In the previous paragraph, describing some geographical characteristics continent, we have given a number of figures relating to glaciation, and this is inevitable, since it largely determines these characteristics. Here we will describe glaciation in more detail, since it is its thermal regime that determines the peculiarities of the interaction of this continent with the atmosphere.
The lack of accurate data on the subglacial relief, their incompleteness allows only an approximate estimate of the volume Antarctic ice. It is believed that with an average level of subglacial relief equal to +410 m, the volume of the ground part of Antarctica's glaciation is equal to 23.0 million km3, and with an average level of -198 m it is equal to 30.4 million km3. The latter value is one and a half times the volume of all other ice on the globe.
The volume of shelves and tongues of outlet glaciers is 0.6 million km3. The length of the outer edge of these glaciers is 15 thousand km, which is equal to half the length coastline Antarctica. The thickness of the ice shelves, equal to 300-375 m at the base, changes to 40-50 m at the sea edge.
The snow line - the level above which snow lies all year round - located in the Southern Hemisphere on Tierra del Fuego and New Zealand at an altitude of 1000-1800 m above sea level, decreases on the shores of Antarctica. On the northwestern coast of the Antarctic Peninsula it is located at an altitude of 50-200 m, and to the south it drops to sea level.
The glaciation of Antarctica is fueled by precipitation brought by air currents from the ocean. As the moist air mass passes, the intensity of snowfall on the mainland decreases. Observations have established that average speed nutrition on the surface of the continent varies from 70 g/cm2 per year at the edge of glaciation to 3 g/cm2 in the central regions.
In certain areas of the surface, the melting of the glacier under the influence of various reasons from the surface and snow blowing prevail over its arrival, but the area of such areas does not exceed 1.2% of the area of the entire glaciation. Such conditions arise around ice-free land areas on the hilly surface of the edges of glaciation, in the mountainous regions of the continent. For the entire Antarctica, the arrival of snow in terms of water minus the flow rate for the above reasons is 2160±410 km*/year.
The main source of glaciation consumption is its spreading and breaking off at the edges of the barrier and ice shelves. At present, there is still insufficient data to determine the spreading rate, and especially in internal areas. However, it has been established that the horizontal component of the speed of ice movement in the ground ice cover increases from the central regions to the edge of the glaciation, and the speed of movement of some outlet glaciers reaches 1250 m/year.
If we proceed from the calculated income article of glaciation and assume that its regime is steady, then the average speed forward motion of the modern edge of the Antarctic ice shell should be approximately 233 m/year. Moreover, the average ice turnover period for all glaciation areas turns out to be 9.55-12.60 thousand years.
Observations made to date in very large number points on the coast of Antarctica show that in some places the edge of glaciation is stationary, while in others it is slowly thinning and retreating.
The thermal regime of glaciation and its features are characterized by the following figures. Glaciation surface temperature due to all components heat balance, is close in value to the air temperature. The low thermal conductivity of ice, and especially firn, causes a complex thermal regime in the upper layer of glaciation, characterized by the spread of seasonal and other temperature fluctuations on the surface. This leads to the fact that in winter months at some depth, the temperature is higher than the air temperature and the glaciation surface, and in summer, on the contrary, lower than the air temperature, which leads to some climatic features internal regions Antarctica.
The depth at which temperature fluctuations attenuate depends on the thermal conductivity coefficient and the period of fluctuations. The longer the period, the deeper the temperature waves penetrate into the glaciation. At this depth, the temperature is close to the average annual air temperature at the surface.
Attenuation level annual changes temperature is located in Antarctica at a depth of 15-20 m.
The temperature at the depth of attenuation of annual fluctuations reaches -60 ° C in the central regions of the continent and (-8) - (- 15) ° C on the periphery of glaciation. The average temperature at this level for the entire Antarctica is -35.5°C.
Below the layer of attenuation of annual fluctuations, the temperature in the glaciation thickness begins to decrease with depth. At the Baird station the gradient of depression is 0.026°C per 100 m, and at the edge of the glaciation it is 3-4°C. This decrease is explained by the influx of cold ice into lower layers from the central regions.
In the bottom layers of ice, the temperature should increase with depth due to the heat coming from the interior of the planet and the heat released due to the movement of the ice sheet. An approximate calculation shows that most of the lower limit of glaciation should experience a temperature of 0°C. This leads to bottom melting estimated at 50 km3/year.
Within the Antarctic Circle, around the South Pole, there is the continent of Antarctica, covered with a thick ice sheet and officially discovered in 1820 by the Russian Antarctic expedition of F.F. Bellingshausen and M.P. Lazarev. However, back in the 16th century. there were maps on which this continent was depicted free of ice with all its mountains and river valleys. Scientists believe that the Antarctic ice sheet formed in ancient times, before the advent of civilization. Who made these maps? When did Antarctica become covered with ice? The secrets of Antarctica have not yet been revealed. It still remains a harsh and insufficiently studied continent, dangerous for the lives of researchers.
CONCERNING THE TIME OF THE APPEARANCE OF THE ANTARCTICA ICE COVER and there are many versions of her past. Academician V.M. Kotlyakov believes that the continent was covered with ice no later than 5 million years ago, but most likely 30-35 million years ago. Other scientists suggest that Antarctica was completely ice-free about 15,000 years ago, and partially ice-free about 6,000 years ago. There is also a version about 20 or 30 thousand years old maps that recorded Antarctica without ice cover. It turns out that a developed civilization, with experienced cartographers and surveyors, existed or temporarily stayed on Earth (it’s even scary to imagine!) tens of millions or from 15 to 30 thousand years ago.
Or maybe in very distant times the Earth was explored by aliens from outer space? After all, there is evidence of the existence in ancient times of the continent Mu in the Pacific Ocean, on which aliens lived from one of the planets of the constellation Coma Berenices. Perhaps they were the first civilized inhabitants of the Earth, whose level of development in many ways exceeded the current one. There is an opinion that they passed on their knowledge to the inhabitants of Atlantis. The Mu civilization died about 700 thousand years ago. French scientist Robert Carreau wrote in “The Book of Lost Worlds”: “The fact of the existence of the continent of Mu is based on so much evidence of archeology and culture that it would be stupid not to take them into account.”
A number of scientists identify the disappeared Atlantis with modern Antarctica, which until the end of the last ice age was approximately 3000 km to the north, within more favorable latitudes, but as a result of a powerful simultaneous movement earth's crust moved to its current position. This shift occurred between 14,500 and 12,500 BC. According to the theory of catastrophes, such a one-time displacement is quite acceptable. But not everyone accepts the theory of catastrophes, although some facts associated with Antarctica are difficult to explain unless viewed from the perspective of sudden, catastrophic and geological changes. It is possible that Atlantis has not disappeared; the remnants of its ancient civilization are now hidden under the thick ice cover of modern Antarctica.
Antarctica today is the coldest continent on our planet. The climate of the interior parts of the continent is especially harsh, where even in summer the average air temperature does not rise above -30 degrees C, and in winter it is below -70 degrees C. The absolute minimum temperature (-89.20 degrees C) was recorded in 1983 at the Vostok station, which is considered the Earth's pole of cold.
ANTARCTICA IS A HARSH, RUTLESS, ALMOST LIFELESS ICY DESERT. She was like this throughout official history humanity. Robert Scott, who led the English expedition to the South Pole in 1911 and died along with all his companions on the way back, wrote in his diary before his death: “Great God, what a terrible place!”
But has Antarctica always been like this? Facts suggest that long ago in Antarctica they grew deciduous trees(fossilized stumps were found at latitude 840 22’), the climate was warm. 300 km from the South Pole, coal deposits, a mass of fossils with imprints of leaves and stems, petrified wood, and thick limestone deposits rich in corals (and they are formed only in warm waters) were discovered. These finds indicate that Antarctica once had a temperate or even subtropical climate. A study of fossilized trees and plants showed that parts of Antarctica were ice-free about 2.5 million years ago, and some areas were ice-free only 100 thousand years ago. Consequently, already at that time, cartographers of a civilization unknown to us could capture the relief of Antarctica on maps.
Over the years, expeditions were sent to Antarctica, scientific bases and stations were founded. Although there is no permanent population on the mainland, there are dozens of scientific stations, where from 4,000 people live in summer and up to 1,000 people in winter. For science, Antarctica is a giant laboratory for studying the nature of the Earth and space. The main objects of research here are cold and ice. Antarctica is called the "cuisine" of Earth's weather.
Almost all Antarctic researchers are men. The first women researchers there appeared at foreign stations. Of the Soviet scientists, Professor M.V. Klenova was the first to visit Antarctica. The story of her trip there is interesting. She was not included in the expedition and she turned to A.I. Mikoyan, who was then in charge of work on the ice continent. A.I. Mikoyan refused M.V. Klenova’s request, saying that he did not allow women to be included in the Antarctic expedition. To this M.V. Klenova replied that she was not a woman, but a professor, which amused the People's Commissar and received permission, but with the condition not to leave the ship for the mainland. This story was told by M.V. Klenova herself in 1964 on the ship "Akademik Kurchatov", on which she went on a voyage to Atlantic Ocean, and we, employees of the Kaliningrad branch of the Institute of Oceanology of the USSR Academy of Sciences, came to conduct it.
The first woman to reach the South Pole alone was 33-year-old Briton Felicity Aston, who skied from the Ross Sea ice shelf to the South Pole in 70 days in 2011. She worked for 3 years as a meteorologist on an English Antarctic expedition, and in 2009 she led a women's group that went to the South Pole and returned safely. In 1997, Borge Ousland from Norway reached the South Pole in 64 days, but she used a mobile sail to save energy. Therefore, the palm still belongs to the British.
THE FIRST WOMEN WINTERED IN ANTARCTICA IN 1947.
as part of the American expedition. In 1974 there were already four of them. In 1978-1979 During the summer, 80 women worked at US stations. Then they began to stay for the winter. In 1990-1991 An all-female winter camp was organized at the German station. However, after just six months, it became necessary to send male specialists to the station to bring the station’s infrastructure facilities into normal technical condition. Only 6 women from Russia spent the winter in Antarctica: five were the wives of expedition leaders, the sixth was documentary filmmaker Olga Stefanova.
The scourge of Antarctica is fires, which is due to the dryness there, which is the same as in the Sahara. Fires in Antarctica are difficult to extinguish because... water exists there in the form of ice.
Since 1957, tourists began to visit Antarctica. Polar exoticism attracts the curious and, of course, the rich. A trip to the South Pole is the most expensive trip in the world (minimum cost – $40,000). In 1979, an American plane carrying tourists crashed on the northern slope of Mount Erebus. 257 people died.
According to satellite data, Antarctica loses 160 billion tons of ice every year. Today, the Antarctic ice sheet is melting twice as fast as it was four years ago and 10 times faster than 600 years ago. Numerous expeditions of Antarctic researchers over the past several decades have greatly polluted the environment. ice continent, That's why ecological problems are very acute here.
Antarctica attracts scientists with its mineral wealth. It is estimated that there is more coal here than on all other continents combined. There is talk about the presence of oil. Ores of lead, nickel, copper, manganese, and molybdenum were discovered. There are rich deposits of iron.
But the secrets of Antarctica are still not revealed. In recent years, phenomena have emerged that are difficult to explain: a time portal in the form of rotating time vortices, discovered by American and English physicists; a mysterious glow from under the ice of Lake Vostok; enough heat(from 10 to 18 degrees C) of water in the lake (due to what heat source is the water heated?); abnormally high magnetic activity near the southeastern shore of the lake; an unknown mechanism discovered by an American spy satellite under the thickness of an Antarctic glacier, etc.
Were there any great catastrophes?
Primitive organisms became more complex until, through a long line of ancestors, man finally arose. Gradually, the gaps in the geological record were filled, and the harmonious picture of the development of the Earth was already close to completion. It seemed that the prediction of the founder of scientific geology, Charles Lyell, made back in 1830, was coming true: “The order in nature, from the earliest periods, was monotonous in the sense in which we consider it monotonous now, and we hope that it will remain so and for the future."
And yet there were disasters!
Signs of dramatic changes were observed simultaneously throughout the entire Earth. Over the last billion years highest value had four great catastrophes - 650, 230, 65 and 35 million years ago.
The first of them was associated with the largest glaciation in the history of the Earth. Its traces have been found on all continents except Antarctica, which is now covered with glaciers and THEREFORE poorly studied. There are signs of glaciation in equatorial regions as well. It may be objected that the continents are moving, and those areas that are now on the equator were once near the poles. But now we have learned to determine the latitude of ancient continents. It turned out that Scotland and Belarus, where glacial deposits with an age of about 650 million years were discovered, were at the equator at that time. This means that glaciers then reached the equator. Before this, the Sun provided several percent less heat than it does now. But there was much more in the atmosphere carbon dioxide, and the greenhouse effect warmed the Earth. Plants appeared in the oceans (blue-green, and then “real” algae), they consumed and decomposed carbon dioxide, and “having eaten their own blanket,” brought the Earth to almost complete glaciation. As a result, many algae died out, and the “blanket” gradually recovered.
The second catastrophe occurred 230 million years ago, shortly after another major glaciation. It was not worldwide and covered only polar and part of temperate latitudes Southern Hemisphere. As has now been proven, climate aridity is associated with glaciations. Ocean water flowed into huge bays surrounded by deserts and evaporated into them. Salts precipitated. One of these bays was located in the east of the East European Plain. The salt left the ocean, but the water, in the course of its great cycle, returned to it. As a result, the salinity of the ocean waters has decreased significantly. Not all marine organisms were able to survive it. According to some data, 97 percent of the organisms that previously lived in the seas and oceans became extinct. The disaster did not affect terrestrial fauna and flora.
Sixty-five million years ago, the most mysterious event in geological history. Dinosaurs and other giant reptiles that had dominated for more than a hundred million years suddenly became extinct. Together with them the inhabitants became extinct 
ammonites, belemnites and many types of microscopic organisms that formed the seas. Dozens of hypotheses have been proposed to explain the extinction, but among them there is not a single one that would be convincing from the point of view of all or at least the majority of researchers. The theory of dinosaur extinction has yet to be created.
In the Mesozoic, when dinosaurs lived, a warm climate reigned throughout the Earth. The water on the surface of the oceans in the polar regions had a temperature of 15 and sometimes 18 degrees. Approximately the same conditions prevailed at the beginning of the Cenozoic - the “age of mammals” - until 35 million years ago. But then very quickly, almost instantly (on the scale of geological time, this “instant” lasted about one hundred thousand years) the temperature everywhere dropped by several degrees. In the tropics it became colder than now, but in the temperate and polar latitudes after the cold snap the temperature was still much higher than today.
Reasons for the cold snap
Until recently, temperature changes were judged mainly from the remains of animals and plants. The cooling was indicated by the extinction of heat-loving species. But it was always possible to say that in the past organisms lived under different conditions than now, and extinction is not associated with cooling, but with something else. Now “thermometers” have been found that allow us to more objectively judge the conditions of the past. The isotopic composition of oxygen contained in ancient organisms is determined. In addition to the most common isotope with atomic weight 16, there is also an isotope with atomic weight 18 - the so-called heavy oxygen. But in the remains of ancient organisms, the content of heavy oxygen varies depending on the temperature of the water in which they lived. The oxygen thermometer showed that about 35 million years ago there was a cooling, and not any other change in the environment.
What was the cause of the cold snap? There are many hypotheses. The first of them is the hypothesis of a decrease in the luminosity of the Sun. But astrophysicists are against it - neither the Sun nor stars similar to it can dramatically change their luminosity. It does not decrease, but grows very slowly and gradually - by about one 
percentage over 100 million years. Some botanists have suggested that the tilt of the earth's axis suddenly changed. Experts in celestial mechanics refuse to even discuss such a hypothesis; it seems completely ridiculous to them.
Is it possible to explain the cooling by the fact that the Earth’s “blanket” has become leaky - the greenhouse effect of its atmosphere has decreased? To do this, the carbon dioxide content in it had to decrease. It depends on how quickly plants consume carbon dioxide. The more lush the vegetation, the higher the photosynthesis and the lower the CO content in the atmosphere. But when it gets colder, the vegetation becomes less lush, and the carbon dioxide content in the air increases. The greenhouse effect inhibits cooling caused by other factors.
Maybe the Earth “changed clothes” into different, lighter clothes? After all, we, too, dress in white to escape the heat. White surfaces reflect Sun rays. For the Earth to become more white, extensive glaciers, sea ice and snow fields must appear. They only appear when low temperatures. An increase in albedo (reflectivity) can support cooling, but cannot be its cause.
Before 35 million years ago, snow and ice probably did not exist anywhere except high mountains. But the polar latitudes received the same amount solar heat how much do they get it now. Where did the extra heat come from? In winter, there is ice in the Sea of Azov, but the southwestern part Barents Sea never freezes. This is explained by the fact that a warm current approaches the northern shores of Europe. Maybe 40-50 million years ago it was more powerful? Alas, this explanation does not fit either. Once upon a time there was no sea at all between Scandinavia and Greenland. Fifty-five million years ago they began to slowly move away from each other, and only about 30 million years ago it became established deep sea communication between the Norwegian-Greenland and Polar basins. There was no sea through which the ancient Gulf Stream could flow!
The oceans and the Earth's atmosphere form a single climate machine. Location of continents Northern Hemisphere did not create conditions for the warm climate of the Arctic. But the situation was saved by the Southern Hemisphere. Australia was then much further south and formed a single continent with Antarctica. South America was connected to it - there was no Drake Passage. In such conditions warm currents, caused by easterly winds in subtropical latitudes, turned south along the eastern shores South America and Australia and reached Antarctica. Within its borders a fairly warm climate prevailed and forests of southern beech grew. It was through Antarctica that marsupials, many representatives of the plant world and even freshwater crustaceans penetrated from America to Australia. Two huge eddies in the Southern Hemisphere - one in the Pacific and the other in the Atlantic and Indian Oceans - warmed the temperate and polar latitudes. There was so much heat that it was enough to heat the Northern Hemisphere.
55 million years ago, Australia began to slowly move north. But there was an isthmus between it and Antarctica for a long time, and then the strait was narrow and shallow. Only 35 million years ago south of Australia A powerful ocean current arose, driven by westerly winds. This has fundamentally changed climatic conditions the whole Earth. Two whirlpools of the Southern Hemisphere merged into one. Now, from the southeastern coast of South America (still connected with Antarctica), the waters of the ocean made an almost round-the-world journey near the coast of Antarctica, the southwestern coast of South America and turned north. Further along the equator they were already driven easterly winds. Through a wide and deep strait between Australia (although it had moved away from Antarctica, it was much further south than now) and Southeast Asia, the current penetrated into Indian Ocean, then turned south and... the cycle repeated.
Glaciers cover Antarctica
In the far and cold south for a time long journey The waters had time to cool greatly. Then the cooled waters penetrated into tropical latitudes and cooled them as well. The cooling caused the growth of glaciers in East Antarctica. The names East and West Antarctica are arbitrary. In essence, any part of this continent will be north of the South Pole. But European travelers usually went to Antarctica via the Atlantic Ocean. For them, its more rugged part, adjacent to South America, was in the west, and the main, more massive part was in the east. If you mentally remove the modern ice cover, then West Antarctica will turn into an archipelago of islands, while East Antarctica will still remain a continent.
For glaciers to grow, it is necessary that the snow that falls during the winter does not have time to melt in the summer. There is more and more snow, gradually turning into ice under the weight of the overlying layers. Having accumulated in large masses, the ice begins to flow, like lava (but much slower). Streams of ice move in the mountain valleys, while on the plains huge ice sheets and domes with relatively steep edges and a flat middle, similar to loaves, form. This analogy is not accidental - after all, the dough takes the shape of a loaf according to the same hydromechanical laws by which ice takes the shape of a dome. Both dough and ice can be considered very viscous liquids.
In the center of East Antarctica are the Gamburtsev Mountains. Now they are buried under the ice. The mountains were discovered by measuring the thickness of the glacier.
On the tops of the Gamburtsev Mountains, glaciers could have appeared even before the cold snap began. When the temperature dropped, glaciers occupied the entire mountain range. A cold air mass formed above it, which cooled surrounding area. The larger the glaciers became, the better the conditions were for their further growth. Very quickly (of course, in a geological sense), in just a few tens of thousands of years, glaciers occupied the entire East Antarctica and reached its shores. But they almost never descended into the sea and almost never gave birth to icebergs.
The emergence of an ice sheet covering an area of 10 million square kilometers had a huge impact on the climate and greatly intensified the initial cooling. Ice covered seven percent of the entire land surface. Snow began to fall and sea ice appeared. Huge white surfaces reflected the sun's rays. As a result, the entire Earth has become colder - not only in the Southern, but also in the Northern Hemisphere. The cooling was accompanied by increased aridity - it was at this time that the Sahara Desert was formed.
The growth of glaciers also caused a decrease in sea levels. Water constantly evaporates from its surface, but just as constantly it returns back - the moisture that is carried by air currents to land, then flows down rivers again into the ocean. But when glaciers grow, the snow that falls on them does not return to the ocean, but is used to build glaciers: the volume of water bound in the glaciers is, as it were, subtracted from the volume of the ocean. 35 million years ago, sea levels dropped by about sixty meters. As a result, vast shallow waters turned into dry land. The sea has left most of the East European Plain and Western Siberia.
The vegetation has changed dramatically. Before the cold snap began, palm trees grew all the way to the coast of the Kara and Okhotsk seas. When it became colder, they survived only in the southern part of the East European Plain, in Central Asia and in the Vladivostok region.
But the animal world has undergone the most important changes. Until 35 million years ago, polytuberculates were widespread - small animals similar to rodents, but with a completely different internal structure. They became extinct and were replaced by rodents. Ancient predators and ancient ungulates became extinct, and in their place the development of modern predators and ungulates began. Changes in the order of primates are of great importance. Until 35 million years ago, only lemurs and tarsiers were common - lower primates. Now lemurs are found in Madagascar, but in the rest tropical zone Most of them died out with the onset of cooling. Lemurs were replaced by monkeys.
So, the main features of the nature around us were formed 35 million years ago as a result of the beginning of glaciation in East Antarctica. Glaciation was a cause, but it was not the root cause. Everything, as we already know, began with the separation of Australia and Antarctica and the movement of Australia to the north.
The Long Journey of Earth's Nature
35 million years ago, only the basic features of modern nature arose, but it was still not very similar to what we see today. The earth had a long and difficult journey ahead of it. Australia's northward movement continued; about 20 million years ago, the deep-sea strait that separated it from South-East Asia(shallow straits still exist there). The equatorial current of the Pacific Ocean, which had previously penetrated into the Indian Ocean, turned south along the coast of Australia and began to warm the temperate latitudes of the Southern Hemisphere. In the north, deep-sea communication was finally established between the Norwegian-Greenland and Polar basins, and it was penetrated warm waters. Warming occurred in both the north and the extreme south.
Alas, it was short-lived. 25 million years ago, South America began to move away from Antarctica. 12-14 million years ago the strait between them became quite wide and deep. The Southern Circular Current began to pass through the Drake Passage, encircling Antarctica. Water exchange between tropical and temperate latitudes of the Southern Hemisphere has again sharply decreased. It got colder in the polar latitudes, but it became warmer in the tropics - cold waters from the south no longer reached there. It was then that modern climatic contrasts arose, when some places suffer from heat, while others suffer from cold. The glaciers of Antarctica have increased - they also occupied West Antarctica.
Cooling in temperate latitudes caused increased aridity. It was then, about 12 million years ago, that the steppes arose in the south of the East European Plain. Herds of hipparions roamed the steppes of Eurasia and the savannas of Africa - three-toed relatives of horses that moved from America along the land “bridge” that existed on the site of the modern Bering Strait. Ramapithecus, which can be considered our direct ancestors, spread to southern Asia and Africa. Their height was small - about a meter, but they already walked on two legs.
About three million years ago, ice sheets appeared in the Northern Hemisphere. They covered Greenland, Iceland and the land that was in place of the Barents Sea. The emergence of new genera of animals - elephants, bulls and horses - is associated with new cooling and increased aridity. In East Africa, Australopithecus (descendants of Ramapithecus) began to hunt using the first stone tools - they turned into people.
About a million years ago, glaciation swept across the temperate latitudes of the Northern Hemisphere. At the edge of the glacier, very cold and dry steppes dominated, mammoths and hairy rhinoceroses grazed in them. The glaciers advanced and then retreated again. Our time falls on one of the periods of least development of glaciers.
Will acknowledging drastic changes lead to some incorrect conclusions? Indeed, at the beginning of the 19th century, some believed that after each catastrophe there follows a new “act of divine creation.” The author of the “catastrophe theory” himself, Georges Cuvier, did not write anything like this. In his opinion, the deserted continent was inhabited by animals that came from other places. Cuvier did not specify how they appeared there. Some of Cuvier’s students wrote about “divine creation”, trying to reconcile his views with religious ideology.
What is the situation today, when no one doubts the validity of evolutionary theory? It has now been proven that many organisms that suddenly appeared after the disaster actually existed before it, but were very rare or found only in certain limited areas. When the “masters of the Earth” perished, the former pariahs came to the forefront of geological history. They quickly multiplied, spread widely and became the new masters of the Earth. At first, there were no organisms that could master all the conditions suitable for life. This gave impetus to rapid evolution.
Monkeys, for example, existed before the latest disaster, but were much less common than lemurs. It is possible that if warm and humid climate preserved, lemurs would still dominate today. At one of the reports I gave in Moscow, the question was asked: “If the glaciation of Antarctica had not begun, then we would have lived among subtropical forests? I had to give the following answer: “There would indeed be subtropical forests here, but it would not be us who would live in them, but lemurs with huge eyes.” Cooling increased the rate of evolution many times over. Great catastrophes are, in essence, revolutions in the development of the organic world. Without them, it would have developed much more slowly.
In this regard, we recall the words of the great English naturalist of the 17th century, William Harvey: “Do not praise, do not blame - everyone worked well.” Once upon a time, supporters of Georges Cuvier and Charles Lyell argued fiercely among themselves. Now it is clear that both were right. Both slow and gradual development and disasters are explained by natural causes.
The last great “catastrophe” is associated with the beginning of glaciation in Antarctica. Will another catastrophe occur if human-caused warming causes glaciers to melt and sea levels to rise by 70 meters? A look into the past shows that " global flood" will not be. After all, 20-30 million years ago the volume of glaciers was already close to what it is today. At that time, a rather warm climate prevailed in temperate and polar latitudes. The ice sheet of East Antarctica was melting at the edges, but did not decrease in size - much more snow fell on its surface than now.
In my opinion, the upcoming warming will also lead to heavy snowfalls. The largest ice sheets may even increase their thickness as a result. They will produce fewer icebergs and melt a little at the edges, but will not decrease in volume until the volume of melting exceeds the volume of snow water received by the glaciers each year. For this to happen, a warming of 10-12 degrees is needed. Only after this will Antarctica's glaciers begin to disintegrate and sea levels to rise. But there is no talk of such warming in the foreseeable future. With less warming, sea levels could even drop slightly as Antarctic glaciers become thicker.
Homo sapiens, Homo sapiens, evolved from apes that spread widely 35 million years ago. If humanity lives up to this high title and acts wisely, the last great “catastrophe” will not truly turn into a catastrophe.
D. Kvasov, Doctor of Geographical Sciences
The ice of the Arctic and Antarctic is not at all eternal. Nowadays, due to the impending global warming caused by the environmental crisis of thermal and chemical pollution of the atmosphere, the mighty shields of frost-bound water are melting. This threatens a great disaster for a vast territory, which includes low-lying coastal lands of different countries, primarily European ones (for example, Holland).
But since the ice sheet of the poles is capable of disappearing, it means that it once arose during the development of the planet. "White caps" appeared - a very long time ago - within some limited interval of the geological history of the Earth. Glaciers cannot be considered an integral property of our planet as a cosmic body.
Comprehensive (geophysical, climatological, glaciological and geological) studies southern continent and many other areas of the planet have convincingly proven that the ice cover of Antarctica arose relatively recently. Similar conclusions were drawn regarding the Arctic.
Firstly, data from glaciology (the science of glaciers) indicate a gradual increase in ice cover over the past millennia. For example, the glacier covering the Ross Sea was much smaller in area just 5,000 years ago than it is now. It is assumed that at that time it occupied only half of the current territory it covers. Until now, according to some experts, the slow freezing of this gigantic tongue of ice continues.
Drilling wells in the thickness continental ice gave unexpected results. The cores clearly showed how successive layers of ice froze over the last 10-15 thousand years. IN different layers Spores of bacteria and plant pollen were found. Consequently, the ice sheet of the continent grew and actively developed during the last millennia. This process was influenced by climatic and other factors, since the rate of formation of ice layers varies.
Some of the bacteria found frozen in the Antarctic ice (up to 12 thousand years old) were revived and studied under a microscope. At the same time, a study of air bubbles immured in these huge layers of frozen water was organized. Work in this area has not been completed, but it is clear that scientists have evidence of the composition of the atmosphere in the distant past.
Geological studies have confirmed that glaciation is a short-term natural phenomenon. The oldest global glaciation discovered by scientists occurred over 2000 million years ago. Then these colossal catastrophes were repeated quite often. The Ordovician glaciation occurs in an era 440 million years removed from our time. During this climate cataclysm, a great many marine invertebrates died. There were no other animals at that time. They appeared much later to become victims of the next freezing attacks that covered almost all continents.
The last glaciation, apparently, has not yet ended, but has retreated for a while. The great retreat of the ice occurred about 10 thousand years ago. Since then, powerful ice shells that once covered Europe, a large part of Asia and North America have remained only in Antarctica, on the Arctic islands and on top of the waters of the North Sea. Arctic Ocean. Modern humanity lives in the so-called period. interglacial period, which should be replaced by a new advance of ice. Unless, of course, they melt completely first.
Geologists have received a lot of interesting facts about Antarctica itself. The Great White Continent apparently was once completely ice-free and had an even and warm climate. 2 million years ago, dense forests, like taiga, grew on its coasts. In ice-free spaces, it is possible to systematically find fossils from a later, Middle Tertiary time - imprints of leaves and twigs of ancient heat-loving plants.
Then, over 10 million years ago, despite the cooling that began on the continent, the local expanses were occupied by vast groves of laurels, chestnut oaks, cherry laurel trees, beech trees and other subtropical plants. It can be assumed that these groves were inhabited by animals characteristic of that time - mastodons, saber-tooths, hipparions, etc. But much more striking are the ancient finds in Antarctica.
In the central part of Antarctica, for example, the skeleton of the fossil lizard Lystrosaurus was found - not far from the South Pole, in outcrops rocks. Large reptile two meters long, it had an unusually terrible appearance. The age of the find is 230 million years.
Lystrosaurs were, like other animal lizards, typical representatives of heat-loving fauna. They inhabited hot, swampy lowlands, abundantly overgrown with vegetation. Scientists have discovered an entire belt in geological deposits South Africa, overflowing with the bones of these animals, which was called the Lystrosaurus Zone. Something similar was found on the South American continent, as well as in India. It is obvious that in the early Triassic period, 230 million years ago, the climate of Antarctica, Hindustan, South Africa and South America was similar, since the same animals could live there.
Scientists are looking for an answer to the riddle of the birth of glaciers - what global processes, invisible in our interglacial era, 10 thousand years ago bound a huge part of the land and the World Ocean under a shell of solidified water? What causes such drastic climate change. None of the hypotheses are convincing enough to become generally accepted. Nevertheless, it is worth remembering the most popular ones. Among the hypotheses, three can be distinguished, conventionally called cosmic, planetary-climatic and geophysical. Each of them gives preference to a certain group of factors or one decisive factor that served as the root cause for the cataclysm.
The space hypothesis is based on data from geological surveys and astrophysical observations. When establishing the age of moraine and other rocks deposited by ancient glaciers, it turned out that climatic catastrophes occurred with strict frequency. The ground froze in a time interval that seemed specially designated for this. Each great cold snap is separated from the others by approximately 200 million years. This means that after every 200 million years of the dominance of a warm climate, a long winter reigned on the planet, and powerful ice caps formed. Climatologists turned to materials accumulated by astrophysicists: what could be responsible for such an incredibly long time between several iterative (regularly occurring) events in the atmosphere and hydrosphere of a space object? Perhaps with cosmic events comparable in scale and time frame?
Calculations by astrophysicists call such an event the revolution of the Sun around the galactic core. The dimensions of the Galaxy are extremely large. The diameter of this cosmic disk reaches a size of approximately 1000 trillion km. The Sun is located at a distance of 300 trillion km from the galactic core, so the full revolution of our star around the center of the system takes such a colossal period of time. Apparently, on its way, the Solar System crosses some area in the Galaxy, under the influence of which another glaciation occurs on Earth.
This hypothesis is not accepted scientific world, although many seem convincing. However, scientists do not have facts on the basis of which it could be proven or at least convincingly confirmed. There are no facts confirming the galactic influence on the million-year fluctuations in the planet’s climate, except strange coincidence there are no numbers. Astrophysicists have not found a mysterious region in the Galaxy where the Earth begins to freeze. The type of external influence that could cause something like this to happen has not been found. Some suggest a decrease in solar activity. It seems that the “cold zone” reduced the intensity of the flow of solar radiation, and as a result, the Earth began to receive less heat. But these are just assumptions.
Supporters original version came up with a name for the imaginary processes occurring in the stellar system. Full turn The solar system around the galactic core was called the galactic year, and the short interval during which the Earth remains in an unfavorable “cold zone” was called the cosmic winter.
Some supporters of the extraterrestrial origin of glaciers are looking for climate change factors not in the distant Galaxy, but inside the Solar System. For the first time such an assumption was made in 1920, its author was the Yugoslav scientist M. Milankovic. He took into account the inclination of the earth to the plane of the ecliptic and the inclination of the ecliptic itself to the solar axis. According to Milankovitch, the answer to the great glaciations should be sought here.
The fact is that depending on these inclinations the amount of radiant energy of the Sun reaching earth's surface. In particular, different latitudes receive different numbers of rays. The relative position of the axes of the Sun and Earth, changing over time, causes fluctuations in the number solar radiation in different regions of the planet and under certain circumstances leads to fluctuations in the stage of alternation of warm and cold phases.
In the 90s XX century this hypothesis has been thoroughly tested using computer models. Numerous external influences on the location of the planet relative to the Sun - the Earth’s orbit slowly evolved under the influence of the gravitational fields of neighboring planets, the trajectory of the Earth’s movement was gradually transformed.
French geophysicist A. Berger compared the obtained figures with geological data, with the results of radioisotope analysis of marine sediments, showing temperature changes over millions of years. Temperature fluctuations in ocean waters completely coincided with the dynamics of the process of transforming the earth's orbit. Consequently, the cosmic factor could well have provoked the onset of climate cooling and global glaciation.
At the moment, it cannot be said that the Milankovitch conjecture has been proven. First, it requires additional long-term checks. Secondly, scientists tend to be of the opinion that global processes could not be caused by the action of only one factor, especially if it is external. Most likely, there was synchronization of the actions of various natural phenomena, and the decisive role in this amount belonged to the Earth’s own elements.
The planetary-climate hypothesis is based precisely on this position. The planet is a huge climatic machine, which with its rotation directs the movement of air currents, cyclones and typhoons. The inclined position relative to the plane of the ecliptic causes non-uniform heating of its surface. In a sense, the planet itself is a powerful climate control device. And her internal forces are the reasons for his metamorphosis.
These internal forces include mantle currents, or so-called. convection currents in layers of molten magmatic matter that compose the mantle layer underlying the earth's crust. The movements of these currents from the core of the planet to the surface give rise to earthquakes and volcanic eruptions, and mountain-building processes. These same currents cause the appearance of deep splits in the earth's crust, called rift zones (valleys), or rifts.
Rift valleys are numerous on the ocean floor, where the crust is very thin and easily breaks through the pressure of convection currents. Volcanic activity is extremely high in these areas. Here, mantle material is constantly pouring out from the depths. According to the planetary-climate hypothesis, it is magma outpourings that play a decisive role in the oscillatory process of historical transformation of the weather regime.
Rift faults on the ocean floor, during periods of greatest activity, release enough heat to cause intense evaporation of seawater. This causes a lot of moisture to accumulate in the atmosphere, which then falls as precipitation onto the Earth’s surface. In cold latitudes, precipitation falls in the form of snow. But since their loss is too intense and the number is large, then snow cover becomes more powerful than usual.
The snow cap melts extremely slowly; for a long time, the influx of precipitation exceeds its outflow - melting. As a result, it begins to grow and transforms into a glacier. The planet's climate is also gradually changing as a stable area of non-melting ice forms. After some time, the glacier begins to expand, since the dynamic system of uneven inflow and outflow cannot remain in balance, and the ice increases to incredible sizes and binds almost the entire planet.
However, the maximum of glaciation simultaneously becomes the beginning of its degradation. Having reached a critical point, an extremum, ice growth stops, encountering stubborn resistance from other natural factors. The dynamics became reversed; the rise gave way to a decline. However, the victory of “summer” over “winter” does not come immediately. Initially, a protracted “spring” begins for several thousand years. This is a change of short bouts of glaciation with warm interglacials.
Earth civilization was formed in the era of the so-called. Holocene interglacial. It began about 10,000 years ago, and, according to mathematical models, it will end in end of III thousand AD, i.e. around 3000. From this moment the next cold snap will begin, which will reach its apogee after 8000 of our calendar.
The main argument of the planetary-climate hypothesis is the fact of periodic changes in tectonic activity in rift valleys. Convection currents in the bowels of the Earth excite the earth's crust with varying strengths, and this leads to the existence of such eras. Geologists have materials that convincingly prove that climate fluctuations are chronologically linked to periods of greatest tectonic activity of the subsoil.
Rock deposits show that the next climate cooling was accompanied by significant movements of powerful blocks of the earth's crust, which were accompanied by the appearance of new faults and the rapid release of hot magma from both new and old rifts. However, the same argument is used by supporters of other hypotheses to confirm their correctness.
These hypotheses can be considered as variations of a single geophysical hypothesis, since it is based on data about the geophysics of the planet, namely, it relies entirely on paleogeography and tectonics in its calculations. Tectonics studies the geology and physics of the process of movement of crustal blocks, and paleogeography studies the consequences of such movement.
As a result of multimillion-year displacements of colossal masses of solid matter on the earth's surface, the outlines of the continents, as well as the topography, changed significantly. The fact that thick layers of marine sediments or bottom silts are found on land directly indicates movements of crustal blocks, accompanied by its subsidence or uplift in this region. For example, the Moscow region is composed of large quantities limestones, replete with remains sea lilies and corals, as well as clayey rocks containing mother-of-pearl shells of ammonites. It follows from this that the territory of Moscow and its environs was flooded at least twice sea waters- 300 and 180 million years ago.
Each time, as a result of the displacement of huge blocks of the crust, either a lowering or raising of a certain section of it occurred. In the case of subsidence, ocean waters invaded the continent, an advance of seas and transgression occurred. As the seas rose, they retreated (regression), the land surface grew, and often mountain ranges rose in place of the former salt basin.
The ocean is a powerful regulator and even generator of the Earth's climate due to its colossal heat capacity and other unique physical and chemical properties. This water reservoir controls the most important air flows, air composition, precipitation and temperature patterns over vast land areas. Naturally, an increase or decrease in its surface area affects the nature of global climate processes.
Each transgression significantly increased the area of salt waters, while regression of the seas significantly reduced this area. Accordingly, climate fluctuations occurred. Scientists have found that periodic planetary cooling approximately coincided in time with periods of regression, while the advance of seas onto land was invariably accompanied by climate warming. It would seem that another mechanism of global glaciations has been found, which is perhaps the most important, if not exclusive. However, there is another climate-forming factor that accompanies tectonic movements - mountain building.
The advance and retreat of ocean waters passively accompanied the growth or destruction of mountain ranges. The earth's crust, under the influence of convection currents, wrinkled into chains of the highest peaks here and there. Therefore, an exclusive role in long-period climatic fluctuations should still be given to the process of mountain building (orogenesis). Not only the surface area of the ocean, but also the direction of air flows depended on it.
If a mountain range disappeared or a new one appeared, then the movement of large air masses changed dramatically. Following this, the long-term weather regime in the area was transformed. Thus, as a result of mountain building throughout the planet, local climates radically changed, which led to a general degeneration of the Earth’s climate. As a result, the emerging trend towards global cooling only gained momentum.
The last glaciation is tied to the era of the Alpine mountain building that is ending before our eyes. The result of this orogeny was the Caucasus, the Himalayas, the Pamirs and many other highest mountain systems on the planet. The eruptions of volcanoes Santorini, Vesuvius, Bezymianny and others were provoked by this very process. We can say that today this hypothesis dominates modern science, although not fully proven.
The hypothesis received an unexpected development, and in application to the climatology of Antarctica. The ice continent acquired its current appearance entirely due to tectonics, but the decisive role was played neither by regression nor by changes in air currents (these factors are considered secondary). The main influencing factor should be called water cooling. Nature froze Atlantis in exactly the same way as a person cools a nuclear reactor.
The “nuclear” version of the geophysical hypothesis is based on the theory of continental drift and paleontological finds. Modern scientists do not doubt the existence of movement of continental plates. Since the blocks of the earth's crust are mobile due to mantle convection, this mobility is accompanied by a horizontal displacement of the continents themselves. They crawl slowly, at a speed of 1-2 cm per year, along the molten mantle layer.
The relative position of the continents changed over time, which affected the Earth's climate, since air and ocean currents depended on it. Fossilized bones of Lystrosaurus in Antarctica and extremely numerous similar finds in Africa, South America and India confirm the assumption of scientists that once all these southern lands, including Australia, were united into one supercontinent.
The single southern continent of Gondwana existed for over 200 million years: from 240 to 35 million years ago. About 35 million years ago, tectonic movements of the crust finally split it into the current “pieces,” one of which was Antarctica. The split had a negative impact on her climate as she found herself isolated.
Previously, the Antarctic coast was washed by only two cold currents, the effect of which was fully compensated by warm ocean currents coming from Australia, docked with Antarctica. After all the pieces of the supercontinent spread out in different directions and left Antarctica alone in the middle of the ocean, it began to be actively washed by many currents, which over time formed a continuous stream - the so-called. circumpolar current.
It surrounded Antarctica and gained strength as the “fifth ocean” grew and deepened - southern waters Antarctic region. Every second, the current carries more water than all the rivers on the planet, which is not surprising given the average depth of the “southern ocean” of 3 km. The current covers all layers of water to the very bottom, being the greatest climatic barrier in nature. This fantastic barrier absorbs all the heat that is supplied to the white continent from the outside.
It turned out that a drop in air temperature in the Antarctic region of just 3 °C was sufficient for the barrier to begin to act like a refrigerator. Now the increase in snow and ice cover was inevitable even if the relatively warm regime remained on the continent. The glacier gradually, in the process of growth, displaced heat to the outskirts, where it was absorbed by the circumpolar current.
The very first ice caps on the white continent began to grow 30 million years ago on the Gamburtsev Mountains, today completely hidden under an ice shell. Approximately 25-20 million years ago, glacier tongues descended onto the plains and from that moment the complete glaciation of Antarctica became inevitable. Thus, according to one of the models, the formation of the ice sheet of the last continent discovered by man took place.
Life in the Arctic is intensifying 5821
Now Antarctica is one of the places on Earth where warming is happening especially quickly. And before that, for 37 million years, Antarctica cooled. During this period, the temperature there never increased, and only in the last 50 years have scientists observed a reverse process, when the coldest continent began to warm up.
This conclusion was made by a group of scientists led by Dr. John B. Anderson from Rice University (Houston, USA) based on spore-pollen analysis, subglacial drilling and seismic measurements in the area of the Antarctic Peninsula - the northern tip of Antarctica.
History of the continent - slow freezing
As Anderson says, at the very beginning of its history, Antarctica was a fairly warm continent - the air temperature did not drop below plus 10 degrees. And only after completely separating from Gondwana did it begin to cool. Why this happened is not completely clear. There are only hypotheses on this score, around which there are fierce debates. Most scientists attribute the cooling of Antarctica to a simultaneous decrease in carbon dioxide levels in the atmosphere and its isolation from the supercontinent.
The first glaciers appeared in the mountains of Antarctica approximately 37–34 million years ago. At the same time, according to Anderson, the carbon dioxide content in the atmosphere began to decrease - then it reached modern values (390 ppm). And if at first Antarctica had a mild climate and lush vegetation prevailed there, then at that time most angiosperms disappeared. For the next few tens of millions of years, forests with birches and conifers dominated the continent, and tundra extended. The cooling continued, the forests gradually disappeared, and the tundra took their place. About 12 million years ago, Antarctica was still covered with shrubs, mosses and lichens.
A further drop in the concentration of carbon dioxide in the atmosphere, the formation of the Drake Passage, which finally separated Antarctica from South America, and the formation of the Antarctic Circumpolar Cold Current led to the continent being completely covered in ice. “The latest ice to appear was in the north of the Antarctic Peninsula - approximately 5-3 million years ago. The Antarctic Peninsula was the last to be covered by ice. When the ice had already covered the entire continent, there was still a piece of tundra there,” says Anderson.
Modern Antarctica
Now Antarctica is getting warmer. For example, over the past 50 years, the average winter temperature on the Antarctic Peninsula has increased by 6 degrees - this is five times more than the global average. If previously the ice around the peninsula remained all year round, now it melts in the summer. Another evidence of warming is that in summer the coast of the Antarctic Peninsula is freed from ice, covered with grasses and mosses, and then it is difficult to believe that this is Antarctica.
An article by Dr. Anterson and his colleagues on what Antarctica looked like over the past 37 million years is published in the latest issue of the journal PNAS.
Antarctica is covered in carnivorous grass
April 9, 2011. The turf pike, which covers the coast of the Antarctic Peninsula and islands off the coast of Antarctica in summer, assimilates nitrogen in a special way. According to scientists, it is this that will allow the pike to occupy the soon leading positions in the region.
Scientists from several universities, led by Dr. Paul W. Hill of Bangor University, discovered unique way, with the help of which a vascular plant (Antarctic pike, also known as turf pike) on one of the islands off the coast of Antarctica absorbs nitrogen. The pike does not wait for microorganisms to convert organic matter into mineral components (this process occurs very slowly in these latitudes). It immediately absorbs proteins - short peptides. It has always been believed that only mushrooms and animals can do this, but in flora- mosses.
The unique ability allowed the pike to seize a dominant position on the island of Sainey (this is one of the South Orkney Islands), where scientists conducted their research, and practically displace mosses.
Green Antarctica
“Many people believe that Antarctica is always completely covered with snow and ice. But in the summer, on the Antarctic Peninsula and the islands surrounding the continent itself, the snow melts, and plants appear there - mosses and two types of vascular plants - Colobanthus quitensis(Colobanthus Quito) and Deschampsia Antarctica ( Antarctic pike ) " says Paul Hill.
According to scientists, over the past 50 years the climate along the Antarctic coast has been warming faster than anywhere else on Earth. Summer temperatures there have increased by about one degree Celsius, and summer period became longer. Naturally, the plants immediately responded to these changes.
Antarctic pike (Deschampsia Antarctica)
Typically, the coastal ecosystems of Saini Island were dominated by mosses. But in recent years, scientists have observed another trend: cereals are taking the leading positions. Although mosses Sanionia uncinata are still found quite often and, as a rule, they are the first to populate a new territory. As they die, a small layer of soil forms. And then other settlers can easily grow there. True, in this case a problem arises - competition for resources: nutrients and light necessary for photosynthesis.
The Antarctic pike managed to win the competition. Its sharp leaves penetrate the moss, so they easily get the right amount of light. With nutrients, however, the situation is more complicated.
A New Way to Absorb Nitrogen
Plants need nitrogen to live. But they are able to assimilate only its inorganic compounds, for example, ammonium salts and nitric acid salts. And organic nitrogen can only be converted into mineral compounds by soil microorganisms. Some plants form a symbiosis with them for this purpose. However, according to Hill, plants in Antarctica do not do this. But vascular plants somehow coped with this problem. To understand how, Dr. Hill and his colleagues conducted the following experiment: they introduced special labeled forms of organic nitrogen into the soil and watched how plants absorbed them.
“The ability of plants to absorb nitrogen in the very first stages of mineralization is the key to success. In our studies, we showed that in Antarctica, Antarctic pike absorbs nitrogen through its roots in the form of short peptides. This is the very initial stage of protein conversion in the soil. In this way, these plants absorb nitrogen three times faster than the absorption of amino acids, nitrates or ammonium salts. And 160 times faster than the mosses with which this grass competes,” write the authors of the study. In their opinion, if the temperature in Antarctica rises even more, then organic matter will decompose faster. This will provide additional benefits to pike and it looks like this grass will continue its expansion along the coast.
“The rapid pathway we discovered for nitrogen assimilation has implications not only for Antarctic ecosystems. If it turns out that plants in temperate and tropical latitudes can act in the same way, then this can be used to create new technologies in agriculture“says study co-author Kevin Newsham of the British Antarctic Survey.
For more information on how grasses compete with mosses in Antarctica and acquire nitrogen, see the article “Vasclular plant success in a warming Antarctic may be due to efficient nitrogen acquisition,” published in the latest issue of the journal Nature Climate Change.
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