Seas: characteristics and types. What is the difference between sea water and fresh water

Our planet is called blue for a reason. In photographs from space, it is indeed blue. And all because three-quarters of its surface is covered with water - 361 million square meters. km is covered by the World Ocean - part of the water shell of the planet's hydrosphere. The hydrosphere is oceans, seas, rivers, lakes, ponds, swamps and even small springs. Everything is clear with rivers and lakes, but what is the difference between the sea and the ocean, do we swim in the sea or still in the ocean? Even the father of a third-grader can be puzzled by the question. Is the sea different from the ocean? Let's figure it out.

What are we talking about?

Everyone studied geography at school and remember that the World Ocean is divided into five oceans:

• Quiet or Veliky is the largest and oldest, its area is 178.6 million square meters. km;
• Atlantic - 92 million sq. km;
• Indian (ocean of ancient civilizations) - 76 million sq. km);
• Arctic - 15 million sq. km);
• Southern, about the boundaries of which scientists are still arguing - 86 million square meters. km).

With the oceans, what about the seas? What is the difference between the sea and the ocean, the photo below will not explain. Official geography reports that there are ninety seas on our planet, but disputes in scientific circles do not subside, and different numbers can be found in different sources. If experts argue, how can the layman understand?

The boundaries of the seas and oceans

By definition, an ocean is a body of water between continents. The sea is considered to be isolated water masses (land, islands, underwater ridges, etc.). The boundaries of the seas are often conditional, and on this basis, the seas are marginal (oceanic), interisland and closed (inland). With the boundaries of the second and third is more or less clear. But oceanic? These are the seas that are part of the ocean. Logical conclusion: the sea is smaller than the ocean. What is the difference between a sea and an ocean other than size?

Water and ecosystem indicators

What distinguishes the sea from the ocean is the chemical composition of the water. Oceanic seas differ from oceans in their special flow regime. The water in the sea, due to inflow from fresh water, is almost always less saline than in the ocean. Accordingly, its own ecosystem is created with its own flora and fauna. Although there is an exception - the Barents Sea. It has the most salty water, the percentage of salt in its water is 35%.

bottom quality

For oceanologists, the main thing in the question of how the sea differs from the ocean lies in the nature of the bottom surface. Oceans are characterized by the presence of oceanic crust. The bottom of the seas is always a shelf or slope of the continents, which repeats the geological structure of the mainland land. Exceptions are the Philippine and Sargasso Seas. These two bodies of water do not have land boundaries, they are located in the middle of the ocean and are separated from the waters of the ocean by underwater ridges.

Depth

Most seas are shallower than oceans. This is understandable, because they occupy the coastal zone of the continents. However, the "bottom" of the Earth - Mariana Trench- located in the Philippine Sea in the middle of the Pacific Ocean. This is a tectonic fault, the depth of which, according to 2009 data, is 10,902 meters below sea level, the maximum depth to which the Nereus underwater unmanned vehicle could then descend. The only apparatus in the world capable of withstanding pressure of 6,000 pascals at such a depth belongs to the American company WHO. By the way, the highest mountain on the planet, Everest, can easily fit in this hollow, and even with a margin of approximately one kilometer.

But even here there are exceptions. For example, the shallowest sea is the Sea of ​​Azov. Its greatest depth is only 18 meters, the height of a six-story building. And it is also the most continental, which means that it is located very far from ocean waters. That is why it is one of the warmest.

Current differences

The difference between the ocean and the sea is in the quantity and quality of the currents. In the ocean there are surface warm and cold currents of water masses. They can find each other, intersect. The sea is characterized by the presence of one, either warm or cold current, with a clear route.

Waves of the seas and oceans

Everyone who has rested on the sea or the ocean has seen the waves and understands how the sea differs from the ocean. In the ocean, the waves are much larger. There is no calm on ocean beaches. And all because the wave in the ocean is not limited coastal zone and can gain more power. And if the ocean wave does not break on coral reefs near the coast, then this is where the paradise for surfers is located. The latest world record was set by American surfer Garret McNamara, who conquered a 34-meter high wave off the coast of Portugal in Nazar Bay, which is recognized as the generator of the highest waves not only in the Atlantic.

little confusion

Throughout the development of civilization, man has been in close contact with the coast of the water surface. And in the process of the development of navigation, when there was no oceanology yet, many water areas were given names that did not correspond to their geographical status. For example, the Mediterranean Sea includes the Tyrrhenian, Ionian, Adriatic, Balearic, Alboran, Cypriot, Levantine, Legurian Seas, although modern science considers them bays of the Mediterranean.

The Caspian and the Dead, which are large salt lakes, have also been named seas. But the Persian Gulf is the sea of ​​​​the Indian Ocean, and the Mexican - the Atlantic.

Afterword

So, what will dad answer to a third grader when he asks how the sea differs from the ocean? Briefly, the answer may sound like this: apart from the size and pronounced restrictive boundaries, salinity of water and the composition of flora and fauna, the presence of various kinds of currents and geological features of the bottom, in general, almost nothing. Although swimming in ocean waters is always more dangerous than in more peaceful sea waters.

Fish are a numerous superclass (according to the traditional classification) of aquatic animals that play a huge role in human life. It includes three classes - cartilaginous fish, lobe-finned and ray-finned, and about 95 percent (more than 20 thousand) of species known today belong to ray-finned ones. Fish are common in almost all water bodies of the planet (except for the most extreme - like hot springs), both fresh and salty. What is the difference between sea fish and river or lake fish? It is clear that with such an abundance of species, in order to describe all the nuances, a scientific monograph will be needed, but nevertheless we will try to understand the issue at least in general terms.

Fresh or salty?

Fish live in water bodies regardless of their salinity. Representatives of one species are able to live permanently either in salt or sea water. And only higher taxonomic units - a genus or order (a species is a subdivision of a genus) - can boast that its representatives are both among the inhabitants of the sea and among freshwater fish. The difference between sea fish and river fish is often quite arbitrary. For example, some species of marine fish go to the rivers to spawn, and river inhabitants go to the sea. Such fish are called anadromous: those who go to spawn from rivers to the sea are catadromous, and those who are vice versa are anadromous.

Anadromous fish species:

• whitefish;
• sturgeons;
• salmon.

Catadromous fish:

• acne;
• goby;
• mullet.

These fish (the most famous of them are sturgeon and salmon) have the ability to tolerate large fluctuations in water salinity. A similar feature is due to the fact that the evolution of, for example, salmon, previously proceeded in fresh water, and only later they moved to the ocean. Sometimes it happens that purely freshwater fish calmly go out to sea; this occurs where the seawater is highly diluted by the runoff of the inflowing river. Such, for example, is the "Marquis's Puddle", as Petersburgers ironically call the Neva Bay - that part of the Gulf of Finland, where the main river of our Northern capital flows. The Baltic Sea, which is already not very salty, is so diluted in this place that before, during winter fishing, fishermen even took water from here to make tea.

Comparison

If we consider the general differences between marine and river fish, regardless of taxonomy, then the first thing that catches your eye is the difference in size. The average marine fish is much larger than its freshwater counterpart. By the way, the largest fish is a marine inhabitant - a whale shark, reaching a length of twenty meters, and the smallest fish, as you might guess, is freshwater. In Latin, her name is Paedocypris progenetica (she lives in peat bogs), but she does not have a Russian name, because this fish is found in Indonesia. Adult females of this species reach a length of only 7.9 mm. However, there will still not be a clear victory in the “smallest” dispute, since the Panamanian photocoryne, another contender for this title, has almost the same dimensions, and the Guinness Book of Records points to both species as competitors, without giving anyone primacy.

What else can be said about the differences? The meat of sea fish is much richer in iodine, and therefore, it can be recommended to residents of regions where this element is in short supply (this is almost all of Russia). They are usually less bony than their river counterparts, so they are easier to process for cooking. And most importantly: marine fish most often live in a cleaner environment, because our rivers, both large and small, as a result economic activity people are often heavily contaminated. And the seas and especially the ocean expanses are much cleaner.

In general, what is the difference between sea and river fish - does it matter? And from those, and from others, you can cook very tasty dishes. Here, someone will like something: someone crucian carp in sour cream, someone - puffer fish or shark fin soup. If you are so interested in all the nuances of the difference between marine and freshwater fish, study biology, or rather, its section - ichthyology. This science specializes in fish.

Few people think about the difference between the sea and the ocean, except for size. Many of the reservoirs are located on the same square kilometers. In addition, these terms are often used incorrectly. And this is a common mistake. It is necessary to know the main signs of the ocean and the sea. There are certain subtleties that allow you to determine the type of reservoir.

What is the sea?

To understand how the sea differs from the ocean, you should understand what each of the reservoirs is. There are several main differences. So, the sea is a certain part of the oceans. As a rule, the boundaries of this reservoir are separated by land. It could be underwater. An example is the Sargasso Sea. It can also be separated by a series of islands or archipelagos. In this case, Baffin or the South China Sea can be cited as an example. Often this type of reservoir is separated by the outlines of the continents or peninsulas. An example would be the Mediterranean or the Arabian Sea. But this is not the main feature.

So what is the difference between seas and oceans? There is a broken bond between them. Therefore, the sea has several features of the hydrological regime. Here, indicators of transparency, salinity and water temperature are often measured. In addition, the sea has its own system of currents, as well as fauna and flora, which differs from the oceanic.

Main groups

What is the difference between the sea and the ocean? You can visually tell the difference. After all, the ocean is ten times larger. On the this moment There are 63 seas on the Earth's surface. Conventionally, they are divided into several groups and classified according to the degree of isolation from the parent ocean. There are marginal and inland seas. The latter are cut deep into the continents. An example is the Baltic, Black, Marble and Mediterranean. They are connected to the ocean only by a system of straits. In addition, these reservoirs have a clear difference. They have their own indicator of water salinity and the endemicity of living organisms that inhabit them.

As for the marginal seas, they are located along the coast of the mainland. These reservoirs are less isolated from the ocean. At the same time, their waters are regularly and actively mixed. Examples include the Tasman, East China and Norwegian Seas.

Exception to the rule

Of course, any rule can have an exception. What is the difference between the sea and the ocean if it has no shores? This should include Sargasso. It has no shores. This sea is located in the middle of the Atlantic Ocean. And to be more precise, in tropical latitudes.

There are also bodies of water that are only called seas. Take at least Dead and Caspian. In fact, they are not seas. According to some indicators, they fit into the category of "lakes".

In addition, there are historical names. This should include the Tyrrhenian or Ligurian Sea, which are one of the parts of the Mediterranean Sea.

What is an ocean?

Of course, not everyone understands how the seas differ from the oceans and how to determine whether a reservoir belongs to a certain category. So what's the difference? What is an ocean? This is also part of the oceans. At the moment, four such reservoirs have been identified: the Arctic, Indian, Atlantic and the largest - Pacific. In some foreign schools, there is also a fifth ocean - the South. It surrounds the coast of Antarctica. Its second boundary is the course of the Western winds. In some countries, the Arctic Ocean is not considered an ocean at all. It is called the giant sea. Here the Arctic Ocean is one of the parts of the Atlantic Ocean.

With this classification, it is very difficult to understand how the sea differs from the ocean. Each of the reservoirs has its own bottom topography, salinity index, temperature regime and current system. However, an active exchange of water masses was noted. If you wish, you can get from one point to another without stepping on land.

The boundaries of the oceans are the slopes of the continents, individual islands, as well as meridians passing through points from Australia, Africa and South America to Antarctica. They are united by a system of straits: Magellan, Drake or Bering.

It is worth noting that all the oceans occupy up to 71% of the planet's surface. That is why scientists believe that the Earth has the wrong name. It was more logical to call her Aqua or Ocean.

How is the sea different from the ocean?

At the moment, the following differences can be distinguished:

1. The sea is a unit of a particular ocean. The ocean is an essential part of the World Ocean, which occupies 2/3 of the planet.
2. Sizes of reservoirs.
3. There are 4 oceans and 63 seas on Earth.
4. flow system. The ocean has surface cold and warm water masses. The sea has only one current. It can be a surface warm or cold current.
5. The bottom of the ocean is the earth's oceanic crust, and near the sea is the continental plume. The exceptions are Sargasso and

How many seas are on earth? Nobody can tell you the exact answer. For example, the International Hydrographic Bureau identifies only 54 seas, some scientists believe that there are more than 90 seas on our planet (not counting the Caspian, Dead and Galilee, which are often referred to as lakes). The most common version is that there are still 81 seas. Such a discrepancy arises due to the fact that scientists interpret the very concept of "sea" in different ways.

The most common interpretation: sea ​​- a body of water separated by parts of land or elevations of underwater relief . From a geological point of view, the seas are young formations. The deepest were formed at the break of tectonic plates, for example, the Mediterranean. Smaller ones are formed on the outskirts of the continents when the continental shoals are flooded.

Characteristics of the seas

The seas are actively involved in the creation of the temperature regime the globe. Sea water is very "lazy" and heats up slowly. Therefore, for example, the water in the Mediterranean Sea becomes warmest not in July, when it is hot, but in September. As the level drops, the water cools down quickly. At the bottom of the deep seas- about 0ºC. At the same time, salt water begins to freeze at a temperature of -1.5 ºC; - 1.9 ºC.

Warm and cold currents move huge masses of water - warm or cold. This greatly affects the formation of the climate.

An important role is also played by the ebbs and flows, the frequency of their change and height. The occurrence of ebbs and flows is associated with a change in the phases of the moon.

Known interesting feature water in the sea. When immersed, the sea gradually "eats" the colors. At a depth of 6 m, scarlet colors disappear, at a depth of 45 m - orange, 90 m - yellow, at a depth of more than 100 m only purple and greenish shades remain. Therefore the most colorful undersea world located at shallow depths.

Sea types

There are several classifications that unite the seas according to certain criteria. Consider the most popular.

1. Over the oceans(list of seas by oceans)

2. By degree of isolation

Internal - do not have access to the ocean (isolated), or are connected with them through the straits (semi-isolated). In fact, isolated seas (Aral, Dead) are considered to be lakes. And the straits connecting the semi-isolated seas with the ocean are so narrow that they do not lead to mixing of deep waters. Example - Baltic, Mediterranean.

Marginal - located on the shelf, have an extensive network of underwater currents and free access to the ocean. They are separated from each other by islands or underwater hills.

Interisland - such seas are surrounded by a close group of islands that prevent connection with the ocean. Most of these seas among the islands of the Malay Archipelago are Javanese, Sulawesi.

Intercontinental - seas lying at the junction of continents - Mediterranean, Red.

3. According to the salinity of the waters distinguish slightly saline (Black) and highly saline (Red) seas.

4. By the degree of indentation of the coastline There are seas with a strongly indented and slightly indented coastline. But, for example, the Sargasso Sea has no coastline at all.

The coastlines are characterized by the presence of bays, estuaries, bays, spits, cliffs, peninsulas, beaches, fjords and headlands.

The difference between the sea and the lake, the bay and the ocean

Despite the great similarity of interpretations of the concepts "sea", "lake", "bay" and "ocean", these words are not synonymous.

So, the sea differs from the lake:

Size. The sea is always bigger.

The degree of salinity of the waters. In the sea, water is always mixed with salt, while in lakes it can be fresh, brackish and salty.

Geographic location. Lakes are always located within continents and are surrounded on all sides by land. The seas most often have a connection with the ocean.

It is more difficult to separate seas and oceans. It's all about size here. It is generally accepted that the sea is only a part of the ocean that has unique flora and fauna. The sea may differ from the ocean in the degree of salinity of the water and in relief.

The bay is also an integral part of the ocean, deeply incised into the land. Unlike the sea, it always has a free connection with the ocean. In some cases, the name of the bay was assigned to the water areas, which, according to their hydrological characteristics, are more likely to be seas. For example, Hudson Bay, California, Mexico.

The most salty sea

(Dead Sea)

If we consider the Dead Sea as a sea, and not a lake, then the palm in terms of the degree of salinity of the waters will belong to this area. The salt concentration here is 340 g/l. Because of the salt, the density of the water is such that it is impossible to drown in the Dead Sea. By the way, this is why there are no fish and plants in the Dead Sea, only bacteria live in such a saline solution.

Of the recognized seas, the Red Sea is considered the most salty. 1 liter of water contains 41 g of salt.

In Russia, the most salty sea is the Barents Sea (34-37g/l).

The biggest sea

(Philippine Sea)

The largest sea in the world is the Philippine (5726 thousand sq. km). It is located in the western part of the Pacific Ocean between the Taiwan, Japanese and Philippine islands. This sea is also the deepest in the world. The greatest depth was recorded in the Mariana Trench - 11022 m. The territory of the sea covers 4 climatic zones at once: from equatorial to subtropical.

The largest sea in Russia is Beringovo (2315 thousand sq. Km.)

Dear readers, hello! We all know perfectly well that salt is an indispensable seasoning for cooking various dishes. It reacts very quickly to the receptors of the tongue and creates a richness of taste. In shops and supermarkets we are offered big choice types of this product, among which the most popular is cooking and sea. AT recent times we hear more and more often that it is better to use sea salt instead of table salt. Let's try to figure out how they differ from each other.

How is sea salt different from table salt?

For more than 4,000 years, people have been extracting sea salt from the sea, which is obtained by evaporating water under the influence of wind and sun, i.e. through natural climatic conditions.

According to the type of origin, edible table salt is divided into boiling, stone, cage and self-planting.

Stone is a crushed mineral halite, which is mined in salt mines and quarries.

Vyvarochnaya - small and snow-white. It is obtained from the halite of lake water or water passed through salt layers. Then they are processed: evaporated, cleaned of impurities, bleached and substances are added that prevent the absorption of moisture, which prevents it from caking. And it should be noted that these additives are not at all harmless to human health.

Seed water is obtained by artificial evaporation of lake salt water or sea water, and self-planting is salt that has settled to the bottom of salt lakes.

Both salts contain NaCl. Only in chemical composition sea ​​salt, in addition to sodium chloride, a large number of macro- and microelements. This is due to the fact that it is obtained from sea water, which contains many minerals. The main ones are potassium, magnesium, manganese, zinc, bromine, iodine and others (more than 40 types) that the human body needs. In certain proportions, all these minerals help boost immunity, improve digestion, normalize blood pressure and work of the heart muscle, relieve stress.

In turn, table salt, having gone through a multi-stage chemical purification process, contains only pure NaCl (up to 99%) and is characterized by a complete absence of useful substances.

Of course, sodium chlorite plays an important role in the body. This mineral is involved in the formation of hydrochloric acid, which is necessary for the stomach to activate digestive enzymes. Sodium chloride is one of the electrolytes that serve for the full functioning of the body.

In order to maintain the water-salt balance, sodium and chlorine ions must be contained in a certain amount. The norm of consumption is 5 grams of salt per day (one teaspoon), taking into account all the products in which it is contained.

With excessive salt intake, the body's need for water increases. Salt, containing practically only NaCl, has the property of retaining fluid, which contributes to the formation of edema and increased blood pressure. In addition, there is a load on the heart and kidneys.

Sea salt contains potassium salts. Potassium displaces sodium and reduces swelling. Potassium is an indispensable trace element of our body, without which the functioning of all cells is impossible.

Especially sea salt is rich in iodine content. It is present in it from its very nature. This element is necessary for the thyroid gland, which controls all metabolic processes our body, and it is also useful for pregnant women for the normal development of the fetus. Salt does not contain iodine.

Recently, iodine deficiency has been observed in people in the body. According to statistics, 35% of Russians suffer from this problem. Therefore, table salt began to be made iodized. Previously, potassium iodite was used for this, but this compound was fragile and two weeks after the product was packaged, the iodine evaporated. Since 1998, potassium iodate has been used, which made it possible to significantly increase the period of content of this element in the product up to a year. It should be noted that potassium iodate is a strong oxidizing agent and has increased toxicity compared to potassium iodite. Sea salt has no expiration date.

There is one more distinguishing feature. Sea salt has a more pronounced salty taste than regular salt. Therefore, when cooking, it is used in smaller quantities.

In addition, I suggest watching this interesting video.

Good health to you!