Movements of ocean water - class-IX

The current systems of the Indian Ocean are largely controlled and modified by landmasses and monsoon winds. The currents in the northern Indian Ocean change their flow direction twice a year due to north-east and south-west monsoon winds.

The ocean water current which flow slowly is called Drift. They are affected by atmospheric circulation and the wind belts. When the wind blows over the sea's surface in one direction for a period of time, the stress force produced by friction between the air and the sea water cause the sea water to flow.

The Challenger Deep in the Mariana Trench is the deepest known point in Earth's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about 2,550 kilometres (1,580 mi) long with an average width of 69 kilometres (43 mi).

The ocean water current which flow speedily is called Stream. The Gulf Stream is typically 100 kilometers wide and 800 meters to 1,200 meters deep. The current velocity is fastest near the surface with the maximum speed typically about 2.5 meters per second.

Ocean currents act much like a conveyer belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics. Thus, currents regulate global climate, helping to counteract the uneven distribution of solar radiation reaching Earth’s surface. Without currents, regional temperatures would be more extreme—super hot at the equator and frigid toward the poles—and much less of Earth’s land would be habitable.

The Gulf Stream is a well-known warm ocean current that originates in the Gulf of Mexico and flows across the Atlantic.

The Labrador current is a cold current that flows from the Arctic Ocean southwards along the coast of Labrador.

Indian Ocean Tsunami of 2004, hit the coast of several countries of South and Southeast Asia in December 2004. An earthquake undersea of magnitude 9.1 struck off the coast of the Indonesian Island of Sumatra. Tens of thousands were reported dead and missing in Sri Lanka and India. The tsunami and its aftereffect were responsible for great devastation and loss at the end of the Indian Ocean.

A tsunami is a series of waves caused by earthquakes or undersea volcanic eruptions. Tsunamis are giant waves and the speed of these waves depends on ocean depth rather than the distance from the source of the wave. Similarly, seismic waves are waves of energy that travel through the Earth's layers and are a result of earthquakes, volcanic eruptions.

Waves are most commonly caused by wind. This kind of wave is found globally across the open ocean and along the coast. However, most potential precarious waves are caused by underwater disturbances that displace large amounts of water quickly such as earthquake, underwater volcanic eruption or landslide i.e., slippage of the seafloor along an earthquake fault. These cause very big waves known as tsunamis.

Wave periods: Tides have the longest period (12-24 hours), followed by Tsunamis (minutes to hours), and Wind waves (seconds). Decreasing order: Tides, Tsunami, Wind waves (3, 1, 2).

The tsunami height on the continental shelf is lower for steeper slope in comparison to flatter slope. This shows that, as the continental slope becomes flatter, more energy is transmitted to the shelf and higher tsunami height is observed.

All stream currents are westerly bound currents while California currents are easterly bound currents

Brazil current is the western boundary current of the South Atlantic subtropical gyre. It transports warm water polewards. Near 22 S, the Brazil current splits; one component flows eastward and the other component hugs the coast and flows toward the southwest and interacts with the colder Malvinas Current.

The Gulf Stream, together with its northern extension the North Atlantic Drift is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and stretches to the tip of Florida, and follows the eastern coastlines of the United States 

The Kuroshio is a north-flowing ocean current on the west side of the North Pacific Ocean. It is similar to the Gulf Stream in the North Atlantic and is part of the North Pacific ocean gyre. As the Gulf stream, it is a strong western boundary current.

California Current is a Pacific Ocean current that moves southward along the western coast of North America, beginning off southern British Columbia and ending off southern Baja California Peninsula. It is considered an Eastern boundary current due to the influence of the North American coastline on its course.

Labrador, Canary, and Benguela are all cold currents. Kuroshio is a warm current.

When cold and warm ocean current meet, the warm ocean current condenses after getting in contact with cold air and it results into fog.

Ocean currents may be cold, warm and hot. Warm ocean currents originate near the equator and move towards the poles or higher latitudes while cold currents originate near the poles or higher latitudes and move towards the tropics or lower latitude.