محمد طلال هديب
07-03-2009, 02:12 PM
Seas and Ocean
Seas
A sea is either a large expanse of saline water (http://en.wikipedia.org/wiki/Salinity) connected with an ocean (http://en.wikipedia.org/wiki/Ocean), or a large, usually saline, lake (http://en.wikipedia.org/wiki/Lake) that lacks a natural outlet such as the Caspian Sea (http://en.wikipedia.org/wiki/Caspian_Sea) and the Dead Sea (http://en.wikipedia.org/wiki/Dead_Sea). The term is used colloquially as synonymous with ocean, as in "the tropical sea" or "down to the sea shore", or even "sea water (http://en.wikipedia.org/wiki/Sea_water)" to refer to water of the ocean. Large lakes, such as the Great Lakes (http://en.wikipedia.org/wiki/Great_Lakes), are sometimes referred to as inland seas. Many seas are marginal seas (http://en.wikipedia.org/wiki/Marginal_sea), in which currents (http://en.wikipedia.org/wiki/Ocean_current) are caused by ocean winds; others are mediterranean seas (http://en.wikipedia.org/wiki/Mediterranean_sea_%28oceanogra phy%29), in which currents are caused by differences in salinity (http://en.wikipedia.org/wiki/Salinity) and temperature (http://en.wikipedia.org/wiki/Temperature).
The International Hydrographic Organization (http://en.wikipedia.org/wiki/International_Hydrographic_Org anization) (IHO) is the world authority when it comes to defining seas. The current defining document is the Special publication S-23, Limits of Oceans and Seas (http://www.iho.shom.fr/PUBLICATIONS/download.htm), 3rd edition, 1953. The second edition dated back to 1937, and the first to 1928. A fourth edition draft was published in 1986 but so far several naming disputes (such as the one over the Sea of Japan (http://en.wikipedia.org/wiki/Sea_of_Japan_naming_dispute)) have prevented its ratification.
List of seas (by ocean)
† Not listed in IHO S-23 4th ed.
Ambiguous terminology
Some bodies of water that are called "seas" are not actually seas; there are also some seas that are not called "seas". The following is an incomplete list of such potentially confusing names.
· The Sea of Galilee (http://en.wikipedia.org/wiki/Sea_of_Galilee) is a small freshwater lake with a natural outlet, which is properly called Lake Tiberias or Lake Kinneret on modern Israeli maps, but its original name remains in use.
· The Sea of Cortés is more commonly known as the Gulf of California (http://en.wikipedia.org/wiki/Gulf_of_California).
· The Persian Gulf (http://en.wikipedia.org/wiki/Persian_Gulf) is a sea.
· The Dead Sea (http://en.wikipedia.org/wiki/Dead_Sea) is actually a lake, as is the Caspian Sea (http://en.wikipedia.org/wiki/Caspian_Sea).
Extraterrestrial seas
Lunar maria (http://en.wikipedia.org/wiki/Lunar_mare) are vast basaltic plains on the Moon (http://en.wikipedia.org/wiki/Moon) that were thought to be bodies of water by early astronomers, who referred to them as "seas".
Liquid water may have existed on the surface of Mars (http://en.wikipedia.org/wiki/Mars) in the distant past, and several basins on Mars have been proposed as dry sea beds. The largest is Vastitas Borealis (http://en.wikipedia.org/wiki/Vastitas_Borealis); others include Hellas Planitia (http://en.wikipedia.org/wiki/Hellas_Planitia) and Argyre Planitia (http://en.wikipedia.org/wiki/Argyre_Planitia).
Liquid water is thought to be present under the surface of several moons (http://en.wikipedia.org/wiki/Natural_satellite), most notably Europa (http://en.wikipedia.org/wiki/Europa_%28moon%29).
Liquid hydrocarbons are thought to be present on the surface of Titan (http://en.wikipedia.org/wiki/Titan_%28moon%29), though it may be more accurate to describe them as "lakes" rather than "seas".
Science
The term "sea" has also been used in quantum physics (http://en.wikipedia.org/wiki/Quantum_physics). Dirac sea (http://en.wikipedia.org/wiki/Dirac_sea) is an interpretation of the negative energy states that comprises the vacuum.
Ocean
http://www.jo1sat.com/file:///C:/DOCUME~1/3B5D~1/LOCALS~1/Temp/msohtmlclip1/01/clip_image001.gif
Animated map exhibiting the world's oceanic waters. A continuous body of water encircling the Earth (http://en.wikipedia.org/wiki/Earth), the world (global) ocean (http://en.wikipedia.org/wiki/World_Ocean) is divided into a number of principal areas. Five oceanic divisions are usually reckoned: Pacific (http://en.wikipedia.org/wiki/Pacific_Ocean), Atlantic (http://en.wikipedia.org/wiki/Atlantic_Ocean), Indian (http://en.wikipedia.org/wiki/Indian_Ocean), Arctic (http://en.wikipedia.org/wiki/Arctic_Ocean), and Southern (http://en.wikipedia.org/wiki/Southern_Ocean); the last two listed are sometimes consolidated into the first three.
An ocean (from Ωκεανός, Okeanos (Oceanus) (http://en.wikipedia.org/wiki/Oceanus) in Greek (http://en.wikipedia.org/wiki/Greek_********)) is a major body of saline water (http://en.wikipedia.org/wiki/Seawater), and a principal component of the hydrosphere (http://en.wikipedia.org/wiki/Hydrosphere). Approximately 71% of the Earth (http://en.wikipedia.org/wiki/Earth)'s surface (http://en.wikipedia.org/wiki/Surface) (an area of some 361 million square kilometers (http://en.wikipedia.org/wiki/Square_kilometre)) is covered by ocean, a continuous body of water (http://en.wikipedia.org/wiki/World_Ocean) that is customarily divided into several principal oceans and smaller seas (http://en.wikipedia.org/wiki/Sea). More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic salinity (http://en.wikipedia.org/wiki/Salinity) is around 35 parts per thousand (http://en.wikipedia.org/wiki/Parts_per_thousand) (ppt) (3.5%), and nearly all seawater has a salinity in the range of 31 to 38 ppt.
Overview
Though generally recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the World Ocean (http://en.wikipedia.org/wiki/World_Ocean) or global ocean.[1] (http://en.wikipedia.org/wiki/Ocean#_note-0#_note-0)[2] (http://en.wikipedia.org/wiki/Ocean#_note-UNAoO#_note-UNAoO) This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography (http://en.wikipedia.org/wiki/Oceanography).[3] (http://en.wikipedia.org/wiki/Ocean#_note-1#_note-1) The major oceanic divisions are defined in part by the continents (http://en.wikipedia.org/wiki/Continent), various archipelagos (http://en.wikipedia.org/wiki/Archipelago), and other criteria: these divisions are (in descending order of size) the Pacific Ocean (http://en.wikipedia.org/wiki/Pacific_Ocean), the Atlantic Ocean (http://en.wikipedia.org/wiki/Atlantic_Ocean), the Indian Ocean (http://en.wikipedia.org/wiki/Indian_Ocean), the Southern Ocean (http://en.wikipedia.org/wiki/Southern_Ocean) (which is sometimes subsumed as the southern portions of the Pacific, Atlantic, and Indian Oceans), and the Arctic Ocean (http://en.wikipedia.org/wiki/Arctic_Ocean) (which is sometimes considered a sea (http://en.wikipedia.org/wiki/Sea) of the Atlantic). The Pacific and Atlantic may be further subdivided by the equator (http://en.wikipedia.org/wiki/Equator) into northerly (http://en.wikipedia.org/wiki/North) and southerly (http://en.wikipedia.org/wiki/South) portions. Smaller regions of the oceans are called seas, gulfs (http://en.wikipedia.org/wiki/Headlands_and_bays), bays (http://en.wikipedia.org/wiki/Bay) and other names. There are also some smaller bodies of saltwater that are on land and not interconnected with the World Ocean, such as the Aral Sea (http://en.wikipedia.org/wiki/Aral_Sea), and the Great Salt Lake (http://en.wikipedia.org/wiki/Great_Salt_Lake) – though they may be referred to as 'seas', they are actually salt lakes (http://en.wikipedia.org/wiki/Salt_lake).
Geologically, an ocean is an area of oceanic crust covered by water. Oceanic crust is the thin layer of solidified volcanic basalt (http://en.wikipedia.org/wiki/Basalt) that covers the Earth's mantle (http://en.wikipedia.org/wiki/Mantle_%28geology%29) where there are no continents. From this perspective, there are three oceans today: the World Ocean and the Caspian and Black Seas (http://en.wikipedia.org/wiki/Black_Sea), the latter two having been formed by the collision of Cimmeria (http://en.wikipedia.org/wiki/Cimmerian_plate) with Laurasia (http://en.wikipedia.org/wiki/Laurasia). The Mediterranean Sea (http://en.wikipedia.org/wiki/Mediterranean_Sea) is very nearly a discrete ocean, being connected to the World Ocean through the Strait of Gibraltar (http://en.wikipedia.org/wiki/Strait_of_Gibraltar), and indeed several times over the last few million years movement (http://en.wikipedia.org/wiki/Plate_tectonics) of the African continent (http://en.wikipedia.org/wiki/Africa) has closed the strait off entirely. The Black Sea is connected to the Mediterranean through the Bosporus (http://en.wikipedia.org/wiki/Bosporus), but this is in effect a natural canal (http://en.wikipedia.org/wiki/Canal) cut through continental rock some 7,000 years ago, rather than a piece of oceanic sea floor like the Strait of Gibraltar.
Seas
A sea is either a large expanse of saline water (http://en.wikipedia.org/wiki/Salinity) connected with an ocean (http://en.wikipedia.org/wiki/Ocean), or a large, usually saline, lake (http://en.wikipedia.org/wiki/Lake) that lacks a natural outlet such as the Caspian Sea (http://en.wikipedia.org/wiki/Caspian_Sea) and the Dead Sea (http://en.wikipedia.org/wiki/Dead_Sea). The term is used colloquially as synonymous with ocean, as in "the tropical sea" or "down to the sea shore", or even "sea water (http://en.wikipedia.org/wiki/Sea_water)" to refer to water of the ocean. Large lakes, such as the Great Lakes (http://en.wikipedia.org/wiki/Great_Lakes), are sometimes referred to as inland seas. Many seas are marginal seas (http://en.wikipedia.org/wiki/Marginal_sea), in which currents (http://en.wikipedia.org/wiki/Ocean_current) are caused by ocean winds; others are mediterranean seas (http://en.wikipedia.org/wiki/Mediterranean_sea_%28oceanogra phy%29), in which currents are caused by differences in salinity (http://en.wikipedia.org/wiki/Salinity) and temperature (http://en.wikipedia.org/wiki/Temperature).
The International Hydrographic Organization (http://en.wikipedia.org/wiki/International_Hydrographic_Org anization) (IHO) is the world authority when it comes to defining seas. The current defining document is the Special publication S-23, Limits of Oceans and Seas (http://www.iho.shom.fr/PUBLICATIONS/download.htm), 3rd edition, 1953. The second edition dated back to 1937, and the first to 1928. A fourth edition draft was published in 1986 but so far several naming disputes (such as the one over the Sea of Japan (http://en.wikipedia.org/wiki/Sea_of_Japan_naming_dispute)) have prevented its ratification.
List of seas (by ocean)
† Not listed in IHO S-23 4th ed.
Ambiguous terminology
Some bodies of water that are called "seas" are not actually seas; there are also some seas that are not called "seas". The following is an incomplete list of such potentially confusing names.
· The Sea of Galilee (http://en.wikipedia.org/wiki/Sea_of_Galilee) is a small freshwater lake with a natural outlet, which is properly called Lake Tiberias or Lake Kinneret on modern Israeli maps, but its original name remains in use.
· The Sea of Cortés is more commonly known as the Gulf of California (http://en.wikipedia.org/wiki/Gulf_of_California).
· The Persian Gulf (http://en.wikipedia.org/wiki/Persian_Gulf) is a sea.
· The Dead Sea (http://en.wikipedia.org/wiki/Dead_Sea) is actually a lake, as is the Caspian Sea (http://en.wikipedia.org/wiki/Caspian_Sea).
Extraterrestrial seas
Lunar maria (http://en.wikipedia.org/wiki/Lunar_mare) are vast basaltic plains on the Moon (http://en.wikipedia.org/wiki/Moon) that were thought to be bodies of water by early astronomers, who referred to them as "seas".
Liquid water may have existed on the surface of Mars (http://en.wikipedia.org/wiki/Mars) in the distant past, and several basins on Mars have been proposed as dry sea beds. The largest is Vastitas Borealis (http://en.wikipedia.org/wiki/Vastitas_Borealis); others include Hellas Planitia (http://en.wikipedia.org/wiki/Hellas_Planitia) and Argyre Planitia (http://en.wikipedia.org/wiki/Argyre_Planitia).
Liquid water is thought to be present under the surface of several moons (http://en.wikipedia.org/wiki/Natural_satellite), most notably Europa (http://en.wikipedia.org/wiki/Europa_%28moon%29).
Liquid hydrocarbons are thought to be present on the surface of Titan (http://en.wikipedia.org/wiki/Titan_%28moon%29), though it may be more accurate to describe them as "lakes" rather than "seas".
Science
The term "sea" has also been used in quantum physics (http://en.wikipedia.org/wiki/Quantum_physics). Dirac sea (http://en.wikipedia.org/wiki/Dirac_sea) is an interpretation of the negative energy states that comprises the vacuum.
Ocean
http://www.jo1sat.com/file:///C:/DOCUME~1/3B5D~1/LOCALS~1/Temp/msohtmlclip1/01/clip_image001.gif
Animated map exhibiting the world's oceanic waters. A continuous body of water encircling the Earth (http://en.wikipedia.org/wiki/Earth), the world (global) ocean (http://en.wikipedia.org/wiki/World_Ocean) is divided into a number of principal areas. Five oceanic divisions are usually reckoned: Pacific (http://en.wikipedia.org/wiki/Pacific_Ocean), Atlantic (http://en.wikipedia.org/wiki/Atlantic_Ocean), Indian (http://en.wikipedia.org/wiki/Indian_Ocean), Arctic (http://en.wikipedia.org/wiki/Arctic_Ocean), and Southern (http://en.wikipedia.org/wiki/Southern_Ocean); the last two listed are sometimes consolidated into the first three.
An ocean (from Ωκεανός, Okeanos (Oceanus) (http://en.wikipedia.org/wiki/Oceanus) in Greek (http://en.wikipedia.org/wiki/Greek_********)) is a major body of saline water (http://en.wikipedia.org/wiki/Seawater), and a principal component of the hydrosphere (http://en.wikipedia.org/wiki/Hydrosphere). Approximately 71% of the Earth (http://en.wikipedia.org/wiki/Earth)'s surface (http://en.wikipedia.org/wiki/Surface) (an area of some 361 million square kilometers (http://en.wikipedia.org/wiki/Square_kilometre)) is covered by ocean, a continuous body of water (http://en.wikipedia.org/wiki/World_Ocean) that is customarily divided into several principal oceans and smaller seas (http://en.wikipedia.org/wiki/Sea). More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic salinity (http://en.wikipedia.org/wiki/Salinity) is around 35 parts per thousand (http://en.wikipedia.org/wiki/Parts_per_thousand) (ppt) (3.5%), and nearly all seawater has a salinity in the range of 31 to 38 ppt.
Overview
Though generally recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the World Ocean (http://en.wikipedia.org/wiki/World_Ocean) or global ocean.[1] (http://en.wikipedia.org/wiki/Ocean#_note-0#_note-0)[2] (http://en.wikipedia.org/wiki/Ocean#_note-UNAoO#_note-UNAoO) This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography (http://en.wikipedia.org/wiki/Oceanography).[3] (http://en.wikipedia.org/wiki/Ocean#_note-1#_note-1) The major oceanic divisions are defined in part by the continents (http://en.wikipedia.org/wiki/Continent), various archipelagos (http://en.wikipedia.org/wiki/Archipelago), and other criteria: these divisions are (in descending order of size) the Pacific Ocean (http://en.wikipedia.org/wiki/Pacific_Ocean), the Atlantic Ocean (http://en.wikipedia.org/wiki/Atlantic_Ocean), the Indian Ocean (http://en.wikipedia.org/wiki/Indian_Ocean), the Southern Ocean (http://en.wikipedia.org/wiki/Southern_Ocean) (which is sometimes subsumed as the southern portions of the Pacific, Atlantic, and Indian Oceans), and the Arctic Ocean (http://en.wikipedia.org/wiki/Arctic_Ocean) (which is sometimes considered a sea (http://en.wikipedia.org/wiki/Sea) of the Atlantic). The Pacific and Atlantic may be further subdivided by the equator (http://en.wikipedia.org/wiki/Equator) into northerly (http://en.wikipedia.org/wiki/North) and southerly (http://en.wikipedia.org/wiki/South) portions. Smaller regions of the oceans are called seas, gulfs (http://en.wikipedia.org/wiki/Headlands_and_bays), bays (http://en.wikipedia.org/wiki/Bay) and other names. There are also some smaller bodies of saltwater that are on land and not interconnected with the World Ocean, such as the Aral Sea (http://en.wikipedia.org/wiki/Aral_Sea), and the Great Salt Lake (http://en.wikipedia.org/wiki/Great_Salt_Lake) – though they may be referred to as 'seas', they are actually salt lakes (http://en.wikipedia.org/wiki/Salt_lake).
Geologically, an ocean is an area of oceanic crust covered by water. Oceanic crust is the thin layer of solidified volcanic basalt (http://en.wikipedia.org/wiki/Basalt) that covers the Earth's mantle (http://en.wikipedia.org/wiki/Mantle_%28geology%29) where there are no continents. From this perspective, there are three oceans today: the World Ocean and the Caspian and Black Seas (http://en.wikipedia.org/wiki/Black_Sea), the latter two having been formed by the collision of Cimmeria (http://en.wikipedia.org/wiki/Cimmerian_plate) with Laurasia (http://en.wikipedia.org/wiki/Laurasia). The Mediterranean Sea (http://en.wikipedia.org/wiki/Mediterranean_Sea) is very nearly a discrete ocean, being connected to the World Ocean through the Strait of Gibraltar (http://en.wikipedia.org/wiki/Strait_of_Gibraltar), and indeed several times over the last few million years movement (http://en.wikipedia.org/wiki/Plate_tectonics) of the African continent (http://en.wikipedia.org/wiki/Africa) has closed the strait off entirely. The Black Sea is connected to the Mediterranean through the Bosporus (http://en.wikipedia.org/wiki/Bosporus), but this is in effect a natural canal (http://en.wikipedia.org/wiki/Canal) cut through continental rock some 7,000 years ago, rather than a piece of oceanic sea floor like the Strait of Gibraltar.