Ice Age history. How people survived the Ice Age

The oldest glacial deposits known today are about 2.3 billion years old, which corresponds to the lower Proterozoic geochronological scale.

They are represented by fossilized mafic moraines of the Gowganda Formation in the southeastern Canadian Shield. The presence in them of typical iron-shaped and teardrop-shaped boulders with polishing, as well as the occurrence on a bed covered with hatching, indicates their glacial origin. If the main moraine in English-language literature is denoted by the term till, then more ancient glacial deposits that have passed the stage lithification(petrification), usually called tillites. The sediments of the Bruce and Ramsay Lake formations, also of Lower Proterozoic age and developed on the Canadian Shield, also have the appearance of tillites. This powerful and complex complex of alternating glacial and interglacial deposits is conventionally assigned to one glacial era, called the Huronian.

Deposits of the Bijawar series in India and the Transvaal and Witwatersrand series in India are correlated with the Huronian tillites. South Africa and the Whitewater series in Australia. Consequently, there is reason to talk about the planetary scale of the Lower Proterozoic glaciation.

As the Earth further developed, it experienced several equally large ice ages, and the closer to modern times they took place, the greater the amount of data we have about their features. After the Huronian era, the Gneissian (about 950 million years ago), Sturtian (700, perhaps 800 million years ago), Varangian, or, according to other authors, Vendian, Laplandian (680-650 million years ago), then Ordovician are distinguished (450-430 million years ago) and, finally, the most widely known Late Paleozoic Gondwanan (330-250 million years ago) glacial eras. Standing somewhat apart from this list is the Late Cenozoic glacial stage, which began 20-25 million years ago, with the appearance of the Antarctic ice sheet and, strictly speaking, continues to this day.

According to the Soviet geologist N.M. Chumakov, traces of the Vendian (Lapland) glaciation were found in Africa, Kazakhstan, China and Europe. For example, in the basin of the middle and upper Dnieper, drilling wells uncovered layers of tillites several meters thick dating back to this time. Based on the direction of ice movement reconstructed for the Vendian era, it can be assumed that the center of the European ice sheet at that time was located somewhere in the Baltic Shield region.

Gondwanan ice age has attracted the attention of specialists for almost a century. At the end of the last century, geologists discovered in southern Africa, near the Boer settlement of Neutgedacht, in the river basin. Vaal, well-defined glacial pavements with traces of shading on the surface of gently convex “ram foreheads” composed of Precambrian rocks. This was a time of struggle between the theory of drift and the theory of sheet glaciation, and the main attention of researchers was focused not on the age, but on the signs of the glacial origin of these formations. The glacial scars of Neutgedacht, “curly rocks” and “ram’s foreheads” were so well defined that A. Wallace, a well-known like-minded person of Charles Darwin, who studied them in 1880, considered them to belong to the last ice age.

Somewhat later, the late Paleozoic age of glaciation was established. Glacial deposits were discovered underlying carbonaceous shales with plant remains from the Carboniferous and Permian periods. In the geological literature, this sequence is called the Dvaika series. At the beginning of this century, the famous German specialist on modern and ancient glaciation of the Alps A. Penck, who was personally convinced of the amazing similarity of these deposits with young Alpine moraines, managed to convince many of his colleagues of this. By the way, it was Penkom who proposed the term “tillite”.

Permocarbonaceous glacial deposits have been found on all continents of the Southern Hemisphere. These are the Talchir tillites, discovered in India back in 1859, Itarare in South America, Kuttung and Kamilaron in Australia. Traces of the Gondwana glaciation have also been found on the sixth continent, in the Transantarctic Mountains and the Ellsworth Mountains. Traces of synchronous glaciation in all these territories (with the exception of the then unexplored Antarctica) served as an argument for the outstanding German scientist A. Wegener in putting forward the hypothesis of continental drift (1912-1915). His rather few predecessors pointed out the similarity of the outlines of the western coast of Africa and the eastern coast South America, which resemble parts of a single whole, as if torn in two and distant from each other.

It has been repeatedly pointed out the similarity of the Late Paleozoic flora and fauna of these continents, their commonality geological structure. But it was precisely the idea of ​​the simultaneous and, probably, single glaciation of all the continents of the Southern Hemisphere that forced Wegener to put forward the concept of Pangea - a great proto-continent that split into parts, which then began to drift across the globe.

By modern ideas, South part Pangea, called Gondwana, split about 150-130 million years ago, in the Jurassic and early Cretaceous periods. The modern theory of global plate tectonics, which grew out of A. Wegener’s guess, allows us to successfully explain all the currently known facts about the Late Paleozoic glaciation of the Earth. Probably, the South Pole at that time was close to the middle of Gondwana and a significant part of it was covered with a huge ice shell. Detailed facies and textural studies of tillites suggest that its feeding area was in East Antarctica and possibly somewhere in the Madagascar region. It has been established, in particular, that when the contours of Africa and South America are combined, the direction of glacial striations on both continents coincides. Together with other lithological materials, this indicates the movement of Gondwanan ice from Africa to South America. Some other large glacial streams that existed during this glacial era have also been restored.

The glaciation of Gondwana ended in the Permian period, when the proto-continent still retained its integrity. This may have been due to the migration of the South Pole towards the Pacific Ocean. Subsequently, global temperatures continued to gradually increase.

The Triassic, Jurassic and Cretaceous periods of the Earth's geological history were characterized by fairly even and warm climatic conditions over most of the planet. But in the second half of the Cenozoic, about 20-25 million years ago, the ice again began its slow advance on South Pole. By this time, Antarctica had occupied a position close to its modern one. The movement of the fragments of Gondwana led to the fact that there were no significant areas of land left near the southern polar continent. As a result, according to the American geologist J. Kennett, a cold climate arose in the ocean surrounding Antarctica. circumpolar current, which further contributed to the isolation of this continent and the deterioration of its climatic conditions. Near the planet's South Pole, ice from the most ancient glaciation of the Earth that has survived to this day began to accumulate.

In the Northern Hemisphere, the first signs of the Late Cenozoic glaciation, according to various experts, are between 5 and 3 million years old. It is impossible to talk about any noticeable shifts in the position of the continents over such a short period of time by geological standards. Therefore, the cause of the new ice age should be sought in the global restructuring of the energy balance and climate of the planet.

The classic region, which has been used for decades to study the history of the ice ages of Europe and the entire Northern Hemisphere, is the Alps. Proximity to the Atlantic Ocean and Mediterranean Sea provided a good moisture supply to the Alpine glaciers, and they sensitively responded to climate change by a sharp increase in their volume. At the beginning of the 20th century. A. Penk, having researched geomorphological structure alpine foothills, came to the conclusion that there were four major ice ages experienced by the Alps in the recent geological past. These glaciations were given the following names (from oldest to youngest): Günz, Mindel, Riss and Würm. Their absolute ages remained unclear for a long time.

Around the same time, information began to arrive from various sources that the lowland territories of Europe had repeatedly experienced the advance of ice. As actual position material accumulates polyglacialism(the concept of multiple glaciations) became increasingly stronger. By the 60s. of our century, the scheme of fourfold glaciation has received wide recognition in our country and abroad European plains, close to the Alpine scheme of A. Penk and his co-author E. Brückner.

Naturally, the deposits of the last ice sheet, comparable to the Würm glaciation of the Alps, turned out to be the most well studied. In the USSR it was called Valdai, in Central Europe - Vistula, in England - Devensian, in the USA - Wisconsin. The Valdai glaciation was preceded by an interglacial period, which in its climatic parameters was close to modern conditions or slightly more favorable. Based on the name of the reference size in which the deposits of this interglacial were exposed (the village of Mikulino, Smolensk region) in the USSR, it was called Mikulinsky. According to the Alpine scheme, this period of time is called the Riess-Würm interglacial.

Before the beginning of the Mikulino interglacial age, the Russian Plain was covered with ice from the Moscow glaciation, which, in turn, was preceded by the Roslavl interglacial. The next step down was the Dnieper glaciation. It is considered to be the largest in size and is traditionally associated with the Rissian Ice Age of the Alps. Before the Dnieper Ice Age, the warm and humid conditions of the Likhvin interglacial existed in Europe and America. The deposits of the Likhvin era are underlain by rather poorly preserved sediments of the Oka (Mindel in the Alpine scheme) glaciation. The Dook Warm Time is considered by some researchers to be no longer an interglacial, but a pre-glacial era. But in the last 10-15 years everything appears more messages about new, more ancient glacial deposits uncovered in various points of the Northern Hemisphere.

Synchronizing and linking the stages of the development of nature, reconstructed from various initial data and in different geographical locations of the globe, is a very serious problem.

Few researchers today doubt the fact of the natural alternation of glacial and interglacial eras in the past. But the reasons for this alternation have not yet been fully elucidated. The solution to this problem is hampered, first of all, by the lack of strictly reliable data on the rhythm of natural events: the stratigraphic scale of the Ice Age itself causes a large number of critical comments and so far there is no reliably verified version of it.

Only the history of the last glacial-interglacial cycle, which began after the degradation of the ice of the Ris glaciation, can be considered relatively reliably established.

The age of the Ris Ice Age is estimated at 250-150 thousand years. The Mikulin (Riess-Würm) interglacial that followed reached its optimum about 100 thousand years ago. Approximately 80-70 thousand years ago on everything globe a sharp deterioration in climatic conditions is recorded, marking the transition to the Würm glacial cycle. During this period, in Eurasia and North America they degrade broadleaf forests, giving way to the landscape of cold steppe and forest-steppe, there is a rapid change of faunal complexes: the leading place in them is occupied by cold-tolerant species - mammoth, hairy rhinoceros, giant deer, arctic fox, lemming. At high latitudes, old ice caps increase in volume and new ones grow. The water needed for their formation is draining from the ocean. Accordingly, its level begins to decrease, which is recorded along the ladder of marine terraces on the now flooded areas of the shelf and on the islands of the tropical zone. The cooling of ocean waters is reflected in the restructuring of the complexes of marine microorganisms - for example, they die out foraminifera Globorotalia menardii flexuosa. The question is how far did they advance at this time? continental ice, is still debatable.

Between 50 and 25 thousand years ago, the natural situation on the planet again improved somewhat - the relatively warm Middle Würmian interval began. I. I. Krasnov, A. I. Moskvitin, L. R. Serebryanny, A. V. Raukas and some other Soviet researchers, although the details of their construction differ quite significantly from each other, are still inclined to compare this period of time with an independent interglacial.

This approach, however, is contradicted by the data of V.P. Grichuk, L.N. Voznyachuk, N.S. Chebotareva, who, based on an analysis of the history of the development of vegetation in Europe, deny the existence of a large cover glacier in the early Würm and, therefore, do not see grounds for identifying the Middle Wurm interglacial epoch. From their point of view, the early and middle Wurm corresponds to a time-extended period of transition from the Mikulino interglacial to the Valdai (Late Wurm) glaciation.

In all likelihood, this controversial issue will be resolved in the near future thanks to increasingly wide application radiocarbon dating methods.

About 25 thousand years ago (according to some scientists, somewhat earlier), the last continental glaciation of the Northern Hemisphere began. According to A. A. Velichko, this was the time of the most severe climatic conditions during the entire Ice Age. An interesting paradox: the coldest climate cycle, the thermal minimum of the late Cenozoic, was accompanied by the smallest area of ​​glaciation. Moreover, this glaciation was very short in duration: having reached the maximum limits of its distribution 20-17 thousand years ago, it disappeared after 10 thousand years. More precisely, according to data summarized by the French scientist P. Bellaire, the last fragments of the European ice sheet broke up in Scandinavia between 8 and 9 thousand years ago, and the American ice sheet completely melted only about 6 thousand years ago.

The peculiar nature of the last continental glaciation was determined by nothing more than excessively cold climatic conditions. According to paleofloristic analysis data summarized by the Dutch researcher Van der Hammen and co-authors, average July temperatures in Europe (Holland) at this time did not exceed 5°C. Average annual temperatures V temperate latitudes decreased by approximately 10°C compared to modern conditions.

Oddly enough, excessive cold prevented the development of glaciation. Firstly, it increased the rigidity of the ice and, therefore, made it more difficult for it to spread. Secondly, and this is the main thing, the cold shackled the surface of the oceans, forming an ice cover on them that descended from the pole almost to the subtropics. According to A. A. Velichko, in the Northern Hemisphere its area was more than 2 times greater than the area of ​​modern sea ice. As a result, evaporation from the surface of the World Ocean and, accordingly, the moisture supply of glaciers on land sharply decreased. At the same time, the reflectivity of the planet as a whole increased, which further contributed to its cooling.

The European ice sheet had a particularly poor diet. The glaciation of America, which received its nourishment from the unfrozen parts of the Pacific and Atlantic oceans, was in much more favorable conditions. This was due to his significant big square. In Europe, glaciers of this era reached 52° N. latitude, while on the American continent they descended 12° to the south.

An analysis of the history of the Late Cenozoic glaciations of the Earth’s Northern Hemisphere allowed specialists to draw two important conclusions:

1. Ice ages have occurred many times in the recent geological past. Over the past 1.5-2 million years, the Earth has experienced at least 6-8 major glaciations. This indicates the rhythmic nature of climate fluctuations in the past.

2. Along with rhythmic and oscillatory climate changes, a tendency towards directional cooling is clearly visible. In other words, each subsequent interglacial turns out to be cooler than the previous one, and the glacial eras become more severe.

These conclusions relate only to natural patterns and do not take into account the significant anthropogenic impact on the environment.

Naturally, the question arises about what prospects such a development of events promises for humanity. Mechanical curve extrapolation natural processes into the future makes us expect the beginning of a new ice age within the next few millennia. It is possible that such a deliberately simplified approach to forecasting will turn out to be correct. In fact, the rhythm of climate fluctuations is becoming shorter and shorter and the modern interglacial era should soon end. This is also confirmed by the fact that the climatic optimum (the most favorable climatic conditions) of the post-glacial period has long passed. In Europe the optimal natural conditions took place 5-6 thousand years ago, in Asia, according to the Soviet paleogeographer N.A. Khotinsky - even earlier. At first glance, there is every reason to believe that the climate curve is descending towards a new glaciation.

However, it is far from so simple. In order to seriously judge the future state of nature, it is not enough to know the main stages of its development in the past. It is necessary to find out the mechanism that determines the alternation and change of these stages. The temperature change curve itself cannot in this case serve as an argument. Where is the guarantee that starting tomorrow the spiral will not begin to unwind? the opposite side? And in general, can we be sure that the alternation of glaciations and interglacials reflects some single pattern of natural development? Perhaps each glaciation separately had its own independent cause, and, therefore, there is no basis at all for extrapolating the generalizing curve into the future... This assumption looks unlikely, but it also has to be kept in mind.

The question of the causes of glaciations arose almost simultaneously with the glacial theory itself. But if the factual and empirical part of this direction of science has achieved enormous progress over the past 100 years, then the theoretical understanding of the results obtained, unfortunately, went mainly in the direction of quantitatively adding ideas that explain this development of nature. Therefore, at present there is no generally accepted scientific theory of this process. Accordingly, there is no single point of view on the principles of compiling a long-term geographical forecast. IN scientific literature One can find several descriptions of hypothetical mechanisms that determine the course of global climate fluctuations. As new material about the Earth's glacial past accumulates, a significant part of the assumptions about the causes of glaciations are discarded and only the most acceptable options remain. Probably, the final solution to the problem should be sought among them. Paleogeographical and paleoglaciological studies, although they do not provide a direct answer to the questions that interest us, nevertheless serve as practically the only key to understanding natural processes on a global scale. This is their enduring scientific significance.

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The last ice age led to the appearance woolly mammoth and a huge increase in the area of ​​glaciers. But it was only one of many that cooled the Earth throughout its 4.5 billion years of history.

So, how often does the planet experience ice ages and when should we expect the next one?

Major periods of glaciation in the history of the planet

The answer to the first question depends on whether you are talking about large glaciations or small ones that occur during these long periods. Throughout history, the Earth has experienced five major periods of glaciation, some of which lasted for hundreds of millions of years. In fact, even now the Earth is experiencing a large period of glaciation, and this explains why it has polar ice caps.

The five main ice ages are the Huronian (2.4–2.1 billion years ago), the Cryogenian glaciation (720–635 million years ago), the Andean-Saharan glaciation (450–420 million years ago), and the Late Paleozoic glaciation (335–260 million years ago). million years ago) and Quaternary (2.7 million years ago to the present).

These major periods of glaciation may alternate between smaller ice ages and warm periods (interglacials). At the beginning of the Quaternary glaciation (2.7-1 million years ago), these cold ice ages occurred every 41 thousand years. However, significant ice ages have occurred less frequently over the past 800,000 years—about every 100,000 years.

How does the 100,000 year cycle work?

The ice sheets grow for about 90 thousand years and then begin to melt during the 10 thousand year warm period. Then the process is repeated.

Given that the last ice age ended about 11,700 years ago, perhaps it's time for another one to begin?

Scientists believe we should be experiencing another ice age right now. However, there are two factors associated with the Earth's orbit that influence the formation of warm and cold periods. Considering also how much carbon dioxide we emit into the atmosphere, the next ice age won't start for at least 100,000 years.

What causes an ice age?

The hypothesis put forward by Serbian astronomer Milutin Milanković explains why cycles of glacial and interglacial periods exist on Earth.

As a planet orbits the Sun, the amount of light it receives from it is affected by three factors: its inclination (which ranges from 24.5 to 22.1 degrees on a 41,000-year cycle), its eccentricity (the change in the shape of its orbit around of the Sun, which fluctuates from the near circle to oval shape) and its swing (one complete swing occurs every 19-23 thousand years).

In 1976, a landmark paper in the journal Science presented evidence that these three orbital parameters explained the planet's glacial cycles.

Milankovitch's theory is that orbital cycles are predictable and very consistent in the history of the planet. If the Earth is experiencing an ice age, it will be covered with more or less ice, depending on these orbital cycles. But if the Earth is too warm, no change will occur, at least in terms of increasing amounts of ice.

What can affect the warming of the planet?

The first gas that comes to mind is carbon dioxide. Over the past 800 thousand years, carbon dioxide levels have ranged from 170 to 280 parts per million (meaning that out of 1 million air molecules, 280 are carbon dioxide molecules). A seemingly insignificant difference of 100 parts per million results in glacial and interglacial periods. But carbon dioxide levels are significantly higher today than in past periods of fluctuation. In May 2016, carbon dioxide levels over Antarctica reached 400 parts per million.

The Earth has warmed up this much before. For example, during the time of dinosaurs the air temperature was even higher than it is now. But the problem is that in modern world it is growing at a record pace because we have released too much carbon dioxide into the atmosphere in a short time. Moreover, given that the rate of emissions is not currently decreasing, we can conclude that the situation is unlikely to change in the near future.

Consequences of warming

The warming caused by this carbon dioxide will have big consequences because even a small increase in the Earth's average temperature can lead to dramatic changes. For example, the Earth was on average only 5 degrees Celsius colder during the last ice age than it is today, but this led to a significant change in regional temperatures, the disappearance of huge parts of flora and fauna, and the emergence of new species.

If global warming causes all the ice sheets of Greenland and Antarctica to melt, sea levels will rise by 60 meters compared to today's levels.

What causes major ice ages?

The factors that caused long periods of glaciation, such as the Quaternary, are not as well understood by scientists. But one idea is that a massive drop in carbon dioxide levels could lead to colder temperatures.

For example, according to the uplift and weathering hypothesis, when plate tectonics causes mountain ranges to grow, new exposed rock appears on the surface. It easily weathers and disintegrates when it ends up in the oceans. Marine organisms use these rocks to create their shells. Over time, stones and shells take carbon dioxide from the atmosphere and its level drops significantly, which leads to a period of glaciation.

History of the Ice Age.

The causes of ice ages are cosmic: changes in solar activity, changes in the position of the Earth relative to the Sun. Planetary cycles: 1). 90 - 100 thousand-year cycles of climate change as a result of changes in the eccentricity of the earth's orbit; 2). 40 - 41 thousand-year cycles of change in the tilt of the earth's axis from 21.5 degrees. up to 24.5 degrees; 3). 21 - 22 thousand-year cycles of changes in the orientation of the earth's axis (precession). The results of volcanic activity have a significant impact - darkening earth's atmosphere dust and ash.
The oldest glaciation took place 800 - 600 million years ago during the Laurentian period of the Precambrian era.
About 300 million years ago, the Permocarbon glaciation occurred at the end of the Carboniferous - beginning Permian period Paleozoic era. At this time, there was only one supercontinent on planet Earth, Pangea. The center of the continent was located near the equator, the edge reached the south pole. Ice ages gave way to warming periods, and then to cold periods again. Such climate changes lasted from 330 to 250 million years ago. During this time, Pangea shifted north. About 200 million years ago, an even, warm climate was established on Earth for a long time.
About 120 - 100 million years ago in the Cretaceous period Mesozoic era The continent of Gondwana broke away from the continent of Pangea and remained in the Southern Hemisphere.
At first Cenozoic era, in the early Paleogene during the Paleocene era - ca. 55 million years ago there was a general tectonic uplift earth's surface at 300 - 800 meters, the split of Pangea and Gondwana into continents and planet-wide cooling began. 49 - 48 million years ago, at the beginning of the Eocene era, a strait formed between Australia and Antarctica. About 40 million years ago, mountain continental glaciers began to form in West Antarctica. Throughout the Paleogene period, the configuration of the oceans changed, and the Northern Ocean was formed. Arctic Ocean, Northwest Passage, Labrador and Baffin seas, Norwegian-Greenland basin. Along the northern shores of the Atlantic and Pacific Oceans High blocky mountains rose, and the underwater Mid-Atlantic Ridge developed.
At the border of the Eocene and Oligocene - about 36 - 35 million years ago, Antarctica moved to the south pole, separated from South America and was cut off from warm equatorial waters. 28 - 27 million years ago, continuous covers of mountain glaciers formed in Antarctica and then, during the Oligocene and Miocene, the ice sheet gradually filled the entire Antarctica. The continent of Gondwana finally split into continents: Antarctica, Australia, Africa, Madagascar, Hindustan, South America.
15 million years ago, glaciation began in the Arctic Ocean - floating ice, icebergs, and sometimes solid ice fields.
10 million years ago, a glacier in the Southern Hemisphere went beyond Antarctica into the ocean and about 5 million years ago reached its maximum, covering the ocean with an ice sheet to the coasts of South America, Africa, and Australia. Floating ice reached the tropics. At the same time, during the Pliocene era, glaciers began to appear in the mountains of the continents of the Northern Hemisphere (Scandinavian, Ural, Pamir-Himalayan, Cordillera) and 4 million years ago filled the islands of the Canadian Arctic archipelago and Greenland. North America, Iceland, Europe, Northern Asia were covered with ice 3 - 2.5 million years ago. The Late Cenozoic Ice Age reached its maximum in the Pleistocene era, about 700 thousand years ago. This same ice age continues to this day.
So, 2 - 1.7 million years ago the Upper Cenozoic - Quaternary period began. Glaciers in the Northern Hemisphere on land have reached mid-latitudes; in the Southern Hemisphere, continental ice has reached the edge of the shelf, icebergs up to 40-50 degrees. Yu. w. During this period, about 40 stages of glaciation were observed. The most significant were: Pleistocene glaciation I - 930 thousand years ago; Pleistocene glaciation II - 840 thousand years ago; Danube glaciation I - 760 thousand years ago; Danube glaciation II - 720 thousand years ago; Danube glaciation III - 680 thousand years ago.
During the Holocene era, there were four glaciations on Earth, named after valleys
Swiss rivers, where they were first studied. The oldest is the Gyuntz glaciation (in North America - Nebraska) 600 - 530 thousand years ago. Günz I reached its maximum 590 thousand years ago, Günz II peaked 550 thousand years ago. Mindel Glaciation (Kansas) 490 - 410 thousand years ago. Mindel I reached its maximum 480 thousand years ago, Mindel II peaked 430 thousand years ago. Then came the Great Interglacial, which lasted 170 thousand years. During this period, the Mesozoic warm climate seemed to return, and the Ice Age ended forever. But he came back.
The Riss glaciation (Illinois, Zaal, Dnieper) began 240 - 180 thousand years ago, the most powerful of all four. Riess I reached its maximum 230 thousand years ago, Riess II peaked 190 thousand years ago. The thickness of the glacier in Hudson Bay reached 3.5 kilometers, the edge of the glacier in the North Mountains. America reached almost to Mexico, on the plain it filled the basins of the Great Lakes and reached the river. Ohio, went south along the Appalachians and reached the ocean in the southern part of the island. Long Island. In Europe, the glacier filled all of Ireland, Bristol Bay, and the English Channel at 49 degrees. With. sh., North Sea at 52 degrees. With. sh., passed through Holland, southern Germany, occupied all of Poland to the Carpathians, Northern Ukraine, descended along the Dnieper to the rapids, along the Don, along the Volga to Akhtuba, along Ural mountains and then walked across Siberia to Chukotka.
Then came a new interglacial, which lasted more than 60 thousand years. Its maximum occurred 125 thousand years ago. In Central Europe at that time there were subtropics, moist deciduous forests grew. Subsequently they changed coniferous forests and dry prairies.
115 thousand years ago the last historical glaciation of Wurm (Wisconsin, Moscow) began. It ended approximately 10 thousand years ago. Early Würm peaked ca. 110 thousand years ago and ended approx. 100 thousand years ago. The largest glaciers covered Greenland, Spitsbergen, and the Canadian Arctic archipelago. 100 - 70 thousand years ago, an interglacial period reigned on Earth. Middle Wurm - approx. 70 - 60 thousand years ago, was much weaker than the Early and even more so the Late. The last ice age - Late Wurm - was 30 - 10 thousand years ago. The maximum of glaciation occurred between 25 and 18 thousand years ago.
The stage of the greatest glaciation in Europe is called Egga I - 21-17 thousand years ago. Due to the accumulation of water in glaciers, the level of the World Ocean dropped by 120 - 100 meters below the present level. 5% of all water on Earth was in glaciers. About 18 thousand years ago, a glacier in the North. America reached 40 degrees. With. w. and Long Island Islands. In Europe, the glacier reached the line: o. Iceland - o. Ireland - Bristol Bay - Norfolk - Schleswig - Pomerania - Northern Belarus - Moscow vicinity - Komi - Middle Urals at 60 degrees With. w. - Taimyr - Putorana plateau - Chersky ridge - Chukotka. Due to lowering sea levels, land in Asia was located north of the New Siberian Islands and in the northern part of the Bering Sea - “Beringia”. The two Americas were connected by the Isthmus of Panama, which blocked the connection between the Atlantic and Pacific Oceans, resulting in the formation of the powerful Gulf Stream. In the middle part of the Atlantic Ocean from America to Africa there were many islands and the largest among them was the island of Atlantis. The northern tip of this island was at the latitude of Cadiz (37 degrees north latitude). The archipelagos of the Azores, Canaries, Madeira, and Cape Verde are the submerged peaks of the outlying ridges. Ice and polar fronts from the north and south came as close as possible to the equator. The water in the Mediterranean Sea was 4 degrees. With colder modern. The Gulf Stream flowed around Atlantis and ended off the coast of Portugal. The temperature gradient was greater, the winds and currents were stronger. In addition, there were extensive mountain glaciations in the Alps, Tropical Africa, the mountains of Asia, Argentina and Tropical South America, New Guinea, Hawaii, Tasmania, New Zealand and even in the Pyrenees and the mountains of the north-west. Spain. The climate in Europe was polar and temperate, the vegetation was tundra, forest-tundra, cold steppes, taiga.
Stage II of Egg was 16 - 14 thousand years ago. The slow retreat of the glacier began. At the same time, a system of glacier-dammed lakes was formed at its edge. Glaciers up to 2-3 kilometers thick with their mass crushed and sank the continents into magma and thereby raised the ocean floor, forming mid-ocean ridges.
About 15 - 12 thousand years ago, the Atlantean civilization arose on an island heated by the Gulf Stream. The "Atlanteans" created a state, an army, and had possessions in North Africa as far as Egypt.
Early Dryas stage (Luga) 13.3 - 12.4 thousand years ago. The slow retreat of glaciers continued. About 13 thousand years ago, a glacier melted in Ireland.
Tromso-Lyngen stage (Ra; Bölling) 12.3 - 10.2 thousand years ago. About 11 thousand years ago
The glacier melted on the Shetland Islands (the last in the UK), in Nova Scotia and on the island. Newfoundland (Canada). 11 - 9 thousand years ago a sharp rise in the level of the World Ocean began. When the glacier was released from the load, the land began to rise and the bottom of the oceans to fall, tectonic changes in the earth's crust, earthquakes, volcanic eruptions, and floods. Atlantis also perished from these cataclysms around 9570 BC. The main centers of civilization, cities, and the majority of the population perished. The remaining "Atlanteans" partly degraded and went wild, and partly died out. Possible descendants of the “Atlanteans” were the “Guanches” tribe in the Canary Islands. Information about Atlantis was preserved by the Egyptian priests and told about it to the Greek aristocrat and legislator Solon c. 570 BC Solon's narrative was rewritten and brought to posterity by the philosopher Plato c. 350 BC
Preboreal stage 10.1 - 8.5 thousand years ago. Global warming has begun. In the Azov-Black Sea region, sea regression (reduction in area) and water desalination occurred. 9.3 - 8.8 thousand years ago a glacier melted in the White Sea and Karelia. About 9 - 8 thousand years ago the fjords of Baffin Island, Greenland, Norway were freed from ice, and the glacier on the island of Iceland retreated 2 - 7 kilometers from the coast. 8.5 - 7.5 thousand years ago the glacier melted on the Kola and Scandinavian peninsulas. But the warming was uneven; in the Late Holocene there were 5 cold snaps. The first - 10.5 thousand years ago, the second - 8 thousand years ago.
7 - 6 thousand years ago, glaciers in the polar regions and mountains took mainly their modern shape. 7 thousand years ago there was a climatic optimum on Earth (the highest average temperature). The current average global temperature is 2 degrees Celsius lower, and if it drops another 6 degrees Celsius, a new ice age will begin.
About 6.5 thousand years ago, a glacier was localized on the Labrador Peninsula in the Torngat Mountains. About 6 thousand years ago, Beringia finally sank and the land “bridge” between Chukotka and Alaska disappeared. The third cooling in the Holocene occurred 5.3 thousand years ago.
About 5,000 years ago, civilizations formed in the valleys of the Nile, Tigris, Euphrates, and Indus rivers, and modern historical period On the Earth. 4000 - 3500 years ago the level of the World Ocean became equal to the modern level. The fourth cold snap in the Holocene occurred about 2800 years ago. Fifth - the "Little Ice Age" in 1450 - 1850. with a minimum of approx. 1700 The global average temperature was 1 degree C lower than today. There were harsh winters, cold summers in Europe, North. America. The bay in New York was freezing. Mountain glaciers have greatly increased in the Alps, the Caucasus, Alaska, New Zealand, Lapland and even the Ethiopian Highlands.
Currently, the interglacial period continues on Earth, but the planet continues its cosmic path and global changes and climate change is inevitable.

Hello readers! I have prepared for you new article. I would like to talk about the Ice Age on Earth.Let's figure out how these ice ages come, what are the causes and consequences...

Ice Age on Earth.

Imagine for a moment that the cold has shackled our planet, and the landscape has turned into an icy desert (more about deserts), over which fierce northern winds rage. Our Earth looked like this during the Ice Age - from 1.7 million to 10,000 years ago.

Almost every corner of the globe preserves memories of the process of the formation of the Earth. The hills running like a wave over the horizon, the mountains touching the sky, the stone that was taken by man to build cities - each of them has its own story.

These clues, in the course of geological research, can tell us about a climate (climate change) that was significantly different from today.

Our world was once shackled by a thick sheet of ice that made its way from the frozen poles to the equator.

Earth was a gloomy and gray planet in the grip of the cold that carried snow storms from the north and south.

Frozen planet.

Based on the nature of the glacial deposits (settled debris) and the surfaces worn away by the glacier, geologists concluded that there were in fact several periods.

Back in the Precambrian period, about 2300 million years ago, the first ice age began, and the last, and best studied, took place between 1.7 million years ago and 10,000 years ago in the so-called. Pleistocene era. This is what is simply called the Ice Age.

Thaw.

Some lands managed to escape this merciless grip, where there was usually also cold, but winter did not reign over the entire Earth.

Vast areas of deserts and tropical forests were located near the equator. For the survival of many species of plants, reptiles and mammals, these oases of warmth played a significant role.

In general, the glacial climate was not always cold. The glaciers crawled several times from north to south before retreating.

In some parts of the planet, the weather between ice attacks was even warmer than it is today. For example, the climate in southern England was almost tropical.

Paleontologists, thanks to fossilized remains, claim that elephants and hippos once roamed the banks of the Thames.

Such periods of thaw - also known as interglacial stages - lasted several hundred thousand years until the cold returned.

The ice flows, once again moving south, left behind destruction, thanks to which geologists can accurately determine their path.

On the body of the Earth, the movement of these large masses of ice has left two types of “scars”: sedimentation and erosion.

When a moving mass of ice wears away soil along its path, erosion occurs. Entire valleys in the bedrock were hollowed out by rock fragments carried by the glacier.

The movement of crushed stone and ice acted like a giant grinding machine that polished the ground underneath and created large furrows called glacial striations.

Over time, the valleys widened and deepened, acquiring a clear U-shape.

When a glacier (about what glaciers are) shed the rock fragments it carried, sediments were formed. This usually occurred when the ice melted, leaving piles of coarse gravel, fine-grained clay and huge boulders scattered over a vast area.

Causes of glaciation.

Scientists still don’t know exactly what glaciation is called. Some believe that temperatures at the Earth's poles over the past millions of years are lower than at any time in Earth's history.

Continental drift (read more about continental drift) could be the reason for this. About 300 million million years ago, there was only one giant supercontinent - Pangea.

The breakup of this supercontinent occurred gradually, and eventually the movement of continents left the Arctic Ocean almost completely surrounded by land.

Therefore, now, unlike in the past, there is only a slight mixing of the waters of the Arctic Ocean with warm waters to the south.

This leads to the following situation: the ocean never warms up well in the summer and is constantly covered with ice.

Antarctica is located at the South Pole (more about this continent), which is very far from warm currents, which is why the continent sleeps under the ice.

The cold is returning.

There are other reasons for global cooling. According to assumptions, one of the reasons is the degree of tilt of the earth's axis, which is constantly changing. Together with irregular shape orbit means that the Earth is further from the Sun at some periods than at others.

And if the quantity changes even by a percentage solar heat, this could lead to a difference in temperature on Earth of as much as a degree.

The interaction of these factors will be quite sufficient for the start of a new ice age. It is also believed that the Ice Age may cause dust to accumulate in the atmosphere as a result of pollution.

Some scientists believe that the collision of a giant meteor with the Earth ended the age of dinosaurs. This caused a huge cloud of dust and dirt to rise into the air.

Such a catastrophe could block the entry of the Sun's rays (more about the Sun) through the atmosphere (more about the atmosphere) of the Earth and cause it to freeze. Similar factors may contribute to the onset of a new ice age.

In about 5,000 years, some scientists predict a new ice age will begin, while others argue that the ice age never ended.

Considering that the Pleistocene ice age, which was the last, ended 10,000 years ago, it is possible that we are now experiencing an interglacial stage, and the ice may return after some time.

On this note, I end this topic. I hope that the story about the Ice Age on Earth did not “freeze” you 🙂 And finally, I suggest you subscribe to the latest articles by mail so as not to miss their release.

Great Quaternary Glaciation

All geological history Geologists have divided the Earth, which has lasted for several billion years, into eras and periods. The last of these, which continues to this day, is the Quaternary period. It began almost a million years ago and was marked by the extensive spread of glaciers across the globe - the Great Glaciation of the Earth.

The northern part of the North American continent, a significant part of Europe, and possibly also Siberia were under thick ice caps (Fig. 10). IN southern hemisphere under the ice, as now, was the entire Antarctic continent. There was more ice on it - the surface of the ice sheet rose 300 m above its modern level. However, Antarctica was still surrounded on all sides by a deep ocean, and the ice could not move north. The sea prevented the Antarctic giant from growing, and the continental glaciers of the northern hemisphere spread to the south, turning the flourishing spaces into an icy desert.

Man is the same age as the Great Quaternary Glaciation of the Earth. His first ancestors - ape people - appeared at the beginning Quaternary period. Therefore, some geologists, in particular the Russian geologist A.P. Pavlov, proposed calling the Quaternary period Anthropocene (in Greek “anthropos” - man). Several hundred thousand years passed before man took on his modern appearance. The advance of glaciers worsened the climate and living conditions of ancient people who had to adapt to the harsh nature around them. People had to lead sedentary image life, build houses, invent clothes, use fire.

Having reached their greatest development 250 thousand years ago, Quaternary glaciers began to gradually shrink. The Ice Age was not uniform throughout the Quaternary. Many scientists believe that during this time glaciers completely disappeared at least three times, giving way to interglacial eras when the climate was warmer than today. However, these warm eras were replaced by cold snaps again, and the glaciers spread again. We now live, apparently, at the end of the fourth stage of the Quaternary glaciation. After the liberation of Europe and America from under the ice, these continents began to rise - this is how the earth’s crust reacted to the disappearance of the glacial load that had been pressing on it for many thousands of years.

The glaciers “left”, and after them vegetation, animals, and, finally, people settled to the north. Since glaciers retreated unevenly in different places, humanity settled unevenly.

Retreating, the glaciers left behind smoothed rocks - “ram's foreheads” and boulders covered with shading. This shading is formed by the movement of ice along the surface of the rocks. It can be used to determine in which direction the glacier was moving. The classic area for these traits to appear is Finland. The glacier retreated from here quite recently, less than ten thousand years ago. Modern Finland is a land of countless lakes lying in shallow depressions, between which rise low “curly” rocks (Fig. 11). Everything here reminds us of the former greatness of the glaciers, their movement and enormous destructive work. You close your eyes and you immediately imagine how slowly, year after year, century after century, a powerful glacier crawls here, how it plows out its bed, breaks off huge blocks of granite and carries them south, towards the Russian Plain. It is no coincidence that it was while in Finland that P. A. Kropotkin thought about the problems of glaciation, collected many scattered facts and managed to lay the foundations of the theory of the Ice Age on Earth.

There are similar corners at the other “end” of the Earth - in Antarctica; Not far from the village of Mirny, for example, there is the Banger “oasis” - an ice-free land area with an area of ​​600 km2. When you fly over it, small chaotic hills rise under the wing of the plane, and strangely shaped lakes snake between them. Everything is the same as in Finland and... not at all similar, because in Banger’s “oasis” there is no main thing - life. Not a single tree, not a single blade of grass - only lichens on the rocks and algae in the lakes. Probably, all the territories recently freed from under the ice were once the same as this “oasis”. The glacier left the surface of the Banger “oasis” only a few thousand years ago.

The Quaternary glacier also spread to the territory of the Russian Plain. Here the movement of the ice slowed down, it began to melt more and more, and somewhere on the site of the modern Dnieper and Don rivers flowed from under the edge of the glacier. powerful streams melt water Here was the border of its maximum distribution. Later, on the Russian Plain, many remains of the spread of glaciers were found and, above all, large boulders, like those that were often encountered on the path of Russian epic heroes. The heroes stopped in thought at such a boulder old fairy tales and epics before choosing your long road: right, left or straight. These boulders have long stirred the imagination of people who could not understand how such colossi ended up on a plain among a dense forest or endless meadows. They came up with various fairy-tale reasons, including the “universal flood”, during which the sea allegedly brought these stone blocks. But everything was explained much more simply - it would have been easy for a huge flow of ice several hundred meters thick to “move” these boulders a thousand kilometers.

Almost halfway between Leningrad and Moscow there is a picturesque hilly lake region - the Valdai Upland. Here among the thick coniferous forests and plowed fields splash the waters of many lakes: Valdai, Seliger, Uzhino and others. The shores of these lakes are indented, there are many islands on them, densely overgrown with forests. It was here that the border of the last spread of glaciers on the Russian Plain passed. These glaciers left behind strange shapeless hills, the depressions between them were filled with their meltwater, and subsequently the plants had to work a lot to create good living conditions for themselves.

On the causes of great glaciations

So, glaciers were not always on Earth. Even in Antarctica, coal has been found - a sure sign that there was a warm and humid climate with rich vegetation. At the same time, geological data indicate that the great glaciations were repeated on Earth several times every 180-200 million years. The most characteristic traces of glaciations on Earth are special rocks - tillites, that is, the fossilized remains of ancient glacial moraines, consisting of a clayey mass with the inclusion of large and small hatched boulders. Individual tillite strata can reach tens and even hundreds of meters.

The reasons for such major climate changes and the occurrence of the great glaciations of the Earth still remain a mystery. Many hypotheses have been put forward, but none of them can yet claim to be a scientific theory. Many scientists searched for the cause of the cooling outside the Earth, putting forward astronomical hypotheses. One hypothesis is that glaciation occurred when, due to fluctuations in the distance between the Earth and the Sun, the amount of solar heat received by the Earth changed. This distance depends on the nature of the Earth's motion in its orbit around the Sun. It was assumed that glaciation occurred when winter occurred at aphelion, that is, the point of the orbit furthest from the Sun, at the maximum elongation of the earth's orbit.

However, recent research by astronomers has shown that just changing the amount of solar radiation hitting the Earth is not enough to cause an ice age, although such a change would have its consequences.

The development of glaciation is also associated with fluctuations in the activity of the Sun itself. Heliophysicists have long found out that dark spots, flares, and prominences appear on the Sun periodically, and have even learned to predict their occurrence. It turned out that solar activity changes periodically; There are periods of different durations: 2-3, 5-6, 11, 22 and about a hundred years. It may happen that the culminations of several periods of different durations coincide, and solar activity will be especially high. So, for example, it happened in 1957 - just during the International Geophysical Year. But it may be the other way around - several periods of reduced solar activity will coincide. This may cause the development of glaciation. As we will see later, such changes in solar activity are reflected in the activity of glaciers, but they are unlikely to cause a great glaciation of the Earth.

Another group of astronomical hypotheses can be called cosmic. These are assumptions that the cooling of the Earth is influenced by various parts of the Universe that the Earth passes through, moving through space along with the entire Galaxy. Some believe that cooling occurs when the Earth “floats” through areas of global space filled with gas. Others are when it passes through clouds of cosmic dust. Still others argue that “cosmic winter” on Earth occurs when the globe is in apogalactia - the point furthest from the part of our Galaxy where the most stars are located. At the present stage of scientific development, there is no way to support all these hypotheses with facts.

The most fruitful hypotheses are those in which the cause of climate change is assumed to be on the Earth itself. According to many researchers, cooling, causing glaciation, can occur as a result of changes in the location of land and sea, under the influence of the movement of continents, due to a change in direction sea ​​currents(thus, the Gulf Stream was previously diverted by a promontory of land extending from Newfoundland to the Cape Verde Islands). There is a widely known hypothesis according to which, during the eras of mountain building on Earth, the rising large masses of the continents fell into higher layers of the atmosphere, cooled and became places of origin of glaciers. According to this hypothesis, glaciation epochs are associated with mountain building epochs, moreover, they are conditioned by them.

The climate can change significantly as a result of changes in the tilt of the earth's axis and the movement of the poles, as well as due to fluctuations in the composition of the atmosphere: there is more volcanic dust or less carbon dioxide in the atmosphere, and the earth becomes significantly colder. IN Lately Scientists began to link the appearance and development of glaciation on Earth with a restructuring of atmospheric circulation. When, under the same climatic background of the globe, too much precipitation falls into individual mountainous regions, glaciation occurs there.

Several years ago, American geologists Ewing and Donn put forward a new hypothesis. They suggested that the Arctic Ocean, now covered with ice, thawed at times. In this case, increased evaporation occurred from the surface of the ice-free Arctic sea, and flows of moist air were directed to the polar regions of America and Eurasia. Here, above the cold surface of the earth, heavy snow fell from the humid air masses, which did not have time to melt during the summer. This is how ice sheets appeared on the continents. Spreading out, they descended to the north, surrounding the Arctic Sea with an icy ring. As a result of the transformation of part of the moisture into ice, the level of the world's oceans dropped by 90 m, the warm Atlantic Ocean stopped communicating with the Arctic Ocean, and it gradually froze. Evaporation from its surface stopped, snow began to fall on the continents less, and the nutrition of glaciers worsened. Then the ice sheets began to thaw, decrease in size, and the level of the world's oceans rose. Once again, the Arctic Ocean began to communicate with the Atlantic Ocean, its waters became warmer, and the ice cover on its surface began to gradually disappear. The cycle of glaciation began all over again.

This hypothesis explains some facts, in particular several advances of glaciers during the Quaternary period, but it also does not answer the main question: what is the cause of the Earth's glaciations.

So, we still do not know the causes of the great glaciations of the Earth. With a sufficient degree of certainty we can only speak about the last glaciation. Glaciers usually shrink unevenly. There are times when their retreat is delayed for a long time, and sometimes they quickly advance. It has been noted that such fluctuations in glaciers occur periodically. The longest period of alternating retreats and advances lasts for many centuries.

Some scientists believe that climate changes on Earth, which are associated with the development of glaciers, depend on the relative positions of the Earth, the Sun and the Moon. When these three celestial bodies are in the same plane and on the same straight line, the tides on Earth increase sharply, the circulation of water in the oceans and the movement of air masses in the atmosphere change. Ultimately, the amount of precipitation around the globe increases slightly and the temperature decreases, which leads to the growth of glaciers. This increase in the moisture content of the globe is repeated every 1800-1900 years. The last two such periods occurred in the 4th century. BC e. and the first half of the 15th century. n. e. On the contrary, in the interval between these two maxima, conditions for the development of glaciers should be less favorable.

On the same basis, it can be assumed that in our modern era glaciers should be retreating. Let's see how glaciers actually behaved over the last millennium.

Development of glaciation in the last millennium

In the 10th century Icelanders and Normans, sailing through the northern seas, discovered the southern tip of an immensely large island, the shores of which were overgrown with thick grass and tall bushes. This amazed the sailors so much that they named the island Greenland, which means “Green Country”.

Why was the now most glaciated island on the globe so prosperous at that time? Obviously, the peculiarities of the then climate led to the retreat of glaciers and the melting of sea ice in the northern seas. The Normans were able to travel freely on small ships from Europe to Greenland. Villages were founded on the shores of the island, but they did not last long. Glaciers began to advance again, the “ice coverage” of the northern seas increased, and attempts in subsequent centuries to reach Greenland usually ended in failure.

By the end of the first millennium AD, mountain glaciers in the Alps, Caucasus, Scandinavia and Iceland had also retreated significantly. Some passes that were previously occupied by glaciers have become passable. The lands freed from glaciers began to be cultivated. Prof. G.K. Tushinsky recently examined the ruins of settlements of Alans (ancestors of the Ossetians) in the Western Caucasus. It turned out that many buildings dating back to the 10th century are located in places that are now completely unsuitable for habitation due to frequent and destructive avalanches. This means that a thousand years ago not only did the glaciers “move” closer to the mountain ridges, but avalanches did not occur here either. However, later winters became increasingly harsh and snowy, and avalanches began to fall closer to residential buildings. The Alans had to build special avalanche dams, their remains can still be seen today. In the end, it turned out to be impossible to live in the previous villages, and the mountaineers had to settle lower in the valleys.

The beginning of the 15th century was approaching. Living conditions became more and more harsh, and our ancestors, who did not understand the reasons for such a cold snap, were very worried about their future. Increasingly, records of cold and difficult years appear in chronicles. In the Tver Chronicle you can read: “In the summer of 6916 (1408) ... then the winter was heavy and cold and snowy, too snowy,” or “In the summer of 6920 (1412) the winter was very snowy, and therefore in the spring there was the water is great and strong.” The Novgorod Chronicle says: “In the summer of 7031 (1523) ... the same spring, on Trinity Day, a great cloud of snow fell, and snow lay on the ground for 4 days, and many bellies, horses and cows froze, and birds died in the forest " In Greenland, due to the onset of cooling by the middle of the 14th century. stopped engaging in cattle breeding and farming; The connection between Scandinavia and Greenland was disrupted due to the abundance of sea ice in the northern seas. In some years, the Baltic and even the Adriatic Sea froze. From the XV to the XVII century. mountain glaciers advanced in the Alps and the Caucasus.

The last major glacial advance dates back to the middle of the last century. In many mountainous countries they have come quite far. Traveling through the Caucasus, G. Abikh in 1849 discovered traces of the rapid advance of one of the Elbrus glaciers. This glacier has invaded Pine forest. Many trees were broken and lay on the surface of the ice or protruded through the body of the glacier, and their crowns were completely green. Documents have been preserved that tell about frequent ice avalanches from Kazbek in the second half of the 19th century. Sometimes, due to these landslides, it was impossible to drive along the Georgian Military Road. Traces of rapid advances of glaciers at this time are known in almost all inhabited mountainous countries: in the Alps, in the west North America, in Altai, Central Asia, as well as in the Soviet Arctic and Greenland.

With the advent of the 20th century, climate warming begins almost everywhere on the globe. It is associated with a gradual increase in solar activity. The last maximum of solar activity was in 1957-1958. During these years there was a large number of sunspots and extremely strong solar flares. In the middle of our century, the maxima of three cycles of solar activity coincided - eleven-year, secular and super-century. One should not think that increased solar activity leads to increased heat on Earth. No, the so-called solar constant, i.e. the value showing how much heat comes to each section of the upper boundary of the atmosphere, remains unchanged. But the flow of charged particles from the Sun to the Earth and the overall impact of the Sun on our planet are increasing, and the intensity of atmospheric circulation throughout the Earth is increasing. Streams of warm and humid air from tropical latitudes rush to the polar regions. And this leads to quite dramatic warming. In the polar regions it gets warmer sharply, and then it gets warmer all over the Earth.

In the 20-30s of our century, the average annual air temperature in the Arctic increased by 2-4°. The sea ice limit has moved north. The Northern Sea Route has become more passable for sea vessels, and the period of polar navigation has lengthened. The glaciers of Franz Josef Land, Novaya Zemlya and other Arctic islands have been retreating rapidly over the past 30 years. It was during these years that one of the last Arctic ice shelves, located on Ellesmere Land, collapsed. Nowadays, glaciers are retreating in the vast majority of mountainous countries.

Just a few years ago, almost nothing could be said about the nature of temperature changes in Antarctica: there was too little weather stations and there was almost no expeditionary research at all. But after summing up the results of the International Geophysical Year, it became clear that in Antarctica, as in the Arctic, in the first half of the 20th century. the air temperature rose. There is some interesting evidence for this.

The oldest Antarctic station is Little America on the Ross Ice Shelf. Here, from 1911 to 1957, the average annual temperature increased by more than 3°. In Queen Mary Land (in the area of ​​modern Soviet research) for the period from 1912 (when the Australian expedition led by D. Mawson conducted research here) to 1959, the average annual temperature increased by 3.6 degrees.

We have already said that at a depth of 15-20 m in the thickness of snow and firn, the temperature should correspond to the average annual one. However, in reality, at some inland stations, the temperature at these depths in the wells turned out to be 1.3-1.8° lower than the average annual temperatures for several years. Interestingly, as we went deeper into these holes, the temperature continued to decrease (down to a depth of 170 m), whereas usually with increasing depth the temperature of the rocks becomes higher. Such an unusual decrease in temperature in the thickness of the ice sheet is a reflection of the colder climate of those years when the snow was deposited, now at a depth of several tens of meters. Finally, it is very significant that the extreme limit of iceberg distribution in the Southern Ocean is now located 10-15° latitude further south compared to 1888-1897.

It would seem that such a significant increase in temperature over several decades should lead to the retreat of Antarctic glaciers. But this is where the “complexities of Antarctica” begin. They are partly due to the fact that we still know too little about it, and partly they are explained by the great originality of the ice colossus, completely different from the mountain and Arctic glaciers familiar to us. Let’s still try to understand what is happening now in Antarctica, and to do this, let’s get to know it better.