Dnieper glaciation
was maximum in the Middle Pleistocene (250-170 or 110 thousand years ago). It consisted of two or three stages.
Sometimes the last stage of the Dnieper glaciation is distinguished as an independent Moscow glaciation (170-125 or 110 thousand years ago), and the period of relatively warm time separating them is considered as the Odintsovo interglacial.
At the maximum stage of this glaciation, a significant part of the Russian Plain was occupied by an ice sheet, which, in a narrow tongue along the Dnieper valley, penetrated south to the mouth of the river. Aurelie. In most of this territory there was permafrost, and the average annual air temperature was then no higher than -5-6°C.
In the southeast of the Russian Plain, in the Middle Pleistocene, the so-called “Early Khazar” rise in the level of the Caspian Sea by 40-50 m occurred, which consisted of several phases. Their exact dating is unknown.
Mikulin interglacial
The Dnieper glaciation followed (125 or 110-70 thousand years ago). At this time, in the central regions of the Russian Plain, winter was much milder than now. If currently the average January temperatures are close to -10°C, then during the Mikulino interglacial they did not fall below -3°C.
The Mikulin time corresponded to the so-called “late Khazar” rise in the level of the Caspian Sea. In the north of the Russian Plain, there was a synchronous rise in the level of the Baltic Sea, which was then connected to Lakes Ladoga and Onega and, possibly, the White Sea, as well as the Arctic Ocean. The total fluctuation in the level of the world's oceans between the eras of glaciation and melting of ice was 130-150 m.
Valdai glaciation
After the Mikulino interglacial there came,
consisting of the Early Valdai or Tver (70-55 thousand years ago) and Late Valdai or Ostashkovo (24-12:-10 thousand years ago) glaciations, separated by the Middle Valdai period of repeated (up to 5) temperature fluctuations, during which the climate was much colder modern (55-24 thousand years ago).
In the south of the Russian Platform, the early Valdai is associated with a significant “Attelian” decrease - by 100-120 meters - in the level of the Caspian Sea. This was followed by the “early Khvalynian” rise in sea level by about 200 m (80 m above the original level). According to calculations by A.P. Chepalyga (Chepalyga, t. 1984), the moisture supply to the Caspian basin of the Upper Khvalynian period exceeded its losses by approximately 12 cubic meters. km per year.
After the “early Khvalynian” rise in sea level, there followed the “Enotaevsky” decrease in sea level, and then again the “late Khvalynian” increase in sea level by about 30 m relative to its original position. The maximum of the Late Khvalynian transgression occurred, according to G.I. Rychagov, at the end of the Late Pleistocene (16 thousand years ago). The Late Khvalynian basin was characterized by temperatures of the water column slightly lower than modern ones.
The new drop in sea level occurred quite quickly. It reached a maximum (50 m) at the very beginning of the Holocene (0.01-0 million years ago), about 10 thousand years ago, and was replaced by the last - “New Caspian” sea level rise of about 70 m about 8 thousand years ago.
Approximately the same fluctuations in the water surface occurred in the Baltic Sea and the Arctic Ocean. The general fluctuation in the level of the world's oceans between the eras of glaciation and melting of ice was then 80-100 m.
According to radioisotope analysis of more than 500 different geological and biological samples taken in southern Chile, mid-latitudes in the western Southern Hemisphere experienced warming and cooling at the same time as mid-latitudes in the western Northern Hemisphere.
Chapter " The world in the Pleistocene. The Great Glaciations and the Exodus from Hyperborea"
/
Eleven Quaternary glaciationsperiod and nuclear wars
© A.V. Koltypin, 2010
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. To modern man lucky: he lives in the interglacial period, one of the warmest periods of the planet’s life. 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 preservation of fire. The upright ancestors moved freely in open areas, and their life no longer depended on collecting the fruits of 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. Wide rivers flowed here, one and a half times larger in size than the Tigris and Euphrates. The Sahara in certain periods became a wet savannah. Last time this happened 9000 years ago. This can be confirmed by rock paintings, which 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. The effectiveness of “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 they were preserved and passed on from generation to generation. important technologies processing tools, making and maintaining fire, as well as various human adaptations for everyday survival. 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 species of animals, a person in harsh conditions faced 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 has become important factor resettlement of people to regions whose climate became suitable for the emergence of agriculture.
About two million years ago, at the end of the Neogene, continents began to rise again and volcanoes came to life all over the Earth. A huge amount of volcanic ash and soil particles were thrown into the atmosphere and polluted its upper layers to such an extent that the rays of the Sun simply could not penetrate to the surface of the planet. The climate became much colder, huge glaciers formed, which, under the influence of their own gravity, began to move from mountain ranges, plateaus and hills to the plains.
One after another, like waves, periods of glaciation rolled over Europe and North America. But just recently (in a geological sense) the climate of Europe was warm, almost tropical, and its animal population consisted of hippos, crocodiles, cheetahs, antelopes - approximately the same as what we see now in Africa. Four periods of glaciation - Günz, Mindel, Ris and Würm - expelled or destroyed heat-loving animals and plants, and the nature of Europe became basically what we see it now.
Under the pressure of glaciers, forests and meadows perished, rocks collapsed, rivers and lakes disappeared. Furious blizzards howled over the ice fields, and along with the snow, atmospheric dirt fell onto the surface of the glacier and it gradually began to clear.
When the glacier retreated for a short time, tundras with their permafrost remained in place of the forests.
The greatest period of glaciation was the Rissky - it occurred about 250 thousand years ago. The thickness of the glacial shell, which bound half of Europe and two-thirds of North America, reached three kilometers. Altai, Pamir and the Himalayas disappeared under the ice.
South of the glacier boundary now lay cold steppes, covered with sparse grassy vegetation and groves of dwarf birch trees. Even further south, the impenetrable taiga began.
Gradually the glacier melted and retreated to the north. However, he stopped off the coast of the Baltic Sea. An equilibrium arose - the atmosphere, saturated with moisture, let in just enough sunlight so that the glacier did not grow and did not completely melt.
The great glaciations unrecognizably changed the Earth's topography, its climate, animal and flora. We can still see their consequences - after all, the last, Würm glaciation began only 70 thousand years ago, and the ice mountains disappeared from the northern coast of the Baltic Sea 10-11 thousand years ago.
Heat-loving animals retreated further and further south in search of food, and their place was taken by those that could better withstand the cold.
Glaciers advanced not only from the Arctic regions, but also from the mountain ranges - the Alps, Carpathians, Pyrenees. At times the thickness of the ice reached three kilometers. Like a giant bulldozer, the glacier smoothed out the uneven terrain. After his retreat, a marshy plain covered with sparse vegetation remained.
This is what the polar regions of our planet presumably looked like in the Neogene and during the Great Glaciation. The area of permanent snow cover increased tenfold, and where the glaciers reached, it was as cold as in Antarctica for ten months of the year.
Humanity was born and grew stronger during the period of the great glaciations of the planet. These two facts are quite enough for us to show special interest in the problems of ice age. A great many books and magazines are regularly dedicated to them - mountains of facts and hypotheses. Even if you are lucky enough to master them, the fuzzy outlines of new hypotheses, guesses, and assumptions will inevitably loom ahead.
Nowadays, scientists from all countries and all specialties have found common language. This is mathematics: numbers, formulas, graphs.
Why glaciations of the Earth occur is still unclear. Not because it is difficult to find the cause of the cold snap. Rather, because too many reasons have been found. At the same time, scientists cite many facts in defense of their opinions, use formulas and the results of long-term observations.
Here are some hypotheses (out of a huge number):
It's all the Earth's fault
1) If our planet was previously in a molten state, it means that over time it cools down and becomes covered with glaciers.
Unfortunately, this simple and clear explanation contradicts all available scientific data. Glaciations also occurred in the “young years” of the Earth.
2) Two hundred years ago, the German philosopher Herder suggested that the Earth's poles move.
Geologist Wegner “turned this idea inside out”: it is not the poles that move to the continents, but blocks of continents that float to the poles along the fluid, underlying shell of the planet. It has not yet been possible to convincingly prove the movement of continents. And is that the only problem? In Verkhoyansk, for example, it is much colder than at the North Pole, but glaciers still do not form there.
3) Up the mountain slopes, after every kilometer of ascent, the air temperature decreases by 5-7 degrees. Movements that began millions of years ago earth's crust have now led to its rise by 300-600 meters. The reduction in the area of the oceans further cooled the planet: after all, water is a good heat accumulator.
But what about multiple glacier advances during the same era? The surface of the earth could not fluctuate so often, up and down.
4) For the growth of glaciers, not only cold weather is necessary, but also a lot of snow. This means that if for some reason the ice of the Arctic Ocean melts, its waters will evaporate intensely and fall on the nearest continents. Winter snows will not have time to melt during the short northern summer, and ice will begin to accumulate. All this is speculation, with almost no evidence. (By the way, I thought that it would be great if our education, in addition to standard subjects and topics, also included such unusual, but at the same time important topics as the theory of glaciation of the Earth.)
A place in the sun
Astronomers are accustomed to thinking in the language of mathematics. Their conclusions about the causes and rhythms of glaciations are distinguished by accuracy, clarity and... raise many doubts. The distance from the Earth to the Sun and the tilt of the Earth's axis do not remain constant. They are influenced by the planets and the shape of the Earth (it is not a sphere and the axis of its own rotation does not pass through its center).
The Serbian scientist Milanković constructed a graph showing the increase or decrease in the amount of solar heat over time for a certain parallel, depending on the position of the Earth relative to the Sun. Subsequently, these graphs were refined and supplemented. Revealed amazing coincidence them with glaciations. It would seem that everything has become absolutely clear.
However, Milankovic made his schedule only for last million years of Earth's life. And before? And then the position of the Earth relative to the Sun changed periodically, and there were no glaciations for tens of millions of years! This means that the influence of secondary reasons has been accurately calculated, while the most important ones have remained unaccounted for. It's the same as determining hours, minutes, seconds solar eclipses, not knowing on what days and years eclipses will occur.
They tried to eliminate this shortcoming of astronomical theory by assuming the movement of continents to the poles. But continental drift in itself has not been proven.
Pulse of a star
At night the stars twinkle in the sky. It's a beautiful sight - optical illusion, something like a mirage. Well, what if the stars and ours really twinkle (of course, very slowly)?
Then the cause of glaciations should be sought in the Sun. But how to catch the leisurely fluctuations of its radiation that last for millennia?
The connection between the Earth's climate and sunspots has not yet been reliably established. The upper layers of the atmosphere react sensitively to increased solar activity. They transmit their excitement to the surface of the Earth. During years of high solar activity, more precipitation accumulates in lakes and seas, and tree rings thicken.
The evidence for eleven-year and hundred-year cycles of solar activity is quite convincing. By the way, they can be traced in layered sediments deposited millions and even hundreds of millions of years ago. Our luminary is distinguished by enviable constancy.
But long-term solar cycles, with which glaciations can be associated, are almost completely unstudied. Exploring them is a matter for the future.
Nebulae...
Some scientists invoke cosmic forces to explain glaciations. The simplest thing: on your galactic journey solar system passes more or less heated parts of space.
There is another opinion: the intensity of the Milky Way's radiation changes periodically. At the beginning of the last century, another hypothesis was proposed. Giant clouds of cosmic dust hover in interstellar space. When the Sun passes through these clusters (like an airplane in the clouds), dust particles absorb some of the sun's rays destined for the Earth. The planet is cooling. When gaps occur among the cosmic cloud, the heat flow increases and the Earth “warms” again.
Mathematical calculations refuted this assumption. It turned out that the density of nebulae is low. At a short distance from the Earth to the Sun, the influence of dust will have almost no effect.
Other researchers associated the increase in solar activity with its passage through cosmic hydrogen clouds, believing that then, due to the influx of new material, the brightness of the Sun could increase by 10 percent.
This hypothesis, like some others, is difficult to refute or prove.
How could it be.
Too often adherents of one particular scientific theory are irreconcilable with their opponents and the general unity in the search for truth gives way to uncoordinated efforts. Currently, this disadvantage is increasingly being overcome. Increasingly, scientists are in favor of generalizing multiple hypotheses into a single whole.
Perhaps on your own space path The Sun, falling into different regions of the Galaxy, either increases or decreases the strength of its radiation (or this occurs due to internal changes in the Sun itself). A slow decline or rise in temperature begins across the entire surface of the Earth, where the main source of heat is the sun's rays.
If during a slow “solar cooling” significant uplifts of the earth’s crust occur, the land area increases, the direction and strength of the winds, and with them the ocean currents, change, then the climate in the circumpolar regions can deteriorate significantly. (An additional influence of pole movement or continental drift cannot be ruled out).
Air temperature changes will occur quickly, while the oceans will still store heat. (In particular, the Northern Ocean will not yet be Arctic). Evaporation from their surface will be high, and the amount of precipitation, especially snow, will increase.
The earth will enter an ice age.
Against the backdrop of general cooling, the influence of astronomical factors on the climate will be more clearly revealed. But not as clearly as shown in the Milankovitch graph.
It will be necessary to take into account possible fluctuations in the radiation of the Sun itself. How do ice ages end?
The movements of the earth's crust subside, the Sun becomes hotter. Ice, water, and wind smooth out mountains and hills. More and more precipitation is accumulating in the oceans, and from this, and most importantly from the beginning of the melting of glaciers, sea levels are rising, water is advancing onto land. Due to the increase in water surface - additional “warming” of the Earth.
Warming, like glaciation, is growing like an avalanche. The first minor climate changes entail others, and more and more new ones are connected to them...
Finally, the surface of the planet will smooth out. Streams of warm air will flow freely from the equator to the poles. The abundance of seas, storers of solar heat, will help moderate the climate. There will be a long period of “thermal calm” for the planet. Until the coming glaciations.
Traces of ancient cold snaps, left by widespread ice sheets, are found on all modern continents, on the bottom of the oceans, and in sediments of different geological eras.
The Proterozoic era began with the accumulation of the first, oldest glacial deposits found so far. In the period from 2.5 to 1.95 billion years BC, the Huronian era of glaciation was noted. About a billion years later, a new, Gneisses, glaciation era began (950-900 million years ago), and after another 100-150 thousand years, the Stera Ice Age began. The Precambrian ends with the Varangian glaciation era (680-570 million years BC).
The Phanerozoic begins with the warm Cambrian period, but after 110 million years from its beginning the Ordovician glaciation was noted (460-410 million years BC), and about 280 million years ago the Gondwana glaciation culminated (340-240 million years BC). ). The new warm era continued until approximately the middle of the Cenozoic era, when the modern Cenozoic era of glaciation began.
Taking into account the phases of development and completion, the ice ages have occupied about half the time of the Earth's evolution over the past 2.5 billion years. Climatic conditions during glacial periods they were more variable than during warm “ice-free” periods. Glaciers retreated and advanced, but invariably remained at the planet's poles. During the glaciation eras, the average temperature of the Earth was 7-10 °C lower than during warm eras. When the glaciers grew, the difference increased to 15-20 °C. For example, in the warmest period closest to us, the average temperature on Earth was about 22 °C, and now - in the Cenozoic ice age- only 15 °C.
The Cenozoic era is an era of gradual and consistent decrease in average temperature on the Earth's surface, an era of transition from a warm era to an era of glaciation, which began about 30 million years ago. The climate system in the Cenozoic changed in such a way that about 3 million years ago the general drop in temperature was replaced by almost periodic fluctuations, which is associated with the periodic growth of glaciation.
In high latitudes the cooling was most severe - several tens of degrees - while in the equatorial zone it was several degrees. Climatic zonation close to modern one was established about 2.5 million years ago, although the areas of severe Arctic and Antarctic climate in that era were smaller, and the boundaries of temperate, subtropical and tropical climates were at higher latitudes. Fluctuations in climate and glaciation of the Earth consisted of alternating “warm” interglacial and “cold” glacial eras.
During the “warm” eras, the Greenland and Antarctic ice sheets had sizes close to modern ones - 1.7 and 13 million square meters. km respectively. During cold eras, glaciers, of course, increased, but the main increase in glaciation occurred due to the emergence of large ice sheets in North America and Eurasia. The area of glaciers reached approximately 30 million km³ in the Northern Hemisphere and 15 million km³ in the Southern Hemisphere. The climatic conditions of the interglacials were similar to modern ones and even warmer.
About 5.5 thousand years ago, the “climatic optimum” was replaced by the so-called “Iron Age cooling”, which culminated about 4 thousand years ago. Following this cooling, a new warming began, which continued into the first millennium AD. This warming is known as the “minor climatic optimum” or the period of “forgotten geographical discoveries”.
The first explorers of new lands were Irish monks who, thanks to improved navigation conditions in the North Atlantic due to warming, discovered the Faroe Islands, Iceland and, as modern scientists assume, America in the middle of the first millennium. Following them, this discovery was repeated by the Vikings of Normandy, who at the beginning of this millennium settled the Faroe Islands, Iceland and Greenland, and subsequently reached America. The Vikings swam to approximately the latitude of the 80th parallel, and ice as an obstacle to navigation is practically not mentioned in the ancient sagas. In addition, if in modern Greenland the inhabitants are mainly engaged in catching fish and sea animals, then in the Norman settlements cattle breeding was developed - excavations have shown that cows, sheep and goats were bred here. In Iceland, cereals were cultivated, and the grape growing area overlooked Baltic Sea, i.e. was north of the modern one by 4-5 geographical degrees.
In the first quarter of our millennium, a new cooling began, which lasted until mid-19th V. Already in the 16th century. sea ice cut off Greenland from Iceland and destroyed the settlements founded by the Vikings. The last record of Norman settlers in Greenland dates back to 1500. Natural conditions in Iceland in the 16th-17th centuries they became unusually harsh; Suffice it to say that from the beginning of the cold spell until 1800, the population of the country was halved due to famine. On the plains of Europe and Scandinavia, severe winters became frequent, previously unfrozen reservoirs became covered with ice, crop failures and livestock deaths became more frequent. Individual icebergs reached the coast of France.
The warming that followed the Little Ice Age began as early as late XIX century, but as a large-scale phenomenon it attracted the attention of climatologists only in the 30s. 20th century, when a significant increase in water temperature in the Barents Sea was discovered.
In the 30s air temperatures in moderate and especially high northern latitudes were significantly higher than at the end of the 19th century. Thus, winter temperatures in western Greenland increased by 5 °C, and in Spitsbergen - even by 8-9 °C. The largest global increase in average surface temperature during the warming climax was only 0.6°C, but even this small change—a fraction of that during the Little Ice Age—was associated with a marked change in the climate system.
Mountain glaciers reacted violently to warming, retreating everywhere, and the magnitude of this retreat was hundreds of meters in length. The ice-filled islands that existed in the Arctic disappeared; only in the Soviet sector of the Arctic from 1924 to 1945. The ice area during the navigation period at this time decreased by almost 1 million km², i.e. half. This allowed even ordinary ships to sail to high latitudes and make end-to-end voyages along the Northern Sea Route during one navigation. The amount of ice in the Greenland Sea has also decreased, despite the fact that the removal of ice from the Arctic basin has increased. The duration of the ice blockade of the Icelandic coast has been reduced from 20 weeks at the end of the 19th century. up to two weeks in 1920-1939. Everywhere there was a retreat to the north of the boundaries of permafrost - up to hundreds of kilometers, the depth of thawing of frozen soils increased, and the temperature of the frozen layer increased by 1.5-2 °C.
The warming was so intense and long-lasting that it led to changes in the boundaries of ecological areas. The gray-headed thrush began nesting in Greenland, and swallows and starlings appeared in Iceland. The warming of ocean waters, especially noticeable in the north, has led to changes in the spawning and feeding areas of commercial fish: thus, cod and herring appeared in commercial quantities off the coast of Greenland, and Pacific sardine appeared in Peter the Great Gulf. Around 1930, mackerel appeared in the waters of Okhotsk, and in the 1920s. - saury. There is a well-known statement by the Russian zoologist, academician N.M. Knipovich: “In just a decade and a half or even a shorter period of time, such a change occurred in the distribution of representatives of the marine fauna that is usually associated with the idea of long geological intervals.” Warming also affected the Southern Hemisphere, but to a much lesser extent, and it was most clearly manifested in winter in the high latitudes of the Northern Hemisphere.
At the end of the 1940s. signs of cooling appeared again. After some time, the reaction of glaciers became noticeable, which in many parts of the Earth went on the offensive or slowed down their retreat. After 1945, there was a noticeable increase in the area of Arctic ice, which began to appear more often off the coast of Iceland, as well as between Norway and Iceland. From the beginning of the 40s to the end of the 60s. XX century The ice area in the Arctic basin increased by 10%.