Ocean - Océano
|Subdivisions|| Antarctic , Atlantic , |
Arctic , Indian , Pacific
|Inland islands||Islands of the world|
|Surface||361 000 000 km²|
|Volume||1 300 000 000 km³|
Average: 3900 m |
Maximum: 11 034 m ( Challenge chasm )
The ocean is a body of water that makes up much of the hydrosphere of a celestial body . [ 1 ] On Earth, an ocean is one of the main conventional divisions of the World Ocean , and "separates two or more continents ." [ 2 ] The oceans occupy most of the planet's surface .
The Pacific and Atlantic Oceans are often distinguished into North and South , depending on whether they are in the Northern or Southern Hemisphere: North Atlantic and South Atlantic , and North Pacific and South Pacific .
The depth of the ocean varies depending on the areas of the oceanic relief , but it is scarce compared to its surface. The average depth is estimated to be approximately 3,900 meters. The deepest part is in the Mariana Trench, reaching a depth of 11,034 m.
The following table summarizes some characteristics of the 5 oceans.
|Ocean||Adjacent continents||Area (km²)||Average depth (m)|
|Antarctic glacial||Antarctica||20 327 000||3270|
|Arctic glacial||North America , Asia and Europe||14 056 000||1205|
|Atlantic||America, Europe and Africa||106 500 000||3646|
|Indian||Africa, Asia, Oceania||68 556 000||3741|
|peaceful||Asia, Oceania and America||155 557 000||4280|
In the oceans there is a superficial layer of warm water (12 ° C to 30 ° C) that reaches a variable depth depending on the areas, from a few dozen meters to 50 or 100 m. Below this layer the water has temperatures between 5 ° C and –1 ° C. The boundary between the two layers is called a thermocline . The water is warmest in the temperate, equatorial zones and coldest near the poles . And, also, warmer in summer and colder in winter.
Until recently, they were thought to have formed about 4 billion years ago, after a period of intense volcanic activity , when the planet's surface temperature cooled to allow the water to be in a liquid state . Although the controversy continues, a study by scientist Francis Albarède , from the French National Center for Scientific Research (CNRS), published in the journal Nature estimates that its origin is in the collision of giant asteroids covered with ice that collided with the Earth. between 80 and 130 million years after the formation of the planet. [ 4 ]
It is believed that water, being a universal substance, has been around since the planet was being formed [ 5 ] and then it arrived in greater quantities from the asteroid belt , and not from the Oort cloud as previously believed, since in This last zone has a higher concentration of deuterium (forming heavy water ) compared to what exists on earth. This fact was confirmed in the direct analyzes that were made of the comets coming from the Oort cloud, such as the last one carried out by the Rosetta probe . [ 6 ] [ 7 ]
It contains solid substances in solution, the most abundant being sodium and chlorine which, in their solid form, combine to form sodium chloride or common salt and, together with magnesium , calcium and potassium , constitute about 90 % of elements dissolved in seawater. In addition there are other elements but in minimal quantities.
The Argo program has deployed more than 3,000 floats in the oceans to record the salinity and temperature of the surface layer of the oceans. Each of the floats is programmed to sink to a depth of 2,000 meters, and will drift at that depth for approximately 10 days. Subsequently, the float will emerge back to the surface continuously measuring the temperature and salinity. Once the float reaches the surface, the data is sent to a satellite, so that scientists and the public have access to this information about the state of the oceans within hours of the data is captured.
Salinity depends on the amount of salts it contains. Approximately an average of 3.5% of the mass of water, corresponds to substances in solution. If there is a lot of evaporation, a greater amount of water disappears, leaving the dissolved substances, so salinity increases.
This is rare in the polar regions, especially in the summer when the ice is diluted in the water. In seas like the Baltic , there is also little salinity.
It should be noted that in its great extension, the ocean presents each and every one of the existing natural chemical elements, either by runoff from these on the continents or existing reserves in it.
Most of the water on Earth , 94%, is found in the oceans, from which a greater quantity of pure water evaporates than that which returns in the form of precipitation . The volume of water in the oceans remains unchanged as they receive water through rivers.
The water in the oceans is also salty due to the eruption of underwater volcanoes. Volcanic rock provides salts.
In water, dissolved, there are practically all the elements, in a minute quantity, but because the oceans have such a colossal volume, they constitute inexhaustible reserves of raw materials, although, with the exception of sodium chloride (common salt), its extraction offers little profitability. These elements, in decreasing order, are the following (in parentheses the content in grams per liter): 1st Chlorine (19); 2nd Sodium (10.5); 3rd Magnesium (1.35); 4th Sulfur (0.885); 5th Calcium (0.400); 6th Potassium (0.380); 7th Bromine (0.065); ... 39th Silver (0.000 000 3); ... 57th Gold (0.000 000 004).
A common way of thinking is that the water in the oceans is blue mainly due to the reflection of the blue color of the sky. In fact, water itself has a slight blue color when stored in large quantities. Reflection of the sky contributes to the water looking blue but it is not the main reason. The origin is due to the absorption by the water molecules of the "red" photons from the incident light, being one of the few cases in nature produced by vibration and electronic dynamics. [ 9 ]
Seawater is rarely still, moving in waves , tides or currents. The waves are due to the wind blowing over the surface. The height of a wave is given by the speed of the wind, the length of time it has blown and the distance the wave has traveled. The highest wave recorded was 64 meters [ citation needed ] , but they are generally much lower. They play a fundamental role in the formation of the coasts .
They are a type of waves whose origin is earthquakes, tidal waves or the eruption of underwater volcanoes. They displace large amounts of water very quickly, modifying the surface of the sea and creating waves that move away from the area of the earthquake or the volcano. They get to travel at 750 km / h. In the open sea they cause little damage, since they are low (less than 1 meter). In shallow water it slows down but increases its height to 10 meters or more and often causes catastrophic damage upon reaching shore.
The tides are caused by the gravitational attraction of the moon and the sun . The attraction is greatest on the face of the Earth that faces the Moon, causing a high tide or high tide. The Sun, being at a greater distance, produces a less effect than the Moon. These can become causes of flooding in coastal populations.
Spring tides are called the moments in which the maximum attraction occurs, and are formed when the Moon, the Sun and the Earth are on the same line, that is, during the Full Moon or New Moon phases, for what occurs every 14 days, that is, twice a month.
They are less intense tides that occur when the Moon and the Sun form a right angle with the Earth, because the attractions of both, being in opposite directions, subtract from each other instead of adding. Of course, despite its smaller size, the attraction of the Moon is greater because it is closer. These tides occur in the First Quarter and Last Quarter phases.
It is the difference between high and low tide levels, which varies by location, from less than 1 meter in the Mediterranean Sea and the Gulf of Mexico , to 14.5 meters in the Bay of Fundy , on the eastern coast of Canada .
The marine currents near the surface of the oceans are driven by the winds, which carry them with them. They move at a slower speed than the wind and do not have the same direction as them, since they twist to one side due to the Earth's rotation or Coriolis force . They change direction to the right of their trajectory in the boreal hemisphere and to the left in the southern hemisphere
The 28 ocean currents are:
- North Equatorial Current
- South Equatorial Current
- Equatorial countercurrent
- Northern Pacific drift
- North Atlantic drift
- Norway current
- Spitzberg current
- Irminger current
- Circumatlantic current
- Alaska Stream
- Greenland current
- Labrador Stream
- Kuril Stream
- Falklands current
- Canary Islands current
- Benguela current
- California Stream
- Humboldt current
- Western Australian Current
- Gulf Stream
- Kuroshio current
- Brazilian current
- Guiana Current
- Eastern Australian Current
- Somalia current
- Mozambique current
- Needle Current
- Child Current
In oceanography it is a large system of rotating marine currents , particularly those that are related to large movements of the wind. The spins are caused by the Coriolis effect ; along the planetary vortex with horizontal and vertical friction, which determines the circulation pattern for the wind loop ( torque ). [ 10 ]
There are five major gyres, two in the north and two in the south for the Pacific and Atlantic oceans, respectively, and one for the Indian oceans. There are also others: the tropical gyres, the subtropical gyres, and the subpolar gyres.
It has been proven that in the gyres of the Atlantic and North Pacific there is a large accumulation of marine debris floating adrift. They are known as the great North Pacific garbage patch and the North Atlantic garbage patch .
The main ocean accidents are:
- The continental margin , which is the portion of the seabed that is closest to the mainland. It's divided in:
- Continental platform or submarine platform: it is the shallowest, reaches 200 m deep, being quite flat. The water that covers it usually contains abundant marine life and most of the fishing is done in this area. Here is a quarter of the world's oil and gas production , coming from the rocks below these platforms.
- Continental slope , escarpment, or continental escarpment. The extent of the slope varies depending on the ocean in which it is found. It has a steeper slope than the previous one and is between 200 to 3000 meters deep, approximately.
- Continental border . It is located in the final part of the slope and would mark the limit with the ocean floor.
- Oceanic ridges . They are vast and rugged underwater mountain ranges, generally located in the center of the oceans. On average they are 1000 km wide with a height of 3000 m. They form a more or less connected system 80,000 km long, receiving different names, for example, the Mid-Atlantic Ridge , the Reykjanes Ridge or the Eastern Pacific Ridge .
- Abyssal plains . They are formed between the ocean ridges and the continental margins. They are very flat and uniform areas, around 4000 m deep. They make up about 40% of the ocean floor.
- Underwater volcanoes
- Oceanic or abyssal trenches . They are the deepest parts of the oceans, with an average depth of 7000 to 8000 m, which can be thousands of kilometers long. The Las Marianas Trench is the deepest on the planet with more than 11,000 m below sea level.
|Oceanic trench||Location||Depth (m)|
|Challenger or Mariana Trench||Pacific (southern Mariana Islands )||11 034|
|Tonga Trench||Pacific (Northwest New Zealand )||10 822|
|Japan Trench||Pacific (eastern Japan )||10 554|
|Kuril or Kamchatka Trench||Pacific (southern Kuril Islands )||10 542|
|Philippine Trench||Pacific (eastern Philippines )||10 540|
|Kermadec Trench||Pacific (Northeast New Zealand )||10 047|
|Fosa de Bougainville||Pacific (eastern New Guinea )||9140|
|Puerto Rico Trench||Atlantic (eastern Puerto Rico )||8800|
|South Sandwich Trench||Atlantic (east of the South Sandwich Islands )||8428|
|Peru-Chile Trench||Pacific (western Peru and Chile )||8065|
|Aleutian Trench||Pacific (southern Aleutian Islands )||7822|
|Cayman Trench||Caribbean Sea (southern Cuba )||7680|
|Java Trench||Indian (south of the island of Java )||7450|
|Cape Verde Trench||Atlantic (western Cape Verde Islands )||7292|
Earth's oceans also play a vital role in cleaning the atmosphere , and some human activities can severely alter them. The oceans absorb huge amounts of carbon dioxide . In turn, the phytoplankton absorb carbon dioxide and release oxygen . George Small explains the importance of this life cycle: "70% of the oxygen added to the atmosphere each year comes from plankton in the sea." However, some scientists warn that phytoplankton could seriously decrease due to the reduction of ozone in the atmosphere, for which man is believed to be responsible.
Some countries agree to limit the wastes they allow to be dumped into the sea, others refuse to do so. The famous ocean explorer Jacques Cousteau warned: "We have to save the oceans if we want to save humanity."
The concentration of fish in small areas of the ocean and their scarcity elsewhere is significant. As William Ricker , a fisheries biologist, has warned : "The sea is not an unlimited reservoir of food energy." And the underwater explorer Jacques Cousteau also warned, returning from a global underwater exploration, that life in the oceans has decreased by 40% since 1950 due to overfishing and pollution .
The scientific marine Swiss Jacques Piccard predicted that given the current rate of pollution, the oceans of the world would be devoid of life in 25 years. He said that due to its shallow depth, the Baltic would be the first to die. Then the Adriatic and the Mediterranean would die, which do not have strong enough currents to carry pollution. Also, the French submarine explorer Jacques Cousteau said that the destruction of the oceans has already been carried out by 20-30%. He predicted "the end of everything in 30 to 50 years unless immediate action is taken." Part of this pollution is due to the fact that society has for centuries had the wrong concept that they have an inexhaustible capacity to receive waste .
The oceans cover 71% of the earth's surface, they are being very frequently polluted by human activity and the overexploitation of natural resources. Around 5 garbage islands have been located with a huge amount of waste, these are formed due to marine currents (natural eddies), the size of the most affected area is 3.4 million km² , which is located in the North Pacific Ocean. The most polluting countries are China, Indonesia, the Philippines, Thailand and Vietnam, these countries discharge the largest amount of plastic waste into the sea than the rest of the countries in the world combined.
- Annex: Oceans and seas of the world according to the IHO
- Marine ecosystem
- Ocean planet
- Deep ocean
- Ocean pollution
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