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Geography how many oceans. The World Ocean and its parts. World ocean - video

World Ocean- this is a salty, watery shell of the Earth that surrounds islands and continents. The totality of all the largest bodies of water on Earth. Something we just couldn't live without. The composition of the World includes all four oceans of our planet.

World Ocean

Most of the world is covered by seas and oceans. , which means that the water world is simply obliged to surprise us with interesting and extraordinary facts, which, by the way, it does. The world ocean is the totality of all the seas and oceans on Earth. This name comes from

• Greek Okeanos - the great river flowing around the Earth,
• English world Ocean,
• German . weltmeer,
• French Ocean, Ocean Mondial,
• Spanish Oceano, Oceano mundial)

Here it is important to answer correctly the question of how many oceans are there in the world? The French scientist de Florier introduced the term for the components of the World Ocean. This term is "the world's oceans". The names of these oceans are

In total, on the map you will find five oceans, which, together with the seas, represent a large organism with its own life and its own stories. The world ocean directly affects a huge number of natural processes, which is why it is a close object of various studies. So the nature of the currents determines the climate of the regions, and in the salty water unsuitable, at first glance, for life, there is a whole underwater world, with its large and very small representatives. oceans of the world rich in various fossils, in addition, they are a source of energy and food. The inhabitants of a large number of coastal areas are engaged in fishing, which is very often their main source of income. In this article, I will answer the most popular questions about the oceans.

The volume of the world ocean

The oceans are constantly exchanging with environment energy, warmth. He is an inexhaustible source for humanity. How big is this source? Let's find out. The ocean is an accumulation of water, the first to measure its amount was John Murray. And in 1983, Leningrad scientists Shiklomanov and Sokolov carried out their measurements. The data they published states that the volume of the world's oceans is 1.338 billion km 3 of water. Murray's measurements were corrected by only 1%.

World Ocean Map

Sea level rise

Many scientists are concerned sea ​​level rise. This is due to an anomaly in the Canadian Arctic Archipelago. An increase in the overall temperature leads to an increase in the melting of the ice mass. Gradually, over the course of three years, the archipelago loses its snow cover, and the volume of water increases by 60 km 3 when the temperature rises by only 1 0 .

World ocean - video

The video film "Secrets of the World Ocean" is its history and impact on our survival and on the planet.

film "Secrets of the deep sea. unknown world”- a popular science film made by oceanologists about what can be seen if the oceans are drained.

I hope that these two videos made the same impression on you as they did on me.

Which ocean is the largest in the world

The largest ocean in the world- Quiet, occupying a third of the World. This ocean is rightfully considered one of the most beautiful, amazing and beautiful, with a unique and diverse fauna. He also holds the record for the number of islands, which are 10 thousand. You can talk about this ocean endlessly. It is full of secrets, mysteries and mystical stories. It owes its name to the journey of Magellan, who sailed on its waters for three months. For all the time, the captain and his team have never struggled with bad weather. This ocean includes such seas as the Yellow, Japan, Bering, Tasman, Coral, Java, and East China seas. Also, very important international air and sea routes pass through the Pacific Ocean.

What is the smallest ocean in the world

The smallest ocean in the world- Arctic. Located between North America and Eurasia, it occupied only 4% of the area of ​​the entire World Ocean. It is also ten times smaller than the largest Pacific Ocean. Despite its rather modest size, this representative of the aquatic world has a unique fauna and is rich in stories.

What is the saltiest ocean in the world

List of oceans of the world complements and the saltiest ocean in the world, which is Atlantic. Despite the fact that it collects a large amount of fresh water, the percentage of salt here is 35.4%. The Atlantic Ocean is very interesting. In almost every place, the percentage of salt is the same. This feature is unique to him. The Indian Ocean, for example, does not fit this rule at all, since in some of its sections the salt saturation is several times higher than the salinity of the Atlantic Ocean.

Which ocean is the warmest in the world

The Pacific Ocean will appear several times in the lists of the most-most. This time he became the first, as he received the title of "C warmest ocean in the world". Despite the fact that there has always been a lot of controversy and doubt about this fact, just think a little logically, and it will become clear that this ocean deserves the title of the warmest. So the ice cover and the proximity to Antarctica of such oceans as the Arctic Ocean and the Atlantic definitely exclude them from possible contenders for this title. Only the Indian Ocean is in doubt, because it includes the warmest seas and currents. However, it also neighbors Antarctica, which deprives it of the opportunity to be called the warmest ocean. The coldest ocean is the Arctic Ocean. He is also the smallest.

The oceans and its parts: what else is worth knowing

• Scientists note that the moon has been studied much better than the oceans. We know only about 3% of the information about him.
• Despite the thickness of the water at the bottom, in some places there are underwater waterfalls. Currently, 7 such natural phenomena are known.
• Underwater rivers are located at the bottom - areas in which methane, hydrogen sulfide, seeps through cracks and mixes with water.
• The deepest point of the World Ocean is called the Mariana Trench. The maximum depth is over 11 km.
• Nearly 2.2 million different species of organisms live in the depths of the waters.
• The whale shark is one of the largest fish on earth. Its mass reaches 21.5 tons.
• The average depth of the world ocean is 3.984 km.
• At a depth of 1 km, you can find organisms that are amazing in appearance. They often look very intimidating.

The most beautiful ocean in the world

It is difficult to say which is the most beautiful ocean in the world, since each part of the World Ocean has its own charms and its own unique beauty. That is why you need to visit all the oceans and determine the favorite for yourself. Well, I'll help you a little - look at the photos of the ocean.

Oceans of the world - photo

Nearly 95% of all water on Earth is salty and unusable. It consists of seas, oceans and salt lakes. Collectively, all this is called the World Ocean. Its area is three-quarters of the entire area of ​​the planet.

The oceans - what is it?

The names of the oceans have been familiar to us since elementary school. This is the Pacific, otherwise called the Great, Atlantic, Indian and Arctic. All of them together are called the World Ocean. Its area is more than 350 million km2. This is the largest area even on a planetary scale.

The continents divide the World Ocean into four oceans known to us. Each of them has its own characteristics, its own unique underwater world, which changes depending on the climatic zone, the temperature of the currents and the bottom topography. The map of the oceans shows that they are all interconnected. None of them is surrounded by land on all sides.

The science that studies the oceans is oceanology

How do we know that there are seas and oceans? Geography is a school subject that introduces us to these concepts for the first time. But a special science, oceanology, is engaged in a deeper study of the oceans. It considers water expanses as an integral natural object, studies the biological processes occurring inside it, and its relationship with other constituent elements of the biosphere.

This science studies the ocean depths in order to achieve the following goals:

• increasing the efficiency and ensuring the safety of underwater and surface navigation;
• optimization of the use of minerals from the ocean floor;
• maintaining the biological balance of the oceanic environment;
• improvement of meteorological forecasts.

How did the modern names of the oceans come about?

The name of each geographical object is given for a reason. Any name has certain historical background or is associated with characteristic features one territory or another. Let's find out when and how the names of the oceans originated and who came up with them.

• Atlantic Ocean. The works of the ancient Greek historian and geographer Strabo described this ocean, calling it Western. Later, some scientists called it the Hesperid Sea. This is confirmed by a document dated 90 BC. Already in the ninth century AD, Arab geographers voiced the name "Sea of ​​Darkness", or "Sea of ​​Darkness". It received such a strange name because of the clouds of sand and dust that the winds raised above it, constantly blowing from the African continent. For the first time, the modern name sounded in 1507, after Columbus reached the shores of America. Officially, such a name was fixed in geography in 1650 in the scientific works of Bernhard Waren.
• The Pacific Ocean was named so by the Spanish navigator. Despite the fact that it is quite stormy and there are often storms and tornadoes, during the expedition of Magellan, which lasted a year, the weather was always good, calm was observed, and this was the reason to think that the ocean was really quiet and calm. When the truth was revealed, no one began to rename the Pacific Ocean. In 1756, the explorer Bayush suggested calling it the Great, since it is the largest ocean of all. To this day, both of these names are used.
• The reason for giving the name was the many ice floes drifting in its waters, and, of course, the geographical location. His second name - Arctic - comes from the Greek word "arktikos", which means "northern".
• With the name of the Indian Ocean, everything is extremely simple. India is one of the first countries known to the ancient world. The waters that wash its banks were named after her.

four oceans

How many oceans are on the planet? This question seems to be the simplest, but for many years it has caused discussions and disputes among oceanologists. The standard list of oceans looks like this:

2. Indian.

3. Atlantic.

4. Arctic.

But since ancient times, there has been another opinion, according to which the fifth ocean stands out - the Antarctic, or the South. Arguing for such a decision, oceanologists cite as evidence the fact that the waters washing the shores of Antarctica are very peculiar and the system of currents in this ocean differs from the rest of the water expanses. Not everyone agrees with this decision, so the problem of dividing the World Ocean remains relevant.

The characteristics of the oceans are different depending on many factors, although it may seem that they are all the same. Let's get acquainted with each of them and find out the most important information about all of them.

Pacific Ocean

It is also called the Great, because it has the largest area among all. The Pacific Ocean basin occupies a little less than half the area of ​​​​all the world's water spaces and is equal to 179.7 million km².

The composition includes 30 seas: Japan, Tasmanovo, Javanese, South China, Okhotsk, Philippine, New Guinea, Savu Sea, Halmahera Sea, Koro Sea, Mindanao Sea, Yellow, Visayan Sea, Aki Sea, Solomonovo, Bali Sea, Samair Sea, Coral, Banda, Sulu, Sulawesi, Fiji, Moluckoe, Komotes, Seram Sea, Flores Sea, Sibuyan Sea, East China Sea, Bering Sea, Amudesena Sea. All of them occupy 18% of the total area of ​​the Pacific Ocean.

It is also the leader in terms of the number of islands. There are about 10 thousand of them. The largest islands in the Pacific Ocean are New Guinea and Kalimantan.

More than a third of the world's reserves are in the depths of the seabed natural gas and oil, the active extraction of which occurs mainly in the shelf zones of China, the United States of America and Australia.

Many transport routes connecting the countries of Asia with South and North America.

Atlantic Ocean

It is the second largest in the world, and this is clearly demonstrated by the map of the oceans. Its area is 93,360 thousand km2. The Atlantic Ocean basin contains 13 seas. All of them have a coastline.

An interesting fact is that in the middle of the Atlantic Ocean there is the fourteenth sea - Sargasovo, called the sea without coasts. Its boundaries are ocean currents. It is considered the largest sea in the world in terms of area.

Another feature of this ocean is the maximum inflow of fresh water, which is provided by the large rivers of North and South America, Africa and Europe.

In terms of the number of islands, this ocean is the exact opposite of the Pacific. There are very few of them here. But it is in the Atlantic Ocean that the largest island on the planet - Greenland - and the most remote island - Bouvet - are located. Although sometimes Greenland is ranked among the islands of the Arctic Ocean.

Indian Ocean

Interesting facts about the third largest ocean will make us wonder even more. The Indian Ocean was the first known and explored. He is the custodian of the largest complex of coral reefs.

The waters of this ocean hold a secret that has not yet been properly explored. The fact is that luminous circles of the correct form periodically appear on the surface. According to one version, this is the glow of plankton rising from the depths, but their ideal spherical shape is still a mystery.

Not far from the island of Madagascar, you can observe a one-of-a-kind natural phenomenon - an underwater waterfall.

Now some facts about the Indian Ocean. Its area is 79,917 thousand km2. The average depth is 3711 m. It washes 4 continents and has 7 seas. Vasco da Gama is the first explorer to swim across the Indian Ocean.

Interesting facts and characteristics of the Arctic Ocean

It is the smallest and coldest of all oceans. Area - 13,100 thousand km 2. It is also the shallowest, the average depth of the Arctic Ocean is only 1225 m. It consists of 10 seas. By the number of islands, this ocean ranks second after the Pacific.

The central part of the ocean is covered with ice. In the southern regions, floating ice floes and icebergs are observed. Sometimes you can find whole ice 30-35 m thick. It was here that the infamous Titanic crashed, colliding with one of them.

Despite the harsh climate, the Arctic Ocean is a habitat for many species of animals: walruses, seals, whales, gulls, jellyfish and plankton.

depth of the oceans

We already know the names of the oceans and their features. But what is the deepest ocean? Let's look into this issue.

The contour map of the oceans and the ocean floor shows that the bottom relief is as diverse as the relief of the continents. Under the thickness sea ​​water recesses, depressions and elevations like mountains are hidden.

The average depth of all four oceans taken together is 3700 m. The Pacific Ocean is considered the deepest, the average depth of which is 3980 m, followed by the Atlantic - 3600 m, followed by the Indian - 3710 m. The last in this list, as already mentioned, is the Arctic Ocean, the average depth of which is only 1225 m.

Salt is the main feature of ocean waters

Everyone knows how the water of the seas and oceans differs from fresh river water. Now we will be interested in such a characteristic of the oceans as the amount of salt. If it seems to you that the water is equally salty everywhere, you are very much mistaken. Salt concentrations in ocean waters can vary greatly, even within a few kilometers.

The average salinity of ocean waters is 35 ‰. If we consider this indicator separately for each ocean, then the Arctic Ocean is the least salty of all: 32 ‰. Pacific Ocean - 34.5 ‰. The salt content in the water is low here due to the large amount of precipitation, especially in the equatorial zone. Indian Ocean - 34.8‰. Atlantic - 35.4 ‰. It is important to note that bottom waters have a lower salt concentration than surface waters.

The most salty seas of the World Ocean are the Red (41 ‰), the Mediterranean Sea and the Persian Gulf (up to 39 ‰).

World ocean records

• The deepest place in the World Ocean is its depth of 11,035 m from the surface water level.
• If we consider the depth of the seas, then the Philippine sea is considered the deepest. Its depth reaches 10,540 m. The second place in this indicator is the Coral Sea with a maximum depth of 9140 m.
• The largest ocean is the Pacific. Its area is larger than the area of ​​the entire earth's land.
• The most salty sea is the Red Sea. It is located in the Indian Ocean. Salt water well supports all objects that fall into it, and it takes a lot of effort to drown in this sea.
• The most mysterious place is located in the Atlantic Ocean, and its name is Bermuda Triangle. It is associated with many legends and mysteries.
• The most poisonous sea creature is the blue-ringed octopus. He lives in the Indian Ocean.
• The largest accumulation of corals in the world - the Great Barrier Reef, is located in the Pacific Ocean.

The largest oceans are the Pacific, Atlantic and Indian. The Pacific Ocean (area 178,684,000 km²) is round in plan and occupies almost half of the water surface of the globe. The Atlantic Ocean (91,660,000 km²) is shaped like a wide S, with its western and eastern coasts nearly parallel. The Indian Ocean, with an area of ​​76,174,000 km², has the shape of a triangle.

The Arctic Ocean with an area of ​​​​only 14,750,000 km² is surrounded by land on almost all sides. Like Quiet, it has a rounded shape. Some geographers identify another ocean - the Antarctic, or the South - a body of water surrounding Antarctica with an area of ​​20,327,000 km².

ocean and atmosphere

The oceans, the average depth of which is approx. 4 km, contains 1350 million km3 of water. The atmosphere, enveloping the entire Earth in a layer several hundred kilometers thick, with much great reason than the World Ocean can be considered as a "shell". Both the ocean and the atmosphere are the fluids in which life exists; their properties determine the habitat of organisms. Circulation flows in the atmosphere affect the general circulation of water in the oceans, and the properties of ocean waters largely depend on the composition and temperature of the air. In turn, the ocean determines the main properties of the atmosphere and is a source of energy for many processes occurring in the atmosphere. The circulation of water in the ocean is affected by winds, the rotation of the Earth, and land barriers.

Ocean and climate

It is well known that the temperature regime and other climatic characteristics of the area at any latitude can change significantly in the direction from the ocean coast to the interior of the mainland. Compared to land, the ocean heats up more slowly in summer and cools more slowly in winter, smoothing out temperature fluctuations on adjacent land.

The atmosphere receives from the ocean a significant part of the heat coming to it and almost all of the water vapor. The vapor rises, condenses, and forms clouds that are carried by the winds and support life on the planet, falling as rain or snow. However, only surface water; more than 95% of the water is in the depths, where its temperature remains virtually unchanged.

Composition of sea water

The ocean water is salty. The salty taste comes from the 3.5% dissolved minerals it contains—mainly sodium and chlorine compounds—the main ingredients in table salt. Magnesium is next in number, followed by sulfur; all common metals are also present. Of the non-metallic components, calcium and silicon are especially important, since they are involved in the structure of the skeletons and shells of many marine animals. Due to the fact that the water in the ocean is constantly mixed by waves and currents, its composition is almost the same in all oceans.

sea ​​water properties

The density of sea water (at a temperature of 20 ° C and a salinity of approx. 3.5%) is approximately 1.03, i.e. slightly higher than the density of fresh water (1.0). The density of water in the ocean varies with depth due to the pressure of the overlying layers, as well as depending on temperature and salinity. In the deepest parts of the ocean, the waters tend to be saltier and colder. The densest masses of water in the ocean can remain at depth and maintain a lower temperature for more than 1000 years.

Since sea water has a low viscosity and high surface tension, it offers relatively little resistance to the movement of a ship or swimmer and flows quickly from various surfaces. The predominant blue color of sea water is associated with the scattering of sunlight by small particles suspended in water.

Sea water is much less transparent to visible light than air, but more transparent than most other substances. The penetration of sunlight into the ocean to a depth of 700 m has been recorded. Radio waves penetrate the water column only to a shallow depth, but sound waves can propagate under water for thousands of kilometers. The speed of sound propagation in sea water fluctuates, averaging 1500 m per second.

The electrical conductivity of sea water is about 4000 times higher than that of fresh water. The high salt content prevents its use for irrigation and irrigation of agricultural crops. It is also unsuitable for drinking.

inhabitants

Life in the ocean is extremely diverse - more than 200,000 species of organisms live there. Some of them, such as the lobe-finned coelacanth fish, are living fossils whose ancestors flourished here more than 300 million years ago; others have appeared more recently. Most marine organisms are found in shallow waters where sunlight penetrates to promote photosynthesis. Zones enriched with oxygen and nutrients, such as nitrates, are favorable for life. Widely known is the phenomenon of "upwelling" (English upwelling), - the rise to the surface of deep sea waters enriched with nutrients; wealth is associated with it organic life on some coasts. Life in the ocean is represented by a wide variety of organisms - from microscopic single-celled algae and tiny animals to whales exceeding 30 m in length and larger than any animal that has ever lived on land, including the largest dinosaurs. Oceanic biota is divided into the following main groups.

Plankton

Plankton is a mass of microscopic plants and animals that are not capable of independent movement and live in the near-surface well-lit layers of water, where they form floating "feeding grounds" for larger animals. Plankton consists of phytoplankton (including plants such as diatoms) and zooplankton (jellyfish, krill, crab larvae, etc.).

Nekton

Nekton consists of free-floating organisms in the water column, mostly predatory, and includes more than 20,000 species of fish, as well as squid, seals, sea lions, and whales.

Benthos

Benthos consists of animals and plants that live on or near the ocean floor, both at great depths and in shallow water. Plants represented by various algae (for example, brown ones) are found in shallow water, where sunlight penetrates. Of the animals, sponges, sea lilies (at one time considered extinct), brachiopods, and others should be noted.

food chains

More than 90% of the organic substances that form the basis of life in the sea are synthesized under sunlight from minerals and other components by phytoplankton, which abundantly inhabit the upper layers of the water column in the ocean. Some organisms that make up zooplankton eat these plants and in turn are a food source for larger animals that live at greater depths. Those are eaten by larger animals that live even deeper, and this pattern can be traced to the very bottom of the ocean, where the largest invertebrates, such as glass sponges, receive the nutrients they need from the remains of dead organisms - organic detritus that sinks to the bottom from the overlying water column. However, it is known that many fish and other free-roaming animals have managed to adapt to extreme conditions. high pressure, low temperature and constant darkness, characteristic of great depths.

Waves, tides, currents

Like the entire universe, the ocean is never at rest. A variety of natural processes, including such catastrophic ones as underwater earthquakes or volcanic eruptions, cause the movement of ocean waters.

Waves

Ordinary waves are caused by wind blowing at varying speeds over the surface of the ocean. First, ripples appear, then the surface of the water begins to rise and fall rhythmically. Although the water surface rises and falls at the same time, individual particles of water move along a trajectory that is almost vicious circle, with virtually no horizontal displacement. As the wind gets stronger, the waves get higher. In the open sea, the height of the crest of a wave can reach 30 m, and the distance between adjacent crests is 300 m.

Approaching the shore, the waves form breakers of two types - diving and sliding. Diving breakers are characteristic of waves that originated at a distance from the coast; they have a concave front, their crest overhangs and collapses like a waterfall. Sliding breakers do not form a concave front, and the wave declines gradually. In both cases, the wave rolls onto the shore and then rolls back.

catastrophic waves

Catastrophic waves can occur as a result of a sharp change in the depth of the seabed during the formation of faults (tsunamis), during severe storms and hurricanes (storm surges), or during avalanches and landslides of cliffs.

Tsunamis can propagate in the open ocean at speeds up to 700–800 km/h. When approaching the shore, the tsunami wave slows down, and its height simultaneously increases. As a result, a wave with a height of up to 30 m or more (relative to the mean ocean level) rolls onto the coast. Tsunamis have a huge destructive force. Although areas close to seismically active zones such as Alaska, Japan, Chile suffer the most from them, waves from distant sources can cause significant damage. Similar waves occur during explosive volcanic eruptions or the collapse of crater walls, as, for example, during the volcanic eruption on the island of Krakatau in Indonesia in 1883.

Even more destructive can be storm waves generated by hurricanes (tropical cyclones). Repeatedly similar waves crashed on the coast in the upper part of the Bay of Bengal; one of them in 1737 led to the death of about 300 thousand people. Now, thanks to a significantly improved early warning system, it is possible to warn the population of coastal cities in advance of approaching hurricanes.

Catastrophic waves caused by landslides and rock falls are relatively rare. They arise as a result of the fall of large blocks of rock into deep-sea bays; in this case, a huge mass of water is displaced, which falls on the shore. In 1796, a landslide came down on the island of Kyushu in Japan, which had tragic consequences: three huge waves generated by it claimed the lives of approx. 15 thousand people.

tides

Tides roll on the shores of the ocean, as a result of which the water level rises to a height of 15 m or more. The main cause of tides on the surface of the Earth is the attraction of the Moon. There are two high tides and two low tides every 24 hours and 52 minutes. Although these level fluctuations are only noticeable near the coast and in the shallows, they are known to manifest themselves in the open sea as well. Many very strong currents in the coastal zone are caused by tides, therefore, for safe navigation, sailors need to use special tables of currents. In the straits connecting the Inland Sea of ​​Japan with the open ocean, tidal currents reach a speed of 20 km / h, and in the Seymour-Narrows Strait off the coast of British Columbia (Vancouver Island) in Canada, a speed of approx. 30 km/h.

currents

Currents in the ocean can also be created by waves. Coastal waves approaching the shore at an angle cause relatively slow alongshore currents. Where the current deviates from the shore, its speed increases sharply - a discontinuous current is formed, which can be dangerous for swimmers. The rotation of the Earth causes major ocean currents to move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Some of the currents are associated with the richest fishing grounds, such as the Labrador Current off the eastern coast of North America and the Peruvian Current (or Humboldt) off the coast of Peru and Chile.

Turbid currents are among the strongest currents in the ocean. They are caused by the movement of a large volume of suspended sediment; these sediments can be carried by rivers, be the result of waves in shallow water, or be formed by a landslide on an underwater slope. Ideal conditions for the origin of such currents exist in the tops of submarine canyons located near the coast, especially at the confluence of rivers. Such currents develop speeds from 1.5 to 10 km / h and sometimes damage submarine cables. After the 1929 earthquake with its epicenter in the area of ​​the Great Newfoundland Bank, many transatlantic cables connecting Northern Europe and the USA were damaged, probably due to strong turbidity currents.

Shores and coastlines

The maps clearly show an extraordinary variety of coastlines. Examples include indented coastlines with islands and winding straits (in Maine, southern Alaska, and Norway); shores of relatively simple outline, as on much of the west coast of the United States; deeply penetrating and branching bays (for example, Chesapeake) in the middle part of the Atlantic coast of the USA; protruding low-lying coast of Louisiana near the mouth of the Mississippi River. Similar examples can be given for any latitude and any geographic or climatic region.

Shore evolution

First of all, let's look at how the sea level has changed over the past 18 thousand years. Just before that, most of the land at high latitudes was covered by huge glaciers. As these glaciers melted, melt water entered the ocean, as a result of which its level rose by about 100 m. At the same time, many mouths of the rivers were flooded - this is how estuaries were formed. Where glaciers have created valleys deepened below sea level, deep bays (fjords) have formed with numerous rocky islands, as, for example, in the coastal zone of Alaska and Norway. When attacking low-lying coasts, the sea also flooded the river valleys. On the sandy coasts, as a result of wave activity, low barrier islands were formed, stretched along the coast. Such forms are found off the southern and southeastern coasts of the United States. Sometimes barrier islands form accumulative coastal protrusions (for example, Cape Hatteras). At the mouths of rivers carrying a large amount of sediment, deltas appear. On tectonic block shores experiencing uplifts that compensated for sea level rise, rectilinear abrasion ledges (cliffs) can form. On the island of Hawaii, as a result of volcanic activity, lava flows flowed into the sea and lava deltas formed. In many places, the development of the coast proceeded in such a way that the bays formed during the flooding of the mouths of the rivers continued to exist - for example, the Chesapeake Bay or the bays on the northwestern coast of the Iberian Peninsula.

In the tropics, rising sea levels promoted more intensive growth of corals on the outer (marine) side of the reefs, so that lagoons formed on the inner side, separating the barrier reef from the coast. A similar process also took place where, against the background of a rise in sea level, the island was submerged. At the same time, the barrier reefs on the outer side were partially destroyed during storms, and coral fragments were piled up by storm waves above calm sea level. Reef rings around submerged volcanic islands have formed atolls. In the last 2000 years, there has been practically no rise in the level of the World Ocean.

Beaches

Beaches have always been highly valued by man. They are composed mainly of sand, although there are also pebble and even small boulder beaches. Sometimes sand is a shell crushed by waves (the so-called shell sand). In the profile of the beach, sloping and almost horizontal parts stand out. The angle of inclination of the coastal part depends on the sand that composes it: on beaches composed of fine sand, the frontal zone is the most gentle; on coarse-grained sand beaches, the slopes are somewhat greater, and the steepest ledge is formed by pebble and boulder beaches. The rear zone of the beach is usually located above sea level, but sometimes huge storm waves flood it too.

There are several types of beaches. For the coasts of the United States, the most typical are long, relatively straight beaches, bordering the barrier islands from the outside. Such beaches are characterized by alongshore hollows, where currents dangerous for swimmers can develop. On the outer side of the hollows there are sand bars stretched along the coast, where the destruction of the waves occurs. With strong waves, discontinuous currents often occur here.

Irregularly shaped rocky shores usually form many small bays with small isolated stretches of beaches. These bays are often protected from the sea by rocks or underwater reefs protruding above the surface of the water.

On the beaches, formations created by waves are common - beach festoons, ripple marks, traces of wave splash, gullies formed during the runoff of water at low tide, as well as traces left by animals.

When beaches are washed away during winter storms, sand moves towards open sea or along the coast. When the weather is calmer in summer, new masses of sand come to the beaches, brought by rivers or formed when coastal ledges are washed away by waves, and thus the beaches are restored. Unfortunately, this compensatory mechanism is often disrupted by human intervention. The construction of dams on rivers or the construction of bank protection walls prevents the flow of material to the beaches to replace the material washed away by winter storms.

In many places, sand is carried by waves along the coast, mainly in one direction (the so-called alongshore sediment flow). If coastal structures (dams, breakwaters, piers, groins, etc.) block this flow, then the beaches “upstream” (i.e., located on the side from which the sediment comes from) are either washed away by waves or expand beyond sediment input, while the "downstream" beaches are hardly fed by new sediments.

The relief of the bottom of the oceans

At the bottom of the oceans are huge mountain ranges, deep crevices with steep walls, extended ridges and deep rift valleys. In fact, the seabed is no less rugged than the land surface.

Shelf, continental slope and continental foot

The platform that fringes the continents and is called the continental shelf, or shelf, is not as flat as it was once believed. Rock ledges are common on the outer part of the shelf; Bedrock often comes out on the part of the continental slope adjacent to the shelf.

The average depth of the outer edge (edge) of the shelf separating it from the continental slope is approx. 130 m. Near the shores subjected to glaciation, hollows (troughs) and depressions are often noted on the shelf. So, off the fjord coasts of Norway, Alaska, and southern Chile, deep-water areas are found near the modern coastline; deep water troughs exist off the coast of Maine and in the Gulf of St. Lawrence. Glacier-carved troughs often run across the entire shelf; in some places along them there are shallows exceptionally rich in fish, for example, the banks of Georges or the Great Newfoundland.

Shelves off the coast, where there was no glaciation, have a more uniform structure, however, they often have sandy or even rocky ridges that rise above general level. During the Ice Age, when the level of the ocean dropped due to the fact that huge masses of water accumulated on land in the form of ice sheets, river deltas were created in many places of the current shelf. In other places on the outskirts of the continents, at the then sea level marks, abrasion platforms were cut into the surface. However, the results of these processes, which took place under the conditions of the low level of the World Ocean, were significantly transformed tectonic movements and sedimentation in the subsequent postglacial epoch.

The most surprising thing is that in many places on the outer shelf one can still find deposits that formed in the past, when the sea level was more than 100 m below the present. There are also found the bones of mammoths who lived in the Ice Age, and sometimes the tools of primitive man.

Speaking about the continental slope, the following features should be noted: firstly, it usually forms a clear and well-defined boundary with the shelf; secondly, it is almost always crossed by deep submarine canyons. The average angle of inclination on the continental slope is 4°, but there are also steeper, sometimes almost vertical sections. At the lower boundary of the slope in the Atlantic and Indian Oceans there is a gently sloping surface, called the "continental foot". Along the periphery of the Pacific Ocean, the continental foot is usually absent; it is often replaced by deep sea trenches, where tectonic movements (faults) generate earthquakes and where most tsunamis originate.

submarine canyons

These canyons, cut into the seabed for 300 m or more, are usually characterized by steep sides, a narrow bottom, and sinuosity in plan; like their land-based counterparts, they receive numerous tributaries. The deepest known underwater canyon, the Grand Bahama Canyon, is incised for almost 5 km.

Despite the similarity to the formations of the same name on land, the majority of submarine canyons are not ancient river valleys submerged below sea level. Turbid currents are quite capable of both working out a valley at the bottom of the ocean, and deepening and transforming a flooded river valley or a depression along a fault line. Submarine valleys do not remain unchanged; sediment transport is carried out along them, as evidenced by the signs of ripples on the bottom, and their depth is constantly changing.

deep sea trenches

Much has become known about the relief of the deep parts of the ocean floor as a result of large-scale research that unfolded after the Second World War. The greatest depths are confined to the deep-sea trenches of the Pacific Ocean. The deepest point - the so-called. "Challenger Deep" - is located within the Mariana Trench in the southwest Pacific Ocean. The following are the greatest depths of the oceans, with their names and locations:

• Arctic - 5527 m in the Greenland Sea;
• Atlantic - Puerto Rico Trench (off the coast of Puerto Rico) - 8742 m;
• Indian - Sunda (Yavansky) trench (west of the Sunda archipelago) - 7729 m;
• Quiet - the Mariana Trench (near the Mariana Islands) - 11,033 m; the Tonga trench (near New Zealand) - 10,882 m; Philippine Trench (near the Philippine Islands) - 10,497 m.

Mid-Atlantic Ridge

The existence of a large underwater ridge stretching from north to south across the central part of the Atlantic Ocean has long been known. Its length is almost 60 thousand km, one of its branches stretches into the Gulf of Aden to the Red Sea, and the other ends off the coast of the Gulf of California. The width of the ridge is hundreds of kilometers; its most striking feature is the rift valleys that can be traced along almost its entire length and resemble the East African rift zone.

An even more surprising discovery was that the main ridge is crossed at right angles to its axis by numerous ridges and hollows. These transverse ridges are traced in the ocean for thousands of kilometers. At the places where they intersect with the axial ridge, there are so-called. fault zones, which are associated with active tectonic movements and where the centers of large earthquakes are located.

A. Wegener's Continental Drift Hypothesis

Until about 1965, most geologists believed that the position and shape of the continents and ocean basins remained unchanged. There was a rather vague notion that the Earth was contracting, and that this contraction resulted in the formation of folded mountain ranges. When in 1912 the German meteorologist Alfred Wegener proposed the idea that the continents were moving (“drifting”) and that the Atlantic Ocean was formed in the process of widening a crack that split an ancient supercontinent, this idea was met with incredulity, despite a lot of evidence in its favor. (the similarity of the outlines of the eastern and western coasts of the Atlantic Ocean; the similarity of fossil remains in Africa and South America; traces of the great glaciations of the Carboniferous and Permian periods in the interval 350–230 million years ago in areas now located near the equator).

Growth (spreading) of the ocean floor. Gradually, Wegener's arguments were reinforced by the results of further research. It has been suggested that rift valleys within mid-ocean ridges originate as extensional fissures, which are then filled by rising magma from the depths. The continents and adjacent parts of the oceans form huge plates moving away from the underwater ridges. The frontal part of the American Plate is pushing against the Pacific Plate; the latter, in turn, moves under the mainland - a process called subduction occurs. There is a lot of other evidence in favor of this theory: for example, the confinement of earthquake centers, marginal deep-sea trenches, mountain ranges and volcanoes to these areas. This theory makes it possible to explain almost all major landforms of continents and ocean basins.

Magnetic anomalies

The most convincing argument in favor of the hypothesis of the expansion of the ocean floor is the alternation of bands of direct and reverse polarity (positive and negative magnetic anomalies), traced symmetrically on both sides of the mid-ocean ridges and running parallel to their axis. The study of these anomalies made it possible to establish that the spreading of the oceans occurs on average at a rate of several centimeters per year.

Plate tectonics

Another proof of the likelihood of this hypothesis was obtained with the help of deep-sea drilling. If, as follows from historical geology, the expansion of the oceans began in the Jurassic, no part of the Atlantic Ocean can be older than this time. Deep-sea boreholes have penetrated Jurassic deposits (formed 190–135 million years ago) in some places, but older ones have not been found anywhere. This circumstance can be considered weighty evidence; at the same time, it leads to the paradoxical conclusion that the ocean floor is younger than the ocean itself.

ocean research

Early research

The first attempts to explore the oceans were purely geographical in nature. Travelers of the past (Columbus, Magellan, Cook, etc.) made long tedious voyages across the seas and discovered islands and new continents. The first attempt to explore the ocean itself and its bottom was made by the British expedition on the Challenger (1872-1876). This voyage laid the foundations of modern oceanology. The echo sounding method, developed during the First World War, made it possible to compile new maps of the shelf and the continental slope. Special oceanological scientific institutions that appeared in the 1920s and 1930s extended their activities to deep-sea areas.

Modern stage

Real progress in research, however, begins only after the end of the Second World War, when the navies of various countries took part in the study of the ocean. At the same time, many oceanographic stations received support.

The leading role in these studies belonged to the USA and the USSR; on a smaller scale, similar work was carried out by Great Britain, France, Japan, West Germany and other countries. In about 20 years, it was possible to get a fairly complete picture of the topography of the ocean floor. On the published maps of the bottom relief, a picture of the distribution of depths emerged. Great importance they also acquired studies of the ocean floor using echo sounding, in which sound waves are reflected from the surface of bedrock buried under loose sediments. Now more is known about these buried deposits than about the rocks of the continental crust.

Submersibles with a crew on board

A big step forward in ocean research was the development of deep-sea submersibles with portholes. In 1960, Jacques Picard and Donald Walsh on the bathyscaphe "Trieste" I dived in the deepest known area of ​​the ocean - the "Abyss of the Challenger" 320 km southwest of Guam. The "diving saucer" by Jacques-Yves Cousteau turned out to be the most successful among devices of this type; with its help, it was possible to discover the amazing world of coral reefs and underwater canyons to a depth of 300 m. Another apparatus, Alvin, descended to a depth of 3650 m (with a design diving depth of up to 4580 m) and was actively used in scientific research.

deep sea drilling

Just as the concept of plate tectonics revolutionized geological theory, deep sea drilling revolutionized the understanding of geological history. An advanced drilling rig allows you to pass hundreds and even thousands of meters in igneous rocks. If it was necessary to replace the blunt bit of this installation, a casing string was left in the well, which could be easily detected by a sonar mounted on a new drill pipe bit, and thus continue drilling the same well. Cores from deep-sea wells have made it possible to fill in many gaps in the geological history of our planet and, in particular, have provided much evidence for the correctness of the ocean floor spreading hypothesis.

ocean resources

As the planet's resources increasingly struggle to meet the needs of a growing population, the ocean is becoming increasingly important as a source of food, energy, minerals and water.

Ocean food resources

Tens of millions of tons of fish, shellfish and crustaceans are caught in the oceans every year. In some parts of the oceans, modern factory ship fishing is very intensive. Some species of whales are almost completely exterminated. Continued intensive fishing may cause severe damage to such valuable commercial fish species as tuna, herring, cod, sea ​​bass, sardine, hake.

Fish farming

Large areas of the shelf could be singled out for fish breeding. At the same time, you can fertilize the seabed to ensure the growth of marine plants that feed on fish.

Mineral resources of the oceans

All the minerals that are found on land are also present in sea water. Salts, magnesium, sulfur, calcium, potassium, bromine are most common there. Recently, oceanologists have discovered that in many places the ocean floor is literally covered with a scattering of ferromanganese nodules with a high content of manganese, nickel and cobalt. Phosphorite concretions found in shallow water can be used as a raw material for the production of fertilizers. Sea water also contains valuable metals such as titanium, silver and gold. Currently, only salt, magnesium and bromine are extracted from sea water in significant quantities.

Oil

A number of large oil fields are already being developed on the shelf, for example, off the coast of Texas and Louisiana, in the North Sea, the Persian Gulf and off the coast of China. Exploration is ongoing in many other areas, such as off the coast of West Africa, off the east coast of the United States and Mexico, off the coast of Arctic Canada and Alaska, Venezuela and Brazil.

The ocean is a source of energy

The ocean is an almost inexhaustible source of energy.

Tidal energy

It has long been known that tidal currents passing through narrow straits can be used for energy in the same way as waterfalls and dams on rivers. Thus, for example, a tidal hydroelectric power station has been successfully operating in Saint-Malo in France since 1966.

Wave energy

Wave energy can also be used to generate electricity.

Thermal Gradient Energy

Nearly three-quarters of the solar energy that hits Earth comes from the oceans, so the ocean is the perfect giant heat sink. Energy generation, based on the use of the temperature difference between the surface and deep layers of the ocean, could be carried out on large floating power plants. Currently, the development of such systems is in the experimental stage.

Other resources

Other resources include pearls, which are formed in the body of some mollusks; sponges; algae used as fertilizers, food products and food additives, as well as in medicine as a source of iodine, sodium and potassium; deposits of guano - bird droppings mined on some atolls in the Pacific Ocean and used as fertilizer. Finally, desalination makes it possible to obtain fresh water from sea water.

ocean and man

Scientists believe that life originated in the ocean about 4 billion years ago. The special properties of water have had a huge impact on human evolution and still make life possible on our planet. Man used the seas as a way of trade and communication. Sailing the seas, he made discoveries. He turned to the sea in search of food, energy, material resources and inspiration.

Oceanography and Oceanology

Ocean research is often subdivided into physical oceanography, chemical oceanography, marine geology and geophysics, marine meteorology, ocean biology, and engineering oceanography. In most countries with access to the ocean, oceanographic research is being carried out.

International organizations

Among the most significant organizations involved in the study of the seas and oceans is the UN Intergovernmental Oceanographic Commission.