Scientific proof of the existence of the Ice Age. Causes of Ice Ages

Just during the powerful development of all forms of life on our planet, a mysterious glacial period with its new temperature fluctuations. We have already talked about the reasons for the appearance of this ice age earlier.

Just as the change of seasons led to the selection of more perfect, more adaptable animals and created various breeds of mammals, so now, in this ice age, man stands out from the mammals, in an even more painful struggle with the advancing glaciers than struggle with the changing seasons spanning millennia. Here it was not enough to simply adapt by significantly changing the body. What was needed was a mind that could turn nature itself to its advantage and conquer it.

We have finally reached the highest stage of life development: . He took possession of the Earth, and his mind, developing further and further, learned to embrace the entire universe. With the advent of man, a completely new era of creation truly began. We still stand at one of its lowest levels, we are the simplest among creatures gifted with reason, dominating the forces of nature. The beginning of the path to unknown majestic goals has come!

There have been at least four major ice ages, which in turn break up again into smaller waves of temperature fluctuations. Between the ice ages lay warmer periods; then, thanks to melting glaciers, the damp valleys were covered with lush meadow vegetation. Therefore, it was during these interglacial periods that herbivores could develop especially well.

In the deposits of the Quaternary era, which closes the ice ages, and in the deposits of the Deluvian era, which followed the last general glaciation of the globe, and the direct continuation of which is our time, we come across huge pachyderms, namely the mastodon mammoth, the fossilized remains of which we still have Now we often find it in the tundra of Siberia. Even with this giant, primitive man dared to get involved in a fight, and, in the end, he emerged victorious.

Mastodon (restored) from the Deluvian era.

We involuntarily return our thoughts again to the emergence of the world if we look at the blossoming of the beautiful present from chaotic dark primitive conditions. The fact that in the second half of our research we remained all the time only on our little Earth is explained by the fact that we know all these different stages of development only on it. But, taking into account the uniformity of the matter that forms the world, which we established earlier, and the universality of the forces of nature that govern matter, we will come to complete consistency of all the main features of the formation of the world that we can observe in the sky.

We have no doubt that in the distant universe there must be millions more worlds similar to our Earth, although we do not have any exact information about them. On the contrary, it is among the relatives of the Earth, the other planets of our solar system, which we can better explore due to their greater proximity to us, there are characteristic differences from our Earth, as, for example, sisters of very different ages. Therefore, we should not be surprised if it is on them that we do not encounter traces of life similar to the life of our Earth. Also, Mars with its channels remains a mystery to us.

If we look up at the sky strewn with millions of Suns, then we can be sure that we will meet the gaze of living beings who look at our daylight just as we look at their Sun. Perhaps we are not so far from the time when, having mastered all the forces of nature, man will be able to penetrate into these depths of the universe and send a signal beyond the boundaries of our globe to living beings located on another celestial body - and receive a response from them .

Just as life, at least otherwise we cannot imagine it, came to us from the universe and spread across the Earth, starting with the simplest, so man will eventually expand the narrow horizon that embraces his earthly world, and will communicate with other worlds of the universe, from where these primary elements of life on our planet came. The universe belongs to man, his mind, his knowledge, his power.

But no matter how high our imagination lifts us, we will someday fall down again. The cycle of development of the worlds consists of rise and fall.

Ice Age on Earth

After terrible downpours, like a flood, it became damp and cold. WITH high mountains The glaciers slid lower and lower into the valleys, because the Sun could no longer melt the masses of snow continuously falling from above. As a result, those places where earlier during the summer the temperature was still above zero were also covered with ice by for a long time. We are now seeing something similar in the Alps, where individual “tongues” of glaciers descend significantly below the boundary of eternal snow. Eventually, most of the plains at the foot of the mountains were also covered with ever-increasing ice sheets. A general ice age has arrived, traces of which we can indeed observe everywhere on everything. globe.

It is necessary to recognize the great merit of the world traveler Hans Meyer from Leipzig for the evidence he found that both on Kilimanjaro and on the Cordillera of South America, even in tropical areas, everywhere glaciers at that time descended much lower than at present. The connection outlined here between that extraordinary volcanic activity and the onset of the Ice Age was first suggested by the Sarazen brothers in Basel. How did this happen?

After careful research, the following can be answered to this question. The entire chain of the Andes was formed simultaneously during geological periods, which, of course, amount to hundreds of thousands and millions of years, and its volcanoes were the result of this most enormous mountain-building process on Earth. At this time, almost the entire Earth was dominated by approximately tropical temperature, which, however, very soon after this was to be replaced by a strong general cooling.

Penck found that there were at least four major ice ages, with warmer periods in between. But it seems that these large ice ages are being divided into even more larger number smaller periods of time in which more insignificant universal temperature fluctuations. From here you can see what turbulent times the Earth was going through and what constant agitation the ocean of air was in at that time.

How long this time lasted can only be stated very approximately. It is calculated that the beginning of this ice age can be dated back approximately half a million years ago. Since the last “little glaciation,” only 10 to 20 thousand years have passed, and we are now probably living in only one of those “interglacial periods” that occurred before the last general glaciation.

Through all these ice ages there are traces primitive man, developing from an animal. Tales of the flood, which have come to us from primitive times, may be in connection with the incidents described above. The Persian legend almost certainly points to volcanic phenomena that preceded the onset of the great flood.

This Persian tale describes the great flood as follows: “A great fiery dragon arose from the south. Everything was devastated by him. Day turned into night. The stars have disappeared. The zodiac was covered by a huge tail; only the Sun and Moon could be seen in the sky. Boiling water fell to the Earth and scorched the trees to the very roots. Among the frequent lightning, raindrops the size of a human head fell. Water covered the Earth higher than the height of a man. Finally, after the dragon's struggle lasted 90 days and 90 nights, the enemy of the Earth was destroyed. A terrible storm arose, the water receded, and the dragon sank into the depths of the Earth.”

This dragon, according to the famous Viennese geologist Suess, was nothing more than a powerful volcano, the fiery eruption of which spread across the sky like long tail. All other phenomena described in the legend are fully consistent with the phenomena observed after a strong volcanic eruption.

Thus, on the one hand, we showed that after the splitting and collapse of a huge block the size of a continent, a series of volcanoes should have formed, the eruptions of which were followed by floods and glaciations. On the other hand, we have before our eyes a number of volcanoes in the Andes, located along a huge cliff of the Pacific coast, and we have also proven that soon after the appearance of these volcanoes the Ice Age began. Tales of the flood further complete the picture of this turbulent period in the development of our planet. During the eruption of Krakatoa, we observed on a small scale, but in great detail, the consequences of the volcano's plunge into the depths of the sea.

Taking into account all of the above, we are unlikely to doubt that the relationship between these phenomena was, in fact, such as we assumed. Thus, the entire Pacific Ocean actually arose as a result of the separation and failure of its present bottom, which before that was a huge continent. Was this the “end of the world” as it is usually understood? If the fall happened suddenly, then it was probably the most terrible and most colossal catastrophe that the Earth has ever seen since organic life appeared on it.

This question is now, of course, difficult to answer. But we can still say the following. If the collapse on the Pacific coast had occurred gradually, then those terrible volcanic eruptions, which at the end of the “Tertiary era” occurred along the entire chain of the Andes and very weak consequences of which are still observed there.

If the coastal region sank there so slowly that it took centuries to detect this subsidence, as we still observe today on some sea coasts, then even then all mass movements in the interior of the Earth would occur very slowly, and would only occur occasionally volcanic eruptions.

In any case, we see that there are counteractions to these forces that produce shifts in the earth's crust, otherwise the sudden shaking of earthquakes could not take place. But we also had to recognize that the tensions resulting from these counteractions cannot become too great, because Earth's crust turns out to be plastic, pliable for large ones, but slowly active forces. All these considerations lead us to the conclusion, perhaps against our will, that sudden forces must have manifested themselves in these catastrophes.

Scientists note that the ice age is part of the ice era, when the earth's covers are covered with ice for many millions of years. But many people call the Ice Age a period of Earth’s history that ended about twelve thousand years ago.

It is worth noting that ice age history had a huge number of unique features that have not reached our time. For example, unique animals that were able to adapt to existence in this difficult climate - mammoths, rhinoceroses, saber tooth tigers, cave bears and others. They were covered with thick fur and quite large in size. Herbivores adapted to get food from under the icy surface. Let's take rhinoceroses, they rake ice with their horns and feed on plants. Oddly enough, the vegetation was varied. Of course, many plant species disappeared, but herbivores had free access to food.

Despite the fact that ancient people were small in size and did not have hair, they too were able to survive during the Ice Age. Their life was incredibly dangerous and difficult. They built themselves small dwellings and insulated them with the skins of killed animals, and ate the meat. People came up with various traps to lure large animals there.

Rice. 1 - Ice Age

The history of the Ice Age was first discussed in the eighteenth century. Then geology began to emerge as a scientific branch, and scientists began to find out the origin of the boulders in Switzerland. Most researchers agreed that they had a glacial origin. In the nineteenth century, it was suggested that the planet's climate was subject to sudden cold snaps. And a little later the term itself was announced "glacial period". It was introduced by Louis Agassiz, whose ideas were not initially recognized by the general public, but then it was proven that many of his works were indeed justified.

In addition to the fact that geologists were able to establish the fact that the Ice Age took place, they also tried to find out why it arose on the planet. The most common belief is that the movement of lithospheric plates can block warm ocean currents. This gradually causes the formation of a mass of ice. If large-scale ice sheets have already formed on the surface of the Earth, then they will cause a sharp cooling, reflecting sunlight, and therefore warm. Another reason for the formation of glaciers could be a change in the level of greenhouse effects. The presence of large arctic areas and the rapid spread of plants eliminates Greenhouse effect due to replacement carbon dioxide for oxygen. Whatever the reason for the formation of glaciers, this is a very long process that can also enhance the influence of solar activity on the Earth. Changes in our planet's orbit around the Sun make it extremely susceptible. The distance of the planet from the “main” star also has an influence. Scientists suggest that even during the largest ice ages, the Earth was covered with ice on only one-third of its entire area. There are suggestions that there were also ice ages, when the entire surface of our planet was covered with ice. But this fact remains controversial in the world of geological research.

Today, the most significant glacial massif is the Antarctic. The ice thickness in some places reaches more than four kilometers. Glaciers move at an average speed of five hundred meters per year. Another impressive ice sheet is found in Greenland. About seventy percent of this island is occupied by glaciers, which is one tenth of the ice on our entire planet. On this moment time, scientists believe that the Ice Age will not begin for at least another thousand years. The whole point is that in modern world There is a colossal emission of carbon dioxide into the atmosphere. And as we found out earlier, the formation of glaciers is possible only at a low level of its content. However, this poses another problem for humanity - global warming, which may be no less large-scale than the beginning of the Ice Age.

The Pleistocene Epoch began about 2.6 million years ago and ended 11,700 years ago. At the end of this era, the last ice age to date passed, when glaciers covered vast areas of the Earth's continents. Since the formation of the Earth 4.6 billion years ago, there have been at least five documented major ice ages. The Pleistocene is the first era in which Homo sapiens evolved: by the end of the era, people settled almost throughout the planet. What was the last ice age like?

Ice skating rink as big as the world

It was during the Pleistocene that the continents were located on Earth in the way we are used to. At some point during the Ice Age, sheets of ice covered all of Antarctica, much of Europe, North and South America, and small parts of Asia. IN North America they extended across Greenland and Canada and parts of the northern United States. Remnants of glaciers from this period can still be seen in some parts of the world, including Greenland and Antarctica. But the glaciers did not just “stand still.” Scientists note about 20 cycles when glaciers advanced and retreated, when they melted and grew again.

In general, the climate then was much colder and drier than it is today. Because most of the water on the Earth's surface was frozen, there was little precipitation - about half as much as today. During peak periods, when most water was frozen, global average temperatures were 5 -10°C below today's temperature norms. However, winter and summer still replaced each other. True, you wouldn’t have been able to sunbathe in those summer days.

Life during the Ice Age

While Homo sapiens, in the dire situation of perpetual cold temperatures, began to develop brains to survive, many vertebrates, especially large mammals, also bravely endured the harsh climatic conditions this period. In addition to the well-known woolly mammoths, saber-toothed cats, giant ground sloths and mastodons roamed the Earth during this period. Although many vertebrates went extinct during this period, the Earth was home to mammals that can still be found today, including monkeys, cattle, deer, rabbits, kangaroos, bears, and members of the canine and feline families.

Apart from a few early birds, there were no dinosaurs during the Ice Age: they went extinct at the end of the Cretaceous period, more than 60 million years before the start of the Pleistocene era. But the birds themselves did well during that period, including relatives of ducks, geese, hawks and eagles. The birds had to compete with mammals and other creatures for limited supplies of food and water, since much of it was frozen. Also during the Pleistocene period there were crocodiles, lizards, turtles, pythons and other reptiles.

The vegetation was worse: in many areas it was difficult to find dense forests. Individuals were more common coniferous trees, such as pines, cypress and yew trees, as well as some broad-leaved trees such as beeches and oaks.

Mass extinction

Unfortunately, about 13,000 years ago, more than three-quarters of the large animals of the Ice Age, including woolly mammoths, mastodons, saber-toothed tigers and giant bears, became extinct. Scientists have been arguing for many years about the reasons for their disappearance. There are two main hypotheses: human resourcefulness and climate change, but both cannot explain the planet-scale extinction.

Some researchers believe that, like the dinosaurs, there was some extraterrestrial intervention: recent studies show that an extraterrestrial object, perhaps a comet about 3-4 kilometers wide, could have exploded over southern Canada, almost destroying ancient culture Stone Age, as well as megafauna like mammoths and mastodons.

Based on materials from Livescience.com

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 further development On Earth, it survived several equally large glacial epochs, 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.

The Gondwana 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”.

Permocarbon glacial deposits have been found on all continents 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 of 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.

According to modern ideas, South part Pangea, called Gondwana, split about 150-130 million years ago, in the Jurassic and early Cretaceous periods. Growing from A. Wegener's guess modern theory global plate tectonics makes it possible to successfully explain all 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. Perhaps this was due to migration South Pole in the direction 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 at the 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.

A classic area, on the example of which the history of the ice ages of Europe and everything was studied for decades Northern Hemisphere, are 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 studied the geomorphological structure of the Alpine foothills, came to the conclusion that there were four major glacial epochs 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. century, the scheme of quadruple glaciation of the European plains, close to the Alpine scheme of A. Penck and his co-author E. Brückner, was widely recognized in our country and abroad.

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 primarily by the lack of strictly reliable data on the rhythm of natural events: the stratigraphic scale of the Ice Age itself causes big number criticism and there is no reliably tested version yet.

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, a sharp deterioration in climatic conditions was recorded throughout the globe, 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 stairs of marine terraces on the now flooded areas of the shelf and on the islands 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 of how far continental ice advanced at this time remains 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 in 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 to a greater extent contributed to its cooling.

The European ice sheet had a particularly poor diet. Glaciation of America, fed from 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 extrapolation of the curve of natural processes into the future leads us to expect the beginning of a new ice age within the next few thousand years. 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, optimal natural conditions occurred 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 serve as an argument in this case. Where is the guarantee that starting tomorrow the spiral will not begin to unwind in the opposite direction? 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, there is currently no generally accepted scientific theory 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 among them you should look final decision Problems. 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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Over the past million years, an ice age has occurred on Earth approximately every 100,000 years. This cycle actually exists, and different groups of scientists at different times tried to find the reason for its existence. True, there is no prevailing point of view on this issue yet.

More than a million years ago the cycle was different. The Ice Age was replaced by climate warming approximately every 40 thousand years. But then the frequency of glacial advances changed from 40 thousand years to 100 thousand. Why did this happen?

Experts from Cardiff University have offered their own explanation for this change. The results of the scientists' work were published in the authoritative publication Geology. According to experts, the main reason for the change in the frequency of ice ages is the oceans, or rather, their ability to absorb carbon dioxide from the atmosphere.

By studying the sediments that make up the ocean floor, the team discovered that the concentration of CO 2 changes from layer to layer of sediment with a period of exactly 100 thousand years. It is likely, scientists say, that excess carbon dioxide was extracted from the atmosphere by the ocean surface and the gas was then bound. As a result, the average annual temperature gradually decreases, and another ice age begins. And it so happened that the duration of the ice age more than a million years ago increased, and the heat-cold cycle became longer.

“The oceans likely absorb and release carbon dioxide, and when there is more ice, the oceans absorb more carbon dioxide from the atmosphere, making the planet colder. When there is little ice, the oceans release carbon dioxide, so the climate becomes warmer,” says professor Carrie Lear. “By studying the concentration of carbon dioxide in the remains of tiny creatures (here we mean sedimentary rocks - editor's note), we learned that during periods when the area of ​​​​glaciers increased, the oceans absorbed more carbon dioxide, so we can assume that there is less of it in the atmosphere.”

Seaweed, according to experts, played a major role in the absorption of CO 2, since carbon dioxide is an essential component of the photosynthesis process.

Carbon dioxide moves from the ocean into the atmosphere as a result of upwelling. Upwelling or rise is a process in which deep ocean waters rise to the surface. It is most often observed at the western borders of continents, where it moves colder, nutrient-rich waters from the depths of the ocean to the surface, replacing warmer, nutrient-poor surface waters. It can also be found in almost any area of ​​the world's oceans.

A layer of ice on the surface of the water prevents carbon dioxide from entering the atmosphere, so if a significant portion of the ocean freezes, it extends the duration of the ice age. “If we believe that the oceans release and absorb carbon dioxide, then we must understand that large amounts of ice prevent this process. It's like a lid on the surface of the ocean,” says Professor Liar.

With an increase in the area of ​​glaciers on the ice surface, not only the concentration of “warming” CO 2 decreases, but also the albedo of those regions covered with ice increases. As a result, the planet receives less energy, which means it cools even faster.

Now the Earth is in an interglacial, warm period. The last ice age ended about 11,000 years ago. Since then, the average annual temperature and sea level have been constantly rising, and the amount of ice on the surface of the oceans has been decreasing. As a result, scientists believe, a large amount of CO 2 enters the atmosphere. Plus, humans also produce carbon dioxide, and in huge quantities.

All this led to the fact that in September the concentration of carbon dioxide in the Earth's atmosphere increased to 400 parts per million. This figure increased from 280 to 400 parts per million in just 200 years of industrial development. Most likely, CO 2 in the atmosphere will not decrease in the foreseeable future. All this should lead to an increase average annual temperature on Earth by approximately +5°C in the next thousand years.

Scientists at the Department of Climate Science at the Potsdam Observatory recently built a model of the Earth's climate that takes into account the global carbon cycle. As the model showed, even with minimal emissions of carbon dioxide into the atmosphere, the ice sheet of the Northern Hemisphere will not be able to increase. This means that the onset of the next ice age may be delayed by at least 50-100 thousand years. So we are facing another change in the “glacier-warming” cycle, this time it is man who is responsible for it.