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The generic term sea covers several realities and may designate a large body of salt water , a large body of salt water different from the oceans , all areas of salt water and natural open communication throughout the whole of globe or a large extent on the dark surface of the Moon.
Summary |
Definitions
A large area of salt water
This definition confuses the oceans , seas, closed or open and large salt lakes. It is found in a historical context (time of Christopher Columbus , the Atlantic Ocean is called the Ocean Sea) or familiar (as opposed to the sea and the mountains in the holidays, the sea is good? to evoke in contact with coast is distinguished from the latter by its landlocked geographical position generally between land masses or simply limited by the continental shelf. Ex: The Channel communicates with the Atlantic Ocean by the Celtic Sea , but it is distinguished by its middle position between the southern coast of England and the northern coast of France. A sea into contact with an ocean can be distinguished by specific physical conditions. Ex: the Mediterranean communicates with the Atlantic Ocean by the Strait of Gibraltar. It differs from the ocean by its landlocked position between Europe , the Asia ( Middle East ) and Africa and through various marine conditions (temperature difference between ocean and sea fauna and flora distinct tide of lower amplitude for the Mediterranean ...). Another example is the Sargasso Sea with its accumulation of brown algae off the Florida differs arbitrarily from the Atlantic Ocean.
The term seafood is also used to describe certain large lakes , especially when they have no rivers where they flow. This is the case for example of the Caspian Sea or the Sea of Aral. This is often referred to enclosed sea.
A large area in the dark surface of the Moon
Finally, the Great Plains lunar dark, mostly located on the visible surface of the Moon , natural satellite earth are conventionally called "Seas" (ex: Sea of Tranquility ). These great plains basalt had indeed been considered as bodies of water by early astronomers, before use of the telescope by Galileo to observe the sky.
Definition in international law
In international law, called "sea" of space located beyond the low tide.
Sea includes:
Physics
The movements of the sea
The sea is constantly moving. In antiquity, it was attributed to deities : the wrath of Poseidon , the games of Nereids , the monster Scylla and Charybdis.
The movements of the sea are complex to analyze them better, they are decomposed into elementary movements, the causes and laws can be studied separately.
We distinguish movements wave form of vertical oscillations:
- the swell is caused by the wind , her period is around the second or ten seconds and amplitude can reach several tens of meters.
- the lapping movement is that there is a port, it is the combination of waves reflected from the walls.
- the cuttlefish , found in harbors and ponds; a period ranging from one minute to several minutes, their amplitudes are small (a few tens of centimeters).
- the tide is due to the attraction of the moon and sun , and its period is about 12 hours, and its amplitude varies depending on location, can exceed ten meters.
The movements of currents are horizontal displacements.
- Major trends are rooted in differences in density of seawater (due to differences in salinity or temperature). They are regarded as constant.
- More localized currents are generated by wind or tides. They can take a roundabout nature and cause of large eddies as the famous Saltstraumen ( Maelstrom ).
Isolated movements can be caused by catastrophic events ( earthquakes , volcanic eruptions , landslides ) in the form of tsunamis , or solitary wave soliton.
Salinity
A characteristic of seawater is of course to be salty. The salinity is about 37 g / L in the Mediterranean, and about 35 in the oceans (about 27 g sodium chloride and 5 g of other chlorides (magnesium, calcium and potassium), 3 g remainder being mainly composed of sulphates, carbonates and bromides. There is a kg of salt in 30 to 35 liters of seawater
Sea salt is a compound whose full name chemistry is sodium chloride. It tends to dissolve in water to a saturation concentration of 359 g / L. If one tries to increase the concentration beyond this value, by evaporation of water, some salt returns to the solid state ( solidification or crystallization ) and deposits. The value of the salinity of the seas is significantly lower, the salt is not deposited on the seabed. As not all of evaporated Nor, he is trapped in the sea
Some soils and continental rocks contain salt. When these rocks are exposed to rain or water flows underground, part of the salt is dissolved and then the rivers join the sea Because the salt does not remain constant but is discharged, the salinity of rivers remain the most time low.
Salt deposits can be done naturally when the salt concentration of a sea or salt lake has increased beyond saturation. This may occur in inland areas where there is no flow to the oceans as the Dead Sea.
Another case is that of the Mediterranean, which in certain geological epochs worked like a salt marsh : its association with the oceans in the Strait of Gibraltar is narrower, it does not allow water exchange in both directions as is currently produces. On the other hand, evaporation is greater than rainfall and inflows of fresh water (which is always the case), so it is a contribution oceanic compensate the deficit. So there was an entry of salt that was not offset by exports. This has resulted in very significant salt deposits deep in the Mediterranean and apparently he also had an influence on ocean salinity. Indeed, the estimated intake of salt to the global ocean by rivers all over geological time is greater by at least an order of magnitude the mass of salt dissolved in the oceans.
Sea levels
The sea level rises, including the effect of melting ice and continental thermal expansion of water caused by global warming. Rising sea levels pose a serious challenge for all coastal populations and for the economies of many countries Classification A cut of the oceans has been made by the International Hydrographic Organization (IHO) . Some seas are also possible subdivisions. See list of seas and oceans. Several classifications exist, the classification in Law of the Sea does not overlap with that little classification of Oceanography , some synonymous terms in oceanography take on increased significance in geology or geography. The classification used here is that generally used by the geography of a book while the other differences may appear. The terms used are not necessarily exclusive, eg the English Channel is bordered by landmasses and covers a portion of a continental shelf as it is sometimes called sea intercontinental and epicontinental sea . A name based on the temperature of surface waters of the seas also exists but is little used, we speak in this case tropical sea, sea or temperate polar sea. A Mediterranean Sea is almost enclosed sea communicating with the ocean. Mediterranean seas are divided in turn into intracontinental and intercontinental sea depending on the number of continents bordering. A typical example of these seas is the Mediterranean Sea. In the depth of these seas strait linking the oceans is low, which prevents the creation of deep current allowing the mixing of deep waters. An epicontinental sea is a sea covering a portion of a continental shelf. For oceanographers and geographers marginal sea is a synonym for geologists a marginal sea is called only if it is on geologically active continental margins , on the margins of the Pacific Ocean for example, and not that of the Atlantic which are passive. A marginal sea is a sea in broad communication with the ocean that borders it, they are often epicontinental and this term is sometimes used as a synonym of epicontinental sea, the seas are usually involved in the dynamics of the oceans that surround and distinction between these seas and the ocean is more frequently close geographical , ecological or legal oceanographer. An inland sea is a sea not communicating with another sea inland seas are frequently Mediterranean seas. A closed sea is a sea not communicating with any other sea or ocean. The Dead Sea is an inland sea but a lake, legally speaking the Caspian Sea is not considered a sea The sea is a major economic resource for coastal areas: fishing , tourism , transport and logistics (business port ) saline. The European Commission proposed on 20 May to celebrate the sea in Europe, from 2008 to value the culture and maritime heritage. This day will result in operations "open" (open ports), environmental actions involving particular museums and aquariums, conferences, etc.. Commission provides free information and brochures on this initiative. The high seas, like mountains , have long been seen mostly by men as dangerous and hostile environments, mainly for reserve of natural resources (particularly of proteins through the fish). This seems to have been amended in the West with the movement of Romanticism in the late eighteenth century and the romanticism of the early nineteenth century. The beauty of the sea through its natural aspects was then celebrated by poets: his seemingly endless, the strength of its storms, etc.. The sea was then trimmed some human virtues, such as freedom (the famous "free man, you will always cherish the sea" of Baudelaire ). By sea
Type
Mediterranean Sea
epicontinental seas
coastal seas
Inland sea
Seas closed
Sea and Society
Economics
Day of the Sea
Symbolism
References
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