisture and rainfall, while cold currents can lead to aridity.

Spring tides occur when the earth, moon, and sun are aligned, causing their gravitational forces to combine and produce higher high tides and lower low tides.

Neap tides occur during the first and third quarters of the moon phase, when the sun and moon are at right angles to the earth.

The variation between spring and neap tides is evidence that both the sun and the moon exert gravitational influence on the earth's oceans.

While the sun also exerts a gravitational pull, the moon is the primary driver of tides due to its proximity to the earth.

The hydrosphere encompasses all water found on, under, and over the surface of the earth, including oceans, lakes, and rivers.

The continental shelf is the shallow, submerged extension of the continent that extends from the shoreline to the shelf break.

Ripples are the instant effect of wind on water and they die down as quickly as they form, as the surface tension of the water dampens their efforts.

Waves always travel in the same direction as the wind is blowing: if the wind changes then the waves change with it. Wave size is determined by the strength of the wind, the length of time it has been blowing and the distance it has blown over or the ‘fetch’.

When strong winds blow for longer than a few hours, it gives the water sufficient energy that it then takes on a character of its own. This character and movement is known as swell, and it will march across open areas of water independent of the wind.

Ocean currents are large-scale, continuous movements of seawater driven by wind, the Coriolis effect, and differences in water density.

The north equatorial current turns northward to the obstruction of Philippines and thus gives birth to the Kuroshio current which flows from Taiwan to Ryuku ridge at 30 degrees N latitude. The Kuroshio current is a warm current. The average temperature and salinity are 8 degrees and 35% respectively.

Factors Influencing Nature and Movement of Ocean Currents:

1. Factors related to the earth’s rotation: Gravitational force and force of deflection.

2. Factors originating within the sea: Atmospheric pressure, winds, precipitation, evaporation and insolation.

3. Factors originating within the sea: Pressure gradient, temperature difference, salinity, density and melting of ice.

4. Factors modifying the ocean currents: Direction and shape of the coast, seasonal variations and bottom topography.