With the name of sea it is known to the great concentrations of salty water that occupy the superficial layer of the earth and, in some cases, many meters inward. For instance: Celtic Sea, Arabian Sea, Mediterranean Sea.
There are hundreds of seas, although on many occasions the delimitation criteria led large areas of water to be considered as well. oceans, which limits to a certain extent the extension that it may have.
One of the great concerns of the inhabitants of different parts of the world is the sea, since its extension is an immediate reference to the immensity: 71% of the earth’s surface is water, and of it more than 95% is salty, containing there seas and oceans.
There are several internal classifications regarding the seas. Among all of them, the most common is the one that divides them according to the union they can have with an ocean: open seas and closed seas.
Open seas
The open seas (also called piélagos) are those that are practically completely surrounded by water, which means that they are not too much in contact with the ground. The areas in which the open seas appear are usually embedded in the oceans, and therefore far from the typical land formations: peninsulas, gulfs and bays.
The structure Of these seas, on the contrary, they owe a characteristic of their own product of solar radiation: the intensity of the waves is usually much more intense than in the case of coastal areas, produced by a similar greater intensity in terms of winds.
The depth From this class of seas, organic materials from the decomposition of organisms pass to the bottom, but nevertheless the wide availability of sunlight means that photosynthesis can occur easily.
The oceanic shark It is a characteristic species of the open sea, and it has the usual behavior of wandering looking for possible prey to feed on.
Here we list some open seas.
Examples of open seas
| Sea Laptev | Celtic Sea | Arabian Sea |
| Sea Kara | Sea of Okhotsk | Ligurian Sea |
| Barents Sea | Sea of ireland | Zanj Sea |
| Beaufort Sea | Balearic Sea | Mar del Scotia |
| Argentine sea | North Sea | Yellow sea |
| Tyrrhenian Sea | Caribbean Sea | Norwegian Sea |
| Ionian sea | Sargasso Sea |
Closed seas
The closed seas They are those that do not evacuate large amounts of water to an ocean, but instead appear completely delimited by land. They necessarily appear within a watershed, and therefore it is also called an endorheic lake: precisely the largest lakes are those that enter this group of closed seas.
Unlike open seas, closed seas do not have characteristics that are specific to them for all cases, but vary depending on the case: they often have high salinity, as a result of the accumulation of dissolved salts by its tributaries.
The extension of the closed seas, for its part, is not constant over time but depends on the contributions it receives: there are a large number of closed seas that reduce their size over time. Here we list some closed seas.
Examples closed seas
| Aral Sea | Mediterranean Sea | Great Salt Lake |
| Don Juan Lake | Lake Vanda | Lake Turkana |
| Lake Neusiedl | Lake Natron | Lake natron |
| Lake Baljash | Lake Chad | Lake eyre |
| Mar Chiquita Lagoon | Caspian Sea | Lake of Coipasa |
| Valencia lake | Dead Sea | Sea Urmía |
| Texcoco Lake | Salty lake |
Continental seas
Within the closed seas there appears a special group that is that of the continental seas. These are found within the continents but are communicated with the oceans by a small strait. The differences between these seas and the oceans are considerable, in terms of temperatures and salinity.