Ocean Currents

Ocean Currents Ocean currents are the routed movements of oceanic water which are constantly flowing within the ocean or on the ocean surface. An ocean current is created by several forces and elements that act upon a unit mass of water in the ocean and such factors on an environmental scale include the gravitational pull of the Moon and the Sun, wind, salinity levels, and the rotation of the earth, temperature and tidal waves. However, the two forces that create the most conducive conditions for a current to form are the Sun and the rotation of the Earth. Advertising We will write a custom essay sample on Ocean Currents specifically for you for only $16.05 $11/page Learn More Physical factors such as the depth of the ocean, contact with other currents and the composition of the shoreline will determine a currents course and potency. Ocean currents are known to surge for great distances and the gravitational centrifugal pull of great currents round the earth has a pivotal role in influencing the global climate especially of islands and coastal regions. It is well know that the California Current makes the weather of the Island of Hawaiian to be cooler as measure up to other regions which are situated at the same latitude, the current is a tropical one leading to the sub-tropical climate of the islands. Ocean currents also determine the marine life of a region because they play a major role in determining the salinity of the water. Currents can carry a large volume of highly saline water for great distances and the marine life of the region where the water gets deposited can significantly be altered. There are different currents are flowing at different levels in the ocean and it is possible for two or more currents to flow through a single region simultaneously but at different levels. There are generally two types of ocean currents depending on the water level where the movement of oceanic water takes place and they are the deep ocean currents and the surface ocean currents. Deep ocean currents are mainly caused by the fluctuation in the mass of water and by gravitational forces acting in the deeper parts of the ocean usually below three thousand feet. Variation in temperature and the salinity levels of the water cause a change in the mass and volume of water leading to deep ocean currents. A submarine river is another term which is used to refer to deep water currents basically because the currents occur in the lower levels of the ocean. The deep ocean currents carry large volumes of water which flow the greatest distances leading to thermohaline circulation. The submarine rivers are at times responsible for transferring deep water plankton and marine life from one part of the ocean to another and also cause the vertical movement of water in the upwelling and down welling parts in the oceans.Advertising Looking for essay on geology? Let's see if we can help you! Get your first paper with 15% OFF Learn More On the other hand, surface ocean currents take place on the upper levels of the ocean and are commonly caused by air currents acting on the ocean’s surface. Surface currents are composed of about ten percent of the total water volume in the ocean and are usually limited to the upper one thousand three hundred feet of the ocean. Surface currents form the Ekman spiral effect which is the circular movement of ocean surface water at a given tangent relative to the prevailing air currents. The Ekman spiral effect is usually in a clockwise direction in the northern hemisphere and in a counter-clockwise spiral in the southern hemisphere due the alternate air movements inflicted. However, the Indian Ocean does not follow this rule due to the strong torrential rains and the atmospheric system in northern region of the ocean which alters its trend twice every year. The southwest torrential rain which occurs off the coast of Somalia is caused by the Great Whirl, which is a stro ng current which has a circular motion. The currents on the ocean basin surface are normally asymmetric with the eastern currents flowing towards the equator and the western currents flowing towards the North and South poles. Such currents are majorly influenced by gravity, with the eastern currents flowing in separate extensive currents whereas the western currents for instance the Gulf Stream are relatively contracted. Deep water current movement patterns are formed through a complex process which begins with the freezing of the water in the ocean. Once the water is frozen, the salt in the ocean water is also condensed in the freezing process and this leads to the creation of a layer of cold salt concentrated water which forms near the surface of the water where freezing generally takes place. The brine then gradually sinks because of the density difference, brine being denser than the water below. The salt concentrated water is more viscous which makes it become denser than the water around it. Consequently, the gelatinous salty liquid sinks, leaving the surface levels of the ocean and will only settle when it gets to a region in the ocean where it bears an equal density to the surrounding ocean water. This process is very prominent in the Greenland and Labrador Seas that are located in the Northern Hemisphere, and the Weddell and Ross Seas in the Southern Hemisphere. Similar to surface currents, most of the current movement takes place on the western sides of ocean basins except that deep ocean currents have their progression towards the north. Advertising We will write a custom essay sample on Ocean Currents specifically for you for only $16.05 $11/page Learn More Surface currents flow in a succession of nearly circular gyres in the ocean basins. Most of the gyres are located in the western regions of the globe where the currents are contracted and carry large volumes of water for example the Gulf Stream, Agulhas and East Aust ralian Currents. The oceanic and atmospheric gyres help to move heat generated in the equatorial regions towards the poles. The polar movements of the ocean currents constitute the northward warm water current in the North Atlantic and in the North Pacific and the southward flow through the East Greenland and Labrador Currents. The surface currents that flow towards the equator move alongside the eastern edges of the gyres and are usually cooler than the currents that flow towards the poles located on the western margins. Air movement causes upwelling and provides the requisite wind stress towards the equatorial region moving water away from the coast and gravitational force pushes cooler subsurface water to replace the unoccupied water spaces. The Southern Ocean region experiences persistent westerly air movement leading to the Antarctic Circumpolar Current, a constant circumglobal current which hinders the formation of gyres. The Antarctic Circumpolar Current allows for the inte gration water from different ocean basins making it the largest current on earth. Sverdrup (Sv), is the standard unit used to measure ocean currents with one Sv being equivalent to a volume flow rate of one million cubic meters per second. The equatorial region experiences little or no gyres and currents here are usually surface currents stirred by the trade winds that originate from the eastern regions of the Northern Hemisphere and the Southern Hemisphere. The North and South Equatorial Currents which move toward the west are formed by trade winds which lead to an upwelling along the equator due to the movement of the southeast trade winds across the equator. Furthermore, the equatorial region does not incur Coriolis force which is potent even with a one degree shift north or south of the equator. The Doldrums region is formed in the equatorial region where the northern and southern currents border. The Doldrums region is generally permeable to the Equatorial Countercurrent wate r that flows back eastwards since the water would otherwise get concentrated on the western boundary allowing the doldrums region to act as an outlet. The velocity of the currents also varies, with the western currents moving faster than the eastern currents.Advertising Looking for essay on geology? Let's see if we can help you! Get your first paper with 15% OFF Learn More Marine life in the oceans is totally dependant on ocean currents for survival. Oxygen derived from the atmosphere is mixed with water through the flux of surface water like waves which are more or less generated by surface currents. For the oxygen to be delivered to the organisms, the oceanic currents and welling are needed to translocate the oxygen to all tiers of the ocean. Furthermore, marine victuals for instant phytoplankton which are minute organisms that are primary in the marine food chain are distributed in the ocean through the ocean currents. The organisms are usually caught in the currents and transported for great distances before being deposited in an ecosystem where they establish sustenance. Therefore ocean currents play an important role to both shallow and deep water organisms because they push food into the organisms’ environment. Surface organisms such as crabs are also reliant on the currents which carry microorganisms from the oceans and deposit them n ear the shores. In addition, currents provide inimitable signals in the life cycle of almost all marine organisms through transport of subtle chemical indicators. Turtles for instance migrate for long distances to mate and the precursor to their migration is the sensing of chemical triggers produced by sources that are more than a thousand miles away which are transported by ocean currents. Warm water used by marine life such as fish and turtles to incubate their eggs is deposited to the nesting grounds through ocean currents. Physical features such as lagoons are put together through the ocean currents which carry marine particles that are then deposited onto the lagoons leading to the expansion of the ecosystem. Due to the fact that ocean currents can move for great distances, they are also likely to spread out toxins in the oceans. For example, DDT which was a deadly insecticide was commonly used in America in the mid twentieth century. Through deltas, slight concentrations of the insecticide were moved to the ocean. The eventual consequence was that the product was found in penguins in both the north and south poles which had led to the thinning of the penguin egg shells. The only possible reason as to how the insecticide moved to such great distances is through ocean currents.

Discover the Lithosphere in Plate Tectonics

Discover the Lithosphere in Plate Tectonics In the field of geology, what is the lithosphere? The lithosphere is the brittle outer layer of the solid Earth. The plates of plate tectonics are segments of the lithosphere. Its top is easy to see its at the Earths surface but the base of the lithosphere is in a transition, which is an active area of research. Flexing the Lithosphere The lithosphere is not totally rigid, but slightly elastic. It flexes when loads are placed on it or removed from it. Ice-age glaciers are one type of load. In Antarctica, for example, the thick ice cap has pushed the lithosphere well below sea level today. In Canada and Scandinavia, the lithosphere is still unflexing where the glaciers melted about 10,000 years ago. Here are some other types of loading: Construction of volcanoesDeposition of sedimentRise in sea levelFormation of large lakes and reservoirs Here are other examples of unloading: Erosion of mountainsExcavation of canyons and valleysDrying up of large water bodiesLowering of sea level The flexing of the lithosphere from these causes is relatively small (usually much less than a kilometer [km]), but measurable. We can model the lithosphere using simple engineering physics, as if it were a metal beam, and get an idea of its thickness. (This was first done in the early 1900s.) We can also study the behavior of seismic waves and place the base of the lithosphere at depths where these waves begin to slow down, indicating softer rock. These models suggest that the lithosphere ranges from less than 20 kilometers  in thickness near the mid-ocean ridges to about 50 km in old oceanic regions. Under the continents, the lithosphere is thicker ... from around 100 to as much as 350 km. These same studies show that underneath the lithosphere is a hotter, softer layer of solid rock named the asthenosphere. The rock of the asthenosphere is viscous rather than rigid and deforms slowly under stress, like putty. Therefore the lithosphere can move across or through the asthenosphere under the forces of plate tectonics. This also means that earthquake faults are cracks that extend through the lithosphere, but not beyond it.   Lithosphere Structure The lithosphere includes the crust (the rocks of the continents and the ocean floor) and the uppermost part of the mantle beneath the crust. These two layers are different in mineralogy but very similar mechanically. For the most part, they act as one plate. Although many people refer to crustal plates, its more accurate to call them lithospheric plates. It appears that the lithosphere ends where the temperature reaches a certain level that causes average mantle rock (peridotite) to grow too soft. But there are many complications and assumptions involved, and we can only say that the temperature would be from about 600 C to 1,200 C. A lot depends on pressure as well as temperature, and the rocks vary in composition due to plate-tectonic mixing. Its probably best not to expect a definitive boundary. Researchers often specify a thermal, mechanical or chemical lithosphere in their papers. The oceanic lithosphere is very thin at the spreading centers where it forms, but it grows thicker with time. As it cools, more hot rock from the asthenosphere freezes onto its underside. Over the course of about 10 million years, the oceanic lithosphere becomes denser than the asthenosphere beneath it. Therefore, most of the oceanic plates are ready for subduction whenever it happens. Bending and Breaking the Lithosphere The forces that bend and break the lithosphere come mostly from plate tectonics. Where plates collide, the lithosphere on one plate sinks down into the hot mantle. In that process of subduction, the plate bends downward as much as 90 degrees. As it bends and sinks, the subducting lithosphere cracks extensively, triggering earthquakes in the descending rock slab. In some cases (such as in northern California) the subducted part can break off completely, sinking into the deep Earth as the plates above it change their orientation. Even at great depths, subducted lithosphere can be brittle for millions of years, as long as it is relatively cool. The continental lithosphere can split, with the bottom part breaking off and sinking. This process is called delamination. The crustal part of the continental lithosphere is always less dense than the mantle part, which in turn is denser than the asthenosphere beneath. Gravity or drag forces from the asthenosphere can pull the crustal and mantle layers apart. Delamination allows the hot mantle to rise and yield melt underneath parts of a continent, causing widespread uplift and volcanism. Places like Californias Sierra Nevada, eastern Turkey and parts of China are being studied with delamination in mind.

Recruitment and selection Essay Example | Topics and Well Written Essays - 3000 words

Recruitment and selection - Essay Example Indeed, the recruitment and selection process helps in finding and employing top quality and proficient workers who meet organisational needs and focus on accomplishment of assigned goals and targets (Iles, 2001 p. 134). It should be emphasised that technology only accelerates the production strength but its employees who plan, organise, lead and control business operations. Therefore, there is dire need to implement right recruitment strategies to select right workers at the right time for business growth, survival and sustainability. The paper will first throw light over importance of Human Resource Management followed by importance of recruitment and selection process. The paper will then discuss various recruitment techniques such as internal and external recruitment, consultation from any HR agency, use of job and career fairs, referrals etc. In addition, the paper will provide an explanation on equality and discrimination followed by a discussion on how issues of Equality affect the recruitment and selection process. Finally, the researcher will provide the conclusion to summarise the findings from and shortcomings of current literature. Human Resource Management refers to managing employees and organisational members. Indeed, HRM is also known as personnel management and it plays vital role in success and growth of any business firm. For instance, the first major responsibility of HR professionals is to prepare a top quality workforce that could meet present and future organisational needs as well as could accomplish assigned targets. Hence, if right workers are not inducted then a company may not be able to form an excellent customer base, relationships with partners, distribution channel members and other stakeholders. Also, the absenteeism and turnover rates may become high that, in turn, increase costs (Caroline &