How to take the whole part out of a fraction. mixed numbers
We remember: How are the waters of the planet divided by salinity? Why travelers and sailors take on sea voyages fresh water?
Keywords:sea water, salinity, water temperature, ppm.
1. Salinity of waters. In all seas and oceans, water has a bitter-salty taste. It is impossible to drink such water. Therefore, sailors leaving on ships to sail take with them a supply of fresh water. Salt water can be desalinated in special plants that are available on ships.
Mostly table salt, which we eat, is dissolved in sea water, but there are other salts (Fig. 92).
* Magnesium salts impart a bitter taste to water. 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 is the ocean water salty? Some scientists believe that the primary ocean was fresh, because it was formed by river waters and rains that fell abundantly on Earth millions of years ago. Rivers have brought and continue to bring salt into the ocean. They accumulate and lead to the salinity of ocean water.
Other scientists suggest that the ocean immediately became salty during its formation, because it was replenished with salty water from the bowels of the Earth. Future research may provide an answer to 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 sea water. Most of them are contained in water in very small quantities: in 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 the surface waters of the oceans
Salinity is expressed in p r o m i l l yae, i.e., in thousandths of a number, and is denoted by - ° / 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 salt (Fig. 92). The salinity of fresh river or lake waters is less than 1°/oo.
The Atlantic Ocean has the most salty surface waters, the Arctic Ocean has the least saline ones (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 the marginal seas usually differs little from the salinity of the adjacent parts of the ocean. The water of the inland seas differs from the water of the open part of the oceans in salinity: it rises in the seas of the hot zone with a dry climate. For example, the salinity of the water in the Red Sea is almost 42°/oo. This is the saltiest sea in the world ocean.
In the seas of the temperate zone, which receive a large amount of river water, the salinity is below average, for example, in the Black Sea - from 17 ° / oo to 22 ° / oo, in the Azov - from 10 ° / oo to 12 ° / oo.
* The salinity of sea water depends on atmospheric precipitation and evaporation, as well as currents, inflow of river water, ice formation and 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 sea water freezes, salinity increases; when people melt, 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 coast, with increasing depth. Salinity changes cover only the upper water column (up to a depth of 1500 - 2000 m). Deeper, salinity remains constant and is approximately equal to the average ocean.
2. Water temperature. The temperature of ocean water at the surface depends on the influx of solar heat. Those parts of the World Ocean that are located in tropical latitudes have a temperature of + 28 0 С - +25 0 С, and in some seas, for example, in the Red Sea, the temperature sometimes reaches +35 0 С. This is the warmest sea of 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 of rivers and lakes turns into ice. Sea water does not freeze. Freezing is prevented by dissolved substances. And the higher the salinity of sea water, the lower its freezing point.
Fig.94. The temperature of the surface waters of the oceans
With strong cooling, sea water, like fresh water, freezes. Sea ice is forming. They constantly cover most of the Arctic Ocean, surround Antarctica, appear in the shallow seas of temperate latitudes in winter, where they melt in summer.
*Up to a depth of 200 m, the water temperature varies depending on the season: in summer the water is warmer, in winter it becomes colder. Below 200 m, the temperature changes due to the inflow of warmer or colder waters by the currents, and in the bottom layers it can increase due to the inflow of hot waters from the oceanic faults. earth's crust. In one of these springs at the bottom of the Pacific Ocean, the temperature reaches 400 0 C.
The temperature of the 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-water 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 oceans? What explains this distribution? 3. How does the temperature of the waters of the World Ocean change with latitude and depth? four*. Why does the salinity in tropical regions reach highest values for the open part of the ocean (up to 37 - 38 ° / oo), and in equatorial latitudes the salinity is much lower?
Practical work.
Determine the 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.
Connoisseur Contest . On earth there is a sea in which a person can be 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 "Sea" in which those who cannot swim can swim.
The Pacific Ocean is the largest and oldest on our planet. It is so huge that it can easily accommodate all the continents and islands combined, and that is why it is often called the Great. The area of the Pacific Ocean is 178.6 million square meters. km, which corresponds to 1/3 of the surface of the entire globe.
general characteristics
The Pacific Ocean is the most important part of the World Ocean, since it contains 53% of the total volume of its water. It stretches from east to west for 19 thousand kilometers, and from north to south - for 16 thousand. Wherein most of its waters are located in the southern latitudes, and the smaller one - in the northern ones.
The Pacific Ocean is not only the largest, but also the deepest water basin. The maximum depth of the Pacific Ocean is 10994 m - this is the depth of the famous Mariana Trench. The average figures fluctuate within 4 thousand meters.
Rice. 1. Mariana Trench.
The Pacific Ocean owes its name to the Portuguese navigator Ferdinand Magellan. During his long journey, calm and calm weather reigned in the oceanic expanses, without a single storm and storm.
The bottom relief is very diverse.
Meet here:
- basins (Southern, North-Eastern, Eastern, Central);
- deep-sea trenches (Marian, Philippine, Peruvian);
- uplands (East Pacific Rise).
The properties of water are formed by interaction with the atmosphere and are largely subject to change. The salinity of the Pacific Ocean is 30-36.5%.
It depends on the location of the waters:
- maximum salinity (35.5-36.5%) is inherent in waters in tropical zones, where a relatively small amount of precipitation is combined with intense evaporation;
- salinity decreases towards the east under the influence of cold currents;
- salinity also decreases under the influence of heavy rainfall, this is especially noticeable at the equator.
Geographical position
The Pacific Ocean is conditionally divided into two regions - southern and northern, the border between which runs along the equator line. Since the ocean is colossal, its boundaries are the coasts of several continents and partially bordering oceans.
In the northern part, the boundary between the Pacific and Arctic Oceans is the line connecting Cape Dezhnev and Cape Prince of Wales.
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Rice. 2. Cape Dezhnev.
In the east, the Pacific Ocean borders the coasts of the South and North America. A little further south, the boundary between the Pacific and Atlantic Oceans extends from Cape Horn to Antarctica.
In the west, the waters of the Pacific Ocean wash Australia and Eurasia, then the border runs along the Bass Strait on the east side, and descends along the meridian south to Antarctica.
Climate features
The climate of the Pacific Ocean is subject to the general latitudinal zonality and the powerful seasonal influence of the Asian continent. Due to the huge occupied area, almost all climatic zones are characteristic of the ocean.
- In the tropical and subtropical zones of the northern hemisphere, the northeast trade winds reign.
- The equatorial zone is characterized by calm weather throughout the year.
- In the tropics and subtropics of the southern hemisphere, the southeast trade wind dominates. In the summer, tropical hurricanes of incredible strength, typhoons, are born in the tropics.
The average air temperature in the equatorial and tropical zones is 25°C. On the surface, the water temperature fluctuates between 25-30 C, while in the polar regions it drops to 0 C.
At the equator, the amount of precipitation reaches 2000 mm, decreasing to 50 mm per year near the coast of South America.
Seas and islands
The coastline of the Pacific Ocean is most indented in the west and least indented in the east. In the north, the Strait of Georgia cuts deep into the mainland. The largest Pacific bays are California, Panama and Alaska.
The total area of the seas, bays and straits belonging to Pacific Ocean, occupies 18% of the total ocean area. Most of the seas are located along the coasts of Eurasia (Okhotsk, Bering, Japanese, Yellow, Philippine, East China), along the Australian coast (Solomon, New Guinea, Tasmanovo, Fiji, Coral). The coldest seas are located near Antarctica: Ross, Amundsen, Somov, Durville, Bellingshausen.
Rice. 3. Coral Sea.
All rivers of the Pacific basin are relatively short, but with a rapid flow of water. The largest river flowing into the ocean is the Amur.
There are about 25 thousand large and small islands in the Pacific Ocean, with unique flora and fauna. For the most part, they are located in the equatorial, tropical and subtropical natural complexes.
The large archipelagos of the Pacific Ocean include the Hawaiian Islands, the Philippine Archipelago, Indonesia, and the largest island is New Guinea.
The urgent problem of the Pacific Ocean is the significant pollution of its waters. Industrial waste, oil spills, thoughtless extermination of the inhabitants of the ocean can cause irreparable harm to the Pacific Ocean, breaking the delicate balance of its ecosystem.
What have we learned?
While studying the topic "Pacific Ocean" we got acquainted with brief description ocean, his geographic location. We found out which islands, seas and rivers belong to the Pacific Ocean, what are the features of its climate, got acquainted with the main environmental problems.
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Geological activity of oceans and seas
Features of the relief of the ocean floor
Destructive and accumulative activity of the sea
Sedimentation in the seas and oceans
General information about the World Ocean
Ocean– continuous water shell Earth surrounding the 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 main volume of the hydrosphere - about 1.35 km 3. Parts of the World Ocean, isolated by land or elevations of the underwater relief and differing from the open part of the ocean in hydrological, meteorological and climatic regimes, are called seas. Conventionally, the seas are also called some open parts of the oceans (Sargasso Sea) and large lakes(Caspian Sea). From a geological point of view, modern seas are young formations: all of them were defined in outlines close to modern ones in the Paleogene-Neogene time, and finally took shape in the Anthropogene. The formation of deep seas is associated with tectonic processes; shallow seas usually arose when the waters of the World Ocean flooded the marginal parts of the continents (shelf seas). The flooding of these areas could be due to two reasons: 1) the rise in the level of the World Ocean (due to the melting of Quaternary glaciers) or 2) the 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 parts of the World Ocean is different and depends on the degree of connection with the open ocean, the climate, the proximity of the mouths major rivers, melting ice, etc.: in the Red Sea, salinity reaches 42‰, while in the Baltic it does not exceed 3-6‰. The maximum salinity is observed in lagoons and bays separated from the sea, located in arid regions. Another reason for the 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 near-bottom areas of the Red Sea, where thermal brines emerge, salinity reaches 310‰. The 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 coming in 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 of layers 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 there are more carbonates in river water). 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 content of sodium chloride 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 is also dissolved in the waters of the seas and oceans. Mostly it is 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 affect sedimentation and biological processes. It is assimilated only by nitrogen-fixing bacteria capable of converting free nitrogen into its compounds. Therefore, compared with 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 the water in the process of 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 in 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 it is contained in sea water in insignificant concentrations (not more than 0.5 ml / l), but the total content of carbon dioxide is approximately 60 times higher than its amount in the atmosphere. While playing essential role in biological processes (being a source of carbon in the construction of a living cell), affects global climatic processes (participating in gas exchange with the atmosphere), determines the features of carbonate sedimentation. In sea water, carbon oxides are distributed 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; therefore, 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 layer of the oxygen minimum.
Hydrogen sulfide in sea water is found in significant quantities in water bodies with difficult water exchange (the Black Sea is a well-known example of "hydrogen sulfide contamination"). The sources of hydrogen sulfide can be hydrothermal waters coming from the depths to the ocean floor, reduction of sulfates by sulfate-reducing bacteria during the decomposition of dead organic matter, release during decay of sulfur-containing organic residues. Oxygen reacts rather quickly with hydrogen sulfide and sulfides, eventually oxidizing them to sulfates.
Important for the processes of oceanic sedimentation is the solubility of carbonates in sea water. 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 tend to be saturated with respect to calcium carbonate, so it does not dissolve in the upper water column immediately after the organisms die. With depth, the water becomes more and more undersaturated with calcium carbonate, and as a result, the rate at some depth of the dissolution rate of the carbonate substance is equal to the rate of its supply. This level is called depth of carbonate compensation. The depth of carbonate compensation varies depending on chemical composition and the temperature of sea water is on average 4500 m. Below this level, carbonates cannot accumulate, which determines the replacement of essentially carbonate sediments by 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 continental shelf) - a slightly inclined, leveled part of the underwater margin of the continents, adjacent to the coast of the land and characterized by a common geological structure with it. Shelf depth is usually up to 100-200 m; 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 are mainly formed as a result of the flooding of the continental margins during the rise in the level of the World Ocean due to the melting of glaciers, as well as due to subsidence of the earth's surface areas associated with the latest tectonic movements. The shelf existed in all geological periods, in some of them growing sharply in size (for example, in the Jurassic and Cretaceous), in others, occupying small areas (Permian). The modern geological epoch is characterized by moderate development of shelf seas.
continental slope is the next of the main elements of the underwater margin of the continents; it is located between the shelf and the continental foot. It is characterized by steeper slopes of the surface compared to the shelf and ocean floor (on average 3-5 0, sometimes up to 40 0) and a significant dissection of the relief. Typical landforms are steps parallel to the crest and base of the slope, as well as submarine canyons, usually originating on the shelf and stretching to the continental foot. Seismic surveys, dredging and deep-sea drilling have established that according to geological structure the continental slope, like the shelf, is a direct continuation of the structures developed on the adjacent parts of the continents.
mainland foot is a plume of accumulative deposits that arose at the foot of the continental slope due to the movement of material down the slope (through turbidity flows, underwater landslides and landslides) and sedimentation of suspension. 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-type crust, or are located partly on the continental, partly on the oceanic crust.
Next are the structures formed on the crust of the oceanic type. The largest elements of the relief of the oceans (and the Earth as a whole) are the ocean floor and mid-ocean ridges. The bed of the ocean is divided by ridges, ramparts 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 terrain, which allows them to be considered as oceanic plates - thalassocratons. Geomorphologically, these areas are represented by abyssal (deep water) accumulative and hilly plains. Accumulative plains have a leveled surface, a slightly inclined surface and are developed mainly along the periphery of the oceans in areas of significant inflow 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: surface depression from the continental foot towards the ocean, the presence of submarine valleys, gradation layering of sediments, and leveled relief. The latter feature is determined by the fact that, moving deep into the ocean basins, sediments bury the primary dissected tectonic and volcanic relief. The hilly abyssal plains are characterized by a dissected relief and a small thickness of sediments. These plains are typical of the inner parts of the basins, remote from the coast. An important element of the relief of these plains are volcanic uplifts and individual volcanic structures.
Another element of the mega-relief is mid-ocean ridges, which are powerful mountain system stretching across all oceans. The total length of the mid-ocean ridges (MOR) is more than 60,000 km, the width is 200-1200 km, and the height is 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 length 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 is represented by modern deposits. MOR regions are characterized by intense manifestation of endogenous activity: seismicity, volcanism, high heat flux.
MOR zones are confined to the boundaries of the lithospheric plates moving apart, here the process of formation of a new oceanic crust takes place due to incoming mantle melts.
Particularly noteworthy are the transition zones from continental to oceanic crust - the margins of the continents. There are two types of continental margins: tectonically active and tectonically passive.
Passive Outskirts represent a direct continuation of the continental blocks, flooded by the waters of the seas and oceans. They include the shelf, the continental slope and the 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 subduction of oceanic plates under the continental ones takes place. These ocarinas are characterized by active endogenous activity; areas of seismic activity and modern volcanism are confined to them. Among the active ocarinas, two main types are distinguished by structure: the western Pacific (island-arc) and the eastern Pacific (Andean). The main elements of the margins of the Western Pacific type are deep-water trenches, volcanic island arcs, and marginal (or interarc) marine basins. The area of the deep-water trench corresponds to the boundary where the plate with the oceanic-type crust is being subducted. The melting of a part of the subducting plate and the rocks of the lithosphere located above (associated with the influx of water in the subducting plate, which sharply lowers the melting temperature of the rocks) leads to the formation of magma chambers, from which melts enter the surface. Due to active volcanism, volcanic islands are formed, stretching parallel to the boundary of the subsidence of the plate. The margins of the East Pacific type are distinguished by the absence of volcanic arcs (volcanism is manifested directly on the margin of the land) and marginal basins. The deep-water trench is replaced by a steep continental slope and a narrow shelf.
Destructive and accumulative activity of the sea
Abrasion (from lat. "abrasion" - scraping, shaving) is the process of destruction of rocks by waves and currents. Abrasion occurs most intensively near the coast under the action of the surf.
The destruction of coastal rocks is composed of the following factors:
wave impact (the strength of which reaches 30-40 t / m 2 during storms);
· abrasive action of clastic material 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 high pressure;
· thermal abrasion, which manifests itself in the thawing of frozen rocks and ice shores, and other types of impact on the coast.
The impact of the abrasion process is manifested to a depth of several tens of meters, and in the oceans up to 100 m or more.
The impact of abrasion on the coast leads to the formation of clastic deposits and certain landforms. The abrasion process proceeds as follows. Hitting the shore, the wave gradually develops a depression at its base - wave-cutting niche, over which hangs a cornice. As the wave-cut niche deepens, under the action of gravity, the cornice collapses, the fragments are at the foot of the coast and, under the influence of waves, turn 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"), which is composed 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 clastic material is carried away from the shore, forming underwater accumulative terraces.
As the abrasion and accumulative terraces develop, the waves find themselves in shallow water, turn up and lose energy before reaching the root bank, because of this, the abrasion process stops.
Depending on the nature of the ongoing processes, the coast can be divided into abrasion and accumulative.
A, B, C - different stages of retreat of the coastal cliff, destroyed by abrasion; A 1 , B 2 , C 3 - different stages of development of the underwater accumulative terrace.
Waves carry out not only destructive work, but also the work of moving and accumulating detrital material. The oncoming wave carries pebbles and sand, which remain on the shore when the wave retreats, this is how beaches are formed. By the beach(from the French "plage" - sloping seashore) is called a strip of sediment on the sea coast in the zone of action of a surf stream. Beaches are distinguished morphologically full profile, having the form of a gentle shaft, and beaches of an 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 of a full profile are typical for accumulative shores, incomplete - mainly for abrasion shores.
When waves are burrowing at depths of a few meters, the material deposited under water (sand, gravel or shell) forms an underwater sand bank. Sometimes the underwater accumulative shaft, growing, protrudes above the surface of the water, stretching parallel to the shore. Such shafts are called bars(from the French "barre" - barrier, shoal).
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 the lagoons is the difference between the salinity of the waters and biological communities.
Sedimentation in the seas and oceans
Various precipitation accumulates in the seas and oceans, which can be divided into the following groups by origin:
· 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;
· volcanic, accumulating as a result of underwater eruptions and due to products of eruption brought from land;
polygenic, i.e. mixed sediments formed due to material of different origin.
In general, the material composition of bottom sediments is determined by the following factors:
· depth of sedimentation area and bottom topography;
hydrodynamic conditions (the presence of currents, the influence of wave activity);
· the nature of the supplied sedimentary material (determined by climatic zonality and distance from the continents);
biological productivity (marine organisms extract minerals from the water and deliver them to the bottom after death (in the form of shells, coral structures, etc.));
volcanism and hydrothermal activity.
One of the determining factors is the depth, which makes it possible to distinguish several zones that differ in the features of sedimentation. Littoral(from lat. "littoralis"- coastal) - the border strip between land and sea, regularly flooded at high tide and drained at low tide. The littoral is the zone of the seabed located between the levels of the highest tide and the lowest tide. nerite zone corresponds to the depths of the shelf (from the Greek. "erites"- sea mollusk). Bathyal zone(from the Greek "deep") roughly 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, slight seasonal fluctuations in temperature and water density; as part of organic world representatives of zoobenthos and fish predominate, vegetable world very poor due to lack of light. abyssal zone(from the Greek "bottomless") corresponds to sea depths of more than 2500 m, which corresponds to deep-water basins. The waters of this zone are characterized by relatively low mobility, constantly low temperature (1-2 0 C, in the polar regions below 0 0 C), constant salinity; is completely missing here. sunlight and enormous pressures are achieved, which determine the originality and poverty of the organic world. Areas deeper than 6000 m are usually distinguished as ultra-abyssal zones corresponding to the deepest parts of the basins and deep-water trenches.
World Ocean- This is a combination of four oceans of our planet: the Pacific, Atlantic, Indian and Arctic. The world ocean washes the shores of all continents, but unlike land, it is single space. The ocean occupies 71% of the surface of our planet (about 360 million km 2).
The bottom of the oceans is composed of a three-layer oceanic-type crust. In contrast to the continental crust, it has a smaller thickness - 5-10 km. In the relief of the bottom of the oceans, it is customary to distinguish the following components: the underwater margins of the continents, the transition zone, and the ocean floor.
In contrast to the continents, the effect of external relief-forming processes is much less pronounced in the oceans. As a result, the ocean floor is more homogeneous than the earth's surface.
Average ocean depths are about 3700 m, while in its open parts the smallest depths are noted in the areas of mid-ocean ridges, and the maximum are confined to deep-sea trenches.
Water masses of the oceans characterized by a number of properties, the main of which are the temperature and salinity of the waters.
World Ocean water temperature changes both horizontally and vertically. The temperature of the surface of the waters varies zonal, decreasing in the direction from the equator to the poles. This is due to the fact that earth's surface near the equator, due to the more sheer fall of the sun's rays, it receives more solar heat. The temperature of the surface waters of the ocean near the equator is 25˚-28˚. Near North Pole the temperature of the surface of the waters can drop to 0˚ and even slightly lower (-1.3˚), as salt water freezes at negative temperatures.
With depth, the temperature of the waters in the World Ocean decreases due to the fact that the sun's rays are not able to heat the entire water column.
Average salinity of the oceans- 35%, that is, 35 g of salts are dissolved in 1 liter of ocean water. The salty taste of sea water is due to the presence of chlorides, and the bitter taste is due to magnesium salts. The salinity index of surface waters is determined by the ratio of the amount of atmospheric precipitation and the amount of evaporation. A large influx of atmospheric moisture distributes water, significant evaporation, on the contrary, increases salinity, since salts do not evaporate with water. The highest salinity of the waters is characteristic of tropical latitudes, and the Red Sea is generally the most saline sea in the world's oceans.
The waters of the oceans are in constant motion. The main types of water dynamics include waves (wind and tsunamis), currents, ebbs and flows.
Surface currents can occur due to various reasons. In accordance with this, the types of flows are distinguished: wind (drift); with uneven distributions of temperatures or salinity (density); tidal due to the attraction of the moon; gradient when changing atmospheric pressure; stock; compensation at low tide of the neighboring water mass, etc.
However, the main reason for the emergence of ocean currents are the winds of the general circulation of the atmosphere: trade winds, westerly transport, and others. In each of the hemispheres, the system of currents forms a kind of giant "eight".
According to the temperature, the currents are divided into warm and cold. In this case, the absolute temperature of the water does not play a role in this case. The temperature of the flowing water relative to the surrounding waters is important. That is, a warm current is a powerful jet of warmer water among colder water. The general direction of warm currents is from the equator to the poles, cold ones, on the contrary, are from the poles to the equator. Ocean currents have a significant impact on the climate of the coastal areas they wash. Thus, cold currents, preventing the rise of air, contribute to a decrease in the amount of precipitation. On the subtropical coasts washed by cold currents (Peruvian, Bengal), coastal deserts are formed (Atacama, Namib).
World Ocean is the birthplace of life on earth. The conditions for the existence of living organisms in water are more favorable than on land. There are no sharp fluctuations in temperature, the surrounding water supports the body of the organism in space. Total number species of living organisms of the World Ocean is approaching 160 thousand. At the same time, most of the biomass of the ocean, in contrast to land, is made up of animals.
The world ocean has great value in economic activity person. The ocean is a source of natural resources. The main thing - biological resources: fish, seafood, sea animal, shells, pearls, etc. In addition to biological, they began to actively use mineral resources, primarily oil and gas from shelf zones. Huge potential energy resources. In addition, the most important transport routes serving world trade pass through the ocean. The coasts of the oceans are widely used for recreational purposes.
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Our planet is covered by 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 the salinity of water? How is it determined and what does it depend on? Can this water be used on the farm? Let's try to answer these questions.
What is the salinity of water?
Most of the water on the planet has salinity. It is commonly referred to as seawater and is found in the 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 acidic bases. Lomonosov defined them as "fragile bodies that can dissolve in water." Many substances are dissolved in sea water. It contains sulfates, nitrates, phosphates, sodium, magnesium, rubidium, potassium cations, etc. Together, these substances are defined as salts.
So what is the salinity of water? This is the content of dissolved substances in it. It is measured in thousandths - ppm, which are indicated by a special symbol -% o. Ppm is 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 the 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, the salts remain and do not erode. As a result, their concentration increases. Freezing has a similar effect. Glaciers contain the largest supply of fresh water on the planet. During their formation, the salinity of the waters of the World Ocean increases.
The melting of glaciers is characterized by 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 salt level also depends on the depth and nature of the currents.
Their highest concentration is on the surface. The closer to the bottom, the less salinity. affect the salt content in a positive direction, cold, on the contrary, reduce it.
Salinity of the oceans
What is the salinity of sea water? We already know that it is far from the same in different parts of the planet. Its performance depends on geographical latitudes, climatic features of the area, the proximity of river objects, etc.
The average salinity of the waters of the World Ocean is 35 ppm. Cold regions near the Arctic and Antarctic are characterized by a lower concentration of substances. Although in winter, when ice forms, the amount of salt increases.
For the same reason, the least saline ocean is the Arctic Ocean (32% o). The highest content is Indian Ocean. It covers the area of the Red Sea and the Persian Gulf, as well as the southern tropical zone, where the salinity is up to 36 ppm.
Quiet and Atlantic Oceans have approximately the same concentration 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 in the Atlantic Ocean.
Salinity of lakes and seas
Most of the lakes on the planet are fresh, as they are fed mainly by precipitation. This does not mean that there are no salts in them at all, just that their content is extremely small. If the amount of dissolved substances exceeds one ppm, then the lake is considered salty or mineral. The Caspian Sea has a record value (13% o). The largest fresh lake is Baikal.
Salt concentration depends on how the water leaves the lake. Fresh water bodies are flowing, while more saline ones are closed and subject to evaporation. The determining factor is also the rocks on which the lakes formed. So, in the area of the Canadian shield rocks poorly soluble in water, therefore, the reservoirs there are “clean”.
The seas are connected to the oceans through straits. Their salinity is somewhat different and affects the average ocean waters. Thus, the concentration of substances in the Mediterranean Sea is 39% o and is reflected in the Atlantic. The Red Sea with an indicator of 41% o greatly raises the average. The most saline 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 activities. It is not suitable for drinking, as well as watering plants. However, many organisms have long adapted to life in it. Moreover, they are very sensitive to changes in its salinity. Based on this, organisms are divided into freshwater and marine.
So, 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. Salt is used for medicinal purposes. In small quantities, water with sea salt is used to restore the body. The therapeutic effect is produced by bathing and taking baths in sea water.