We are at the mercy of autumn and it's getting colder. Are we moving towards an ice age, one of the readers wonders.
The fleeting Danish summer is behind us. The leaves are falling from the trees, the birds are flying south, it's getting darker and, of course, colder too.
Our reader Lars Petersen from Copenhagen has begun to prepare for the cold days. And he wants to know how seriously he needs to prepare.
“When does the next ice age begin? I learned that glacial and interglacial periods alternate regularly. Since we live in an interglacial period, it is logical to assume that the next ice age is ahead of us, right? he writes in a letter to the Ask Science section (Spørg Videnskaben).
We in the editorial office shudder at the thought of the cold winter that lies in wait for us at that end of autumn. We, too, would love to know if we are on the verge of an ice age.
The next ice age is still far away
Therefore, we addressed Sune Olander Rasmussen, lecturer at the Center for Basic Ice and Climate Research at the University of Copenhagen.
Sune Rasmussen studies the cold and gets information about past weather, storms, Greenland glaciers and icebergs. In addition, he can use his knowledge in order to fulfill the role of "foreteller of ice ages."
“In order for an ice age to occur, several conditions must coincide. We cannot accurately predict when the ice age will begin, but even if humanity did not further influence the climate, our forecast is that the conditions for it will develop in the best case in 40-50 thousand years,” Sune Rasmussen reassures us.
Since we are still talking to the “ice age predictor”, we can get some more information about what these “conditions” are in question in order to understand a little more about what the ice age actually is.
What is an ice age
Sune Rasmussen says that during the last ice age, the average temperature on earth was a few degrees cooler than it is today, and that the climate at higher latitudes was colder.
Much of the northern hemisphere was covered in massive ice sheets. For example, Scandinavia, Canada and some other parts of North America were covered with a three-kilometer ice sheet.
The huge weight of the ice cover pressed the earth's crust a kilometer into the Earth.
Ice ages are longer than interglacials
However, 19 thousand years ago, changes in the climate began to occur.
In Greenland, the last remnants of the shell came off very abruptly 11,700 years ago, or to be exact, 11,715 years ago. This is evidenced by the studies of Sune Rasmussen and his colleagues.
This means that 11,715 years have passed since the last ice age, and this is a completely normal interglacial length.
“It's funny that we usually think of the Ice Age as an 'event', when in fact it's just the opposite. The middle ice age lasts 100 thousand years, while the interglacial lasts from 10 to 30 thousand years. That is, the Earth is more often in an ice age than vice versa.
“The last couple of interglacials lasted only about 10,000 years each, which explains the widely held but erroneous belief that our current interglacial is nearing its end,” says Sune Rasmussen.
Three Factors Influence the Possibility of an Ice Age
The fact that the Earth will plunge into a new ice age in 40-50 thousand years depends on the fact that there are small variations in the orbit of the Earth around the Sun. Variations determine how much sunlight hits which latitudes, and thereby affects how warm or cold it is.
Milankovitch cycles are:
1. The orbit of the Earth around the Sun, which changes cyclically about once every 100,000 years. The orbit changes from nearly circular to more elliptical, and then back again. Because of this, the distance to the Sun changes. The farther the Earth is from the Sun, the less solar radiation our planet receives. In addition, when the shape of the orbit changes, so does the length of the seasons.
2. The tilt of the earth's axis, which fluctuates between 22 and 24.5 degrees relative to the orbit of rotation around the sun. This cycle spans approximately 41,000 years. 22 or 24.5 degrees - it seems not such a significant difference, but the tilt of the axis greatly affects the severity of the different seasons. How more Earth tilted, the greater the difference between winter and summer. The Earth's axial tilt is currently at 23.5 and is decreasing, which means that differences between winter and summer will decrease over the next thousand years.
3. The direction of the earth's axis relative to space. The direction changes cyclically with a period of 26 thousand years.
“The combination of these three factors determines whether there are prerequisites for the beginning of the ice age. It is almost impossible to imagine how these three factors interact, but with the help of mathematical models we can calculate how much solar radiation is received by certain latitudes at certain times of the year, as well as received in the past and will receive in the future,” says Sune Rasmussen.
Snow in summer leads to ice age
Summer temperatures play a particularly important role in this context.
Milankovitch realized that for the ice age to start, summers in the northern hemisphere would have to be cold.
If winters are snowy and most of the northern hemisphere is covered in snow, then temperatures and hours of sunshine in summer determine whether snow is allowed to remain all summer.
“If the snow does not melt in the summer, then little sunlight penetrates the Earth. The rest is reflected back into space in a snow-white veil. This exacerbates the cooling that began due to a change in the orbit of the Earth around the Sun,” says Sune Rasmussen.
“Further cooling brings even more snow, which further reduces the amount of absorbed heat, and so on, until the ice age begins,” he continues.
Similarly, a period of hot summers leads to the end of the Ice Age. Then the hot sun melts the ice enough to sunlight again could fall on dark surfaces, like soil or the sea, which absorb it and heat the Earth.
Humans are delaying the next ice age
Another factor that is relevant to the possibility of an ice age is the amount of carbon dioxide in the atmosphere.
Just as snow that reflects light increases the formation of ice or accelerates its melting, the increase in carbon dioxide in the atmosphere from 180 ppm to 280 ppm (parts per million) helped bring the Earth out of the last ice age.
However, ever since industrialization began, people have been pushing the CO2 share further all the time, so it's almost 400 ppm now.
“It took nature 7,000 years to raise the share of carbon dioxide by 100 ppm after the end of the ice age. Humans have managed to do the same in just 150 years. It has great importance whether the Earth can enter a new ice age. This is a very significant influence, which means not only that an ice age cannot begin at the moment,” says Sune Rasmussen.
We thank Lars Petersen for the good question and send the winter gray T-shirt to Copenhagen. We also thank Sune Rasmussen for the good answer.
We also encourage our readers to submit more scientific questions to [email protected]
Did you know?
Scientists always talk about the ice age only in the northern hemisphere of the planet. The reason is that there is too little land in the southern hemisphere on which a massive layer of snow and ice can lie.
With the exception of Antarctica, the entire southern part of the southern hemisphere is covered with water, which does not provide good conditions for the formation of a thick ice shell.
Governments and public organizations are actively discussing the coming "global warming" and measures to combat it. However, there is a well-founded opinion that in reality we are not waiting for warming, but cooling. And in this case, the fight against industrial emissions, which are believed to contribute to warming, is not only pointless, but also harmful.
It has long been proven that our planet is in the "high risk" zone. A relatively comfortable existence provides us with " Greenhouse effect”, that is, the ability of the atmosphere to retain the heat coming from the Sun. Nevertheless, global ice ages occur periodically, which differ in that there is a general cooling and a sharp increase in continental ice sheets in Antarctica, in Eurasia and North America.
The duration of the cooling is such that scientists talk about entire ice ages that lasted hundreds of millions of years. The last, fourth in a row, Cenozoic, began 65 million years ago and continues to this day. Yes, yes, we live in an ice age, which is unlikely to end in the near future. Why do we think that warming is happening?
The fact is that within the ice age there are cyclically repeating periods of time lasting tens of millions of years, which are called ice ages. They, in turn, are subdivided into glacial epochs, consisting of glaciations (glacials) and interglacials (interglacials).
All modern civilization arose and developed in the Holocene - a relatively warm period after the Pleistocene ice age, which reigned only 10 thousand years ago. A slight warming led to the liberation of Europe and North America from the glacier, which allowed the emergence of an agricultural culture and the first cities, which gave impetus to rapid progress.
For a long time, paleoclimatologists could not understand what caused the current warming. It was found that climate change is influenced by a number of factors: changes in solar activity, oscillations of the earth's axis, composition of the atmosphere (primarily carbon dioxide), the degree of salinity of the ocean, the direction of ocean currents and wind roses. Painstaking research has made it possible to isolate the factors that influenced modern warming.
About 20,000 years ago, the glaciers of the Northern Hemisphere moved so far to the south that even a slight increase in the average annual temperature was enough to start melting them. Fresh water filled the North Atlantic, slowing down local circulation and thereby accelerating warming in the Southern Hemisphere.
The change in the direction of winds and currents led to the fact that the water of the Southern Ocean rose from the depths, and carbon dioxide, which had remained "locked" there for thousands of years, was released into the atmosphere. The mechanism of the "greenhouse effect" was launched, which 15 thousand years ago provoked warming in the Northern Hemisphere.
Approximately 12.9 thousand years ago, a small asteroid fell in the central part of Mexico (now at the site of its fall is Lake Cuitzeo). Ashes from fires and dust thrown into the upper atmosphere caused a new local cooling, which also contributed to the release of carbon dioxide from the depths of the Southern Ocean.
The cooling lasted for about 1,300 years, but in the end only increased the "greenhouse effect" due to the rapid change in the composition of the atmosphere. The climate "swing" once again changed the situation, and warming began to develop at an accelerating pace, the northern glaciers melted, freeing Europe.
Today, carbon dioxide coming from the depths of the southern part of the World Ocean is successfully replaced by industrial emissions, and warming continues: during the 20th century, the average annual temperature increased by 0.7 ° - a very significant value. It would seem that overheating, rather than sudden cold weather, should be feared. But not everything is so simple.
It seems that the last onset of cold weather was a very long time ago, but humanity remembers well the events related to the "Little Ice Age". So in the special literature they call the strongest European cooling, which lasted from the 16th to the 19th centuries.
View of Antwerp with the frozen river Scheldt / Lucas van Valckenborch, 1590
Paleoclimatologist Le Roy Ladurie analyzed the collected data on the expansion of glaciers in the Alps and the Carpathians. He points to the following fact: the mines developed in the middle of the 15th century in the High Tatras were covered with ice 20 meters thick in 1570, and in the 18th century the thickness of the ice there was already 100 meters. At the same time, the onset of glaciers began in the French Alps. In written sources, endless complaints appeared from the inhabitants of mountain villages that glaciers were burying fields, pastures and houses under them.
Frozen Thames / Abraham Hondius, 1677
As a result, the paleoclimatologist states, “Scandinavian glaciers, synchronously with Alpine glaciers and glaciers from other regions of the world, have been experiencing the first, well-defined historical maximum since 1695,” and “in subsequent years they will begin to advance again.” One of the most terrible winters of the "Little Ice Age" fell on January-February 1709. Here is a quote from a written source of that time:
From an extraordinary cold, such as neither grandfathers nor great-grandfathers remembered<...>the inhabitants of Russia and Western Europe perished. Birds flying through the air froze. In general, in Europe, many thousands of people, animals and trees died.
In the vicinity of Venice, the Adriatic Sea was covered standing ice. The coastal waters of England were covered with ice. Frozen Seine, Thames. Just as great were the frosts in the eastern part of North America.
In the 19th century, the "Little Ice Age" was replaced by warming, and severe winters were a thing of the past for Europe. But what caused them? And won't this happen again?
Frozen lagoon in 1708, Venice / Gabriel Bella
The potential threat of the onset of another ice age was discussed six years ago, when unprecedented frosts hit Europe. The largest European cities were covered with snow. The Danube, the Seine, the canals of Venice and the Netherlands froze. Due to icing and breakage of high-voltage wires, entire areas were de-energized, classes in schools were stopped in some countries, and hundreds of people froze to death.
All these horrifying events had nothing to do with the concept of "global warming" that had been vehemently debated for a decade before. And then scientists had to reconsider their views. They drew attention to the fact that the Sun is currently experiencing a decline in its activity. Perhaps it was this factor that became decisive, exerting a much greater influence on the climate than “global warming” due to industrial emissions.
It is known that the activity of the Sun changes cyclically over 10-11 years. The last 23rd cycle (since the beginning of observations) was indeed distinguished by high activity. This allowed astronomers to say that the 24th cycle will be unprecedented in intensity, especially since this happened earlier, in the middle of the 20th century. However, in this case, the astronomers were wrong. The next cycle was supposed to start in February 2007, but instead there was an extended period of solar "minimum" and the new cycle started late in November 2008.
Khabibullo Abdusamatov, head of the space research laboratory at the Pulkovo Astronomical Observatory of the Russian Academy of Sciences, claims that our planet passed the peak of warming in the period from 1998 to 2005. Now, according to the scientist, the activity of the Sun is slowly declining and will reach its minimum in 2041, due to which a new "Little Ice Age" will come. The scientist expects the peak of cooling in the 2050s. And it can lead to the same consequences as the cooling in the 16th century.
However, there is still reason for optimism. Paleoclimatologists have established that periods of warming between ice ages are 30-40 thousand years. Ours lasts only 10 thousand years. Humanity has a huge supply of time. If in such a short period of time, by historical standards, people have managed to rise from primitive agriculture to space flight, then we can hope that they will find a way to cope with the threat. For example, learn to control the climate.
Used materials from the article by Anton Pervushin,
last ice age
During this era, 35% of the land was under the ice cover (compared to 10% at present).
The last ice age was not just a natural disaster. It is impossible to understand the life of planet Earth without considering these periods. In the intervals between them (known as interglacial periods), life flourished, but then once again the ice inexorably approached and brought death, but life did not completely disappear. Every ice age has been marked by a struggle for survival different types, there were global climate changes, and in the last of them appeared the new kind who became (over time) dominant on Earth: it was a man.
ice ages
Ice ages are geological periods characterized by a strong cooling of the Earth, during which vast expanses of the earth's surface were covered with ice. high level humidity and, of course, exceptional cold, as well as the lowest sea level known to modern science. There is no generally accepted theory regarding the causes of the onset of the ice age, however, since the 17th century, various explanations have been proposed. According to current opinion, this phenomenon was not caused by one cause, 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. This is similar to what we now call global warming, but on a much larger scale.
The movements of the continents, caused by cyclical changes in the orbit of the Earth around the Sun, and in addition, a 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 in the Precambrian era. Then in the Miocene epoch - 15 million years ago.
The 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 Wurm stage of glaciation began approximately 100,000 years ago, reached its maximum 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 more space than now. Based on the amount of ice that currently covers the planet, one can get some idea of the area 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.
Northern Canada was estimated to have covered 13.3 million km2 of ice, while 147.25 km2 is now under ice. The same difference is observed in Scandinavia: 6.7 million km2 in that period compared to 3910 km2 today.
The ice age began simultaneously in both hemispheres, although in the North the ice spread to more extensive areas. In Europe, the glacier captured most of the British Isles, northern Germany and Poland, and in North America, where the Wurm glaciation is called the "Wisconsin glacial stage", 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 recesses left after the melting of the ice mass.
The sea level dropped by almost 120 m, as a result of which large expanses were exposed that are currently covered sea water. The significance of this fact is enormous, since large-scale human and animal migrations became possible: hominids were able to make the transition from Siberia to Alaska and move from continental Europe to England. It is possible that during the interglacial periods, the two largest ice massifs on Earth - Antarctica and Greenland - have undergone little change over the course of history.
At the peak of glaciation, the indicators of the average temperature drop varied significantly depending on the location: 100 ° C - in Alaska, 60 ° C - in England, 20 ° C - in the tropics and remained practically unchanged at the equator. Conducted studies of the last glaciations in North America and Europe, which occurred during the Pleistocene era, gave the same results in this geological region within the last two (approximately) million years.
The last 100,000 years are of particular importance for understanding the evolution of mankind. Ice ages have become a severe test for the inhabitants of the Earth. After the end of the next glaciation, they again had to adapt, learn to survive. When the climate became warmer, the sea level rose, new forests and plants appeared, the land rose, freed from the pressure of the ice shell.
The hominids turned out to have the most natural data to adapt to the changed conditions. They were able to move to areas with the most food resources, where the slow process of their evolution began.
Not expensive to buy children's shoes in bulk in Moscow
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1.8 million years ago began the Quaternary (anthropogenic) period of the geological history of the earth, which continues to this day.
River basins expanded. There was a rapid development of the fauna of mammals, especially mastodons (which would later become extinct, like many other ancient animal species), ungulates and higher monkeys. In this geological period of the history of the earth, a person appears (hence the word anthropogenic in the name of this geological period).
The Quaternary period is marked by a sharp change in climate throughout the European part of Russia. From a warm and humid Mediterranean, it turned into a temperate cold, and then into a cold Arctic one. 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, also covered the territory of the modern Kashirsky region, including our region. The first glaciation was the coldest; woody vegetation in the Oka region disappeared almost completely. The glacier did not last long. The first Quaternary glaciation reached the Oka valley, which is why it received the name “Oksky glaciation”. The glacier left moraine deposits dominated by boulders of local sedimentary rocks.
But such favorable conditions changed the glacier again. The 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 Western Europe And European part Russia. The boundaries of the languages of the Dnieper glaciation passed in the area of modern Dnepropetrovsk and almost reached Volgograd.
 mammoth fauna |
The climate warmed up again and became Mediterranean. In place of the glaciers, heat-loving and moisture-loving vegetation spread: oak, beech, hornbeam and yew, as well as linden, alder, birch, spruce and pine, hazel. In the marshes, ferns grew, characteristic of modern South America. The restructuring of the river system and the formation of Quaternary terraces in the river valleys began. This period was called the interglacial Oxo-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 were fields of ice, interspersed with intervals of melted hills, between which rivers flowed from melt water and lakes accumulated.
Ice flows of the Dnieper glaciation brought glacial boulders from Finland and Karelia to our region.
The valleys of the old rivers were filled with mid-moraine and fluvioglacial deposits. It warmed up again, and the glacier began to melt. Streams of melt water rushed south along the channels of new rivers. During this period, the third terraces are formed in the river valleys. Large lakes formed in the depressions. The climate was moderately cold.
In our region, forest-steppe vegetation dominated with a predominance of coniferous and birch forests and large areas of steppes covered with wormwood, quinoa, grasses and herbs.
The interstadial epoch 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 Moscow. Some tongues of the glacier reached the Oka valley, but they did not reach the territory of the modern Kashirsky region. The climate was severe, and the landscape of our region becomes close to the steppe tundra. Forests are almost disappearing and their place is taken by steppes.
A new warming has come. The rivers deepened their valleys again. The second terraces of the rivers were formed, 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 terms of climate went through stages from continentally temperate (close to modern) to warm, with a Mediterranean climate. In our region, birch, pine and spruce dominated at first, and then heat-loving oaks, beeches and hornbeams turned green again. In the swamps, the water lily grew, which today you will find only in Laos, Cambodia or Vietnam. At the end of the interglacial period, birch-coniferous forests again dominated.
This idyll was spoiled by the Valdai glaciation. Ice from the Scandinavian Peninsula again rushed to the south. This time the glacier did not reach the Moscow region, but changed our climate to subarctic. For many hundreds of kilometers, including the territory of the present Kashirsky district and rural settlement Znamenskoye, the steppe-tundra stretches, with dried grass and rare shrubs, dwarf birches and polar willows. These conditions were ideal for the mammoth fauna and for primitive man, who then already lived on the borders of the glacier.
During the last Valdai glaciation, the first river terraces formed. The hydrography of our region has finally taken shape.
Traces of glacial epochs are often found in the Kashirsky region, but they are difficult to identify. Of course, large stone boulders are traces of the glacial activity of the Dnieper glaciation. They were brought by ice from Scandinavia, Finland and from the Kola Peninsula. The most ancient traces of the glacier are moraine or boulder loam, which is a random mixture of clay, sand, 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 the sands are homogeneous. They can be observed on the Oka. These include the Belopesotsky sands. Often found in the valleys of rivers, streams, in ravines, layers of flint and limestone gravel are traces of the bed of ancient rivers and streams.
With new warming, the geological epoch of the Holocene began (it began 11,400 years ago), which continues to this day. The modern river floodplains were finally formed. The mammoth fauna died out, and forests appeared in place of the tundra (at first, spruce, then birch, and later mixed). The flora and fauna of our region has acquired the features of modern - the one that we see today. At the same time, the left and right banks of the Oka are still very different in their forest cover. If mixed forests and many open areas prevail on the right bank, then continuous coniferous forests dominate on the left bank - 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 over the past 5 thousand years has been rising only slightly, 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 seen in this chapter that human history is a grain of sand in the history of our planet.
GLACIAL PERIOD
In the distant, distant times, where Leningrad, Moscow, Kyiv are now, everything was different. Dense forests grew along the banks of ancient rivers, and shaggy mammoths with bent tusks, huge furry rhinoceroses, tigers and bears much larger than today roamed there.
Gradually, these places became colder and colder. Far in the north, so much snow fell every year that entire mountains of it accumulated - larger than the present Urals. The snow caked up, turned into ice, then slowly began to spread, spreading in all directions.
Ice mountains have moved over the ancient forests. Cold, evil winds blew from these mountains, trees froze and animals fled from the cold to the south. And the icy mountains crawled further south, twisting the rocks along the way and moving whole hills of earth and stones in front of them. They crawled to the place where Moscow now stands, and crawled even further, into 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 receded, 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 approached from the north. Have you seen the cobblestone pavement? Such small stones are brought by the glacier. And there are boulders the size of a house. They still lie in the north.
But the ice can 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 NUCLEAR ENERGY and keep the glacier out of our land.
When did the ice age end?
Many of us believe that the Ice Age ended a very long time ago and no traces of it remain. But geologists say we are only approaching the end of the ice age. And the inhabitants of Greenland are still living in the Ice Age.
Approximately 25 thousand years ago, the peoples who inhabited the central part of NORTH AMERICA saw ice and snow all year round. A huge wall of ice stretched from the Pacific to the Atlantic Ocean, and north to the very pole. It 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 over one kilometer thick.
But this does not mean that it was always very cold. In the northern part of the United States, the temperature was only 5 degrees below present. The cold summer months caused the 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 "glaciation", warm - "interglacial" period.
The first phase in North America is believed 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.
Ice melting speed last step ice age in different areas was not the same. For example, in the area of present-day Wisconsin in the United States, ice melt began about 40,000 years ago. The ice that covered the New England area in the US 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 was free of ice 17,000 years ago, while Sweden only 13,000 years ago.
Why do glaciers still exist today?
A huge mass of ice, from the formation of which the ice age began in North America, was called the "continental glacier": in the very center its thickness reached 4.5 km. It is possible that this glacier formed and melted four times during the entire ice age.
The glacier that covered other parts of the world has not melted in some places! For example, the huge island of Greenland is still covered by continental ice, 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 a vast continental glacier up to 4 kilometers thick in some places!
So the reason why there are glaciers in some parts of the world is that they have not melted since the Ice Age. But the bulk of the glaciers that are found now, formed recently. They are mainly located in mountain valleys.
They originate in wide, gently sloping, amphitheater-like valleys. Snow falls 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 repeated freezing 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. Such a moving tongue of ice is a mountain glacier.
More than 1200 such glaciers are known in Europe in the Alps! They also exist in the Pyrenees, in the Carpathians, in the Caucasus, as well as in the mountains of southern Asia. There are tens of thousands of these glaciers in southern Alaska, some 50 to 100 km long!
The last ice age ended 12,000 years ago. In the most severe period, glaciation threatened man with extinction. However, after the glacier melted, he not only survived, but also created a civilization.
Glaciers in the history of the Earth
The last ice age in the history of the Earth is the Cenozoic. It began 65 million years ago and continues to this day. Modern man lucky: he lives in the interglacial, in one of the warmest periods of the planet's life. Far behind is the most severe ice age - the Late Proterozoic.
Despite global warming, scientists are predicting a new ice age. And if the real one comes only after millennia, then the Little Ice Age, which will reduce annual temperatures by 2-3 degrees, can 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 about 110,000 years ago and ended in the tenth millennium BC. The peak of cold weather fell on the period of 26-20 thousand years ago, the final stage of the Stone Age, when the glacier was the largest.
Little Ice Ages
Even after the glaciers melted, history has known periods of noticeable cooling and warming. Or, in other words, climate pessimism And optima. Pessima are sometimes referred to as Little Ice Ages. In the XIV-XIX centuries, for example, the Little Ice Age began, and the time of the Great Migration of Peoples was the time of the early medieval pessimum.
Hunting and meat food
There is an opinion according to which the human ancestor was rather a scavenger, since he could not spontaneously occupy a higher ecological niche. And all known tools were used to butcher the remains of animals that were taken from predators. However, the question of when and why a person began to hunt is still debatable.
In any case, thanks to hunting and eating meat, the ancient man received a large supply of energy, which allowed him to better endure the cold. The skins of slaughtered animals were used as clothing, shoes and walls of the dwelling, which increased the chances of surviving in a harsh climate.
bipedalism
Bipedalism appeared millions of years ago, and its role was much more important than in the life of a modern office worker. Having freed his hands, a person could engage in intensive construction of a dwelling, the production of clothing, the processing of tools, the extraction and preservation of fire. The upright ancestors roamed freely in open areas, and their life no longer depended on the collection of fruits from tropical trees. Already millions of years ago, they freely moved over long distances and obtained food in river flows.
Walking upright played an insidious role, but it 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
The fire in the life of an ancient person was originally an unpleasant surprise, not a boon. Despite this, the ancestor of man first learned to “extinguish” it, and only later to 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 through the preparation of protein foods, as well as to remain active at night. This further increased the time to create conditions for survival.
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 receded, 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 herbaceous vegetation, a truly “antediluvian” landscape. Wide rivers flowed here, exceeding the size of the Tigris and Euphrates by one and a half times. Sahara in some periods became a wet savanna. The last time this happened was 9,000 years ago. This can be confirmed by the rock paintings, which depict the 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 "collective work" has shown itself more than once in the construction of parking lots and the manufacture of clothing. Deer and wild horses among ancient people enjoyed no less "honor".
Language and communication
Language was, perhaps, the main life hack of an ancient person. It was thanks to speech that they were preserved and passed down from generation to generation. important technologies processing tools, mining and maintaining fire, as well as various human adaptations for everyday survival. Perhaps in the Paleolithic language, the details of the hunt for large animals and the direction of migration were discussed.
Allerd warming
Until now, scientists are 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 forage plants. As a result of the extermination a large number species of animals, a person in harsh conditions was threatened with 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). Nevertheless, warming has become an important factor in the migration of people to regions whose climate has become suitable for the emergence of agriculture.