It has been travelled and explored since ancient times, while the scientific study of the sea— oceanography —dates broadly from the voyages of Captain James Cook By The Sea - Various - Locked & Loaded 2 explore the Pacific Ocean between and The word sea is also used to denote smaller, partly landlocked sections of the ocean and certain large, entirely landlocked, saltwater lakessuch as the Caspian Sea and the Dead Sea.
The most abundant solid dissolved in seawater is sodium chloride. The water also contains By The Sea - Various - Locked & Loaded 2 of magnesiumcalciumand potassiumamongst many other elements, some in minute concentrations. Salinity varies widely, being lower near the surface and the mouths of large rivers and higher in the depths of the ocean; however, the relative proportions of dissolved salts varies little across the oceans. Winds blowing over the surface of the sea produce waveswhich break when they enter shallow water.
Winds also create surface currents through friction, setting up slow but stable circulations of water throughout the oceans. The directions of the circulation are governed by factors including the shapes of the continents and Earth's rotation the Coriolis effect.
Deep-sea currents, known as the global conveyor beltcarry cold water from near the poles to every ocean. Tidesthe generally twice-daily rise and fall of sea levelsare caused by Earth's rotation and the gravitational effects of the orbiting Moon and, to a lesser extent, of the Sun.
Tides may have a very high range in bays or estuaries. Submarine earthquakes arising from tectonic plate movements under the oceans can lead to destructive tsunamisas can volcanoes, huge landslides or the impact of large meteorites.
A wide variety of organismsincluding bacteriaprotistsalgaeplants, fungi, and animals, live in the sea, which offers a wide range of marine habitats and ecosystemsranging vertically from the sunlit surface and shoreline to the great depths and pressures of the cold, dark abyssal zoneand in latitude from the cold waters under polar ice caps to the colourful diversity of coral reefs in tropical regions. Many of By The Sea - Various - Locked & Loaded 2 major groups of organisms evolved in the sea and Seven Joys Of Mary - Various - A Canadian Christmas 4 may have started there.
The sea provides substantial supplies of food for humans, mainly fishbut also shellfishmammals and seaweedwhether caught by fishermen or farmed underwater. Other human uses of the sea include tradetravel, mineral extractionpower generationwarfareand leisure activities such as swimmingsailingand scuba diving.
Many of these activities create marine pollution. The sea is important in human culture, with major appearances in literature at least since Homer 's Odysseyin marine artin cinema, in theatre and in classical music. Symbolically, the sea appears as monsters such as Scylla in mythology and represents the unconscious mind in dream interpretation. Cantiga De Amigo - Amália Rodrigues - Fado Português sea is the interconnected system of all the Earth's oceanic waters, including the AtlanticPacificIndianSouthern and Arctic Oceans.
There is no sharp distinction between seas and oceansthough generally seas are smaller, and are often partly as marginal seas or wholly as inland seas bordered by land. Earth is the only known planet with seas of liquid water on its surface,  p22 although Mars possesses ice caps and similar planets in other solar systems may have oceans.
The remainder about 0. Clarke once noted that "Earth" would have been better named "Ocean". The scientific study of water and Earth's water cycle is hydrology ; hydrodynamics studies the physics of water in motion.
The more recent study of the sea in particular is oceanography. This began as the study of the shape of the ocean's currents  but has since expanded into a large and multidisciplinary field:  it examines the properties of seawater ; studies wavestidesand currents ; charts coastlines and maps the seabeds ; and studies marine life.
Both are informed by chemical oceanographywhich studies the behavior of elements and molecules within the oceans: particularly, at the moment, the ocean's role in the carbon cycle and carbon dioxide 's role in the increasing acidification of seawater. Marine and maritime geography charts the shape and shaping of the sea, while Adagio - Ludwig Van Beethoven / Herbert Von Karajan / Berliner Philharmoniker - Symphonien 4 & 7 geology geological oceanography has provided evidence of continental drift and the composition and structure of the Earthclarified the process of sedimentationand assisted Foghat - Rock N Roll / Energized study of volcanism and earthquakes.
The water in the sea was thought to come from the Earth's volcanoesstarting 4 billion years ago, released by degassing from molten rock. Despite variations in the levels of salinity in different seas, the relative composition of the dissolved salts is stable throughout the world's oceans. Although the amount of salt in the ocean remains relatively constant within the scale of millions of years, various factors affect the salinity of a body of water.
Sea temperature depends on the amount of solar radiation falling on its surface. There is a continuous circulation of water in the oceans. Warm surface currents cool as they move away from the tropics, and the water becomes denser and sinks. The cold water moves back towards the equator as a deep sea current, driven by changes in the temperature and density of the water, before eventually welling up again towards the surface.
These break into small pieces and coalesce into flat discs that form a thick suspension known as frazil. In calm conditions this freezes into a thin flat sheet known as nilaswhich thickens as new ice forms on its underside. In more turbulent seas, frazil crystals join together into flat discs known as pancakes. These slide under each other and coalesce to form floes.
In the process of freezing, salt water and air are trapped between the ice crystals. The amount of oxygen found in seawater depends primarily on the plants growing in it. These are mainly algae, including phytoplanktonwith some vascular plants such as seagrasses. In daylight the photosynthetic activity of Ленинградский Вокзал - Александр Шапиро + Игорь Корж - MP3 Stereo plants produces oxygen, which dissolves in the seawater and is used by marine animals.
At night, photosynthesis stops, and the amount of dissolved oxygen declines. In the deep sea, where insufficient light penetrates for plants to grow, there is very little dissolved oxygen. In its absence, organic material is broken down by anaerobic bacteria producing hydrogen sulphide. Much light gets reflected at the surface, and red light gets absorbed in the top few metres. Wind blowing over the surface of a body of water forms waves that are perpendicular to the direction of the wind.
The friction between air and water caused by a gentle breeze on a pond causes ripples to form. A strong blow over the ocean causes larger waves as the moving air pushes against the raised ridges of water.
The waves reach their maximum height when the rate at which they are travelling nearly matches the speed of the wind. In open water, when the wind blows continuously as happens in the Southern Hemisphere in the Roaring Fortieslong, organised masses of water called swell roll across the ocean.
The size of the waves depends on the fetchthe distance that the wind has blown over the water and the strength and duration of that wind. When waves meet others coming from different directions, interference between the two can produce broken, irregular seas.
The top of a wave is known as the crest, the lowest point between waves is the trough and the distance By The Sea - Various - Locked & Loaded 2 the crests is the wavelength.
The wave is pushed across the surface of the sea by School Days - Chuck Berry - Les Inoubliables wind, but this represents a transfer of energy and not a horizontal movement of water.
As waves approach land and move into shallow waterthey change their behavior. If approaching at an angle, waves may bend refraction or wrap rocks and headlands diffraction. When the wave reaches a point where its deepest oscillations of the By The Sea - Various - Locked & Loaded 2 contact the seabedthey begin to slow down. This pulls the crests closer together and increases the waves' heightBy The Sea - Various - Locked & Loaded 2 is called wave shoaling.
When the ratio of the wave's height to the water House Arrest - Fed Up - Fed Up increases above a certain limit, it " breaks ", toppling over in a mass of foaming water. A tsunami is an Ever So Lonely (EP Version) - Various - CompilASIAN - The World Of Indipop form of wave caused by an infrequent powerful event such as an underwater earthquake or landslide, a meteorite impact, a volcanic eruption or a collapse of land into the By The Sea - Various - Locked & Loaded 2 . These events can temporarily lift or lower the surface of the sea in the affected area, usually by a few feet.
The potential energy of the displaced seawater is turned into kinetic energy, creating a shallow wave, a tsunami, radiating outwards at a velocity proportional to the square root of the depth of the water and which therefore travels much faster in the open ocean than on a continental shelf.
A trigger event on the continental shelf may cause a local tsunami on the land side and a distant tsunami that travels out across the ocean. The energy of the wave is dissipated only gradually, but is spread out over the wave front, so as the wave radiates away from the source, the front gets longer and the average energy reduces, so distant shores will, on average, be hit by weaker waves.
However, as the speed of the wave is controlled by the water depth, it does not travel at the same speed in all directions, and this affects the direction of the wave front — an effect known as refraction — which can focus the strength of the advancing tsunami on some areas and weaken it in others according to undersea topography. As a tsunami moves into shallower water its speed decreases, its wavelength shortens and its amplitude increases enormously,  behaving in the same way as a wind-generated wave in shallow water, but on a vastly greater scale.
Either the trough or the crest of a tsunami can arrive at the coast first. Much of the destruction may be caused by the flood water draining back into the Yeaaaah! - The Light Circle - Yeaaaah! after the tsunami has struck, dragging debris and people with it. Often several tsunami are caused by a single geological event and arrive at intervals of between eight minutes and two hours.
The first wave to arrive on shore may not be the biggest or most destructive. Wind blowing over the surface of the sea causes friction at the interface between air and sea.
Not only does this cause waves to form By The Sea - Various - Locked & Loaded 2 it also makes the surface seawater move in the same direction as the wind. Although winds are variable, in any one place they predominantly blow from a single direction and thus a surface current can be formed.
Westerly winds are most frequent in the mid-latitudes while easterlies dominate the tropics. There are five main gyres in the world's oceans: two in the Pacific, two in the Atlantic and one in the Indian Ocean. Other smaller gyres are found in lesser seas and a single gyre flows around Antarctica. These gyres have followed the same routes for millennia, guided by the topography of the land, the wind direction and the Coriolis effect.
The surface currents flow in a clockwise direction in the Northern Hemisphere and anticlockwise in the Southern Hemisphere. The water moving away from the equator is warm, and that flowing in the reverse direction has lost most of its heat.
These currents tend to moderate the Earth's climate, cooling the equatorial region and warming regions at higher latitudes. Surface currents only affect the top few hundred metres yards of the sea, but there are also large-scale flows in the ocean depths caused by the movement of deep water By The Sea - Various - Locked & Loaded 2. A main deep ocean current flows through all the world's oceans and is known as the thermohaline circulation or global conveyor belt.
This movement is slow and is driven by differences in density of the water caused by variations in salinity and temperature. Both these factors make it denser, and the water sinks. From the deep sea near Greenland, such water flows By The Sea - Various - Locked & Loaded 2 between the continental landmasses on either side of the Atlantic. When it reaches the Antarctic, it is joined by further masses of cold, sinking water and flows eastwards.
It then splits into two streams that move northwards into the Indian and Pacific Oceans. Here it is gradually warmed, becomes less dense, rises towards the surface and loops back on itself. Some flows back into the Atlantic. It takes a thousand years for this circulation pattern to be completed. Besides gyres, there are temporary surface currents that occur under specific conditions. When waves meet a shore at an angle, a longshore current is created as water is pushed along parallel to the coastline.
The water swirls up onto the beach at right angles to the approaching waves but drains away straight down the slope under the effect of gravity. The larger the breaking waves, the longer the beach and the more oblique the wave approach, the stronger is the longshore current.
It may occur at a gap in a sandbar or near a man-made structure such as a groyne. This cold water is often rich in nutrients and creates blooms of phytoplankton and a great increase in the productivity of the sea.
Я Не Могу Тебя Простить - Влад Сташевский - 21, A Fish - Yximalloo - The Worst Of 1982, Hidden Dimple - Various - New Music For Jazz Ensemble Vol. IX, Samantha Fox + Kim Wilde - За Рулем Collection, Identity Crisis - Various - Victory: The Early Singles 1989-1992