geography 7th grade

World Ocean

The share of the waters of the World Ocean in the hydrosphere is...(%)

97

The main source of atmospheric moisture is...

water vapor

World Ocean

surface of rivers and lakes

green plants

The waters of the World Ocean have... origin

biological

atmospheric

cosmic

mantle

Salt water, compared to fresh water, is characterized by...

lower freezing and boiling temperatures

lower freezing point and higher boiling point

elevated freezing point and reduced boiling point

elevated freezing and boiling temperatures

The dependence of ocean water temperature on geographic latitude is most noticeable...

at the surface of the water

at a depth of 500 m

at a depth of 1000 m

at the bottom

The highest salinity of ocean waters is typical for... latitudes

equatorial

tropical

moderate

arctic

The lowest salinity of ocean waters is typical for... latitudes

equatorial and tropical

tropical and subtropical

subtropical and temperate

temperate and equatorial

The saltiest of seas belongs to... the ocean

Quiet

Arctic

Atlantic

Indian

The highest salinity of the waters of the World Ocean is observed where the amount of precipitation...

exceeds evaporation

equal to evaporation

below evaporation

If you move in the direction from the equator to the poles, then the temperature of the bottom waters...

rises

does not change

goes down

Salt water freezes at...

positive

equal to zero

negative

With depth, the temperature of the waters of the World Ocean changes as follows...

first increases, then remains unchanged

first decreases, then increases

first decreases, then does not change

does not change

The temperature of the North Atlantic Current, compared to the cold Canary Current, ...

higher

the same

below

The main reason for the occurrence of surface currents in the World Ocean is...

underwater earthquakes

constant winds

surface slope

differences in water temperature

The temperature of the water in the World Ocean is determined...

ambient temperature

angle of incidence of sunlight

salinity

Icebergs in the World Ocean penetrate closer to the equator in... hemispheres

northern

southern

The most powerful current in the world's oceans is...

Gulf Stream

Labrador

Western winds

Kuroshio

Actively moving among the inhabitants of the water column...

plankton

nekton

benthos

The most populated part of the World Ocean is...

continental slope

shelf

deep sea trenches

bed

Of the types of economic activity, the least harm to the nature of the World Ocean is caused...

offshore oil and gas production

maritime shipping

fishing

construction of tidal stations

A1. What determines the salinity of ocean water?

on the amount of precipitation

from evaporation

from the influx of river waters

from all of the above reasons

A2. Temperature of surface ocean waters:

is the same everywhere

depends on latitude

changes only with depth

varies with both breadth and depth

A3. Which European navigator's expedition crossed the Pacific Ocean for the first time?

F. Magellan

J. Cook

I.F. Krusenstern

H. Columba

A4. What winds prevail along the northwestern coast of the Pacific Ocean?

trade winds

typhoons

monsoons

Western

A5. Specify the deepest place in the Pacific Ocean.

Java Trench

Kuril Trench

Mariana Trench

Philippine Trench

A6. Why do tsunamis often occur in the Pacific Ocean?

along the edges of the ocean there is a boundary of lithospheric plates

waves are caused by the Earth's gravity

Tsunamis are caused by stormy winds

there is a system of powerful currents in the ocean

A7. Which island is NOT in the Indian Ocean?

Madagascar

Sri Lanka

Taiwan

Socotra

A8. In which part of the Indian Ocean does the monsoon dominate?

in the north

in the south

in the western

in the eastern

A9. Indicate the cold current of the Atlantic Ocean.

Gulf Stream

Brazilian

Canary

Norwegian

A10. In which part of the Atlantic Ocean is oil produced?

in the Gulf of Mexico

in the Bay of Biscay

in the Baltic Sea

in the Mediterranean Sea

A11. Who drifted on the ship "Fram" in the Arctic Ocean?

F. Nansen

O.Yu. Schmidt

G.Ya. Sedov

V.Barents

A12. Specify erroneous statement.

The Arctic Ocean is distinguished by its harsh climate.

The Arctic Ocean is the shallowest.

The seas of the Northern Ocean are internal and only one external.

In the center is the North Pole.

1.The area of ​​which ocean is 178.6 million km2?
A) Atlantic; B) Arctic;
B) Quiet; D) Indian.

2.Which ocean washes the shores of 4 continents?
A) Atlantic; B) Southern;
B) Indian; D) Quiet.

3. There is a current in the Atlantic Ocean:
A) Kuroshio; B) Gulf Stream;
B) Somali.

4. In the Pacific Ocean there is the deepest depression on the planet (11022m):
A) Sunda Trench; B) Greenland Sea;
B) Mariana Trench.

5. -10C; -20C is the average temperature in the surface layer:
A) Arctic Ocean; B) Pacific Ocean;
B) Indian Ocean.

6. The warm Mozambique Current is part of:
A) Arctic Ocean; B) Atlantic Ocean;
B) Indian Ocean.

7. Which ocean has no connection with the Arctic Ocean?
A) Quiet; B) Atlantic;
B) Indian.

8. About the Pacific Ocean we can say:
A) It is the deepest, the most ancient, has many volcanoes, a huge reserve of heat;
B It stretches from subarctic latitudes to Antarctica, according to the theory of lithospheric plates - relatively young;
C) the shallowest, occupies the space of the North Pole.

9. Which ocean basin includes the saltiest sea in the world (Red Sea 42‰)?
A) Atlantic; B) Indian;
B) Quiet.

10. The climate of this ocean is varied, as it lies in all climatic zones:
A) Atlantic; B) Quiet;
B) Indian.

11. The highest degree of pollution with petroleum products occurs in:
A) Quiet; B) Indian;
B) Atlantic.

12. In which ocean is the sea “without shores” (Sargasso) located?
A) Quiet; B) Indian;
B) Atlantic.

13. Which oceans does the Panama Canal connect? (choose 2 oceans)
A) Quiet; B) Indian;

14. Which ocean basin does the Mediterranean Sea belong to?
A) Quiet; B) Indian;
B) Atlantic. D) Arctic.

15. In which ocean is the anomalous zone called “Bermuda” located? triangle"?
A) Quiet; B) Southern;
B) Atlantic. D) Arctic.

16. Which ocean washes the shores of the coldest continent on the planet?
A) Quiet; B) Southern;
B) Atlantic. D) Arctic.

17. Name the smallest ocean in area?
A) Quiet; B) Indian;
B) Atlantic. D) Arctic.

18. In which ocean is the island of Madagascar located?
A) Quiet; B) Indian;
B) Atlantic. D) Arctic.

19. Which ocean was the first European to reach and give it a name?
A) Quiet; B) Indian;
B) Atlantic. D) Arctic.

20. Along which ocean did H. Columbus travel to India and discover the New World?
A) Quiet; B) Indian;
B) Atlantic. D) Arctic.

Answers: 1.B; 2.G; 3.B; 4.B; 5.A; 6.B; 7.B; 8.A; 9.A; 10.A; 11.B; 12.V; 13..A,B; 14.V; 15.V; 16.B; 17.G; 18.B; 19.A; 20.V.

Geological activity of oceans and seas

Features of the relief of the ocean floor

Destructive and accumulative activities of the sea

Sedimentation in seas and oceans

General information about the World Ocean

Ocean- a continuous water shell of the Earth surrounding continents and islands and having a common salt composition. The World Ocean makes up 94% of the hydrosphere and occupies 70.8% of the earth's surface. It is a giant depression of the earth's surface, containing the bulk of the hydrosphere - about 1.35 km 3. Parts of the World Ocean separated by land or elevated underwater relief and differing from the open part of the ocean in hydrological, meteorological and climatic regime are called seas. Conventionally, some open parts of the oceans (Sargasso Sea) and large lakes (Caspian Sea) are also called seas. From a geological point of view, modern seas are young formations: all of them took shape close to modern ones in Paleogene-Neogene times, and were finally formed in the Anthropocene. The formation of deep seas is associated with tectonic processes; shallow seas usually arose when the marginal parts of continents (shelf seas) were flooded by the waters of the World Ocean. The flooding of these areas could be due to two reasons: 1) a rise in the level of the World Ocean (due to the melting of Quaternary glaciers) or 2) subsidence of the earth's crust.

Salinity and composition of sea waters. The average salinity of the waters of the World Ocean is about 35 g/kg (or 35 ‰ - 35 ppm). However, this value is different in different parts of the World Ocean and depends on the degree of connection with the open ocean, climate, proximity to the mouths of large rivers, melting ice, etc.: in the Red Sea salinity reaches 42‰, while in the Baltic it exceeds 3 -6‰. Maximum salinity is observed in lagoons and bays separated from the sea, located in arid regions. Another reason for abnormally high salinity may be the supply of salts with hot aqueous solutions, which is observed in areas with an active tectonic regime; in some bottom areas of the Red Sea, where thermal brines emerge, salinity reaches 310‰. Minimum salinity is typical for seas that have a difficult connection with the ocean and receive a significant amount of river water (the salinity of the Black Sea is 17-18‰), and water areas near the mouths of large rivers.

Sea water is a solution containing more than 40 chemical elements. The sources of salts are river runoff and salts entering during the process of volcanism and hydrothermal activity, as well as during underwater weathering of rocks - halmyrolysis. The total mass of salts is about 49.2 * 10 15 tons, this mass is enough for the evaporation of all ocean waters to cover the surface of the planet with a layer 150 m thick. The most common anions and cations in waters are the following (in descending order): among the anions Cl -, SO 4 2-, HCO 3 -, among the anions Na +, Mg 2+, Ca 2+. Accordingly, in terms of layers, the largest amount falls on NaCl (about 78%), MgCl 2, MgSO 4, CaSO 4. The salt composition of sea water is dominated by chlorides (while river water contains more carbonates). It is noteworthy that the chemical composition of sea water is very similar to the salt composition of human blood. The salty taste of water depends on the sodium chloride content in it; the bitter taste is determined by magnesium chloride, sodium and magnesium sulfates. The slightly alkaline reaction of sea water (pH 8.38-8.40) is determined by the predominant role of alkaline and alkaline earth elements - sodium, calcium, magnesium, potassium.

A significant amount of gases are also dissolved in the waters of the seas and oceans. These are mainly nitrogen, oxygen and CO 2 . At the same time, the gas composition of sea waters is somewhat different from the atmospheric one - sea water, for example, contains hydrogen sulfide and methane.

Most of all, nitrogen is dissolved in sea water (10-15 ml/l), which, due to its chemical inertness, does not participate and does not significantly influence sedimentation processes and biological processes. It is assimilated only by nitrogen-fixing bacteria that are capable of converting free nitrogen into its compounds. Therefore, compared to other gases, the content of dissolved nitrogen (as well as argon, neon and helium) changes little with depth and is always close to saturation.

Oxygen entering waters during gas exchange with the atmosphere and during photosynthesis. It is a very mobile and chemically active component of sea waters, therefore its content is very different - from significant to negligible; in the surface layers of the ocean its concentration usually ranges from 5 to 9 ml/l. The supply of oxygen to the deep ocean layers depends on the rate of its consumption (oxidation of organic components, respiration, etc.), on the mixing of waters and their transfer by currents. The solubility of oxygen in water depends on temperature and salinity; in general, it decreases with increasing temperature, which explains its low content in the equatorial zone and higher content in the cold waters of high latitudes. With increasing depth, the oxygen content decreases, reaching values ​​of 3.0-0.5 ml/l in the oxygen minimum layer.

Carbon dioxide is contained in seawater in small concentrations (no more than 0.5 ml/l), but the total content of carbon dioxide is approximately 60 times higher than its amount in the atmosphere. At the same time, it plays a crucial role in biological processes (being a source of carbon during the construction of a living cell), influences global climatic processes (participating in gas exchange with the atmosphere), and determines the characteristics of carbonate sedimentation. In seawater, carbon oxides are common in free form (CO 2), in the form of carbonic acid and in the form of the HCO 3– anion. In general, the content of CO 2, as well as oxygen, decreases with increasing temperature, so its maximum content is observed in cold waters of high latitudes and in deep zones of the water column. With depth, the concentration of CO 2 increases, since its consumption decreases in the absence of photosynthesis and the supply of carbon monoxide increases during the decomposition of organic residues, especially in the oxygen minimum layer.

Hydrogen sulfide in seawater is found in significant quantities in water bodies with difficult water exchange (a well-known example of “hydrogen sulfide contamination” is the Black Sea). Hydrothermal waters coming from the depths to the ocean floor, the reduction of sulfates by sulfate-reducing bacteria during the decomposition of dead organic matter, and the release of sulfur-containing organic residues during decay can serve as sources of hydrogen sulfide. Oxygen reacts quite quickly with hydrogen sulfide and sulfides, ultimately oxidizing them to sulfates.

The solubility of carbonates in seawater is important for ocean sedimentation processes. Calcium in sea water contains an average of 400 mg/l, but a huge amount of it is bound in the skeletons of marine organisms, which dissolve when the latter die. Surface waters are typically saturated with calcium carbonate, so it does not dissolve in the upper part of the water column immediately after organisms die. With depth, waters become increasingly undersaturated with calcium carbonate, and eventually, at a certain depth, the rate of dissolution of carbonate matter is equal to the rate of its supply. This level is named depth of carbonate compensation. The depth of carbonate compensation varies depending on the chemical composition and temperature of sea water, averaging 4500 m. Below this level, carbonates cannot accumulate, which determines the replacement of essentially carbonate sediments with non-carbonate ones. The depth where the concentration of carbonates is equal to 10% of the dry matter of the sediment is called the critical depth of carbonate accumulation ( carbonate compensation depth).

Features of the relief of the ocean floor

Shelf(or mainland shoal) is a slightly inclined, leveled part of the underwater margin of continents, adjacent to the shores of land and characterized by a common geological structure. The shelf depth is usually up to 100-200 m; The shelf width ranges from 1-3 km to 1500 km (Barents Sea shelf). The outer boundary of the shelf is delineated by an inflection of the bottom topography - the edge of the shelf.

Modern shelves were mainly formed as a result of flooding of the margins of continents when the level of the World Ocean rose due to the melting of glaciers, as well as due to the subsidence of areas of the earth's surface associated with recent tectonic movements. The shelf existed in all geological periods, in some of them it grew sharply in size (for example, in the Jurassic and Cretaceous times), in others, occupying small areas (Permian). The modern geological era is characterized by moderate development of shelf seas.

continental slope is the next of the main elements of the underwater continental margins; it is located between the shelf and the continental foot. It is characterized by steeper surface slopes compared to the shelf and ocean bed (on average 3-5 0, sometimes up to 40 0) and significant dissected relief. Typical forms of relief are steps parallel to the edge and base of the slope, as well as underwater canyons, usually originating on the shelf and extending to the continental foot. Seismic studies, dredging and deep-sea drilling have established that, in terms of geological structure, the continental slope, like the shelf, is a direct continuation of the structures developed in adjacent areas of the continents.

Mainland foot is a plume of accumulative sediments that arose at the foot of the continental slope due to the movement of material down the slope (through turbidity currents, underwater landslides and landslides) and the deposition of suspended matter. The depth of the continental foot reaches 3.5 km or more. Geomorphologically, it is a sloping hilly plain. Accumulative deposits that form the continental foot are usually superimposed on the ocean floor, represented by oceanic crust, or are located partly on continental and partly on oceanic crust.

Next are structures formed on oceanic-type crust. The largest elements of the relief of the oceans (and the Earth as a whole) are the ocean floor and mid-ocean ridges. The ocean floor is divided by ridges, swells and hills into basins, the bottom of which is occupied by abyssal plains. These areas are characterized by a stable tectonic regime, low seismic activity and flat topography, which allows them to be considered as oceanic plates - Thalassocratons. Geomorphologically, these areas are represented by abyssal (deep-sea) accumulative and hilly plains. Accumulative plains have a leveled, slightly inclined surface and are developed primarily along the periphery of the oceans in areas of significant influx of sedimentary material from the continents. Their formation is associated with the supply and accumulation of material by suspension flows, which determines their inherent features: a depression of the surface from the continental foot toward the ocean, the presence of underwater valleys, gradational layering of sediments, and leveled relief. The latter feature is determined by the fact that, moving deeper into the ocean basins, sediments bury the primary dissected tectonic and volcanic relief. The hilly abyssal plains are characterized by dissected topography and low sediment thickness. These plains are typical of the inner parts of basins, distant from the shores. An important element of the relief of these plains are volcanic uplifts and individual volcanic structures.

Another element of the megarelief is mid-ocean ridges, which are a powerful mountain system stretching across all oceans. The total length of mid-ocean ridges (MORs) is more than 60,000 km, width 200-1200 km, height 1-3 km. In some areas, the peaks of the MOR form volcanic islands (Iceland). The relief is dissected, the relief forms are oriented mainly parallel to the extent of the ridge. The sedimentary cover is thin, represented by carbonate biogenic silts and volcanogenic formations. The age of sedimentary strata becomes older with distance from the axial parts of the ridge; in the axial zones the sedimentary cover is absent or represented by modern deposits. The MOR regions are characterized by intense endogenous activity: seismicity, volcanism, and high heat flow.

MOR zones are confined to the boundaries of the separation of lithospheric plates; here the process of formation of new oceanic crust occurs due to incoming mantle melts.

The zones of transition from continental to oceanic crust—the margins of continents—deserve special attention. There are two types of continental margins: tectonically active and tectonically passive.

Passive outskirts represent a direct continuation of continental blocks, flooded by the waters of the seas and oceans. They include the shelf, continental slope and continental foot and are characterized by the absence of manifestations of endogenous activity. Active ocarinas are confined to the boundaries of lithospheric plates, along which the oceanic plates move under the continental ones. These ocarinas are characterized by active endogenous activity; areas of seismic activity and modern volcanism are confined to them. Among active ocarinas, two main types are distinguished by structure: Western Pacific (island arc) and Eastern Pacific (Andean). The main elements of Western Pacific type margins are deep-sea trenches, volcanic island arcs, and marginal (or inter-arc) marine basins. The region of the deep-sea trench corresponds to the boundary at which the subduction of a plate with oceanic crust occurs. Melting of part of the subducting plate and the above-lying rocks of the lithosphere (associated with the influx of water into the subducting plate, which sharply lowers the melting temperature of the rocks) leads to the formation of magma chambers, from which melts flow to the surface. Due to active volcanism, volcanic islands are formed, stretching parallel to the plate subduction boundary. The margins of the East Pacific type are distinguished by the absence of volcanic arcs (volcanism occurs directly on the edge of the land) and marginal basins. The deep-sea trench gives way to a steep continental slope and a narrow shelf.

Destructive and accumulative activities of the sea

Abrasion (from lat. “abrasion” – scraping, shaving) – the process of destruction of rocks by waves and currents. Abrasion occurs most intensely near the shore under the influence of the surf.

The destruction of coastal rocks consists of the following factors:

· wave impact (the force of which reaches 30-40 t/m2 during storms);

· abrasive effect of debris brought by the wave;

· dissolution of rocks;

· compression of air in the pores and cavities of the rock during the impact of waves, which leads to cracking of rocks under the influence of high pressure;

· thermal abrasion, manifested in the thawing of frozen rocks and ice shores, and other types of impact on the shores.

The impact of the abrasion process manifests itself to a depth of several tens of meters, and in the oceans up to 100 m or more.

The impact of abrasion on the shores leads to the formation of clastic deposits and certain forms of relief. The abrasion process proceeds as follows. Hitting the shore, the wave gradually creates a depression at its base - wave-breaking niche, over which the cornice hangs. As the wave-breaking niche deepens under the influence of gravity, the cornice collapses, the debris ends up at the foot of the shore and, under the influence of the waves, turns into sand and pebbles.

The cliff or steep ledge formed as a result of abrasion is called cliff. At the site of the retreating cliff, a abrasion terrace, or bench (English "bench"), consisting of bedrock. The cliff may border directly on the bench or be separated from the latter by a beach. The transverse profile of the abrasion terrace has the form of a convex curve with small slopes near the shore and large slopes at the base of the terrace. The resulting debris material is carried away from the shore, forming underwater accumulative terraces.

As abrasion and accumulative terraces develop, the waves end up in shallow water, become rough and lose energy before reaching the bedrock shore, and because of this, the abrasion process stops.

Depending on the nature of the ongoing processes, shores can be divided into abrasive and accumulative.

A, B, C - various stages of retreat of the coastal cliff, destroyed by abrasion; A 1, B 2, C 3 - various stages of development of an underwater accumulative terrace.

Waves carry out not only destructive work, but also work on the movement and accumulation of debris. The oncoming wave carries out pebbles and sand, which remain on the shore when the wave recedes, thus forming beaches. Beach(from French "plage" - sloping seashore) called a strip of sediment on the sea coast in the zone of action of the surf flow. Morphologically, there are beaches of full profile, which have the appearance of a gently sloping ridge, and beaches of incomplete profile, which are an accumulation of sediment inclined towards the sea, adjacent to the foot of the coastal cliff with its back side. Beaches with a full profile are typical for accumulative shores, while beaches with an incomplete profile are typical for abrasive shores.

When waves pile up at depths of the first meters, the material deposited under water (sand, gravel or shell) forms an underwater sand bank. Sometimes an underwater accumulative shaft, growing, protrudes above the surface of the water, stretching parallel to the shore. Such shafts are called bars(from French "barre" - obstacle, shallow).

The formation of a bar can lead to the separation of the coastal part of the sea basin from the main water area - lagoons are formed. Lagoon (from lat. "lacus" - lake) is a shallow natural water basin, separated from the sea by a bar or connected to the sea by a narrow strait (or straits). The main feature of lagoons is the difference in water salinity and biological communities.

Sedimentation in seas and oceans

Various sediments accumulate in the seas and oceans, which, based on their origin, can be divided into the following groups:

· terrigenous, formed due to the accumulation of products of mechanical destruction of rocks;

· biogenic, formed due to the vital activity and death of organisms;

· chemogenic, associated with precipitation from sea water;

· volcanogenic, accumulating as a result of underwater eruptions and due to eruption products brought from land;

· polygenic, i.e. mixed sediments formed by materials of different origins.

In general, the material composition of bottom sediments is determined by the following factors:

· depth of the sedimentation area and bottom topography;

· hydrodynamic conditions (presence of currents, influence of wave activity);

· the nature of the supplied sedimentary material (determined by climatic zonation and distance from the continents);

· biological productivity (marine organisms extract minerals from water and supply them to the bottom after dying (in the form of shells, coral structures, etc.));

· volcanism and hydrothermal activity.

One of the determining factors is depth, which makes it possible to distinguish several zones that differ in sedimentation characteristics. Littoral(from lat. "litoralis"- coastal) - a border strip between land and sea, regularly flooded at high tide and drained at low tide. The littoral zone is the area of ​​the seabed located between the levels of the highest high tide and the lowest low tide. Nerite zone corresponds to the depths of the shelf (from Greek. "erites"- sea mollusk). Bathyal zone(from the Greek “deep”) approximately corresponds to the area of ​​​​the continental slope and foot and depths of 200 - 2500 m. This zone is characterized by the following environmental conditions: significant pressure, almost complete absence of light, minor seasonal fluctuations in temperature and water density; The organic world is dominated by representatives of zoobenthos and fish; the plant world is very poor due to the lack of light. Abyssal zone(from the Greek “bottomless”) corresponds to sea depths of more than 2500 m, which corresponds to deep-sea basins. The waters of this zone are characterized by relatively weak mobility, constantly low temperature (1-2 0 C, in the polar regions below 0 0 C), constant salinity; Here there is a complete absence of sunlight and enormous pressures are reached, which determine the originality and poverty of the organic world. Areas with a depth of more than 6000 m are usually identified as ultra-abyssal zones, corresponding to the deepest parts of basins and deep-sea trenches.

Let's remember: How are the planet's waters divided by salinity? Why do travelers and sailors take fresh water on sea voyages?

Keywords:sea ​​water, salinity, water temperature, ppm.

1. Water salinity. In all seas and oceans, water has a bitter-salty taste. It is impossible to drink such water. Therefore, sailors setting sail on ships take with them a supply of fresh water. Salt water can be desalinated in special installations that are available on sea vessels.

Mostly table salt is dissolved in sea water, which we eat as food, but there are also other salts (Fig. 92).

* Magnesium salts give water a bitter taste. Aluminum, copper, silver, and gold have been found in ocean water, but in very small quantities. For example, 2000 tons of water contains 1 g of gold.

Why are ocean waters salty? Some scientists believe that the primary ocean was fresh, because it was formed by river waters and rains that fell abundantly on the Earth millions of years ago. Rivers brought and continue to bring salt to the ocean. They accumulate and lead to salinity in ocean water.

Other scientists suggest that the ocean immediately became salty upon its formation, because it was replenished with salty waters from the bowels of the Earth. Future research may answer this question.

Rice. 92. The amount of substances dissolved in ocean water.

** The amount of salts dissolved in ocean water is enough to cover the surface of the land with a layer 240 m thick.

It is assumed that all naturally occurring substances are dissolved in seawater. Most of them are found in water in very small quantities: thousandths of a gram per ton of water. Other substances are contained in relatively large quantities - in grams per kilogram of sea water. They determine its salinity .

SALINITY sea ​​water is the amount of salts dissolved in water.

Rice. 93. Salinity of surface waters of the World Ocean

Salinity is expressed in p r o m i l l y e, i.e. in thousandths of a number, and is denoted -°/oo. The average salinity of the waters of the World Ocean is 35°/oo. This means that every kilogram of sea water contains 35 grams of salts (Fig. 92). The salinity of fresh river or lake waters is less than 1°/oo.

The Atlantic Ocean has the most saline surface waters, the Arctic Ocean has the least saline (see Table 2 in Appendix 1).

The salinity of the oceans is not the same everywhere. In the open part of the oceans, salinity reaches its highest values ​​in tropical latitudes (up to 37 - 38 °/oo), and in the polar regions the salinity of surface ocean waters decreases to 32 °/oo (Fig. 93).

The salinity of water in marginal seas usually differs little from the salinity of adjacent parts of the ocean. The water of inland seas differs from the water of the open part of the oceans in salinity: it increases in the seas of the hot zone with a dry climate. For example, the salinity of water in the Red Sea is almost 42°/oo. This is the saltiest sea in the World Ocean.

In the temperate seas, which receive a large amount of river water, salinity is below average, for example in the Black Sea - from 17°/oo to 22°/oo, in the Azov Sea - from 10°/oo to 12°/oo.

* The salinity of sea water depends on precipitation and evaporation, as well as currents, the influx of river water, the formation of ice and its melting. When seawater evaporates, salinity increases, and when precipitation falls, it decreases. Warm currents usually carry saltier water than cold ones. In the coastal strip, sea waters are desalinated by rivers. When seawater freezes, salinity increases; when seawater melts, on the contrary, it decreases.

The salinity of sea water varies from the equator to the poles, from the open part of the ocean to the shores, with increasing depth. Changes in salinity cover only the upper water column (down to a depth of 1500 - 2000 m). Deeper salinity remains constant and is approximately equal to the average ocean level.

2. Water temperature. The temperature of ocean water at the surface depends on the input of solar heat. Those parts of the World Ocean that are located in tropical latitudes have a temperature of + 28 0 C – +25 0 C, and in some seas, for example in the Red Sea, the temperature sometimes reaches +35 0 C. This is the warmest sea in the World Ocean. In the polar regions, the temperature drops to - 1.8 0 C (Fig. 94). At a temperature of 0 0 C, fresh water in rivers and lakes turns into ice. Sea water does not freeze. Its freezing is prevented by dissolved substances. And the higher the salinity of sea water, the lower its freezing point.

Fig.94. Temperature of surface waters of the World Ocean

With strong cooling, sea water, like fresh water, freezes. Sea ice forms. They constantly cover most of the Arctic Ocean, surround Antarctica, and appear in shallow seas at temperate latitudes in winter, where they melt in summer.

*Up to a depth of 200 m, the water temperature varies depending on the time of year: in summer the water is warmer, in winter it becomes colder. Below 200 m, the temperature changes due to the influx of warmer or colder waters by currents, and in the near-bottom layers it can increase due to the influx of hot water from faults in the oceanic crust. In one of these sources at the bottom of the Pacific Ocean, the temperature reaches 400 0 C.

The temperature of ocean waters also changes with depth. On average, for every 1,000 m of depth, the temperature drops by 2 0 C. At the bottom of deep-sea depressions the temperature is about 0 0 C.

1. What is called the salinity of sea water, how is it expressed? 2. What determines the salinity of sea water and how is it distributed in the World Ocean? What explains this distribution? 3. How does the temperature of the waters of the World Ocean change with latitude and depth? 4*. Why does salinity in tropical areas reach the highest values ​​for the open part of the ocean (up to 37 - 38°/oo), while in equatorial latitudes salinity is much lower?

Practical work.

Determine salinity if 25 g of salts are dissolved in 1 liter of sea water.

2*. Calculate how much salt can be obtained from 1 ton of Red Sea water.

Competition of experts . There is a sea on earth in which a person can stand on the surface of the water like a float (Fig. 95). What is the name of this sea and where is it located? Why does the water in this sea have such properties?

Rice. 95 “The sea” in which non-swimmers can swim.

The water in the sea and in the river are very different. First of all, because in the sea or ocean it has a salty taste. This is due to various factors, and what exactly influences the average salinity of the world’s oceans will be discussed below.

Salinity sign

Scientists have come up with a special designation for salinity. It is called ppm, and is very similar to %, but differs with an additional zero behind it - ‰. Permille shows the volume of a substance dissolved in one liter of water. If we have a component and its quantity is 2 grams per liter of water, then we have a value of 2 ‰.

Why is the water bitter?

Have you noticed what sea water tastes like?

It's not just salty, it's also bitter. This is due to its heterogeneity. It contains 44 different natural elements. But the main ones are salts. We are familiar with cooking - it gives an ordinary taste, as in any food. But the other one, magnesium salt, is very bitter and if there is more of it, then the water will seem disgusting.

There is so much salt in the ocean that if you dry it all and scatter it on land, you will get a layer at least 150 meters high.

Factors Affecting Flavor Levels in Ocean Water

Let's look at what determines the average salinity of the world's oceans:

• Evaporation. The more water leaves its location, the more particulate matter remains in the ocean. Salts do not evaporate.
• Are there glaciers in the ocean, and how intensively are they melting?. Cold environmental conditions can have different effects on the level of salts in water. If the process of ice formation occurs, then all the fresh water goes into the snow, but the minerals remain, increasing their concentration. Conversely, the more glaciers melt, the more they dilute the water.
• Precipitation per year.

  The more fresh rain that waters the ocean, the less salinity it becomes.

• Wastewater quantity. All rivers are fresh, and naturally, the more rivers flow into the world’s waters, the lower the concentration of substances.



Rice. 1. Map of the oceans and salinity values ​​depending on latitude

Places with the lowest and highest ppm values

In the world's oceans, the values ​​of ppm are very different. The highest results are noticeable in the North Atlantic Ocean (between 20° and 30°) and reach a level of 37 ‰. And if you measure the water in the Gulf of Panama, the figure here will be 28‰. The part of the ocean with the lowest value is between two continents and there is so much tropical rainfall that the concentration of particulate elements is low. In the Atlantic, it's the other way around. Latitudes 20°-30° are located close to the equator, which means there is little precipitation and high evaporation.

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The average salinity throughout the entire water area is 35‰.



Rice. 2. Red Sea: view from space

The sea with the highest ppm value is Red (42‰). It has a unique geographical location because no river flows into it, and the arid climate leads to abundant evaporation.

The Baltic Sea is the freshest. The ppm indicator is 1 ‰. Its location in Northern Europe means that, firstly, most European rivers flow into it, and secondly, it has a very rainy climate and few hot days.

Currents also affect the salinity of ocean waters. The biggest is the Gulf Stream. From the south it carries water with a value of 35‰ to the Arctic Ocean, where the salinity is only 10-11‰. And another current, the Labrador current, has the opposite effect. It carries the fresh waters of the Arctic to the hot climate of Central America.



Rice. 3. Labrador Current

What have we learned?

Salinity is a measure of the amount of salt dissolved in one liter of water. Indicated by the ppm symbol (‰). Water in the world's oceans is distributed unevenly and the main factor influencing this is climate. The saltiest place in the world's oceans is between 20° and 30° north latitude in the Atlantic Ocean, and the freshest is the Panama Canal of the Pacific Ocean.

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Our planet is covered with water by 70%, of which more than 96% is occupied by oceans. This means that most of the water on Earth is salty. What is water salinity? How is it determined and what does it depend on? Is it possible to use such water on the farm? Let's try to answer these questions.

What is water salinity?

Most of the water on the planet has salinity. It is usually called sea water and is found in oceans, seas and some lakes. The rest is fresh, its amount on Earth is less than 4%. Before you understand what the salinity of water is, you need to understand what salt is.

Salts are complex substances that consist of cations (positively charged ions) of metals and anions (negatively charged ions) of acid bases. Lomonosov defined them as “fragile bodies that can dissolve in water.” There are many substances dissolved in sea water. It contains sulfates, nitrates, phosphates, cations of sodium, magnesium, rubidium, potassium, etc. Together these substances are defined as salts.

So what is water salinity? This is the content of substances dissolved in it. It is measured in parts per thousand - ppm, which are designated by a special symbol - %o. Permille determines the number of grams in one kilogram of water.

What determines the salinity of water?

In different parts of the hydrosphere and even at different times of the year, the salinity of water is not the same. It changes under the influence of several factors:

• evaporation;
• ice formation;
• precipitation;
• melting ice;
• river flow;
• currents.

When water evaporates from the surface of the oceans, salts remain and do not erode. As a result, their concentration increases. The freezing process has a similar effect. Glaciers contain the largest reserve of fresh water on the planet. During their formation, the salinity of the waters of the World Ocean increases.

The melting of glaciers has the opposite effect, reducing the salt content. In addition to them, the source of fresh water is precipitation and rivers flowing into the ocean. The level of salts also depends on the depth and nature of the currents.

Their greatest concentration is on the surface. The closer to the bottom, the less salinity. influence the salt content in a positive direction; cold ones, on the contrary, reduce it.

Salinity of the World Ocean

What is the salinity of sea water? We already know that it is far from the same in different parts of the planet. Its indicators depend on geographic latitudes, climatic features of the area, proximity to river objects, etc.

The average salinity of the waters of the World Ocean is 35 ppm. Cold areas near the Arctic and Antarctic are characterized by lower concentrations of substances. Although in winter, when ice forms, the amount of salts increases.

For the same reason, the least saline ocean is the Arctic Ocean (32%). The Indian Ocean has the highest content. It covers the Red Sea and Persian Gulf region, as well as the southern tropical zone, where salinity is up to 36 ppm.

The Pacific and Atlantic oceans have approximately equal concentrations of substances. Their salinity decreases in the equatorial zone and increases in subtropical and tropical regions. Some are warm and balance each other out. For example, the non-salty Gulf Stream and the salty Labrador Current in the Atlantic Ocean.

Salinity of lakes and seas

Most lakes on the planet are fresh, as they are fed mainly by sediments. This does not mean that there are no salts in them at all, just that their content is extremely low. If the amount of dissolved substances exceeds one ppm, then the lake is considered saline or mineral. The Caspian Sea has a record value (13%). The largest fresh lake is Baikal.

The concentration of salts depends on how the water leaves the lake. Fresh water bodies are flowing, while saltier ones are closed and subject to evaporation. The determining factor is also the rocks on which the lakes were formed. Thus, in the region of the Canadian Shield, rocks are poorly soluble in water, which is why the reservoirs there are “clean”.

The seas are connected to the oceans through straits. Their salinity is slightly different and affects the average values ​​of ocean waters. Thus, the concentration of substances in the Mediterranean Sea is 39% and is reflected in the Atlantic. The Red Sea, with an indicator of 41%o, greatly raises the average. The saltiest is the Dead Sea, in which the concentration of substances ranges from 300 to 350%o.

Properties and significance of sea water

Not suitable for economic activity. It is not suitable for drinking or watering plants. However, many organisms have long adapted to life in it. Moreover, they are very sensitive to changes in its salinity level. Based on this, organisms are divided into freshwater and marine.

Thus, many animals and plants that live in the oceans cannot live in the fresh water of rivers and lakes. Edible mussels, crabs, jellyfish, dolphins, whales, sharks and other animals are exclusively marine.

People use fresh water for drinking. Salted water is used for medicinal purposes. Water with sea salt is consumed in small quantities to restore the body. The healing effect comes from swimming and bathing in sea water.