Deep ocean zone. Deep-sea zones What are the deep-sea zones of the oceans

200 m corresponding to the continental shelf. The sublittoral zone, as a rule, has the highest biological productivity due to the abundance of nutrients brought from the continent to coastal areas by rivers, good warming in summer, and high illumination sufficient for photosynthesis, which together provide an abundance of plant and animal life forms. The bottom zone of the ocean, sea or large lake is called benthal. It extends along the continental slope from the shelf with a rapid increase in depth and pressure, passes further into the deep oceanic plain and includes deep-water depressions and trenches. Bental, in turn, is subdivided into bathyal - a region of a steep continental slope and abyssal - a region of a deep-water plain with depths in the ocean from 3 to 6 km. Complete darkness prevails here, the water temperature, regardless of the climatic zone, is mainly from 4 to 5 ° C, there are no seasonal fluctuations, the pressure and salinity of the water "reach their highest values, the oxygen concentration is reduced and hydrogen sulfide may appear. The deepest zones of the ocean, corresponding the largest depressions (from 6 to 11 km) are called the ultraabyssal.

Rice. 3.7. Littoral zone of the coast of the Dvina Bay of the White Sea (Yagry Island).
A - tide-lined beach; B - pine stunted forest on coastal dunes

The layer of water in the open ocean or sea, from the surface to the maximum depths of penetration of light into the water column, is called pelagial, and the organisms living in it are called pelagic. According to the experiments, sunlight in the open ocean is able to penetrate to depths of up to 800-1000 m. Of course, its intensity at such depths becomes extremely low and completely insufficient for photosynthesis, but a photographic plate immersed in these layers of the water column, when exposed for 3-5 h is still illuminated. The deepest plants can be found at depths of no more than 100 m. The pelagial is also subdivided into several vertical zones, corresponding in depth to the benthic zones. An epipelagic is a near-surface layer of the open ocean or sea, remote from the coast, in which the daily and seasonal variability of temperature and hydrochemical parameters is expressed. Here, as well as in the littoral and sublittoral zones, photosynthesis occurs, during which plants produce the primary organic matter necessary for all aquatic animals. The lower boundary of the epipelagic zone is determined by the penetration of sunlight to depths where its intensity and spectral composition are sufficient in intensity for photosynthesis. Usually the maximum depth of the epipelagic zone does not exceed 200 m. Bathypelagial - water column of medium depths, twilight zone. And, finally, the abyssopelagial is a deep-sea near-bottom zone of continuous darkness and constant low temperatures (4-6 ° C).
Ocean water, as well as the water of the seas and large lakes, is not uniform in the horizontal direction and is a collection of individual water masses that differ from each other in a number of indicators. Among them are water temperature, salinity, density, transparency, nutrient content, etc. Hydrochemical and hydrophysical features of surface water masses are largely determined by the zonal type of climate in the area of ​​their formation. As a rule, a certain species composition of hydrobionts living in it is associated with specific abiotic properties of the water mass. Therefore, it is possible to consider large stable water masses of the World Ocean as separate ecological zones.
A significant volume of water masses of all oceans and land water bodies is in constant motion. Movements of water masses are caused mainly by external and terrestrial gravitational forces and wind influences. The external gravitational forces that cause the movement of water include the attraction of the Moon and the Sun, which forms the alternation of tides in the entire hydrosphere, as well as in the atmosphere and lithosphere. The forces of gravity cause rivers to flow, i.e. the movement of water in them from high to lower levels, as well as the movement of water masses with unequal density in the seas and lakes. Wind influences lead to the movement of surface waters and create compensatory currents. In addition, the organisms themselves are capable of noticeable mixing of water in the process of moving in it and feeding by filtration. For example, one large freshwater bivalve mollusk Perlovitsa (Unionidae) is able to filter up to 200 liters of water per day, while forming a completely ordered flow of liquid.
The movement of water is carried out mainly in the form of currents. Currents are horizontal, surface and deep. The occurrence of a current is usually accompanied by the formation of an oppositely directed compensatory water flow. The main surface horizontal currents of the World Ocean are the northern and southern trade wind currents (Fig. 3.8), directed

moving from east to west parallel to the equator, and moving between them in the opposite direction, the inter-trade current. Each trade wind current is divided in the west into 2 branches: one passes into the intertrade current, the other deviates towards higher latitudes, forming warm currents. In the direction from high latitudes, water masses move to low latitudes, forming cold currents. The most powerful current in the World Ocean is forming around Antarctica.* Its speed in some areas exceeds 1 m/s. The Antarctic Current carries its cold waters from west to east, but its spur penetrates quite far north along the western coast of South America, creating the cold Peru Current. The warm current Gulf Stream, the second most powerful among ocean currents, is born in the warm tropical waters of the Gulf of Mexico and the Sargasso Sea, gt; further one of its jets is directed towards northeastern Europe, bringing heat to the boreal zone. In addition to surface horizontal currents, there are also deep ones in the World Ocean. The main mass of deep waters is formed in the polar and subpolar regions and, sinking to the bottom here, moves in the direction of tropical latitudes. The speed of deep currents is much lower than surface currents, but nevertheless it is quite noticeable - from 10 to 20 cm / s, which ensures global circulation of the entire thickness of the oceans. The life of organisms that are not capable of active movement in the water column often turns out to be completely dependent on the nature of the currents and the properties of the corresponding water masses. The life cycle of many small crustaceans living in the water column, as well as jellyfish and ctenophores, can almost completely proceed under certain current conditions. *

Rice. 3.8. Scheme of surface ocean currents and boundaries of latitudinal zones in the World Ocean (Konstantinov, 1986).
Zones: 1 - arctic, 2 - boreal, 3 - tropical, 4 - notal, 5 - antarctic

In general, the movement of water masses has a direct and indirect effect on hydrobionts. Direct impacts include horizontal transport of pelagic organisms, vertical movement, and washing out bottom organisms and carrying them downstream (especially in rivers and streams). The indirect effect of moving water on hydrobionts can be expressed in the supply of food and an additional amount of dissolved oxygen, the removal of unwanted metabolic products from the habitat. In addition, currents contribute to smoothing zonal gradients of temperature, water salinity, and nutrient content both on a regional and global scale, ensuring the stability of habitat parameters. Unrest on the surface of water bodies leads to an increase in gas exchange between the atmosphere and the hydrosphere, thereby contributing to an increase in the oxygen concentration in the near-surface layer. The waves also carry out the process of mixing water masses and leveling their hydrochemical parameters, contribute to the dilution and dissolution of various toxicants that have fallen on the surface of the water, such as oil products. The role of waves is especially great near the coasts, where the surf grinds the soil, moves it both vertically and horizontally, carries away soil and silt from some places and deposits them in others. The strength of the surf during storms can be extremely high (up to 4-5 tons per m2), which can have a detrimental effect on the communities of hydrobionts on the seabed of the coastal zone. Near rocky shores, water in the form of splashes in the surf during a major storm can fly up to 100 m! Therefore, underwater life in such areas is often depleted.
The perception of various forms of water movement by hydrobionts is assisted by special receptors. Fish estimate the speed and direction of water flow using the lateral line organs. Crustaceans - with special antennae, molluscs - with receptors in outgrowths of the mantle. Many species have vibroreceptors that perceive water vibrations. They are found in ctenophores in the epithelium, in crayfish in the form of special fan-shaped organs. Aquatic insect larvae perceive the vibration of water with various hairs and bristles. Thus, the majority of aquatic organisms have evolved very effective organs that allow them to navigate and develop in the conditions of the types of movement of the aquatic environment that are relevant to them.
As independent ecological zones of the World Ocean and large land water bodies, one can also consider areas of regular rise of near-bottom water masses to the surface - atellings, which is accompanied by a sharp increase in the amount of biogenic elements (C, Si, N, P, etc.) in the surface layer, which is very positively affects the bioproductivity of the aquatic ecosystem.
Several large upwelling zones are known, which are one of the main areas of the world fishery. Among them are the Peruvian upwelling along the western coast of South America, the Canarian upwelling, the West African (Gulf of Guinea), an area located east of the island. Newfoundland near the Atlantic coast of Canada, etc. Upwellings, smaller in space and time, periodically form in the waters of most marginal and inland seas. The reason for the formation of upwelling is a steady wind, such as a trade wind, blowing from the side of the continent towards the ocean at an angle other than 90 °. The formed surface wind (drift) current gradually turns to the right in the Northern Hemisphere and to the left in the Southern Hemisphere as it moves away from the coast due to the influence of the force of the Earth's rotation. At the same time, at a certain distance from the coast, the formed water flow deepens, and due to the compensatory flow, water enters the surface layers from deep and near-bottom horizons. The upwelling phenomenon is always accompanied by a significant decrease in the surface water temperature.
Very dynamic ecological zones of the World Ocean are areas of frontal division of several heterogeneous water masses. The most pronounced fronts with significant gradients in the parameters of the marine environment are observed when warm and cold currents meet, for example, the warm North Atlantic Current and cold water flows from the Arctic Ocean. In areas of the frontal section, conditions of increased bioproductivity can be created and the species diversity of aquatic organisms often increases due to the formation of a unique biocenosis consisting of representatives of various faunal complexes (water masses).
Areas of deep-water oases are also special ecological zones. Only about 30 years have passed since the moment when the world was simply shocked by the discovery made by the Franco-American expedition. 320 km northeast of the Galapagos Islands at a depth of 2600 m, unexpected for the eternal darkness and cold prevailing at such depths, "oases of life" were discovered, inhabited by many bivalve mollusks, shrimps and amazing worm-like creatures - vestimentifers. At present, such communities have been found in all oceans at depths from 400 to 7000 m in the areas where magmatic matter comes out to the surface of the deep ocean floor. About a hundred of them were found in the Pacific Ocean, 8 - in the Atlantic, 1 - in the Indian; 20 - in the Red Sea, a few - in the Mediterranean Sea [Ron, 1986; Bogdanov, 1997]. The hydrothermal ecosystem is the only one of its kind, it owes its existence to the processes of a planetary scale taking place in the bowels of the Earth. Hydrothermal springs, as a rule, are formed in zones of slow (from 1-2 dr 10 cm per year) expansion of huge blocks of the earth's crust (lithospheric plates), moving in the outer layer of the semi-liquid shell of the Earth's core - the mantle. Here, the hot substance of the shell (magma) pours out, forming a young crust in the form of mid-ocean mountain ranges, the total length of which is more than 70 thousand km. Through cracks in the young crust, ocean waters penetrate into the depths, are saturated with minerals there, heat up and return to the ocean again through hydrothermal springs. These sources of smoke-like dark hot water are called “black smokers” (Fig. 3.9), and colder sources of whitish water are called “white smokers”. The springs are outpourings of warm (up to 30-40 °C) or hot (up to 370-400 °C) water, the so-called fluid, supersaturated with compounds of sulfur, iron, manganese, a number of other chemical elements and myriads of bacteria. The water near the volcanoes is almost fresh and saturated with hydrogen sulfide. The pressure of the erupting lava is so strong that clouds of colonies of bacteria that oxidize hydrogen sulfide rise tens of meters above the Bottom, giving the impression of an underwater blizzard.

. . Rice. 3.9. Deep-sea oasis-hydrothermal spring.

During the study of the unusually rich hydrothermal fauna, more than 450 species of animals have been discovered. Moreover, 97% of them were new to science. As new sources are discovered and already known ones are studied, more and more new types of organisms are constantly being discovered. The biomass of living creatures living in the zone of hydrothermal springs reaches 52 kg or more per square meter, or 520 tons per hectare. This is 10-100 thousand times higher than the biomass on the ocean floor adjacent to the mid-ocean ridges.
The scientific significance of hydrothermal vent research has yet to be assessed. The discovery of biological communities living in zones of hydrothermal vents has shown that the Sun is not the only source of energy for life on Earth. Of course, the bulk of organic matter on our planet is created from carbon dioxide "and water in the most complex reactions of photosynthesis is only due to the energy of sunlight absorbed by the chlorophyll of terrestrial and aquatic plants. But it turns out that in hydrothermal regions, the synthesis of organic matter is possible, based only on the energy of chemical It is released by dozens of species of bacteria, oxidizing the compounds of iron and other metals, sulfur, manganese, hydrogen sulfide and methane raised by sources from the depths of the Earth. The released energy is used to support the most complex chemosynthesis reactions, during which bacterial primary products.This life exists only thanks to chemical, not solar energy, in connection with which it was called chemobios.The role of chemobios in the life of the World Ocean has not yet been studied enough, but it is already obvious that it is very significant.
At present, many important parameters of their vital activity and development have been established for hydrothermal systems. The specificity of their development is known depending on tectonic conditions and positions, location in the axial zone or on the sides of rift valleys, direct connection with ferruginous magmatism. A cyclicity of hydrothermal activity and passivity was found, which is 3-5 thousand and 8-10 thousand years, respectively. The zoning of ore structures and fields has been established depending on the temperature of the hydrothermal system. Hydrothermal solutions differ from sea water by a lower content of Mg, SO4, U, Mo, and an increased content of K, Ca, Si, Li, Rb, Cs, Be.
Hydrothermal regions have more recently been discovered beyond the Arctic Circle as well. This area is located 73 0 north of the Central Atlantic mountain range, between Greenland and Norway. This hydrothermal field is located more than 220 km closer to the North Pole than any previously found "smokers". The discovered springs emit highly mineralized water with a temperature of about 300 °C. It contains salts of hydrosulphuric acid - sulfides. The mixing of the hot spring water with the surrounding ice water leads to the rapid solidification of sulfides and their subsequent precipitation. Scientists believe that the massive deposits of sulfides accumulated around the source are among the largest in the bed of the world's oceans. Judging by their number, smokers have been active here for many thousands of years. The space around the escaping fountains of boiling water is covered with white mats of bacteria that thrive on mineral deposits. Also, scientists have found here a variety of other microorganisms and other living creatures. Preliminary observations led to the conclusion that the ecosystem around the Arctic hydrotherms is a unique formation, significantly different from the ecosystems near other "black smokers".
"Black smokers" are a very interesting natural phenomenon. They make a significant contribution to the total heat flow of the Earth, extract a huge amount of minerals to the surface of the ocean floor. It is believed, for example, that the deposits of copper pyrite ores in the Urals, Cyprus and Newfoundland were formed by ancient smokers. Special ecosystems also arise around the springs, in which, according to a number of scientists, the first life on our planet could have originated.
Finally, the areas of mouths of inflowing rivers and their wide estuaries can be attributed to the number of independent ecological zones of the World Ocean. Fresh river water, pouring into the ocean or sea area, leads to its desalination to a greater or lesser extent. In addition, the waters of the rivers in the lower reaches usually carry a significant amount of dissolved and suspended organic matter, enriching the coastal zone of the oceans and seas with it. Therefore, near the mouths of large rivers, areas of increased bioproductivity arise and typical continental freshwater organisms, brackish-water and typically marine organisms can be found in a relatively small area. The largest river in the world - the Amazon - annually takes out about 1 billion tons of organic silt into the Atlantic Ocean. And with a runoff. About 300 million tons of silt enters the Gulf of Mexico each year from the Mississippi River, which creates very favorable bioproductive conditions in this area against the backdrop of year-round high water temperatures. In some cases, the flow of one or just a few rivers can affect many environmental parameters throughout the sea. For example, the salinity of the entire Sea of ​​Azov is very closely dependent on the runoff dynamics of the Don and Kuban rivers. With an increase in freshwater runoff, the composition of the biocenoses of Azov is changing quite quickly, freshwater and brackish-water organisms that can live and reproduce at a salinity of 2 to 7 g / l become more widespread in it. If the runoff of rivers, especially the Don, is reduced, then prerequisites are created for a more intensive penetration of saline water masses from the Black Sea, while salinity in the Sea of ​​Azov increases (on average, up to 5-10 g / l) and the composition of fauna and flora is transformed into predominantly nautical.
In general, the high bioproductivity, including fishing, of most of the inland seas of Europe, such as the Baltic, Azov, Black and Caspian, is determined mainly by the influx of large amounts of organic matter from the runoff of numerous inflowing rivers.

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Environmental areas world ocean, ecological zones of the World Ocean, - areas (zones) of the oceans, where the systematic composition and distribution of morphological and physiological features of marine organisms are closely related to the environmental conditions surrounding them: food resources, temperature, salt, light and gas regime of water masses, their other physical and chemical properties, physical and chemical properties of marine soils and, finally, with other organisms that inhabit the oceans and form biogeocenotic systems with them. All of these properties experience significant changes from the surface layers to the depths, from the coasts to the central parts of the ocean. In accordance with the indicated abiotic and biotic environmental factors, ecological zones are distinguished in the ocean, and organisms are divided into ecological groups.

All living organisms of the ocean as a whole are divided into benthos, plankton and nekton . The first group includes organisms living on the bottom in an attached or free-moving state. These are mostly large organisms, on the one hand, multicellular algae (phytobenthos), and on the other hand, various animals: mollusks, worms, crustaceans, echinoderms, sponges, coelenterates, etc. (zoobenthos). Plankton consists in most of the small plant (phytoplankton) and animal (zooplankton) organisms that are in suspension in the water and rush along with it, their organs of movement are weak. Nekton- this is a collection of animal organisms, usually large in size, with strong organs of movement - marine mammals, fish, cephalopods, squids. In addition to these three ecological groups, pleuston and hyponeuston can be distinguished.

Playston- a set of organisms that exist in the most superficial film of water, part of their body is immersed in water, and part is exposed above the surface of the water and acts as a sail. hyponeuston- organisms of the surface of the water layer of several centimeters. Each life form is characterized by a certain body shape and some adnexal formations. Nektonic organisms are characterized by a torpedo-shaped body shape, while planktonic organisms have adaptations for hovering (thorns and appendages, as well as gas bubbles or drops of fat that reduce body weight), protective formations in the form of shells, skeletons, shells, etc.

The most important factor in the distribution of marine organisms is the distribution of food resources, both coming from the coast and created in the reservoir itself. According to the method of feeding, marine organisms can be divided into predators, herbivores, filter feeders - seston feeders (seston are small organisms suspended in water, organic detritus and mineral suspension), detritophages and soil eaters.

As in any other body of water, the living organisms of the ocean can be divided into producers, consumers (consumers) and decomposers (returners). The main mass of new organic matter is created by photosynthetic producers that can exist only in the upper zone, which is sufficiently well illuminated by the sun's rays and does not extend deeper than 200 m, but the main mass of plants is confined to the upper water layer of several tens of meters. Near the coasts, these are multicellular algae: macrophytes (green, brown and red) growing in a state attached to the bottom (fucuses, kelp, alaria, sargassum, phyllophora, ulva, and many others), and some flowering plants (zostera phyllospadix, etc. .). Another mass of producers (unicellular planktonic algae, mainly diatoms and peridiniums) inhabits the surface layers of the sea in abundance. Consumers exist at the expense of ready-made organic substances created by producers. This is the whole mass of animals that inhabit the seas and oceans. Decomposers are the world of microorganisms that decompose organic compounds to the simplest forms and re-create from these latter more complex compounds that are necessary for plant organisms for their vital activity. To some extent, microorganisms are also chemosynthetics - they produce organic matter by converting one chemical compound into another. This is how the cyclic processes of organic matter and life in sea waters take place.

According to the physical and chemical features of the ocean water mass and the bottom topography, it is divided into several vertical zones, which are characterized by a certain composition and ecological features of the plant and animal population (see diagram). In the ocean and its constituent seas, two ecological areas are primarily distinguished: the water column - pelagial and the bottom benthal. Depending on the depth benthal divided by sublittoral zone - an area of ​​​​smooth decrease in land to a depth of about 200 m, bathyal– steep slope area and abyssal zone– an area of ​​the oceanic bed with an average depth of 3–6 km. Even deeper areas of the benthal, corresponding to the depressions of the ocean floor, are called ultraabyssal. The edge of the coast that is flooded at high tide is called littoral. Above the level of the tides, the part of the coast moistened by the splashes of the surf is called supralittoral.

Benthos lives in the uppermost horizon - in the littoral. Marine flora and fauna abundantly populate the littoral zone and, in connection with this, develop a number of ecological adaptations to survive periodic drying. Some animals tightly close their houses and shells, others burrow into the ground, others clog under stones and algae or tightly shrink into a ball and excrete on surface mucus that prevents drying. Some organisms get even higher than the highest tide line and are content with the splashing of the waves, irrigating them with sea water. This is the supralittoral zone. The littoral fauna includes almost all large groups of animals: sponges, hydroids, worms, bryozoans, mollusks, crustaceans, echinoderms, and even fish; some algae and crustaceans are selected in the supralittoral. Below the lowest ebb limit (to a depth of about 200 m), the sublittoral, or continental shelf, extends. In terms of the abundance of life, the littoral and sublittoral are in the first place, especially in the temperate zone - huge thickets of macrophytes (fucuses and kelp), accumulations of mollusks, worms, crustaceans and echinoderms serve as abundant food for fish. The density of life in the littoral and sublittoral reaches several kilograms, and sometimes tens of kilograms, mainly due to algae, mollusks and worms. The sublittoral is the main area of ​​human use of the raw materials of the sea - algae, invertebrates and fish. Below the sublittoral there is a bathyal, or continental slope, passing at a depth of 2500-3000 m (according to other sources, 2000 m) into the ocean floor, or abyssal, in turn, subdivided into upper abyssal (up to 3500 m) and lower abyssal (up to 6000 m) subzones . Within the bathyal, the density of life drops sharply to tens of grams and several grams per 1 m3, and in the abyssal to several hundred and even tens of mg per 1 l3. The largest part of the ocean floor is occupied by depths of 4000-6000 m. Deep-water depressions with their greatest depths up to 11000 m occupy only about 1% of the bottom area; this is the ultraabyssal zone. From the coasts to the greatest depths of the ocean, not only the density of life decreases, but also its diversity: many tens of thousands of species of plants and animals live in the surface zone of the ocean, and only a few dozen species of animals are known for the ultra-abyssal.

Pelagial also divided into vertical zones corresponding in depth to the benthal zones: epipelagial, bathypelagial, abyssopelagial. The lower boundary of the epipelagic zone (no more than 200 m) is determined by the penetration of sunlight in an amount sufficient for photosynthesis. Organisms that live in the water column, or pelagial, are pelagos. Like benthic fauna, plankton density also experiences quantitative changes from coasts to the center, parts of the oceans, and from the surface to the depths. Along the coasts, the density of plankton is determined by hundreds of mg per liter, sometimes several grams, and in the middle parts of the oceans, by several tens of grams. In the depths of the ocean, it drops to a few mg or fractions of a mg per 1 m3. The flora and fauna of the ocean undergoes regular changes with increasing depth. Plants live only in the upper 200-meter water column. Coastal macrophytes, in their adaptation to the nature of lighting, experience a change in composition: the uppermost horizons are occupied mainly by green algae, then brown algae come, and red algae penetrate the deepest. This is due to the fact that in water the red rays of the spectrum decay the fastest, and blue and violet rays go deepest. Plants are colored in a complementary color, which provides the best conditions for photosynthesis. The same color change is also observed in benthic animals: in the littoral and sublittoral they are predominantly gray and brown, and with depth, red color is more and more apparent, but the expediency of this color change in this case is different: coloring in an additional color makes them invisible and protects them from enemies. In pelagic organisms and in the epipelagic and deeper there is a loss of pigmentation, some animals, especially coelenterates, become transparent, like glass. In the most superficial layer of the sea, transparency facilitates the passage of sunlight through their body without harmful effects on their organs and tissues (especially in the tropics). In addition, the transparency of the body makes them invisible and saves them from enemies. Along with this, with depth, some planktonic organisms, especially crustaceans, acquire a red color, which makes them invisible in low light. Deep-sea fish do not obey this rule, most of them are painted black, although among them there are depigmented forms.

• to form knowledge about the World Ocean, its parts, boundaries, deep zones;
• to promote independent identification by students of the features of the deep zones of the ocean;

During the classes

Organizing time.

Learning new material.

Dramatization "Brief information about the oceans"

What is the World Ocean?

What parts does it consist of?

(From 4 oceans: Pacific, Atlantic, Indian and Arctic)

Today these oceans are our guests. (Students who are familiar with the "Oceans at a Glance" table on page 81 act as oceans. They show the number plates and maximum depths on a physical map of the world.)

Student: -I am the Pacific Ocean. My area is 180 million km, the average depth is

4028 m, and the maximum 11022 - the Mariana Trench).

(Similar to other oceans)

Student: - And all together we form the World Ocean (hold hands), the "Southern Ocean" runs up to them with the words: "I am the Southern Ocean, I am also part of the World Ocean."

Teacher: - Guys, how many oceans are there?

(Some scientists single out the Southern Ocean, but this is still a moot point. Therefore, it is believed that there are four.)

The teacher's story about the boundaries between oceans and seas using fig. 46 and maps of the oceans.

The boundaries between oceans are land masses.

Conditional boundaries.

The seas are marginal, inland and interisland.

(Students complete the activity on page 82)

Independent reading by students of the paragraph "Deep Zones of the World Ocean" and writing out in a notebook the definitions of concepts in bold.

Checking the completion of the task and showing bottom relief forms on the map of the oceans.

Anchoring

1) To consolidate, we use the headings "Let's check the knowledge", "And now more complex questions" on page 85

Name the oceans of the Earth.

(Pacific, Atlantic, Indian and Arctic)

Which ocean is the largest and which is the smallest?

(The Pacific Ocean is the largest and the Arctic Ocean is the smallest)

What is the sea?

(The sea is a part of the ocean, more or less isolated from it by land or elevations of underwater relief)

What are the boundaries between oceans?

(Where there is land between the oceans, this is an array of land, and where it is not, the boundaries are conventionally drawn along the meridians).

Name the deepest zones of the oceans.

(These are the continental shelf, the continental slope, the ocean floor and the deep-water trench).

What are the features of the layers of water at the bottom of the ocean?

(At the bottom of the ocean - ice water. The average temperature is about + 2 C)

Why is 80% of fish caught in the shelf zone?

(The water here is well warmed by the sun, there is a lot of oxygen, a large amount of organic matter that serves as food for fish is washed off the mainland)

Why are there no deep sea trenches in the Arctic Ocean?

(There are no zones of compression of the earth's crust as in other oceans).

2) Task on the contour map.

Mark the maximum depths of the oceans.

Homework: paragraph 10, assignment of the "Let's work with the map" section on page 85.

Behind the pages of a geography textbook.

Brief information from the history of ocean exploration.

There are several periods in the history of ocean exploration.

First period (7th-1st century BC - 5th century AD)

Reports are presented about the discoveries of the ancient Egyptians, Phoenicians, Romans and Greeks, who sailed the Mediterranean and Red Seas, went to the Atlantic and Indian Oceans.

Second period (5th-17th centuries)

In the early Middle Ages, some contribution to the study of the oceans was made by the Arabs, who sailed the Indian Ocean from the coast of East Africa to the Sunda Islands. In the 10-11 centuries. Scandinavians (Vikings) were the first Europeans to cross the Atlantic Ocean, discovering Greenland and the shores of Labrador. In the 15-16 centuries. Russian Pomors mastered navigation in the White Sea, went to the Barents and Kara Seas, reached the mouth of the Ob. But sea voyages developed especially widely in the 15th-17th centuries. - during the period of great geographical discoveries. The voyages of the Portuguese (Bartolomeu Dias, Vasco da Gama), the Spaniards (Christopher Columbus, Ferdinand Magellan), the Dutch (Abel Tasman and others) provided important information about the ocean. The first information about the depths, about the currents of the World Ocean appeared on the maps. Information about the nature of the Arctic Ocean was accumulated as a result of searches for sea routes along the northern coasts of Eurasia and North America to East Asia. They were led by expeditions by Willem Barents, Henry Hudson, John Cabot, Semyon Dezhnev, and others. In the middle of the 17th century, the accumulated information about individual parts of the World Ocean was systematized, and four oceans were identified.

Third period (18th-19th centuries)

Growing scientific interest in the nature of the oceans. In Russia, the participants of the Great Northern Expedition (1733-1742) studied the coastal parts of the Arctic Ocean.

The second half of the 18th century is the time of round-the-world expeditions. The most important was the voyage of James Cook and the Russian round-the-world expeditions, which only at the beginning of the 19th century. more than 40 were made. Expeditions led by I.F. Kruzenshtern and Yu.F. Lisyansky, F.F. Bellingshausen and M.P. Lazareva, V.I. Golovnina, S.O. Makarova and others collected extensive material on the nature of the World Ocean.

English expedition on the ship "Challenger" in 1872-1876. made a circumnavigation, collected material on the physical properties of ocean water, deep sediments at the bottom of the ocean, ocean currents.

The Arctic Ocean was explored by members of the Swedish-Russian expedition of A. Nordenskiöld on board the ship "Vega". F. Nansen's voyage was made on the Fram, which discovered a deep-water depression in the center of the Arctic Ocean. collected towards the end of the 19th century. the data made it possible to compile the first maps of the distribution of temperature and density of water at different depths, a scheme of water circulation, and bottom topography.

Fourth period (early 20th century)

Creation of specialized scientific maritime institutions that organized expeditionary oceanographic work. During this period, deep-sea trenches were discovered. Russian expeditions G.Ya. worked in the Arctic Ocean. Sedova, V.A. Rusanova, S.O. Makarov.

A special floating maritime institute was created in our country. First they explored the Arctic Ocean and its seas. In 1937, the first drifting station "North Pole" was organized (I.D. Papanin, E.E. Fedorov and others). In 1933-1940. the icebreaker "Sedov" was drifting near the Pole. A lot of new data on the nature of the central part of the Arctic Ocean has been obtained. The expedition on the icebreaking ship "Sibiryakov" in 1932 proved the possibility of sailing along the Northern Sea Route in one navigation.

New period (started in 50s)

In 1957-1959. The International Geophysical Year was held. Dozens of countries of the world participated in his work on the study of the nature of the Earth. Our country carried out research in the Pacific Ocean on board the Vityaz ship, expeditions worked in other oceans on the ships Akademik Kurchatov, Okean, Ob, and others. natural physical and geographical zonality of the World Ocean, the principles of its zoning have been developed. Much attention is paid to the study of the influence of the oceans on the formation of weather and its forecasting. The nature of tropical cyclones, the influence of the greenhouse effect on the change in the level of the Ocean, the quality of the aquatic environment and the factors affecting it are being studied. Biological resources and the reasons that determine their productivity are being studied, and forecasts of changes in the oceans are made in connection with the influence of human economic activity. Seabed surveys are underway.

The earth's crust is continental and oceanic. The mainland is land and there are mountains, plains and lowlands on it - you can see them and you can always walk on them. But what is the oceanic crust like, we learn from the topic “Bottom of the oceans” (grade 6).

Exploring the ocean floor

The first who began to study the oceans were the British. On the warship "Challenger" under the command of George Naes, they passed the entire water area of ​​the world and collected a lot of useful information that scientists systematized for another 20 years. They measured the temperature of water, animals, but most importantly, they were the first to determine the structure of the ocean floor.

The device used to measure depth is called an echo sounder. It is located at the bottom of the ship and periodically sends out a signal so strong that it can reach the bottom, reflect and return to the surface. According to the laws of physics, sound in water moves at a speed of 1500 meters per second. Thus, if the sound returned in 4 seconds, then it reached the bottom already on the 2nd, and the depth in this place is 3000 m.

What does the earth look like underwater?

Scientists identify the main parts of the ocean floor:

• Underwater margin of the continents;
• transition zone;
• Ocean bed.

Rice. 1. Relief of the ocean floor

The mainland always partially goes under water, so the underwater margin is divided into the continental shelf and the continental slope. The phrase "go out to sea" means to leave the border of the continental shelf and the slope.

The continental shelf (shelf) is a part of the land submerged under water to a depth of 200 m. On the map, it is highlighted in pale blue or white. The largest shelf is in the northern seas and on the Arctic Ocean. The smallest is in North and South America.

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The continental shelf warms up well, so this is the main area for resorts, farms for the extraction and cultivation of seafood. Oil is produced in this part of the ocean

The continental slope forms the boundaries of the oceans. The continental slope is considered from the edge of the shelf to a depth of 2 kilometers. If the slope were on land, then it would be a high cliff with very steep, almost straight slopes. But besides their steepness, there is another danger lurking in them - oceanic trenches. These are narrow gorges that go under water for thousands of meters. The largest and most famous trench is the Mariana Trench.

Ocean bed

Where the continental ledge ends, the ocean bed begins. This is its main part, where there are deep-water basins (4 - 7 thousand meters) and hills. The ocean bed is located at a depth of 2 to 6 km. The animal world is presented very poorly, because in this part there is practically no light and it is very cold.

Rice. 2. Image of the ocean floor

The most important place is occupied by the mid-ocean ridges. They are a large mountain system, like on land, only under water, stretching along the entire ocean. The total length of the ranges is about 70,000 km. They have their own complex structure: gorges and deep slopes.

Ridges form at the junctions of lithospheric plates and are sources of volcanoes and earthquakes. Some of the islands have very interesting origins. In those places where volcanic rock accumulated and eventually came to the surface, the island of Iceland was formed. That is why there are many geysers and hot springs, and the country itself is a unique nature reserve.

Rice. 3. Relief of the Atlantic Ocean

ocean floor

The soil of the ocean is marine sediment. They are of two types: continental and oceanic. The first ones formed from land: pebbles, sand, other particles from the shore. The second is bottom sediments formed by the ocean. These are the remains of marine life, volcanic ash.

What have we learned?

The structure of the ocean floor is very uneven. There are three main parts of it: the continental margin (divided into the continental shelf and slope), the transition zone and the ocean floor. It was in its central part that an amazing relief was formed - a mid-ocean ridge, representing a single mountain system encircling almost the entire Earth.

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