The mass of the waters that cover the depressions of the earth's crust forms seas and oceans, which occupy seven out of ten parts of the planet's surface. Together with the rivers, lakes and glaciers form what we call hydrosphere.
The ocean is usually divided into Atlantic, Pacific and Indian, as large units connected to each other by the Arctic and Antarctic polar oceans.
In turn, there are delimited areas of each ocean, close to the continents or even inland, that form the regional seas.
What are the oceans?
We call oceans to the large bodies of salt water that separate the continents. The ocean waters They occupy most of the surface of our planet. Because of its appearance from space, the Earth should be called Water, Ocean or Sea. It hits you more.
Since they were formed, almost 4,000 million years ago, the oceans contain most of the liquid water on Earth. Its operation determines the climates and allows us to explain the diversity of life on our planet, since life started in the water.
In the oceans there is a surface layer of warm water (12º to 30ºC), which reaches a variable depth depending on the areas, from a few tens of meters in some places, to 400 or 500 in others.
Below this layer the water is cold, with temperatures between 5º and -1ºC. Is called thermocline to the limit between these two layers. The water is warmer in the equatorial and tropical areas, and colder near the poles, and temperate zones. And, of course, warmer in summer and colder in winter.
What are the seas? How do they differ from the oceans?
The most obvious difference is seen in its extension, since the seas are smaller than the oceans. They are also usually less deep, more closed, they are close to the land masses, and their waters, at the same latitude and depth, are somewhat warmer.
Marine currents are weaker and more local than ocean currents, and their waves have a lower height. Due to its proximity to the continents, there is more biodiversity in the seas, but they also suffer from greater desertification.
Inside the oceans it's called seas to some areas near the coasts, almost always located on the continental shelf, with small depths. Are the coastal seas which, for historical or cultural reasons, have their own name, such as the North Sea, that of Oman or the Cantabrian.
There's others almost surrounded by continents except for some openings or narrow. Are the continental seas, such as the Mediterranean, Black, Baltic or Japan. There's also inland seas, fully enclosed, which are like huge lakes with salt water, such as the Dead Sea, the Caspian or the practically disappeared Mar de Aral.
The Mediterranean Sea, like other inland seas, shows an exception to the normal distribution of temperatures, since its deep waters are around 13ºC. The cause must be sought in that it is almost isolated when communicating with the Atlantic only through the Strait of Gibraltar and, therefore, the entire body of water is warming up.
He Pacific Ocean It is the largest on the planet and extends from the east coast of Asia to the west of America. Its marine relief is characterized by a great abyssal plain in its central part and the oceanic dorsal that runs in front of the coasts of America, and that turns before the Antarctic to reach Australia.
|Water body||Surface (km²)||Average depth (m)||Maximum Depth (m)|
He Atlantic Ocean It extends from Europe and Africa on its east bank, to America by the west. The most relevant feature of its underwater relief is the huge Atlantic dorsal, which runs from Iceland to near Antarctica.
He Indian Ocean It extends between the eastern coasts of Africa, South Asia, Australia and Antarctica. It is the warmest and also the one with the highest salinity. Its bottom is characterized by a central dorsal that descends from the Arabian Peninsula and forks in two at its midpoint, a branch that goes to South Africa and the other towards Australia.
He Arctic Ocean is special. Some classifications simply consider it as a widening along the north Atlantic Ocean, although it is also in contact with the Pacific through the Bering Strait. Throughout the year it has an increasingly small ice cap, which protects it from atmospheric influences and, in this way, stabilizes the stratification of water bodies.
He Antartic Ocean It is also special, since it corresponds to the southern Atlantic, Indian and Pacific oceans. It completely surrounds Antarctica and covers from its coasts to 60 ° South. The International Hydrographic Organization defined it in the year 2000.
In the reading section there is a whole monographic chapter dedicated to Seas and oceans of the Earth
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