Sea currents. Sea currents are translational movements of masses of water in the seas and oceans, caused by: - ​​the action of friction between water and air; or - pressure gradients arising in water; or - tidal forces of the Moon and the Sun. Sea currents differ: in origin, in the nature of variability, in location and in physical and chemical properties.

Together with the concept of Warm and Cold Sea Currents, we are looking for definitions of these words: Terborch - (Terborch) Gerard (1617-8..1) - Dutch painter. Genre compositions from the life of wealthy townspeople (“A Glass of Lemonade,” c. 1665) are distinguished by calm contemplation, sophistication of silvery color, and masterly rendering of the texture of things. Terem - (from the Greek teremnon - dwelling) - in Dr. Rus''s upper residential tier is rich in mansions and chambers; There were also separate towers (above the gate, on a high basement). Teresina - (Teresina) - a city in the northeast of Brazil, the administrative center of the state. Piaui. 556 thousand inhabitants (1990). International airport. Food, textile industry. University. Philological Academy. Historical Museum. Teptsov - Oleg Pavlovich (b. 1954) - Russian film director, screenwriter. He made his debut in 1984. His success brought him thesis- ""Master Formator"" (1988). He also directed the feature film "The Initiated" (1989), as well as documentaries""Red... Tera... - (from the Greek teras - monster) - a prefix for the formation of names of multiple units, equal in size to 1012 original units; designated T. Example: 1 TN (teranyuton) = 1012 N. Terapiano - Yuri Konstantinovich (1892-1980) - Russian poet, literary critic. From the beginning 20s in exile (Constantinople, Paris). Religious and philosophical motives in lyrics (collections "Insomnia", 1935; "To the Wind", 1938; "Earthly Wandering", 1951;... Teresa - (Teresa) ( Mother Teresa) (in the world Agnes Gonja Bojaxhiu) (b. 1910), founder (1950, India) and abbess of the Catholic Order of Charity. In various countries she founded schools, medical centers, and shelters for the poor. Nobel Prize... Teratology - (from the Greek teras - genus teratos - freak and...logy), the science that studies deformities and malformations in plants, animals and humans. Terai is a strip of swampy foothill plains at the southern foot of the Himalayas, in India and Nepal. Height up to 900 m. Wet tropical forests(jungle) with tall grass. Partially drained and plowed. Teratology - (from the Greek teras - genus teratos - freak and...logy), the science that studies deformities and malformations in plants, animals and humans.

World ocean currents

Oceanic or sea currents are forward movement water masses in the oceans and seas caused by by various forces. Although the most significant cause of currents is wind, they can also be formed due to uneven salinity individual parts ocean or sea, differences in water levels, uneven heating of different areas of water areas. In the depths of the ocean there are eddies created by bottom irregularities; their size often reaches 100-300 km in diameter, they capture layers of water hundreds of meters thick.

If the factors causing currents are constant, then a constant current is formed, and if they are episodic in nature, then a short-term, random current is formed. According to the predominant direction, currents are divided into meridional, carrying their waters to the north or south, and zonal, spreading latitudinally - approx. from geoglobus.ru. Currents with higher water temperatures average temperature for the same latitudes they are called warm, below - cold, and currents that have the same temperature as the surrounding waters are called neutral.

Monsoon currents change direction from season to season, depending on how the offshore monsoon winds blow. Countercurrents move towards neighboring, more powerful and extended currents in the ocean.

The direction of currents in the World Ocean is influenced by the deflecting force caused by the rotation of the Earth - the Coriolis force. In the Northern Hemisphere, it deflects currents to the right, and in the Southern Hemisphere, to the left. The speed of currents on average does not exceed 10 m/s, and their depth extends to no more than 300 m. In the World Ocean, there are constantly thousands of large and small currents that circle the continents and merge into five giant rings. The system of currents in the World Ocean is called circulation and is associated primarily with general circulation atmosphere. Ocean currents redistribute solar heat absorbed by masses of water. They transport warm water, heated by the sun's rays at the equator, to high latitudes, and cold water from the polar regions, thanks to currents, it flows to the south. Warm currents contribute to an increase in air temperature, and cold currents, on the contrary, reduce it. Territories washed by warm currents have a warm and humid climate, while those near which cold currents pass have a cold and dry climate.

The most powerful current The World Ocean is the cold current of the Western Winds, also called the Antarctic Circumpolar (from the Latin cirkum - around - approx. from geoglobus.ru). The reason for its formation is strong and stable westerly winds, blowing from west to east over vast areas of the Southern Hemisphere from temperate latitudes to the coast of Antarctica. This current covers an area 2,500 km wide, extends to a depth of more than 1 km and transports up to 200 million tons of water every second. There are no Western Winds along the current path large massifs land, and it connects in its circular flow the waters of three oceans - the Pacific, Atlantic and Indian.

The Gulf Stream is one of the largest warm currents Northern Hemisphere. It passes through the Gulf Stream and carries the warm tropical waters of the Atlantic Ocean to high latitudes. This gigantic flow of warm water largely determines the climate of Europe, making it soft and warm. Every second, the Gulf Stream carries 75 million tons of water (for comparison: the Amazon, the deepest river in the world, carries 220 thousand tons of water). At a depth of about 1 km, a countercurrent is observed under the Gulf Stream.

UPWELLING

“Floating” is observed in many areas of the World Ocean deep waters to the surface of the sea. This phenomenon, called upwelling (from the English up - upward and well - to gush - approx. from geoglobus.ru), occurs, for example, if the wind drives away warm surface waters, and colder ones rise in their place. The water temperature in upwelling areas is lower than the average at a given latitude, which creates favorable conditions for the development of plankton, and therefore other marine organisms - fish and marine animals that feed on them. Upwelling areas are the most important fishing areas of the World Ocean. They are at western shores continents: Peruvian-Chilean - y South America, California - y North America, Benguela - in South-West Africa, Canary - in West Africa.

LAND BUILDING. Planet Earth consists of a thin, hard shell (crust 10-100 km thick), surrounded by a powerful aquatic hydrosphere and dense atmosphere. The Earth's interior is divided into three main regions: the crust, the mantle and the core. The Earth's crust is the upper part of the Earth's solid shell, with a thickness ranging from one (under the oceans) to several tens of kilometers. (under the continents). It consists of sedimentary layers and well-known minerals and rocks. Its deeper layers consist of various basalts. Beneath the crust is a hard silicate layer (presumably made from olivine) called the mantle, 1-3 thousand km thick, it surrounds the liquid part of the core, central part which is about 2000 km in diameter is solid.

Atmosphere.

The Earth, like most other planets, is surrounded by a gaseous envelope - an atmosphere that consists mainly of nitrogen and oxygen. No other planet has an atmosphere with the same chemical composition as Earth's. It is believed that it arose as a result of long-term chemical and biological evolution. The Earth's atmosphere is divided into several regions according to changes in temperature, chemical composition, physical condition and the degree of ionization of air molecules and atoms. The dense, breathable layers of the earth's atmosphere are no more than 4-5 km thick. Higher up, the atmosphere is very rarefied: its density decreases approximately three times for every 8 km of ascent. In this case, the air temperature first in the troposphere decreases to 220 K, but at an altitude of several tens of kilometers in the stratosphere it begins to increase to 270 K at an altitude of about 50 km, where the border with the next layer of the atmosphere passes - mesosphere(medium atmosphere). The increase in temperature in the upper stratosphere occurs due to the heating effect of ultraviolet and X-rays absorbed here. solar radiation, which does not penetrate into the lower layers of the atmosphere. In the mesosphere, the temperature again decreases to almost 180 K, after which above 180 km in thermosphere its very strong growth begins to values ​​​​of more than 1000 K. At altitudes above 1000 km, the thermosphere turns into the exosphere , from which dissipation of atmospheric gases into interplanetary space occurs outer space. An increase in temperature is associated with the ionization of atmospheric gases - the emergence of electrically conductive layers, which are generally called the earth's ionosphere.

Hydrosphere.

An important feature of the Earth is large number water, constantly present in different proportions in all three states of aggregation- gaseous (water vapor in the atmosphere), liquid (rivers, lakes, seas, oceans and, to a lesser extent, the atmosphere) and solid (snow and ice, mainly in glaciers X). Thanks to water balance The total amount of water on Earth must be conserved. The world ocean occupies most of the Earth's surface (361.1 million km 2 or 70.8% of the Earth's surface area), its average depth is about 3800 m, the greatest - 11,022 m (Mariana Trench in Pacific Ocean), water volume is 1370 million km 3, average salinity is 35 g/l. The area of ​​modern glaciers is about 11% of the land surface, which is 149.1 million km 2 (» 29.2%). The land rises above the level of the World Ocean by an average of 875 m ( highest height 8848 m - peak of Chomolungma in the Himalayas). It is believed that the existence of sedimentary rocks, the age of which (according to radioisotope analysis) exceeds 3.7 billion years, serves as evidence of the existence of vast bodies of water on Earth already in that distant era when the first living organisms supposedly appeared.

World ocean.

The world's oceans are conventionally divided into four oceans. The largest and deepest of them is the Pacific Ocean. With an area of ​​178.62 million km2, it occupies half of the entire water surface Earth. Its average depth (3980 m) is greater than the average depth of the World Ocean (3700 m). Within its boundaries is also the deepest depression - Mariana (11,022 m). More than half the volume of water in the World Ocean is concentrated in the Pacific Ocean (710.4 out of 1341 million km 3). The second largest is the Atlantic Ocean. Its area is 91.6 million km 2, the average depth is 3600 m, the greatest is 8742 m (in the area of ​​​​Puerto Rico), the volume is 329.7 million km 3. Next in size is the Indian Ocean, which occupies an area of ​​76.2 million km 2, an average depth of 3710 m, the greatest depth of 7729 m (near the Sunda Islands), and a water volume of 282.6 million km 3. The smallest and coldest Arctic Ocean, with an area of ​​only 14.8 million km2. It occupies 4% of the World Ocean), has average depth 1220 m (maximum 5527 m), water volume 18.1 million km 3. Sometimes the so-called Southern Ocean (code name southern parts Atlantic, Indian and Pacific oceans adjacent to the Antarctic continent). The oceans include seas. For the life of the Earth, the constantly occurring water cycle (moisture cycle) plays a huge role. This is a continuous closed process of water movement in the atmosphere, hydrosphere and earth's crust, consisting of evaporation, transfer of water vapor in the atmosphere, steam condensation, precipitation and water flow into the World Ocean. In this single process, there is a continuous transition of water from earth's surface into the atmosphere and back.

Sea currents.

Sea currents (ocean currents) are translational movements of masses of water in the seas and oceans, caused by various forces (the action of friction between water and air, pressure gradients arising in water, tidal forces of the Moon and the Sun). To the direction of sea currents great influence exerts the rotation of the Earth, deflecting currents in the Northern Hemisphere to the right, in the Southern Hemisphere - to the left. Sea currents are caused either by the friction of the wind on the surface of the sea (wind currents) or uneven distribution temperature and salinity of water (density currents), or level slope (discharge currents). According to the nature of variability, there are constant, temporary and periodic ( tidal origin), by location - surface, subsurface, intermediate, deep and bottom. According to physical and chemical properties - desalinated and salted.

4. Ocean currents.

© Vladimir Kalanov,
"Knowledge is power."

The constant and continuous movement of water masses is the eternal dynamic state of the ocean. If rivers on Earth flow to the sea along their inclined channels under the influence of gravity, then currents in the ocean are caused by various reasons. The main causes of sea currents are: wind (drift currents), unevenness or changes in atmospheric pressure (barogradient), attraction of water masses by the Sun and Moon (tidal), differences in water densities (due to differences in salinity and temperature), differences in levels created by influx river water from continents (stock).

Not every movement of ocean water can be called a current. In oceanography, sea currents are the forward movement of water masses in the oceans and seas..

Two physical strength cause currents - friction and gravity. Excited by these forces currents are called frictional And gravitational.

Currents in the World Ocean are usually caused by several reasons. For example, the mighty Gulf Stream is formed by the merger of density, wind and discharge currents.

The initial direction of any flow soon changes under the influence of the rotation of the Earth, frictional forces, configuration coastline and bottom.

According to the degree of stability, currents are distinguished sustainable(for example, North and South trade wind currents), temporary (surface currents northern Indian Ocean, caused by monsoons) and periodic(tidal).

Based on their position in the ocean water column, currents can be superficial, subsurface, intermediate, deep And bottom. Moreover, the definition of “surface current” sometimes refers to a fairly thick layer of water. For example, the thickness of inter-trade wind countercurrents in the equatorial latitudes of the oceans can be 300 m, and the thickness of the Somali Current in the northwestern part of the Indian Ocean reaches 1000 meters. It is noted that deep currents are most often directed in the opposite direction compared to those moving above them surface waters.

Currents are also divided into warm and cold. Warm currents move water masses from low geographical latitudes to higher ones, and cold- in the opposite direction. This division of currents is relative: it characterizes only surface temperature moving waters in comparison with surrounding water masses. For example, in the warm North Cape Current (Barents Sea) the temperature of the surface layers is 2–5 °C in winter and 5–8 °C in summer, and in the cold Peruvian Current (Pacific Ocean) - all year round from 15 to 20 °C, in the cold Canary Islands (Atlantic) - from 12 to 26 °C.

The main source of data is ARGO buoys. The fields were obtained using optimal analysis.

Some ocean currents combine with other currents to form a basin-wide gyre.

In general, the constant movement of water masses in the oceans is complex system cold and warm currents and countercurrents, both surface and deep.

The most famous for residents of America and Europe is, of course, the Gulf Stream. Translated from English, this name means Current from the Bay. Previously, it was believed that this current begins in the Gulf of Mexico, from where it rushes through the Strait of Florida into the Atlantic. Then it turned out that the Gulf Stream carries only a small fraction of its flow from this bay. Having reached the latitude of Cape Hatteras on the Atlantic coast of the United States, the current receives a powerful influx of water from the Sargasso Sea. This is where the Gulf Stream itself begins. The peculiarity of the Gulf Stream is that when it enters the ocean, this current deviates to the left, whereas under the influence of the Earth’s rotation it should deviate to the right.

The parameters of this powerful current are very impressive. The surface speed of water in the Gulf Stream reaches 2.0–2.6 meters per second. Even at a depth of 2 km, the speed of the water layers is 10–20 cm/s. When leaving the Strait of Florida, the current carries out 25 million cubic meters of water per second, which is 20 times more than the total flow of all the rivers of our planet. But after adding the flow of water from the Sargasso Sea (Antilles Current), the power of the Gulf Stream already reaches 106 million cubic meters of water per second. This powerful stream moves northeast to the Great Newfoundland Bank, and from here it turns south and, together with the Slope Current that separated from it, is included in the North Atlantic water cycle. The depth of the Gulf Stream is 700–800 meters, and its width reaches 110–120 km. The average temperature of the surface layers of the current is 25–26 °C, and at depths of about 400 m it is only 10–12 °C. Therefore, the idea of ​​the Gulf Stream as warm current It is the surface layers of this flow that create it.

Let us note another current in the Atlantic - the North Atlantic. It runs across the ocean to the east, towards Europe. The North Atlantic Current is less powerful than the Gulf Stream. The water flow here is from 20 to 40 million cubic meters per second, and the speed is from 0.5 to 1.8 km/h, depending on the location. However, the influence of the North Atlantic Current on the climate of Europe is very noticeable. Together with the Gulf Stream and other currents (Norwegian, North Cape, Murmansk), the North Atlantic Current softens the climate of Europe and the temperature regime of the seas washing it. The warm Gulf Stream current alone cannot have such an impact on the climate of Europe: after all, the existence of this current ends thousands of kilometers from the shores of Europe.

Now let's return to the equatorial zone. The air here is much hotter than in other areas. globe. The heated air rises and reaches upper layers troposphere and begins to spread towards the poles. Approximately in the area of ​​28-30° northern and southern latitudes, the cooled air begins to descend. More and more new air masses flowing from the equator area create excess pressure in subtropical latitudes, while above the equator itself due to the outflow of heated air air masses the pressure is constantly low. From the districts high blood pressure air rushes into areas low pressure, that is, to the equator. The rotation of the Earth around its axis deflects the air from the direct meridional direction to the west. This creates two powerful flows of warm air, called trade winds. In the tropics of the Northern Hemisphere, trade winds blow from the northeast, and in the tropics of the Southern Hemisphere - from the southeast.

For simplicity of presentation, we do not mention the influence of cyclones and anticyclones in the temperate latitudes of both hemispheres. It is important to emphasize that the trade winds are the most stable winds on Earth; they blow constantly and cause warm equatorial currents that move huge masses of ocean water from east to west.

Equatorial currents benefit navigation by helping ships cross the ocean from east to west more quickly. At one time, H. Columbus, without knowing anything in advance about the trade winds and equatorial currents, felt their powerful effect during his sea voyages.

Based on the constancy of equatorial currents, the Norwegian ethnographer and archaeologist Thor Heyerdahl put forward a theory about the initial settlement of the Polynesian islands by the ancient inhabitants of South America. To prove the possibility of sailing on primitive ships, he built a raft, which, in his opinion, was similar to the watercraft that the ancient inhabitants of South America could use when crossing the Pacific Ocean. On this raft, called Kon-tiki, Heyerdahl, along with five other daredevils, made a perilous voyage from the coast of Peru to the Tuamotu archipelago in Polynesia in 1947. In 101 days, he swam a distance of about 8 thousand kilometers along one of the branches of the southern equatorial current. The brave men underestimated the power of the wind and waves and almost paid for it with their lives. Up close, the warm equatorial current, driven by the trade winds, is not at all gentle as one might think.

Let us briefly look at the characteristics of other currents in the Pacific Ocean. Part of the waters of the North Equatorial Current in the area of ​​the Philippine Islands turns north, forming the warm Kuroshio Current (in Japanese, “Dark Water”), which in a powerful stream flows past Taiwan and the southern Japanese islands to the northeast. The width of Kuroshio is about 170 km, and the penetration depth reaches 700 m, but in general this current is inferior to the Gulf Stream in terms of fashionability. About 36°N Kuroshio turns into the ocean, moving into the warm North Pacific Current. Its waters flow east, cross the ocean at approximately the 40th parallel and warm the coast of North America all the way to Alaska.

The turn of Kuroshio from the coast was noticeably influenced by the influence of the cold Kuril Current, approaching from the north. This current is called Oyashio (“Blue Water”) in Japanese.

There is another remarkable current in the Pacific Ocean - El Niño (Spanish for “The Baby”). This name was given because the El Niño current approaches the shores of Ecuador and Peru before Christmas, when the arrival of the baby Christ into the world is celebrated. This current does not occur every year, but when it nevertheless approaches the shores of the mentioned countries, it is not perceived as anything other than a natural disaster. The fact is that too warm El Niño waters have a detrimental effect on plankton and fish fry. As a result, the catches of local fishermen are reduced tenfold.

Scientists believe that this treacherous current can also cause hurricanes, rainstorms and other natural disasters.

In the Indian Ocean, waters move along an equally complex system of warm currents, which are constantly influenced by monsoons - winds that blow from the ocean to the continent in summer, and in the opposite direction in winter.

In the strip of forties latitudes of the Southern Hemisphere in the World Ocean, winds constantly blow in the direction from west to east, which gives rise to cold surface currents. The largest of these currents, with almost constant waves, is the Western Wind Current, which circulates in a direction from west to east. It is no coincidence that sailors call the strip of these latitudes from 40° to 50° on both sides of the equator the “Roaring Forties”.

Arctic Ocean mostly covered with ice, but this did not make its waters motionless at all. The currents here are directly observed by scientists and specialists at drifting polar stations. Over the course of several months of drift, the ice floe on which the polar station is located sometimes travels many hundreds of kilometers.

The largest cold current in the Arctic is the East Greenland Current, which carries the waters of the Arctic Ocean into the Atlantic.

In areas where warm and cold currents meet, phenomenon of rising deep waters (upwelling), in which vertical water flows bring deep water to the ocean surface. Together with them, nutrients that are contained in the lower water horizons rise.

IN open ocean Upwelling occurs in areas where currents diverge. In such places, the ocean level drops and deep water inflows. This process develops slowly - a few millimeters per minute. The most intense rise of deep waters is observed in coastal areas (10 - 30 km from the coastline). There are several permanent upwelling areas in the World Ocean that affect the overall dynamics of the oceans and affect fishing conditions, for example: the Canary and Guinea upwellings in the Atlantic, the Peruvian and California upwellings in the Pacific Ocean, and the Beaufort Sea upwelling in the Arctic Ocean.

Deep currents and rises of deep waters are reflected in the nature of surface currents. Even such powerful currents as the Gulf Stream and Kuroshio sometimes wax and wane. The temperature of the water changes in them and deviations from a constant direction and huge eddies are formed. Such changes in sea currents affect the climate of the corresponding land regions, as well as the direction and distance of migration of some species of fish and other animal organisms.

Despite the apparent chaos and fragmentation of sea currents, in fact they represent a certain system. Currents ensure that they have the same salt composition and unite all waters into a single World Ocean.

© Vladimir Kalanov,
"Knowledge is power"

Seafarers about availability ocean currents we found out almost as soon as we started surfing the waters. True, the public paid attention to them only when, thanks to the movement of ocean waters, many great things were accomplished. geographical discoveries, for example, Christopher Columbus sailed to America thanks to the North Equatorial Current. After this, not only sailors, but also scientists began to pay close attention to ocean currents and strive to study them as best and deeply as possible.

Already in the second half of the 18th century. the sailors studied the Gulf Stream quite well and successfully applied the acquired knowledge in practice: from America to Great Britain they walked with the current, and in the opposite direction they kept a certain distance. This allowed them to stay two weeks ahead of ships whose captains were not familiar with the area.

Ocean or sea currents are large-scale movements of water masses in the World Ocean at speeds from 1 to 9 km/h. These flows do not move chaotically, but in a certain channel and direction, which is main reason why they are sometimes called rivers of the oceans: the width of the largest currents can be several hundred kilometers, and the length can reach more than one thousand.

It has been established that water flows do not move straight, but deviate slightly to the side and are subject to the Coriolis force. In the Northern Hemisphere they almost always move clockwise, in the Southern Hemisphere - vice versa. At the same time, currents located in tropical latitudes (they are called equatorial or trade winds) move mainly from east to west. The strongest currents were recorded along the eastern coasts of the continents.

Water flows do not circulate on their own, but are set in motion sufficient quantity factors - wind, rotation of the planet around its axis, gravitational fields The Earth and the Moon, the bottom topography, the outlines of continents and islands, the difference in temperature indicators of water, its density, depth in different places of the ocean and even its physical and chemical composition.

Of all types of water flows, the most pronounced are the surface currents of the World Ocean, the depth of which is often several hundred meters. Their occurrence was influenced by trade winds constantly moving in tropical latitudes in western east direction. These trade winds form the huge flows of the North and South Equatorial Currents near the equator. A smaller part of these flows returns to the east, forming a countercurrent (when the movement of water occurs in the opposite direction from the movement of air masses). Most of them, when colliding with continents and islands, turn to the north or south.

Warm and cold water currents

It must be taken into account that the concepts of “cold” or “warm” currents are conditional definitions. So, despite the fact that the temperature of the water flows of the Benguela Current, which flows along, is 20°C, it is considered cold. But the North Cape Current, which is one of the branches of the Gulf Stream, with temperatures from 4 to 6 ° C, is warm.

• If the temperature indicators of the water flow coincide with the temperature of the surrounding waters, such a flow is called neutral;
• If the current temperature is lower surrounding water, they are called cold. They usually flow from high latitudes to low latitudes (for example, the Labrador Current), or from areas where, due to high river flows, ocean water has low salinity of surface waters;
• If the temperature of the currents is warmer than the surrounding water, then they are called warm. They move from tropical to subpolar latitudes, for example, the Gulf Stream.

Main water flows

On at the moment Scientists have recorded about fifteen main ocean water flows in the Pacific, fourteen in the Atlantic, seven in the Indian and four in the Arctic Ocean.

It is interesting that all currents of the Arctic Ocean move at the same speed - 50 cm/sec, three of them, namely the West Greenland, West Spitsbergen and Norwegian, are warm, and only the East Greenland is a cold current.

But almost all oceanic currents of the Indian Ocean are warm or neutral, with the Monsoon, Somali, Western Australian and Cape Agulhas current (cold) moving at a speed of 70 cm/sec, the speed of the rest varies from 25 to 75 cm/sec. The water flows of this ocean are interesting because, together with the seasonal monsoon winds, which change their direction twice a year, the oceanic rivers also change their course: in winter they mainly flow to the west, in summer - to the east (a phenomenon characteristic only of the Indian Ocean ).

Because Atlantic Ocean stretches from north to south, its currents also have a meridional direction. Water flows located in the north move clockwise, in the south - counterclockwise.

A striking example of the flow of the Atlantic Ocean is the Gulf Stream, which, starting in the Caribbean Sea, carries warm waters to the north, breaking up into several side streams along the way. When the waters of the Gulf Stream find themselves in the Barents Sea, they enter the Arctic Ocean, where they cool and turn south in the form of the cold Greenland Current, after which at some stage they deviate to the west and again join the Gulf Stream, forming a vicious circle.

The currents of the Pacific Ocean are mainly latitudinal and form two huge circles: northern and southern. Since the Pacific Ocean is extremely large, it is not surprising that its water flows have a significant impact on much of our planet.

For example, trade wind water flows transport warm waters from the western tropical shores to the eastern ones, which is why in the tropical zone western part The Pacific Ocean is much warmer opposite side. But in the temperate latitudes of the Pacific Ocean, on the contrary, the temperature is higher in the east.

Deep Currents

Enough long time Scientists believed that deep ocean waters were almost motionless. But soon special underwater vehicles were discovered on great depth both slow and fast flowing water streams.

For example, under the Equatorial Current of the Pacific Ocean at a depth of about one hundred meters, scientists have identified the underwater Cromwell Current, moving eastward at a speed of 112 km/day. Soviet scientists found a similar movement of water flows, but in the Atlantic Ocean: the width of the Lomonosov Current is about 322 km, and maximum speed 90 km/day was recorded at a depth of about one hundred meters. After this, another underwater flow was discovered in the Indian Ocean, although its speed turned out to be much lower - about 45 km/day.

The discovery of these currents in the ocean gave rise to new theories and mysteries, the main one of which is the question of why they appeared, how they were formed, and whether the entire area of ​​the ocean is covered by currents or there is a point where the water is still.

The influence of the ocean on the life of the planet

The role of ocean currents in the life of our planet can hardly be overestimated, since the movement of water flows directly affects the planet’s climate, weather, and marine organisms. Many compare the ocean to a huge heat engine, which is set in motion. This machine creates a continuous exchange of water between the surface and deep layers of the ocean, providing it with oxygen dissolved in the water and influencing the life of marine inhabitants.

This process can be traced, for example, by considering the Peruvian Current, which is located in the Pacific Ocean. Thanks to the rise of deep waters, which lift phosphorus and nitrogen upward, animal and plant plankton successfully develop on the ocean surface, resulting in the organization food chain. Plankton is eaten by small fish, which, in turn, become prey to larger fish, birds, and marine mammals, which, given such food abundance, settle here, making the region one of the most highly productive areas of the World Ocean.

It also happens that a cold current becomes warm: the average temperature environment rises by several degrees, causing warm tropical showers to fall on the ground, which, once in the ocean, kill fish accustomed to cold temperatures. The result is disastrous - it ends up in the ocean huge amount dead small fish, large fish leave, fishing stops, birds leave their nesting places. As a result local population deprived of fish, crops destroyed by rainfall, and profits from the sale of guano (bird droppings) as fertilizer. It can often take several years to restore the previous ecosystem.

Oceanic or sea currents - this is the forward movement of water masses in the oceans and seas, caused by various forces. Although the most significant cause of currents is wind, they can also form because of unequal salinity of individual parts of the ocean or sea, differences in water levels, uneven heating of different areas of water areas. In the depths of the ocean there are vortices created by bottom irregularities; their size often reaches 100-300 km in diameter, they capture layers of water hundreds of meters thick.

If the factors causing currents are constant, then a constant current is formed, and if they are episodic in nature, then a short-term, random current is formed. According to the predominant direction, currents are divided into meridional, carrying their waters to the north or south, and zonal, spreading latitudinally. Currents in which the water temperature is higher than the average temperature for

the same latitudes are called warm, lower ones are called cold, and currents that have the same temperature as the surrounding waters are called neutral.

Monsoon currents change direction from season to season, depending on how the offshore monsoon winds blow. Countercurrents move towards neighboring, more powerful and extended currents in the ocean.

The direction of currents in the World Ocean is influenced by the deflecting force caused by the rotation of the Earth - the Coriolis force. In the Northern Hemisphere, it deflects currents to the right, and in the Southern Hemisphere, to the left. The speed of currents on average does not exceed 10 m/s, and their depth extends to no more than 300 m.

In the World Ocean there are constantly thousands of large and small currents that circle the continents and merge into five giant rings. The system of currents in the World Ocean is called circulation and is associated primarily with the general circulation of the atmosphere.

Ocean currents redistribute solar heat absorbed by masses of water. They transport warm water heated by the sun's rays at the equator to high latitudes, and cold water

Currents of the World Ocean

Upwelling - the rise of cold waters from the depths of the ocean

from the polar regions, thanks to currents, it flows to the south. Warm currents contribute to an increase in air temperature, and cold currents, on the contrary, reduce it. Territories washed by warm currents have a warm and humid climate, while those near which cold currents pass have a cold and dry climate.

The most powerful current in the World Ocean is the cold current of the Western Winds, also called the Antarctic Circumpolar Current (from the Latin cirkum - around). The reason for its formation is strong and stable westerly winds blowing from west to east over vast areas.

areas of the Southern Hemisphere from temperate latitudes to the coast of Antarctica. This current covers an area 2,500 km wide, extends to a depth of more than 1 km and transports up to 200 million tons of water every second. There are no large land masses along the path of the Western Winds, and it connects the waters of three oceans - the Pacific, Atlantic and Indian - in its circular flow.

The Gulf Stream is one of the largest warm currents in the Northern Hemisphere. It passes through the Gulf Stream and carries the warm tropical waters of the Atlantic Ocean to high latitudes. This gigantic flow of warm water largely determines the climate of Europe, making it soft and warm. Every second, the Gulf Stream carries 75 million tons of water (for comparison: the Amazon, the deepest river in the world, carries 220 thousand tons of water). At a depth of about 1 km, a countercurrent is observed under the Gulf Stream.

SEA ICE

When approaching high latitudes, ships encounter floating ice. Sea ice frames Antarctica with a wide border and covers the waters of the Arctic Ocean. Unlike continental ice, formed from atmospheric precipitation and covering Antarctica, Greenland, and the islands of the polar archipelagos, these ices are frozen sea ​​water. In the polar regions sea ​​ice perennial, while in temperate latitudes water freezes only in cold seasons.

How does sea water freeze? When the water temperature drops below zero, a thin layer of ice forms on its surface, which breaks under wind waves. It repeatedly freezes into small tiles, then splits again until it forms the so-called ice lard - spongy ice floes, which then grow together. This type of ice is called pancake ice for its resemblance to rounded pancakes on the surface of the water. Areas of such ice, when frozen, form young ice - nilas. Every year this ice gets stronger and thickens. He might become multi-year ice more than 3 m thick, and may melt if currents carry the ice floes to warmer waters.

The movement of ice is called drift. Covered with drifting (or pack) ice

Ice mountains are melting, taking on bizarre shapes

the space around the Canadian Arctic Archipelago, off the coast of Severnaya and Novaya Zemlya. Arctic ice drifting at speeds of several kilometers per day.

ICEBERGS

Colossal pieces of ice often break off from huge ice sheets and set off on their own voyage. They are called “ice mountains” - icebergs. Without them, the ice sheet in Antarctica would constantly grow. In fact, icebergs compensate for melting and provide a balance to the Antarctic state.

Iceberg off the coast of Norway

tic cover. Some icebergs reach gigantic sizes.

When we want to say that some event or phenomenon in our life can have much more serious consequences than it seems, we say “this is just the tip of the iceberg.” Why? It turns out that approximately 1/7 of the entire iceberg is above water. It can be table-shaped, dome-shaped or cone-shaped. The base of such a huge piece of glacier, located under water, can be much larger in area.

Sea currents carry icebergs far from their birthplaces. A collision with such an iceberg in the Atlantic Ocean caused a

sewing famous ship Titanic in April 1912.

How long does an iceberg live? Breakaways from icy Antarctica Ice mountains can float in the waters of the Southern Ocean for more than 10 years. Gradually they are destroyed, split into smaller parts or, by the will of currents, move to warmer waters and melt.

"FRAM" IN ICE

To find out the path of the drifting ice, the great Norwegian traveler Fridtjof Nansen decided to drift on his ship Fram with them. This bold expedition lasted three whole years (1893-1896). Having allowed the Fram to freeze in the drifting pack ice, Nansen hoped to move with it to the area North Pole, and then leave the ship and continue the journey on dog sleds and skis. However, the drift went further south than expected, and Nansen's attempt to reach the Pole on skis was unsuccessful. Having traveled more than 3,000 miles from the New Siberian Islands to west coast Spitsbergen, the Fram collected unique information about drifting ice and the influence of the Earth's daily rotation on its movement.

The border between land and sea is a line that constantly changes its shape. The oncoming waves carry the smallest particles of suspended sand, roll over pebbles, and grind down rocks. Destroying the coast, especially during strong waves or storms, in one place, they engage in “construction” in another.

The area where coastal waves act is the narrow edge of the shore and its underwater slope. Where the destruction of the coast is mainly taking place, above the water, like

As a rule, there are overhanging rocks - cliffs, the waves “gnaw out” niches in them, creating under them

wonderful grottoes and even underwater caves. This type of shore is called abrasive (from the Latin abrasio - scraping). When sea levels change - and this has happened many times in the recent geological history of our planet - abrasion structures could end up under water or, conversely, on land, far from the modern shore. By

For such forms of coastal relief located on land, scientists reconstruct the history of the formation of ancient coasts.

In areas of a leveled coast with shallow depths and a gentle underwater slope, waves deposit (accumulate) material that was transported from the destroyed areas. Beaches are formed here. At high tide, rolling waves move sand and pebbles deep into the shore, creating a long

ny alongshore levees. During low tide, you can see accumulations of shells and seaweed on such ridges.

Benthos (from the Greek benthos - depth) - living organisms and plants living at depth, at the bottom of oceans and seas.

Nekton (from the Greek nektos - floating) are living organisms capable of independently moving through the water column.

Plankton (from the Greek planktos - wandering) are organisms living in water, transported by waves and currents and unable to move independently in water.

ON THE DEEP FLOORS

The ocean floor descends in giant steps from the coast to the underwater abyssal plains. Each such “underwater floor” has its own life, because the conditions of existence of living organisms: illumination, water temperature, its saturation with oxygen and other substances, the pressure of the water column - change significantly with depth. Organisms react differently to the amount of sunlight and water transparency. For example, plants can live only where illumination allows photosynthesis processes to take place (this is an average depth of no more than 100 m).

The littoral zone is a coastal strip periodically drained at low tide. This includes marine animals carried out of the water by waves, which have adapted to live in two environments at once - aquatic

And air. These are crabs

And crustaceans, sea urchins, mollusks, including mussels. In tropical latitudes there is a border of mangrove forests in the littoral zone, and in temperate zones there are “forests” of kelp algae.

Below the littoral zone is the sublittoral zone (down to depths of 200-250 m), the coastal strip of life on the continental shelf. Towards the poles sunlight penetrates into water very shallowly (no more than 20 m). In the tropics and at the equator, the rays fall almost vertically, which allows them to reach depths of up to 250 m. It is to such depths that algae, sponges, mollusks and light-loving animals, as well as coral structures - reefs, are found in warm seas and oceans. Animals not only attach to the surface of the bottom, but also move freely in the water column.

The largest mollusk that lives in shallow water is the tridacna (its shell valves reach 1 meter). As soon as the prey swims into the open doors, they slam shut and the mollusk begins to digest the food. Some mollusks live in colonies. Mussels - bivalves, attaching their shells to stones and other objects. Mollusks breathe oxygen

dissolved in water, so they are not found in the deeper levels of the ocean.

Cephalopods - octopuses, octopuses, squids, cuttlefish - have several tentacles and move in the water column due to compression

muscles that allow them to push water through a special tube. Among them there are also giants with tentacles up to 10-14 meters! Starfish, sea lilies, urchins

They are attached to the bottom and corals with special suction cups. Sea anemones, similar to strange flowers, pass their prey between their tentacles-“petals” and swallow it with a mouth opening located in the middle of the “flower”.

Millions of fish of all sizes inhabit these waters. Among them are various sharks - some of the largest fish. Moray eels hide in rocks and caves, and stingrays hide at the bottom, the color of which allows them to blend into the surface.

Below the shelf, an underwater slope begins - the bathyal (200 - 3000 m). Living conditions here change with every meter (temperature drops and pressure rises).

Abyssal - ocean bed. This is the most extensive space, occupying more than 70% of the underwater bottom. Its most numerous inhabitants are foraminifera and protozoan worms. Deep-sea sea urchins, fish, sponges, starfish - all have adapted to the monstrous pressure and are not like their relatives in shallow water. At depths where no one can go sun rays, marine inhabitants developed adaptations for lighting - small luminous organs.

Land waters make up less than 4% of all water on our planet. About half of their quantity is contained in glaciers and permanent snow, the rest is in rivers, lakes, swamps, artificial reservoirs, groundwater and underground ice permafrost. All natural waters The lands are called water resources.

The most valuable reserves for humanity are fresh water reserves. There is a total of 36.7 million km3 of fresh water on the planet. They are concentrated primarily in large lakes and glaciers and are unevenly distributed between continents. Antarctica, North America and Asia have the largest reserves of fresh water, South America and Africa have somewhat smaller reserves, and Europe and Australia are the least rich in fresh water.

Groundwater is the water contained in the earth's crust. They are associated with the atmosphere and surface waters and participate in the water cycle on the globe. Underground

Glaciers

- constant snow

Rivers

Lakes

Swamps

Groundwater

- underground permafrost ice

waters are found not only under continents, but also under oceans and seas.

Groundwater forms because some rocks allow water to pass through while others retain it. Atmospheric precipitation falling on the Earth's surface seeps through cracks, voids and pores of permeable rocks (peat, sand, gravel, etc.), and waterproof rocks (clay, marl, granite, etc.) retain water.

There are several classifications of groundwater based on origin, condition, chemical composition and the nature of the occurrence. Water that penetrates the soil after rain or melting snow, wets it and accumulates in soil layer, are called soil. Groundwater lies on the first waterproof layer from the surface of the earth. They are replenished due to the atmosphere

spheral precipitation, filtration of water from streams and reservoirs and condensation of water vapor. The distance from the earth's surface to the groundwater level is called depth of groundwater. She

increases in the wet season, when there is a lot of precipitation or snow melts, and decreases in the dry season.

Below the groundwater there may be several layers of deep groundwater, which are held by impermeable layers. Often interstratal waters become pressure. This occurs when layers of rock form a bowl and the water contained within is under pressure. Such groundwater, called artesian, rises up the drilled well and gushes out. Often artesian aquifers occupy a significant area, and then artesian springs have a high and fairly constant flow of water. Some famous oases North Africa originated from artesian springs. Along faults in the earth's crust artesian waters sometimes rise from aquifers, and between rainy seasons they often dry up.

Groundwater reaches the surface of the Earth in ravines and river valleys in the form sources - springs or springs. They form where a rock aquifer reaches the earth's surface. Because the depth of groundwater varies depending on the season and rainfall, the springs sometimes suddenly disappear and sometimes burst into floods. The water temperature in the springs may vary. Springs with a water temperature of up to 20 °C are considered cold, warm - with a temperature from 20 to 37 °C, and hot -

Permeable rocks

Waterproof rocks

Types of groundwater

mi, or thermal, - with a temperature above 37 ° C. Most hot springs are found in volcanic areas, where groundwater aquifers are heated by hot rocks and molten magma that comes close to the earth's surface.

Mineral groundwater contains many salts and gases and, as a rule, has healing properties.

The importance of groundwater is very great; it can be classified as a mineral along with coal, oil or iron ore. Groundwater feeds rivers and lakes, thanks to them the rivers do not become shallow in the summer, when little rain falls, and do not dry up under the ice. Humans widely use groundwater: they are pumped out of the ground to supply water to residents of cities and villages, for industrial needs and to irrigate agricultural land. Despite the huge reserves, groundwater is renewed slowly, and there is a danger of its depletion and contamination by domestic and industrial wastewater. Excessive water intake from deep horizons reduces the flow of rivers during low-water periods - the period when the water level is lowest.

A swamp is an area of ​​the earth's surface with excessive moisture and stagnant water regime, in which organic matter accumulates in the form of undecomposed plant remains. Swamps exist in all climate zones and on almost all continents of the Earth. They contain about 11.5 thousand km3 (or 0.03%) of the fresh waters of the hydrosphere. The most swampy continents are South America and Eurasia.

Swamps can be divided into two large groups - wetlands, where there is no well-defined peat layer, and peat bogs where peat accumulates. Wetlands include tropical wetlands, saline mangrove swamps, saline swamps of deserts and semi-deserts, grass swamps of the Arctic tundra, etc. Peat swamps occupy about 2.7 million km, which is 2% of the land area. They are most common in the tundra, forest zone and forest-steppe and, in turn, are divided into lowland, transitional and upland.

Lowland swamps usually have a concave or flat surface, where conditions for moisture stagnation are created. They often form along the banks of rivers and lakes, sometimes in flood zones of reservoirs. In such swamps, groundwater comes close to the surface, supplying minerals plants growing here. On

Alder, birch, spruce, sedge, reed, and cattails often grow in lowland swamps. In these bogs, the peat layer accumulates slowly (on average 1 mm per year).

Raised bogs with a convex surface and a thick layer of peat are formed mainly on watersheds. They feed mainly on atmospheric precipitation, which is poor in minerals, so less demanding plants - pine, heather, cotton grass, and sphagnum moss - settle in these swamps.

An intermediate position between lowland and upland ones is occupied by transitional swamps with a flat or slightly convex surface.

Swamps evaporate moisture intensively: the most active ones are swamps of the subtropical climate zone, swampy tropical forests, and in temperate climates - sphagnum-sedge and forest swamps. Thus, swamps increase air humidity, change its temperature, softening the climate of the surrounding areas.

Swamps, like a kind of biological filter, purify water from dissolved substances. chemical compounds and solid particles. Rivers flowing through swampy areas are no different from catastrophes.

trophic spring floods and floods, since their flow is regulated by swamps that gradually release moisture.

Bogs regulate the flow of not only surface water, but also groundwater (especially raised bogs). Therefore, their excessive drainage can harm small rivers, many of which originate in swamps. Swamps are rich hunting grounds: many birds nest here and many game animals live. The swamps are rich in peat, medicinal herbs, mosses and berries. The widespread belief that by growing crops in drained swamps one can get a rich harvest is wrong. Only the first few years are drained peat deposits fertile. Plans for draining swamps require comprehensive studies and economic calculations.

The development of a peat bog is the process of accumulation of peat as a result of the growth, death and partial decomposition of vegetation under conditions of excess moisture and lack of oxygen. The entire thickness of peat in a bog is called a peat deposit. It has a multilayer structure and contains from 91 to 97% water. Peat contains valuable organic and inorganic substances, so it has long been used in agriculture, energy, chemistry, medicine and other fields. For the first time, Pliny the Elder wrote about peat as “combustible earth” suitable for heating food in the 1st century. AD In Holland and Scotland, peat was used as fuel in the 12th-13th centuries. An industrial accumulation of peat is called a peat deposit. Russia, Canada, Finland and the USA have the largest industrial reserves of peat.

Fertile river valleys have long been developed by humans. Rivers were the most important transport routes; their waters irrigated fields and gardens. Populous cities arose and developed on the river banks, and borders were established along the rivers. Flowing water turned the wheels of the mills and later provided electrical energy.

Each river is individual. One is always wide and full of water, while the other has a channel that remains dry for most of the year and only fills with water during rare rains.

A river is a watercourse of significant size, flowing along a depression formed by itself in the bottom of a river valley - a channel. The river with its tributaries forms a river system. If you look down the river, then all the rivers flowing into it from the right are called right tributaries, and those flowing from the left are called left tributaries. The part of the earth's surface and thickness of soils and soils from which the river and its tributaries collect water is called a catchment area.

A river basin is the portion of land that includes a given river system. Between two basins of neighboring rivers there are watersheds,

River basin

The Pakhra River flows through the East European Plain

These are usually highlands or mountain systems. Basins of rivers flowing into the same body of water are combined, respectively, into basins of lakes, seas and oceans. The main watershed of the globe is identified. It separates the basins of rivers flowing into the Pacific and Indian Oceans on the one hand, and the river basins flowing into the Atlantic and North Arctic Oceans, - on the other. In addition, there are drainage areas on the globe: the rivers flowing there do not carry water to the World Ocean. Such drainless areas include, for example, the basins of the Caspian and Aral seas.

Every river begins at its source. This could be a swamp, a lake, a melting mountain glacier, or groundwater coming to the surface. The place where a river flows into an ocean, sea, lake or other river is called an estuary. The length of a river is the distance along the channel between the source and the mouth.

Depending on their size, rivers are divided into large, medium and small. Large river basins are usually located in several geographical areas. The basins of medium and small rivers are located within the same zone. According to the flow conditions, rivers are divided into flat, semi-mountain and mountain. Plain rivers flow smoothly and calmly in wide valleys, and mountain rivers rush violently and rapidly through gorges.

The replenishment of water in rivers is called river recharge. It can be snow, rain, glacial and underground. Some rivers, for example those that flow in equatorial regions (Congo, Amazon and others), are fed by rain, since in these areas of the planet it rains all year round. Most rivers are temperate

climate zone have mixed nutrition: in the summer they are replenished due to rain, in the spring - due to melting snow, and in the winter they are not allowed to run out of groundwater.

The behavior of a river by season - fluctuations in water level, formation and disappearance of ice cover, etc. - is called the river regime. Annually recurring significant increase in water

in the river - flood - on the lowland rivers of the European territory of Russia is caused by intense snow melting in the spring. The rivers of Siberia flowing from the mountains are full of water in the summer when the snow melts

V mountains A short-term rise in water level in a river is called flood It occurs, for example, when heavy rainfall occurs or when snow melts intensively during a thaw in winter. Most low level water in the river is low. It is established in the summer, during which time there is little rainfall and the river is fed mainly by groundwater. Low water also occurs in winter, during severe frosts.

Floods and floods can cause severe floods: melt or rainwater overwhelms the riverbeds, and rivers overflow their banks, flooding not only their valleys, but also the surrounding area. Water flowing from high speed, has a huge destructive force, it demolishes houses, uproots trees, washes away fertile soil from the fields.

Sandy beach on the banks of the Volga

TO DOES IT LIVE IN RIVERS?

IN Not only fish live in rivers. The waters, bottom and banks of rivers are the habitat of many living organisms; they are divided into plankton, nekton and benthos. Plankton includes, for example, green and blue-green algae, rotifers and lower crustaceans. The river benthos is very diverse - insect larvae, worms, mollusks, crayfish. Plants settle on the bottom and banks of rivers - pondweed, reeds, reeds, etc., and algae grow on the bottom. River nekton is represented by fish and some large invertebrates. Among the fish that live in the seas and enter rivers only to spawn are sturgeon (sturgeon, beluga, stellate sturgeon), salmon (salmon, pink salmon, sockeye salmon, chum salmon, etc.). Carp, bream, sterlet, pike, burbot, perch, crucian carp, etc. constantly live in rivers, and grayling and trout live in mountain and semi-mountain rivers. Mammals and large reptiles also live in rivers.

Rivers usually flow at the bottom of extensive relief depressions called river valleys. At the bottom of the valley, the water flow runs along a depression it has created itself - a channel. Water hits one section of the shore, erodes it and carries rock fragments, sand, clay, and silt downstream; in those places where the flow speed decreases, the river deposits (accumulates) the material it carries. But the river carries not only sediments eroded by the river flow; During stormy rains and melting snow, water flowing over the earth's surface destroys soil, loose soil and carries small particles into streams, which then deliver them to rivers. By destroying and dissolving rocks in one place and depositing them in another, the river gradually creates its own valley. The process of erosion of the earth's surface by water is called erosion. It is stronger where the speed of water flow is higher and where the soils are looser. The sediments that make up the bottom of rivers are called bottom sediments or alluvium.

Wandering channels

In China and Central Asia There are rivers in which the bed can shift by more than 10 m in a day. They, as a rule, flow in easily eroded rocks - loess or sand. In a few hours, a water flow can significantly erode one bank of the river, and deposit washed-away particles on the other bank, where the flow slows down. Thus, the channel shifts - “wanders” along the bottom of the valley, for example, on the Amu Darya River in Central Asia up to 10-15 m per day.

The origin of river valleys can be tectonic, glacial and erosional. Tectonic valleys follow the same direction deep faults in the earth's crust. Powerful glaciers that covered during the global glaciation northern regions Eurasia and North America, moving, plowed deep hollows, in which river valleys later formed. During the melting of glaciers, water flows spread to the south, forming extensive depressions in the relief. Later, streams rushed into these depressions from the surrounding hills, forming a large water flow that built its own valley.

Structure of a lowland river valley

Rapids on a mountain river

DRY RIVERS

There are rivers on our planet that fill with water only during rare rains. They are called "wadis" and are found in deserts. Some wadis reach a length of hundreds of kilometers and flow into dry depressions similar to themselves. Gravel and pebbles at the bottom of dry riverbeds suggest that in wetter periods, wadis could have been deep rivers capable of carrying large sediments. In Australia, dry river beds are called creeks, in Central Asia - uzboi.

The valley of lowland rivers consists of a floodplain (part of the valley that is flooded during high water or during significant floods), a channel located on it, as well as valley slopes with several above the floodplain terraces, descending steps to the floodplain. River channels can be straight, meandering, divided into branches or wandering. Winding channels have bends, or meanders. By eroding the bend near the concave bank, the river usually forms a stretch - deep section riverbed, its shallow sections are called riffles. The strip in the riverbed with depths most favorable for navigation is called fairway. The water flow sometimes delays significant amount sediment, forming islands. On large rivers, the height of the islands can reach 10 m and the length can be several kilometers.

Sometimes along the river's path there is a ledge of hard rock. The water cannot wash it away and falls down, forming a waterfall. In those places where the river crosses hard rocks that erode slowly, rapids are formed that block the path of the water flow.

IN estuary the water speed slows down significantly,

And the river deposits most of its sediment. Formed delta is a low-lying plain in the shape of a triangle, here the channel is divided into many branches and channels. River mouths flooded by the sea are called estuaries.

There are a great many rivers on Earth. Some of them flow like small silvery snakes within one forest area and then flow into a larger river. And some are truly huge: descending from the mountains, they cross vast plains and carry their waters to the ocean. Such rivers can flow through the territory of several states and serve as convenient transport routes.

When characterizing a river, take into account its length, average annual water flow and basin area. But not all large rivers have all these outstanding parameters. For example, the longest river in the world, the Nile, is far from the deepest, and its basin area is small. The Amazon ranks first in the world in terms of water content (its water flow is 220 thousand m3 / s - this is 16.6% of the flow of all rivers) and in terms of basin area, but is inferior in length to the Nile. The largest rivers are in South America, Africa and Asia.

The most long rivers world: Amazon (over 7 thousand km from the source of the Ucayali River), Nile (6671 km), Mississippi with the Missouri tributary (6420 km), Yangtze (5800 km), La Plata with the Parana and Uruguay tributaries (3700 km).

The deepest rivers (having maximum values average annual water flow: Amazon (6930 km3), Congo (Zaire) (1414 km3), Ganges (1230 km3), Yangtze (995 km3), Orinoco (914 km3).

The largest rivers on the globe (by basin area): Amazon (7,180 thousand km2), Congo (Zaire) (3,691 thousand km2), Mississippi with its tributary of the Missouri (3,268 thousand km2), La Plata with tributaries of the Parana and Uruguay (3,100 thousand km2), Ob (2990 thousand km2).

Volga - largest river East European Plain

MYSTERIOUS NILE

The Nile is the great African river, its valley is the cradle of a vibrant, distinctive culture that influenced the development of human civilization. The powerful Arab conqueror Amir ibn al-Asi said: “There lies a desert, on both sides it rises, and between the heights is the wonderland of Egypt. And all his wealth comes from the blessed river, flowing slowly through the country with the dignity of a caliph.” In its middle course, the Nile flows through the harshest deserts in Africa - the Arabian and Libyan. It would seem that it should become shallow or dry out during the hot summer. But at the height of summer, the water level in the Nile rises, it overflows its banks, flooding the valley, and as it recedes, it leaves a layer of fertile silt on the soil. This is because the Nile is formed from the confluence of two rivers - the White and Blue Nile, whose sources lie in the subequatorial climatic zone, where in the summer a low pressure area sets in and heavy rainfall occurs. The Blue Nile is shorter than the White Nile, so the rainwater that fills it reaches Egypt earlier, followed by the White Nile flood.

Yenisei - great river Siberia

AMAZON - QUEEN OF RIVERS

The Amazon is the largest river on Earth. It is fed by many tributaries, including 17 large rivers up to 3500 km long, which by their size can themselves be considered

to the great rivers of the world. The source of the Amazon lies in the rocky Andes, where its main tributary, the Marañon, flows from the mountain lake Patarcocha. When the Marañon merges with the Ucayali, the river takes on the name Amazon. The lowland through which this majestic river flows is a country of jungle and swamps. On their way to the east, tributaries continually replenish the Amazon. It is full of water throughout the year, because its left tributaries, located in the northern hemisphere, are full of water from March to September,

A right tributaries located in southern hemisphere, are full of water the other part of the year. During sea ​​tides A water shaft up to 3.54 meters high enters the mouth of the river from the Atlantic and rushes upstream. Locals call this wave “pororoka” - “destroyer”.

MISSISSIPPI - THE GREAT RIVER OF AMERICA

The Indians called the mighty river in the southern part of the North American continent Messi Sipi - “Father of Waters.” Its complex river system with many tributaries looks like a giant tree with a densely branched crown. The Mississippi Basin occupies almost half the territory of the United States of America. Beginning in the Great Lakes region in the north, the high-water river carries its waters south - to the Gulf of Mexico, and its flow is two and a half times greater than Russian river The Volga brings it to the Caspian Sea. The Spanish conquistador de Soto is considered the discoverer of the Mississippi. In search of gold and jewelry, he went deep into the mainland and in the spring of 1541 he discovered the banks of a huge deep river. One of the first colonists, the Jesuit fathers, who spread the influence of their order in the New World, wrote about the Mississippi: “This river is very beautiful, its width is more than one league; everywhere adjoining it are forests full of game, and prairies where there are many bison.” Before the arrival of European colonialists, vast areas in the river basin were occupied by virgin forests and prairies, but now they can only be seen in national parks, most lands are plowed.

The waters of rivers and streams, choosing their path, often fall off cliffs and ledges. This is how waterfalls are formed. Sometimes these are very small steps in the riverbed with minor differences in height between the upper section, from where the water falls, and the lower one. However, in nature there are also absolutely gigantic “steps” and ledges, the height of which reaches many hundreds of meters. Both waterfalls are formed when the water “opens up”, i.e. destroys, exposes areas with harder rocks, carrying away material from more pliable areas. The upper ledge (edge), from which the water falls, is a more durable layer, and downstream, tireless waters destroy less durable rock layers. Such a structure, for example, has the world-famous waterfall on the Niagara River (its name in the Iroquois language means “thundering water”), which connects two of the Great Lakes of North America - Erie and Ontario. Niagara Falls is relatively low - only 51 m (for comparison -

Diagram of water movement in Niagara Falls

Cascade of several waterfalls in Norway. 19th century engraving

The Ivan the Great bell tower in the Moscow Kremlin has a height of 81 m), but is more famous than its tall and full-flowing “brothers”. The waterfall became famous not only because of its location in close proximity to large American and Canadian cities, but also because it was well studied.

A water stream, falling from any height to the foot of the slope, forms a depression, a niche, even in fairly strong rocks. But the upper edge is gradually eroded and destroyed by the action of flowing water. The peaks of the ledge collapse, and... The waterfall seems to retreat back, “backing away” up the valley. Long-term observations of Niagara Falls have shown that such “backward” erosion “eats” the upper ledge of the waterfall by about 1 m over 60 years.

In Scandinavia, glacial landforms are to blame for the formation of waterfalls. There, streams from glacier-lined mountain peaks flow from great heights into the fjords.

The huge waterfalls that arose under the influence of tectonics are very impressive - internal forces Earth. Colossal steps of waterfalls are formed when the river bed is disrupted by tectonic faults. It happens that not one ledge is formed, but several at once. These cascades of waterfalls are incredibly beautiful.

The view of any waterfall is mesmerizing. It's no coincidence that these natural phenomena invariably attract the attention of numerous tourists, often becoming “ business cards» localities and even countries.

IGUAZU FALLS

Lakes are hollows filled with water - natural depressions on the surface of the land that have no connection with the sea or ocean. For a lake to form, two conditions are necessary: ​​the presence of a natural depression - a closed depression in the earth's surface - and a certain volume of water.

There are many lakes on our planet. Their total area is about 2.7 million km2, that is, approximately 1.8% of the entire land area. The main wealth of the lakes is fresh water, So necessary for a person. The lakes contain about 180 thousand km3 of water, and the 20 largest lakes in the world combined contain the majority of all fresh water available to humans.

The lakes are located in a wide variety of natural areas. Most of them are in northern parts Europe and the North American continent. There are a lot of lakes in areas where permafrost is common; there are also lakes in drainless areas, in floodplains and river deltas.

Some lakes are filled only during the wet seasons and remain dry the rest of the year - these are temporary lakes. But most lakes are constantly filled with water.

Depending on their size, lakes are divided into very large, with an area exceeding 1,000 km2, large - with an area from 101 to 1,000 km2, medium - from 10 to 100 km2 and small - with an area of ​​less than 10 km2.

Based on the nature of water exchange, lakes are divided into drainage and drainless. Located in the cat

In the valley, lakes collect water from the surrounding areas, streams and rivers flow into them, while at least one river flows out of drainage lakes, and not a single one flows out of drainage lakes. Drainage lakes include Baikal, Ladoga and Onega lakes, and drainage lakes include Lake Balkhash, Chad, Issyk-Kul, and the Dead Sea. Aral and Caspian Sea also drainless lakes, but thanks to them large sizes and a regime similar to the sea, these bodies of water are conventionally considered seas. There are so-called blind lakes, for example, formed in the craters of volcanoes. Rivers do not flow into them or flow out of them.

Lakes can be divided into fresh, brackish and saline, or mineral. The salinity of water in fresh lakes does not exceed 1% - such water, for example, in Lake Baikal, Lake Ladoga and Lake Onega. The water of brackish lakes has a salinity from 1 to 25%. For example, the salinity of water in Issyk-Kul is 5-8%o, and in the Caspian Sea - 10-12%o. Lakes in which the water has a salinity of 25 to 47%o are called salt lakes. Mineral lakes contain more than 47% salts. Thus, the salinity of the Dead Sea, lakes Elton and Baskunchak is 200-300%. Salt lakes, as a rule, form in arid areas. In some salt lakes, the water is a solution of salts close to saturation. If such saturation is achieved, then salts precipitate and the lake turns into a self-sediment lake.

In addition to dissolved salts, lake water contains organic and inorganic substances and dissolved gases (oxygen, nitrogen, etc.). Oxygen not only enters the lakes from the atmosphere, but is also released by plants during the process of photosynthesis. It is necessary for life and development aquatic organisms, as well as for the oxidation of organic

Lake in the Swiss Alps

of the substance found in the reservoir. If excess oxygen forms in the lake, it leaves the water into the atmosphere.

According to the nutritional conditions of aquatic organisms, lakes are divided into:

- lakes poor in nutrients. These are deep lakes with clear water, which include, for example, Baikal, Lake Teletskoye;

- lakes with high influx nutrients and rich vegetation. These are, as a rule, shallow and warm lakes;

YOUNG AND OLD LAKES

The life of a lake has a beginning and an end. Once formed, it is gradually filled with river sediments and the remains of dead animals and plants. Every year the amount of precipitation at the bottom increases, the lake becomes shallow, overgrown and turns into a swamp. The greater the initial depth of the lake, the longer its life continues. In small lakes, sediment accumulates over many thousands of years, and in deep lakes, over millions of years.

Lakes with excess organic matter, the oxidation products of which are harmful to living organisms.

Lakes regulate river flow and have a significant impact on the climate of the surrounding areas.

They contribute to an increase in precipitation, the number of days with fogs and generally soften the climate. Lakes raise groundwater levels and affect soils, vegetation and fauna surrounding areas.

Lake in a trough of the earth's crust Lake in a crater

The basin of Lake Kaali in Estonia is of meteorite origin. It is located in a crater formed as a result of the fall of a large meteorite.

Glacial lakes fill basins that were formed as a result of glacier activity. As it moved, the glacier plowed up more soft ground, creating depressions in the relief: in some places long and narrow, and in others oval. Over time, they filled with water, and glacial lakes appeared. There are a lot of such lakes in the north of the North American continent, in Eurasia on the Scandinavian and Kola Peninsulas, in Finland, Karelia and Taimyr. In mountainous regions, for example in the Alps and the Caucasus, glacial lakes are located in cirques - bowl-shaped depressions in upper parts mountain slopes, in the creation of which small mountain glaciers and snowfields. Melting and retreating, the glacier leaves a moraine - an accumulation of sand, clay with inclusions of pebbles, gravel and boulders. If a moraine dams a river flowing out from under a glacier, a glacial lake is formed, often having a round shape.

In areas composed of limestones, dolomites and gypsum, as a result of the chemical dissolution of these rocks by surface and groundwater Karst lake basins appear. Thicknesses of sand and clay lying above karst rocks fall into underground voids, forming depressions on the earth's surface, which over time fill with water and become lakes. Karst lakes are also found in caves

rah, they can be seen in the Crimea, the Caucasus, the Urals and other areas.

IN In the tundra, and sometimes in the taiga, where permafrost is widespread, the soil thaws and subsides during the warm season. Lakes appear in small depressions calledthermokarst.

IN in river valleys, when a meandering river straightens its channel, the old section of the channel becomes isolated. This is how they are formed oxbow lakes, often horseshoe-shaped.

Dammed, or dammed, lakes arise in the mountains when, as a result of a collapse, a mass of rocks blocks the river bed. For example,

V In 1911, during an earthquake in the Pamirs, a gigantic mountain collapse occurred, it dammed the Murgab River, and Lake Sarez was formed. Lake Tana in Africa, Sevan in Transcaucasia and many other mountain lakes are dammed.

U on the coasts of the seas, sand spits can separate the shallow coastal area from the sea area, resulting in the formation lake-lagoon. If sandy-clay deposits fence off flooded river mouths from the sea, estuaries are formed - shallow bays with very salty water. There are many such lakes on the coast of the Black and Azov Seas.

Formation of a dammed or dammed lake

Perennial accumulations of ice in the highlands and cold zones of the Earth are called glaciers. All natural ice unite into the so-called glaciosphere - part of the hydrosphere located in solid state. It includes the ice of cold oceans, the ice caps of mountains, and icebergs that have broken off ice mountains from ice sheets. In the mountains, glaciers are formed from snow. First, when snow recrystallizes as a result of alternating melting and new freezing of water inside the snow column, firn is formed.

Distribution of ice on Earth during the Ice Age

which then turns into ice. Under the influence of gravity, ice moves in the form of ice streams. The main condition for the existence of glaciers - both small and large - is constant low temperatures during most of the year, at which the accumulation of snow prevails over its melting. Such conditions exist in the cold regions of our planet - the Arctic and Antarctic, as well as in the highlands.

ICE AGES

IN THE HISTORY OF THE EARTH

IN Several times in the history of the Earth, severe climate cooling led to the growth of glaciers

And the formation of one or more ice sheets. This time is called glacial or

ice ages.

IN Pleistocene (era Quaternary period Cenozoic era) the area covered by glaciers was almost three times larger than the modern one. At this time

V huge ice sheets arose in the mountains and plains of the polar and temperate latitudes, which, growing, covered huge territories in temperate latitudes. You can imagine what the Earth looked like at that time by looking at Antarctica or Greenland.

How do they learn about those ancient ice ages? Moving along the surface, the glacier leaves its traces - the material that it took with it as it moved. Such material is called moraine. The stages of their standing glaciers mark their

Movement of the earth's crust under the colossal load of the ice sheet (1) and after its removal (2)

lami of the terminal moraine. Often, by the name of the place that the glacier reached, it is called a glacial area. The furthest glacier on the territory Eastern Europe reached the Dnieper valley, and this glaciation is called the Dnieper. In North America, traces of maximum southward movement of glaciers belong to two glaciations: in the state of Kansas (Kansas glaciation) and Illinois (Illinois glaciation). The last glaciation reached Wisconsin during the Wisconsin ice age.

The Earth's climate changed dramatically during the Quaternary, or Anthropocene, period, which began 1.8 million years ago and continues to this day. What caused this enormous cooling is a question that scientists are trying to solve.

Dozens of hypotheses try to explain the appearance of huge glaciers by a variety of terrestrial and cosmic causes - the fall of giant meteorites, catastrophic eruptions volcanoes, changes in the direction of ocean currents. The hypothesis of the Serbian scientist Milankovic, proposed in the last century, is very popular, who explained climate change periodic fluctuations the inclination of the planet's rotation axis and the distance of the Earth from the Sun.

Glaciers of Spitsbergen

Glaciation moraines

The ice sheets that currently exist are the remnants of huge ice sheets that existed in temperate latitudes during the last glacial periods. And although today they are not as large as in the past, their size is still impressive.

One of the most significant is the Antarctic Ice Sheet. The maximum thickness of its ice exceeds 4.5 km, and its distribution area is almost 1.5 times larger than the area of ​​Australia. From several dome centers to different sides The ice of many glaciers is spreading. It moves in the form of huge streams at a speed of 300-800 m per year. Occupying the entire Antarctica, the cover in the form of outlet glaciers flows into the sea, giving life to numerous icebergs. Glaciers lying, or rather floating, in the area of ​​the coastline are called shelf glaciers, since they are located in the area of ​​the underwater edge of the continent - the shelf. Such ice shelves exist only in Antarctica. The largest ice shelves are in West Antarctica. Among them ice shelf Ross, where the American Antarctic station McMurdo is located.

Another colossal ice sheet is in Greenland, occupying more than 80% of it

Foothill Glacier

himself big island peace. Greenland's ice accounts for about 10% of all ice on Earth. The speed of ice flow here is much less than

V Antarctica. But Greenland also has its own record holder - a glacier that moves at a very high speed - 7 km per year!

Reticulate glaciation characteristic of the polar archipelagos - Franz Josef Land, Spitsbergen, and the Canadian Arctic Archipelago. This type of glaciation is transitional between cover and mountain. In plan, these glaciers resemble a honeycomb grid, hence the name. Peaks, pointed peaks, rocks, and areas of land protrude from under the ice in many places, like islands in the ocean. They are called nunataks. "Nunatak" is an Eskimo word. IN scientific literature this word came about thanks to the famous polar Swedish explorer Nils Nordenskiöld.

TO The same “half-cover” type of glaciation also includesfoothill glaciers. Often a glacier descending from the mountains along a valley reaches their feet and emerges with wide blades

V melting zone (ablation) to the plain (this type of glaciers is also called Alaskan) or even

on the shelf or in lakes (Patagonian type). Foothill glaciers are among the most spectacular and beautiful. They are found in Alaska, northern North America, Patagonia, extreme south South America, Spitsbergen. The most famous is the Malaspina foothill glacier in Alaska.

Reticulate glaciation of Svalbard

Where latitude and altitude above sea level do not allow snow to melt during the year, glaciers appear - accumulations of ice on mountain slopes and peaks, in saddles, depressions and niches on the slopes. Over time, the snow becomes

spins into firn and then into ice. Ice has the properties of a viscoplastic body and is capable of flow. At the same time he grinds and plows

the surface on which it moves. In the structure of a glacier, a zone of accumulation, or accumulation, of snow and a zone of ablation, or melting, are distinguished. These zones are separated by a food boundary. Sometimes it coincides with the snow line, above which there is snow throughout the year. The properties and behavior of glaciers are studied by glaciologists.

WHAT ARE THERE ARE GLACIERS

Small hanging glaciers lie in depressions on the slopes and often extend beyond the snow line. These are many glaciers of the Alps and Caucasus -

Randklufts - side cracks separating the glacier from the rocks

Bergschrund - crack in the area

glacier feeding, separating the stationary and mobile

glacier parts

Median and lateral moraines

Transverse cracks on the glacier tongue

Basic moraine - material beneath a glacier

for. Tar glaciers fill cup-shaped depressions on the slope - cirques, or cirques. In the lower part, the cirque is limited by a transverse ledge - a crossbar, which is a threshold beyond which the glacier has not crossed for many hundreds of years.

Many mountain-valley glaciers, like rivers, merge from several “tributaries” into one large one that fills the glacial valley. Such glaciers of especially large size (they are also called dendritic or tree-like) are characteristic of the highlands of the Pamirs, Karakoram, Himalayas, and Andes. For each region there are more fractional division glaciers

Summit glaciers occur on rounded or leveled mountain surfaces. The Scandinavian mountains have leveled summit surfaces - plateaus, on which this type of glaciers is common. The plateaus break off with sharp ledges towards the fjords - ancient glacial valleys that have turned into deep and narrow sea bays.

The uniform movement of ice in a glacier can give way to sudden movements. Then the glacier tongue begins to move along the valley at a speed of up to hundreds of meters per day or more. Such glaciers are called pulsating. Their ability to move is due to accumulated tension

V glacial thicker. As a rule, constant observations of a glacier allow one to predict the next pulsation. This helps prevent tragedies like the one that occurred in the Karmadon Gorge in 2003, when the pulsation of the Kolka glacier in the Caucasus caused many populated areas flowering valley were buried under chaotic piles of ice blocks. Pulsating glaciers like these are not that uncommon.

V nature. One of them, the Bear Glacier, is located in Tajikistan, in the Pamirs.

Glacial valleys are U-shaped and resemble a trough. Their name - trog (from German Trog - trough) is connected with this comparison.

When mountain peak covered on all sides by glaciers, gradually destroying the slopes, forming sharp pyramidal peaks - carlings. Over time, neighboring circuses may merge.

Edge of a glacier in the Himalayas

Debris on the surface of a glacier in the Alps

Rivers fed by glaciers, i.e. flowing out from under the glaciers, very muddy and stormy during the melting period in the warm season and, on the contrary, become clean and transparent in winter and autumn. The terminal moraine bank sometimes acts as a natural dam for a glacial lake. During rapid melting, the lake can erode the shaft, and then a mudflow is formed - a mud-stone flow.

WARM AND COLD GLACIERS

On the glacier bed, i.e. the part that comes into contact with the surface may have a different temperature. In the highlands of temperate latitudes and in some polar glaciers, this temperature is close to the melting point of ice. It turns out that a layer of melt water forms between the ice itself and the underlying surface. The glacier moves along it, like lubricant. Such glaciers are called warm, in contrast to cold ones, which are frozen to the bed.

Let’s imagine a snowdrift melting in the spring. As it gets warmer, the snow begins to settle, its boundaries become smaller, retreating from the “winter” ones, streams run from under it... And on the surface of the earth, everything that has accumulated on and in the snow over many years remains lying. winter months: all kinds of dirt, fallen branches and leaves, garbage. Now let's try to imagine

imagine that this snowdrift is several million times larger, which means that the pile of “garbage” after it melts will be the size of a mountain! When a large glacier melts, which is also called retreat, it leaves behind even more material - because its ice volume contains much more “garbage”. All inclusions left by a glacier after melting on the surface of the earth are called moraine or glacial deposits.

The glacier destroys valleys, abrases and scratches rock ledges in its path. In addition, he can carry all this debris to long distances from the place where they were captured by him. From

Melting glacier tongue

Bottom moraine

Lateral moraines

Glacial Lake

Terminal moraine

Mountain glacier deposits

Where the debris is located and how it was transported by the glacier also varies between glacial deposits.

A surface moraine forms on the surface of the glacier - all the material that falls onto the glacier. Most of the debris accumulates on the adjacent slopes. Ridges of lateral moraines form here, and if the glacier consists of several

languages, then when they merge into one language, the lateral moraines become middle-

dynamic. After melting, such moraines look like long mounds stretching along the slopes down the valley.

The glacier is located in constant movement. As a viscoplastic body, it has the ability to flow. Consequently, the fragment that fell on him from the cliff, after some time, may turn out to be quite far from this place. These fragments are collected (accumulated), as a rule, at the edge of the glacier, where the accumulation of ice gives way to melting. The accumulated material follows the contours of the glacier tongue and has the appearance of a curved embankment, partially blocking the valley. When the glacier retreats, the terminal moraine remains in its original place, gradually being eroded by meltwater. When a glacier retreats, several ridges of terminal moraines may accumulate, which will indicate intermediate positions of its tongue.

The glacier has retreated. A moraine swell remained in front of its front. But the melting continues. And behind the final moraine, melted ice begins to accumulate

kovy waters. A glacial lake appears, which is held back by a natural dam. When such a lake breaks through, a destructive mud-stone flow - a mudflow - often forms.

As the glacier moves down the valley, it destroys its base. Often this process, which is called "exaration", occurs unevenly. And then steps are formed in the glacier bed - crossbars (from German Riegel - barrier).

The moraines of cover glaciers are much more extensive and diverse, but they are less well preserved in the relief.

Glacier deposits

After all, as a rule, they are more ancient. And tracing their location on the plain is not as easy as in a mountain glacial valley.

In the last ice age, a huge glacier moved from the region of the Baltic crystalline shield, from the Scandinavian and Kola Peninsula. Where the glacier plowed out the crystalline bed, elongated lakes and long ridges - selgi - formed. There are many of them in Karelia and Finland.

It was from there that the glacier brought fragments of crystalline rocks - granites. During the long transportation of rocks, ice abraded the uneven edges of the fragments, turning them into boulders. To this day, such granite boulders are found on the surface of the earth in all areas of the Moscow region. Fragments brought from afar are called erratic. From maximum stage last glaciation- Dnieper, when the end of the glacier reached the valleys of the modern Dnieper and Don, only moraines and glacial boulders were preserved.

After melting, the cover glacier left behind a hilly space - a moraine plain. In addition, numerous streams of melted glacial waters burst out from under the edge of the glacier. They eroded the bottom and terminal moraines, carried away thin clay particles and left sandy fields in front of the edge of the glacier - outwash (from the Il. sand - sand). Melt water often washed tunnels under melting glaciers that had lost their mobility. In these tunnels, and especially when exiting from under the glacier, washed-up moraine material (sand, pebbles, boulders) accumulated. These accumulations are preserved in the form of long winding shafts - they are called ridges.

IN In cold climates, water in the depths and on the surface freezes to a depth of 500 m or more. Over 25% of the Earth's entire land surface is occupied by permafrost.

IN our country has more than 60% of such territory, because almost all of Siberia lies in its distribution zone.

This phenomenon is called perennial or permafrost. However, the climate can change toward warming over time, so the term "perennial" is more appropriate for this phenomenon.

IN Summer seasons - and they are very short and fleeting here - the top layer of surface soils can thaw. However, below 4 m there is a layer that never thaws. Groundwater can be either under this frozen layer, or remain in a liquid state between permafrost layers (it forms water lenses - taliks) or above the frozen layer. Top layer which is subject to freezing and thawing is calledactive layer.

POLYGONAL SOILS

Ice in the ground can form ice veins. They often appear in frostbite areas (formed by severe frosts) cracks filled with water. When this water freezes, the soil between the cracks begins to compress, because the ice occupies large area than water. A slightly convex surface is formed, framed by depressions. Such polygonal soils cover a significant part of the tundra surface. When the short summer arrives and the ice veins begin to thaw, entire spaces are formed that look like a lattice of pieces of land surrounded by water “channels.”

Among the polygonal formations, stone polygons and stone rings are widespread. With repeated freezing and thawing of the ground, freezing occurs, pushing larger fragments contained in the soil to the surface by ice. In this way, soil is sorted, since it fine particles remain in the center of rings and polygons, and large fragments move to their edges. As a result, shafts of stones appear, framing smaller material. Mosses sometimes settle on it, and in the fall the stone polygons amaze with their unexpected beauty:

bright mosses, sometimes with cloudberry or lingonberry bushes, surrounded on all sides gray stones, look like specially made garden beds. In diameter, such polygons can reach 1-2 m. If the surface is not flat, but inclined, then the polygons turn into stone strips.

The freezing of debris from the ground leads to the formation of a chaotic accumulation of large stones on the top surfaces and slopes of mountains and hills in the tundra zone, merging into stone “seas” and “rivers.” There is a name for them “kurums”.

BULGUNNYAKHI

This Yakut word denotes amazing

On the surface of the planet, not only belts of continuous permafrost stand out in cold natural zones. There are areas with so-called island permafrost. It exists, as a rule, in the highlands, in harsh places with low temperatures, for example in Yakutia, and are remnants - “islands” - of the former, more extensive permafrost belt, preserved since the last ice age