How often does an ice age occur on Earth? (19 photos). Causes of Ice Ages How the glacier moved during the Ice Age

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 are mammoths, rhinoceroses, saber-toothed 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 opinion is that the movement of lithospheric plates can block warm currents in the ocean. 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 by replacing carbon dioxide with 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 thing is that in the 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.

Great Quaternary Glaciation

Geologists have divided the entire geological history of 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 the southern hemisphere, the entire Antarctic continent was under ice, as now. 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 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 of the 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 a sedentary lifestyle, build houses, invent clothing, and use fire.

Having reached 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 me of former greatness glaciers, about 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 for 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, powerful streams of meltwater flowed out from under the edge of the glacier. 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 of ancient fairy tales and epics stopped in thought at such a boulder before choosing their long path: to the right, to the left, or to go 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. Coal has even been found in Antarctica - 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. 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 studies by astronomers have shown that only changes in the amount solar radiation, falling on the Earth is not enough to cause an ice age, although such a change must 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 continents fell into higher layers of the atmosphere, cooled and became places where glaciers originated. 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, from the wet air masses There was heavy snowfall that 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 glacial advances during the Quaternary period, but main question: what is the reason for the glaciations of the Earth - she also does not answer.

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 three of these 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 the northern seas, discovered the southern tip of the vast big island, the banks of which are 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, the melting of sea ice in 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 the 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 of North America, in Altai, in 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, a large number of sunspots and extremely strong solar flares were observed. 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. Northern sea ​​route became more passable for sea vessels, the period of polar navigation extended. 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 were too few meteorological stations and almost no expeditionary research. 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 in a few years. Interestingly, as we went deeper into these wells, the temperature continued to decrease (down to a depth of 170 m), whereas usually with increasing depth the temperature rocks gets taller. 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.

Last Ice Age

During this era, 35% of the land was under ice cover (compared to 10% today).

The last ice age was not just a natural disaster. It is impossible to understand the life of planet Earth without taking these periods into account. In the intervals between them (known as interglacial periods), life flourished, but then once again the ice moved inexorably and brought death, but life did not completely disappear. Each ice age was marked by the struggle for survival of different species, global climate change, and the last one appeared the new kind, who became (over time) dominant on Earth: it was a man.
Ice Ages
Ice ages are geological periods characterized by strong cooling of the Earth, during which vast areas earth's surface covered with ice, observed high level humidity and, naturally, exceptional cold, as well as the lowest known modern science sea ​​level. There is no generally accepted theory regarding the reasons for the onset of the Ice Age, but since the 17th century, a variety of explanations have been proposed. According to the current opinion, this phenomenon was not caused by one reason, but was the result of the influence of three factors.

Changes in the composition of the atmosphere - a different ratio of carbon dioxide (carbon dioxide) and methane - caused a sharp drop in temperature. It's like the opposite of what we now call global warming, but on a much larger scale.

The movements of the continents, caused by cyclic changes in the orbit of the Earth around the Sun, and in addition the change in the angle of inclination of the planet’s axis relative to the Sun, also had an impact.

The earth received less solar heat, it cooled, which led to glaciation.
The earth has experienced several ice ages. The largest glaciation occurred 950-600 million years ago during the Precambrian era. Then in the Miocene era - 15 million years ago.

Traces of glaciation that can be observed at the present time represent the legacy of the last two million years and belong to the Quaternary period. This period is best studied by scientists and is divided into four periods: Günz, Mindel (Mindel), Ries (Rise) and Würm. The latter corresponds to the last ice age.

Last Ice Age
The Würm stage of glaciation began approximately 100,000 years ago, peaked after 18 thousand years and began to decline after 8 thousand years. During this time, the thickness of the ice reached 350-400 km and covered a third of the land above sea level, in other words, three times the area than now. Based on the amount of ice that currently covers the planet, we can get some idea of ​​the extent of glaciation during that period: today, glaciers occupy 14.8 million km2, or about 10% of the earth's surface, and during the Ice Age they covered an area of ​​44 .4 million km2, which is 30% of the Earth's surface.

According to assumptions, in northern Canada, ice covered an area of ​​13.3 million km2, while now there is 147.25 km2 under ice. The same difference is noted in Scandinavia: 6.7 million km2 in that period compared to 3,910 km2 today.

The Ice Age occurred simultaneously in both hemispheres, although in the North the ice spread over larger areas. In Europe, the glacier covered most of the British Isles, northern Germany and Poland, and in North America, where the Wurm glaciation is called the "Wisconsin Ice Age", a layer of ice that descended from the North Pole covered all of Canada and spread south of the Great Lakes. Like the lakes in Patagonia and the Alps, they were formed on the site of depressions left after the melting of the ice mass.

The sea level dropped by almost 120 m, as a result of which large areas were exposed that are currently covered with sea water. The significance of this fact is enormous, since large-scale migrations of humans and animals became possible: hominids were able to make the transition from Siberia to Alaska and move from continental Europe to England. It is quite possible that during interglacial periods, the two largest ice masses on Earth - Antarctica and Greenland - have undergone slight changes throughout history.

At the peak of glaciation, the average temperature drop varied significantly depending on the area: 100 °C in Alaska, 60 °C in England, 20 °C in the tropics and remained virtually unchanged at the equator. Studies of the last glaciations in North America and Europe, which occurred during the Pleistocene era, gave similar results in this geological area within the last two (approximately) million years.

The last 100,000 years are of particular importance to understanding human evolution. Ice ages became a severe test for the inhabitants of the Earth. After the end of the next glaciation, they again had to adapt and learn to survive. When the climate became warmer, sea levels rose, new forests and plants appeared, and the land rose, freed from the pressure of the ice shell.

Hominids had the most natural resources to adapt to changing conditions. They were able to move to areas with the largest number food resources, where the slow process of their evolution began.
It’s not expensive to buy children’s shoes wholesale in Moscow

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1.8 million years ago, the Quaternary (anthropogenic) period of the geological history of the earth began and continues to this day.

River basins expanded. It went fast development fauna of mammals, especially mastodons (which would later become extinct, like many other ancient animal species), ungulates and great apes. In that geological period In the history of the earth, man appears (hence the word anthropogenic in the name of this geological period).

The Quaternary period accounts for sudden change climate throughout the European part of Russia. From warm and humid Mediterranean, it turned into moderately cold, and then into cold Arctic. This led to glaciation. Ice accumulated on the Scandinavian Peninsula, in Finland, on the Kola Peninsula and spread to the south.

The Oksky glacier with its southern edge covered the territory of the modern Kashira region, including our region. The first glaciation was the coldest woody vegetation in the Oka region has disappeared almost completely. The glacier did not last long. The first Quaternary glaciation reached the Oka valley, which is why it received the name “Oka glaciation”. The glacier left moraine deposits dominated by boulders of local sedimentary rocks.

But such favorable conditions were again replaced by a glacier. Glaciation was on a planetary scale. The grandiose Dnieper glaciation began. The thickness of the Scandinavian ice sheet reached 4 kilometers. The glacier moved across the Baltic to Western Europe and European part Russia. The boundaries of the tongues of the Dnieper glaciation passed in the area of ​​modern Dnepropetrovsk and almost reached Volgograd.

Mammoth fauna

The climate warmed again and became Mediterranean. In place of the glaciers, heat-loving and moisture-loving vegetation has spread: oak, beech, hornbeam and yew, as well as linden, alder, birch, spruce and pine, and hazel. Ferns, characteristic of modern South America, grew in the swamps. Perestroika has begun river system and the formation of Quaternary terraces in river valleys. This period was called the interglacial Oka-Dnieper age.

The Oka served as a kind of barrier to the advancement of ice fields. According to scientists, the right bank of the Oka, i.e. our region has not turned into a continuous icy desert. Here there were fields of ice, interspersed with intervals of thawed hills, between which rivers of meltwater flowed and lakes accumulated.

Ice flows of the Dnieper glaciation brought glacial boulders from Finland and Karelia to our region.

The valleys of old rivers were filled with mid-moraine and fluvioglacial deposits. It became warmer again, and the glacier began to melt. Streams of meltwater rushed south along the beds of new rivers. During this period, third terraces are formed in river valleys. Formed in the depressions big lakes. The climate was moderately cold.

Our region was dominated by forest-steppe vegetation with a predominance of coniferous and birch forests and large areas of steppes covered with wormwood, quinoa, cereals and forbs.

The interstadial era was short. The glacier returned to the Moscow region again, but did not reach the Oka, stopping not far from the southern outskirts of modern Moscow. Therefore, this third glaciation was called the Moscow glaciation. Some tongues of the glacier reached the Oka valley, but they did not reach the territory of the modern Kashira region. The climate was harsh, and the landscape of our region is becoming close to the steppe tundra. Forests are almost disappearing and steppes are taking their place.

A new warming has arrived. The rivers deepened their valleys again. Second river terraces were formed, and the hydrography of the Moscow region changed. It was during that period that the modern valley and basin of the Volga, which flows into the Caspian Sea, was formed. The Oka, and with it our river B. Smedva and its tributaries, entered the Volga river basin.

This interglacial period in climate went through stages from continental temperate (close to modern) to warm, with a Mediterranean climate. In our region, at first birches, pine and spruce dominated, and then heat-loving oaks, beeches and hornbeams began to turn green again. In the swamps grew the Brasia water lily, which today can only be found in Laos, Cambodia or Vietnam. At the end of the interglacial period, birch forests again dominated coniferous forests.

This idyll was spoiled by the Valdai glaciation. Ice with Scandinavian Peninsula headed south again. This time the glacier did not reach the Moscow region, but changed our climate to subarctic. For many hundreds of kilometers, including through the territory of the present Kashira district and the rural settlement of Znamenskoye, the steppe-tundra stretches, with dried grass and sparse shrubs, dwarf birches and polar willows. These conditions were ideal for the mammoth fauna and for primitive man, who then already lived on the boundaries of the glacier.

During the last Valdai glaciation, the first river terraces were formed. The hydrography of our region has finally taken shape.

Traces of ice ages are often found in the Kashira region, but they are difficult to identify. Of course, large stone boulders are traces of glacial activity of the Dnieper glaciation. They were brought by ice from Scandinavia, Finland and the Kola Peninsula. The oldest traces of a glacier are moraine or boulder loam, which is a disordered mixture of clay, sand, and brown stones.

The third group of glacial rocks are sands resulting from the destruction of moraine layers by water. These are sands with large pebbles and stones and homogeneous sands. They can be observed on the Oka. These include Belopesotsky Sands. Often found in the valleys of rivers, streams, and ravines, layers of flint and limestone rubble are traces of the beds of ancient rivers and streams.

With the new warming, the geological epoch of the Holocene began (it began 11 thousand 400 years ago), which continues to this day. The modern river floodplains were finally formed. The mammoth fauna became extinct, and forests appeared in place of the tundra (first spruce, then birch, and later mixed). The flora and fauna of our region has acquired modern features - the one we see today. At the same time, the left and right banks of the Oka still differ greatly in their forest cover. If the right bank is dominated mixed forests and many open areas, the left bank is dominated by continuous coniferous forests - these are traces of glacial and interglacial climate changes. On our bank of the Oka, the glacier left fewer traces and our climate was somewhat milder than on the left bank of the Oka.

Geological processes continue today. The earth's crust in the Moscow region has been rising only slightly over the past 5 thousand years, at a rate of 10 cm per century. The modern alluvium of the Oka and other rivers of our region is being formed. What this will lead to after millions of years, we can only guess, because, having briefly become acquainted with the geological history of our region, we can safely repeat the Russian proverb: “Man proposes, but God disposes.” This saying is especially relevant after we have become convinced in this chapter that human history is a grain of sand in the history of our planet.

GLACIAL PERIOD

In distant, distant times, where Leningrad, Moscow, and Kyiv are now, everything was different. Dense forests grew along the banks of ancient rivers, and shaggy mammoths with curved tusks, huge hairy rhinoceroses, tigers and bears much larger than today roamed there.

Gradually it became colder and colder in these places. Far in the north, so much snow fell every year that entire mountains accumulated it - larger than the present-day Ural Mountains. The snow compacted, turned into ice, then began to slowly, slowly creep away, spreading in all directions.

Ice mountains have moved into the ancient forests. Cold, angry winds blew from these mountains, the trees froze and animals fled south from the cold. And the icy mountains crawled further to the south, turning out rocks along the way and moving entire hills of earth and stones in front of them. They crawled to the place where Moscow now stands, and crawled even further, to warm southern countries. They reached the hot Volga steppe and stopped.

Here, finally, the sun overpowered them: the glaciers began to melt. Huge rivers flowed from them. And the ice retreated, melted, and the masses of stones, sand and clay that the glaciers brought remained lying in the southern steppes.

More than once, terrible ice mountains have approached from the north. Have you seen the cobblestone street? Such small stones were brought by the glacier. And there are boulders as big as a house. They still lie in the north.

But the ice may move again. Just not soon. Maybe thousands of years will pass. And not only the sun will then fight the ice. If necessary, people will use ATOMIC ENERGY and prevent the glacier from entering our land.

When did the Ice Age end?

Many of us believe that the Ice Age ended a long time ago and no traces of it remain. But geologists say we are only approaching the end of the Ice Age. And the people of Greenland are still living in the Ice Age.

About 25 thousand years ago, the peoples who inhabited central part NORTH AMERICA, saw ice and snow all year round. A huge wall of ice stretched from Tikhoy to Atlantic Ocean, and to the north - all the way to the Pole. This was during the final stages of the Ice Age, when all of Canada, most of the United States and northwestern Europe were covered in a layer of ice more than one kilometer thick.

But this does not mean that it was always very cold. In the northern part of the United States, temperatures were only 5 degrees lower than today. Cold summer months caused an ice age. At this time, the heat was not enough to melt the ice and snow. It accumulated and eventually covered the entire northern part of these areas.

The Ice Age consisted of four stages. At the beginning of each of them, ice formed moving south, then melted and retreated to the NORTH POLE. This happened, it is believed, four times. Cold periods are called “glaciations”, warm periods are called “interglacial” periods.

The first stage in North America is thought to have begun about two million years ago, the second about 1,250,000 years ago, the third about 500,000 years ago, and the last about 100,000 years ago.

The rate of ice melting during the last stage of the Ice Age was different in different areas. For example, in the area where the modern state of Wisconsin is located in the USA, the melting of ice began approximately 40,000 years ago. The ice that covered the New England region of the United States disappeared about 28,000 years ago. And the territory of the modern state of Minnesota was freed by ice only 15,000 years ago!

In Europe, Germany became ice-free 17,000 years ago, and Sweden only 13,000 years ago.

Why do glaciers still exist today?

The huge mass of ice that began the Ice Age in North America was called the “continental glacier”: in the very center its thickness reached 4.5 km. This glacier may have formed and melted four times during the entire Ice Age.

The glacier that covered other parts of the world did not melt in some places! For example, the huge island of Greenland is still covered by a continental glacier, except for a narrow coastal strip. In its middle part, the glacier sometimes reaches a thickness of more than three kilometers. Antarctica is also covered by an extensive continental glacier, with ice up to 4 kilometers thick in some places!

Therefore, the reason why there are glaciers in some areas of the globe is because they have not melted since the Ice Age. But the bulk of the glaciers found today were formed recently. They are mainly located in mountain valleys.

They originate in wide, gentle, amphitheatrically shaped valleys. Snow gets here from the slopes as a result of landslides and avalanches. Such snow does not melt in the summer, becoming deeper every year.

Gradually, pressure from above, some thawing, and refreezing remove air from the bottom of this snow mass, turning it into solid ice. The impact of the weight of the entire mass of ice and snow compresses the entire mass and causes it to move down the valley. This moving tongue of ice is a mountain glacier.

In Europe, more than 1,200 such glaciers are known in the Alps! They also exist in the Pyrenees, the Carpathians, the Caucasus, and in the mountains of southern Asia. There are tens of thousands of similar glaciers in southern Alaska, some 50 to 100 km long!

The last ice age ended 12,000 years ago. During the most severe period, glaciation threatened man with extinction. However, after the glacier disappeared, he not only survived, but also created a civilization.

Glaciers in the history of the Earth

The last glacial era in the history of the Earth is the Cenozoic. It began 65 million years ago and continues to this day. Modern man is lucky: he lives in an interglacial period, one of the warmest periods in the life of the planet. The most severe glacial era - the Late Proterozoic - is far behind.

Despite global warming, scientists predict the onset of a new ice age. And if the real one will come only after millennia, then the Little Ice Age, which will reduce annual temperatures by 2-3 degrees, may come quite soon.

The glacier became a real test for man, forcing him to invent means for his survival.

Last Ice Age

The Würm or Vistula glaciation began approximately 110,000 years ago and ended in the tenth millennium BC. The peak of cold weather occurred 26-20 thousand years ago, the final stage of the Stone Age, when the glacier was at its largest.

Little Ice Ages

Even after the glaciers melted, history has known periods of noticeable cooling and warming. Or, in another way - climate pessimums And optimums. Pessimums are sometimes called Little Ice Ages. In the XIV-XIX centuries, for example, the Little Ice Age began, and during the Great Migration of Nations there was an early medieval pessimum.

Hunting and meat food

There is an opinion according to which the human ancestor was more of a scavenger, since he could not spontaneously occupy a higher ecological niche. And all known tools were used to cut up the remains of animals that were taken from predators. However, the question of when and why people began to hunt is still a matter of debate.

In any case, thanks to hunting and meat food, ancient man received a large supply of energy, which allowed him to better endure the cold. The skins of killed animals were used as clothing, shoes and walls of the home, which increased the chances of survival in the harsh climate.

Upright walking

Upright walking appeared millions of years ago, and its role was much more important than in the life of modern office worker. Having freed his hands, a person could engage in intensive housing construction, clothing production, processing of tools, production and conservation of fire. Erect walking ancestors moved freely in open areas, and their life no longer depended on collecting fruits tropical trees. Already millions of years ago, they moved freely over long distances and obtained food in river drains.

Upright walking played an insidious role, but it still became more of an advantage. Yes, man himself came to cold regions and adapted to life in them, but at the same time he could find both artificial and natural shelters from the glacier.

Fire

Fire in life ancient man was initially an unpleasant surprise, not a blessing. Despite this, the human ancestor first learned to “extinguish” it, and only later use it for his own purposes. Traces of the use of fire are found in sites that are 1.5 million years old. This made it possible to improve nutrition by preparing protein foods, as well as to remain active at night. This further increased the time to create survival conditions.

Climate

The Cenozoic Ice Age was not a continuous glaciation. Every 40 thousand years, the ancestors of people had the right to a “respite” - temporary thaws. At this time, the glacier was retreating and the climate became milder. During periods of harsh climate, natural shelters were caves or regions rich in flora and fauna. For example, the south of France and the Iberian Peninsula were home to many early cultures.

The Persian Gulf 20,000 years ago was a river valley rich in forests and grassy vegetation, a truly “antediluvian” landscape. Flowed here wide rivers, exceeding the Tigris and Euphrates in size by one and a half times. The Sahara in certain periods became a wet savannah. The last time this happened was 9,000 years ago. This can be confirmed by rock paintings that depict an abundance of animals.

Fauna

Huge glacial mammals, such as bison, woolly rhinoceros and mammoth, became an important and unique source of food for ancient people. Hunting such large animals required a lot of coordination and brought people together noticeably. Efficiency " teamwork» has proven itself more than once in the construction of parking lots and the manufacture of clothing. Deer and wild horses enjoyed no less “honor” among ancient people.

Language and communication

Language was perhaps the main life hack of ancient man. It was thanks to speech that important technologies for processing tools, making and maintaining fire, as well as various human adaptations for everyday survival were preserved and passed on from generation to generation. Perhaps the details of hunting large animals and migration directions were discussed in Paleolithic language.

Allörd warming

Scientists are still arguing whether the extinction of mammoths and other glacial animals was the work of man or caused by natural causes - the Allerd warming and the disappearance of food plants. As a result of extermination large quantity animal species, humans harsh conditions threatened death from lack of food. There are known cases of the death of entire cultures simultaneously with the extinction of mammoths (for example, the Clovis culture in North America). However, warming became an important factor in the migration of people to regions whose climate became suitable for the emergence of agriculture.