Beginning and end of the Ice Age. Ice ages in the history of the earth. Cenozoic Ice Age

Just at the time of the powerful development of all forms of life on our planet, a mysterious ice age begins with its new temperature fluctuations. We have already spoken about the reasons for the appearance of this ice age before.

Just as the change of seasons brought about the selection of better, more adaptable animals and the creation of diverse breeds of mammals, so now, in this Ice Age, man is emerging from the mammals, in an even more painful struggle against the advancing glaciers than the fight against the millennium-spanning change of seasons. Here it was not enough just one adaptation by a significant change in the body. What was needed was a mind that would be able to turn nature itself to its advantage and conquer it.

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

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

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

Mastodon (restored) of the Deluvian era.

We involuntarily return in thought again to the emergence of the world, if we look at the flowering of the beautiful present from the chaotic dark primitive conditions. The fact that in the second half of our research we remained all the time only on our small Earth is due to the fact that we know all these different stages of development only on it. But, taking into account the similarity of the matter that forms the world everywhere and the universality of the forces of nature that control matter, we will come to complete agreement of all the main features of the formation of the world that we can observe in the sky.

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

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

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

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

ice age on earth

After terrible downpours, like a flood, it became damp and cold. From the high mountains, the glaciers slid lower and lower into the valleys, because the Sun could no longer melt the masses of snow continuously falling from above. As a result, even those places where earlier during the summer the temperature was still above zero were also covered with ice for a long time. We are now seeing something similar in the Alps, where individual "tongues" of glaciers descend well below the boundary of eternal snows. In the end, much of the plains at the foot of the mountains were also covered with ever higher piles of ice. A general ice age has come, the traces of which we can indeed observe everywhere on the entire globe.

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

The following question can be answered after careful research. The entire chain of the Andes, during geological periods, which, of course, are calculated in hundreds of thousands and millions of years, was formed simultaneously, and its volcanoes were the result of this grandiose mountain-forming process on Earth. At this time, almost the entire Earth was dominated by approximately tropical temperature, which, however, very soon after that should have been replaced by a strong general cooling.

Penck established that there were at least four great ice ages, with warmer periods in between. But it seems that these great ice ages are divided into a still greater number of smaller periods of time in which more insignificant general temperature fluctuations took place. From this one can see what turbulent times the Earth was going through and in what constant agitation the air ocean was then.

How long this time lasted can only be indicated very roughly. It has been calculated that the beginning of this ice age can be placed about half a million years ago. Since the last “little glaciation”, in all likelihood, only 10 to 20 millennia have passed, and we are now living, probably, only in one of those “interglacial periods” that happened before the last general glaciation.

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

This Persian legend describes the great flood as follows: “From the south rose a great fiery dragon. Everything was devastated by him. Day turned into night. The stars are gone. The zodiac was covered by a huge tail; only the sun and moon could be seen in the sky. Boiling water fell to the Earth and scorched the trees to the very roots. Raindrops the size of a human head fell among the frequent lightning. Water covered the Earth higher than a man's height. Finally, after the dragon fight lasted 90 days and 90 nights, the enemy of the Earth was destroyed. A terrible storm arose, the water receded, the dragon plunged into the depths of the Earth.

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

Thus, on the one hand, we have shown that after the splitting and collapse of a huge block, the size of a mainland, a series of volcanoes should have formed, the eruptions of which were followed by floods and glaciations. On the other hand, we have before our eyes a number of volcanoes in the Andes, located along a huge cliff of the Pacific coast, and we also proved that soon after the emergence of these volcanoes, an ice age began. The tales of the flood complete the picture of this turbulent period in the development of our planet even more. During the eruption of Krakatoa, we observed on a small scale, but in all details, the consequences of the volcano sinking into the depths of the sea.

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

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

If the coastal region were to sink there so slowly that whole centuries were required to detect this sinking, as we still observe at the present time near some sea coasts, then even then all movements of masses in the interior of the Earth would occur very slowly, and only occasionally would occur. volcanic eruptions.

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

The consequences of warming

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

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

The main periods of glaciation in the history of the planet

The answer to the first question depends on whether you mean the big glaciations or the small ones that occur during these long periods. Throughout history, the Earth has experienced five major glaciations, some of them lasting hundreds of millions of years. In fact, even now, the Earth is going through a large period of glaciation, and this explains why it has polar ice.

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

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

How does the 100,000 year cycle work?

Ice sheets grow for about 90,000 years and then begin to melt during the 10,000 year warm period. Then the process is repeated.

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

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

What causes an ice age?

The hypothesis put forward by the Serbian astronomer Milyutin Milanković explains why there are cycles of ice and interglacial periods on Earth.

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

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

Milankovitch's theory is that orbital cycles are predictable and very consistent in a planet's history. If the Earth is going through an ice age, then it will be covered in more or less ice, depending on these orbital cycles. But if the Earth is too warm, no change will occur, at least in regards to the growing amount of ice.

What can affect the warming of the planet?

The first gas that comes to mind is carbon dioxide. Over the past 800,000 years, carbon dioxide levels have fluctuated between 170 and 280 parts per million (meaning that out of 1 million air molecules, 280 are carbon dioxide molecules). A seemingly insignificant difference of 100 parts per million leads to the appearance of glacial and interglacial periods. But carbon dioxide levels are much higher today than they were in past fluctuations. In May 2016, carbon dioxide levels over Antarctica reached 400 parts per million.

The earth has warmed up so much before. For example, during the time of the dinosaurs, the air temperature was even higher than now. But the problem is that in today's world it is growing at a record pace, because we have released too much carbon dioxide into the atmosphere in a short time. In addition, given that emission rates are not declining to date, it can be concluded that the situation is unlikely to change in the near future.

The consequences of warming

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

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

What causes great ice ages?

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

So, for example, according to the uplift and weathering hypothesis, when plate tectonics leads to the growth of mountain ranges, new unprotected rock appears on the surface. It is easily weathered and disintegrates when it enters the oceans. Marine organisms use these rocks to create their shells. Over time, stones and shells take carbon dioxide from the atmosphere and its level drops significantly, which leads to a period of glaciation.

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

Ice Age on Earth.

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

About the process of formation of the Earth keeps memories of almost every corner of the globe. Hills running like a wave beyond the horizon, mountains touching the sky, a stone that was taken by man to build cities - each of them has his own story.

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

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

Earth was a gloomy and gray planet in the grip of cold, carried by snowstorms from the north and south.

Frozen planet.

From the nature of the glacial deposits (deposited clastic material) and the surfaces worn down by the glacier, geologists concluded that there were in fact several periods.

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

thaw.

These ruthless clutches were avoided by some lands, where it was usually also cold, but winter did not reign on the whole Earth.

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

In general, the climate of the glacier was not always cold. Glaciers, before receding, crawled several times from north to south.

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

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

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

Ice streams moving south again left behind destruction, thanks to which geologists can accurately determine their path.

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

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

Like a gigantic grinding machine that polished the ground beneath it and created large furrows called glacial shading, the movement of crushed stone and ice acted.

The valleys widened and deepened over time, acquiring a distinct U-shape.

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

Causes of glaciation.

What is called glaciation, scientists still do not know exactly. Some believe that the temperature at the Earth's poles, for the past millions of years, is lower than at any time in the history of the Earth.

Continental drift (more on continental drift) could be the cause. About 300 million million years ago there was only one giant supercontinent - Pangea.

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

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

It comes down to this situation: the ocean never warms up well in summer, and is constantly covered with ice.

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

The cold is returning.

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

And if the amount of solar heat changes even by a percentage, this can lead to a difference in temperature on Earth by a whole degree.

The interaction of these factors will be enough to start a new ice age. It is also believed that the ice age may cause the accumulation of dust in the atmosphere as a result of its pollution.

Some scientists believe that when a giant meteor collided with the Earth, the age of dinosaurs ended. This led to the fact that a huge cloud of dust and dirt rose into the air.

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

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

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

On this note, I end this topic. I hope that the story about the ice age on Earth did not “freeze” you 🙂 And finally, I suggest you subscribe to the mailing list of fresh articles so as not to miss their release.

During the Paleogene, the northern hemisphere had a warm and humid climate, but in the Neogene (25-3 million years ago) it became much colder and drier. Environmental changes associated with cooling and the appearance of glaciations are a feature of the Quaternary period. This is why it is sometimes called the Ice Age.

Ice ages have happened many times in the history of the Earth. Traces of continental glaciations were found in the layers of the Carboniferous and Permian (300-250 million years), Vendian (680-650 million years), Riphean (850-800 million years). The oldest glacial deposits found on Earth are over 2 billion years old.

No single planetary or cosmic factor has been found to cause glaciation. Glaciations are the result of a combination of several events, some of which play the main role, while others play the role of a "trigger" mechanism. It has been noted that all the great glaciations of our planet coincided with major mountain-building epochs, when the relief of the earth's surface was the most contrasting. The area of ​​the seas has decreased. Under these conditions, climate fluctuations have become more dramatic. Mountains up to 2000 m high, which arose in Antarctica, i.e. directly at the South Pole of the Earth, became the first focus of the formation of sheet glaciers. The glaciation of Antarctica began more than 30 million years ago. The appearance of a glacier there greatly increased the reflectivity, which in turn led to a decrease in temperature. Gradually, the glacier of Antarctica grew both in area and in thickness, and its influence on the thermal regime of the Earth was increasing. The temperature of the ice slowly decreased. The Antarctic continent has become the largest accumulator of cold on the planet. The formation of huge plateaus in Tibet and in the western part of the North American continent has made a great contribution to climate change in the Northern Hemisphere.

It got colder and colder, and about 3 million years ago, the climate of the Earth as a whole became so cold that ice ages periodically began to set in, during which ice sheets captured most of the northern hemisphere. Mountain-building processes are a necessary but still insufficient condition for the occurrence of glaciation. The average heights of the mountains are now not lower, and perhaps even higher than those that were during the glaciation. However, now the area of ​​glaciers is relatively small. Some additional reason is needed directly causing the cooling.

It should be emphasized that any significant decrease in temperature is not required for the occurrence of a major glaciation of the planet. Calculations show that the total average annual decrease in temperature on Earth by 2 - 4? C will cause spontaneous development of glaciers, which in turn will lower the temperature on Earth. As a result, the ice shell will cover a significant part of the Earth's area.

Carbon dioxide plays a huge role in the regulation of the temperature of the near-surface air layers. Carbon dioxide freely passes the sun's rays to the earth's surface, but absorbs most of the planet's thermal radiation. It is a colossal screen that prevents the cooling of our planet. Now the content of carbon dioxide in the atmosphere does not exceed 0.03%. If this figure is halved, then the average annual temperatures in the middle latitudes will decrease by 4–5 ° C, which may lead to the onset of an ice age. According to some reports, the concentration of CO2 in the atmosphere during the ice ages was about a third less than in the interglacials, and sea water contained carbon dioxide 60 times more than the atmosphere.

The decrease in the CO2 content in the atmosphere can be explained by the following mechanisms. If the rate of spreading (pushing apart) and, accordingly, subduction significantly decreased in some periods, then this should have led to the release of a smaller amount of carbon dioxide into the atmosphere. In fact, global average spreading rates show little change over the past 40 million years. If the rate of CO2 replacement was practically unchanged, then the rate of its removal from the atmosphere due to the chemical weathering of rocks increased significantly with the appearance of giant plateaus. In Tibet and America, carbon dioxide combines with rainwater and groundwater to form carbonic acid, which reacts with the silicate minerals of the rocks. The resulting bicarbonate ions are transported to the oceans, where they are consumed by organisms such as plankton and corals, and then deposited on the ocean floor. Of course, these sediments will fall into the subduction zone, melt, and CO2 will again enter the atmosphere as a result of volcanic activity, but this process takes a long time, from tens to hundreds of millions of years.

It may seem that as a result of volcanic activity, the CO2 content in the atmosphere will increase and therefore it will be warmer, but this is not entirely true.

The study of modern and ancient volcanic activity allowed the volcanologist I. V. Melekestsev to connect the cooling and the glaciation that caused it with an increase in the intensity of volcanism. It is well known that volcanism significantly affects the earth's atmosphere, changing its gas composition, temperature, and also polluting it with finely divided material of volcanic ash. Huge masses of ash, measured in billions of tons, are ejected by volcanoes into the upper atmosphere, and then carried by jet streams around the globe. A few days after the 1956 eruption of the Bezymyanny volcano, its ash was found in the upper troposphere above London. North America and Australia. Pollution of the atmosphere with volcanic ash causes a significant decrease in its transparency and, consequently, a weakening of solar radiation by 10-20% against the norm. In addition, ash particles serve as condensation nuclei, contributing to the large development of cloudiness. An increase in cloudiness, in turn, significantly reduces the amount of solar radiation. According to Brooks' calculations, an increase in cloudiness from 50 (typical for the present) to 60% would lead to a decrease in the average annual temperature on the globe by 2 ° C.

Scientists note that the ice age is part of the ice age, when the earth covers ice for long millions of years. But many people call the ice age a segment of the history of the Earth, which 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, rhinos, 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 rhinos, they raked ice with their horns and ate plants. Surprisingly, the vegetation was varied. Of course, many plant species disappeared, but herbivores had free access to food.

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

Rice. 1 - Ice Age

For the first time, the history of the Ice Age was discussed in the eighteenth century. Then geology began to form as a scientific branch, and scientists began to find out what origin the boulders in Switzerland have. Most researchers agreed in a single point of view that they have a glacial beginning. In the nineteenth century, it was suggested that the planet's climate was subject to severe cooling. A little later, the term itself was announced "ice Age". It was introduced by Louis Agassiz, whose ideas were not at first recognized by the general public, but then it was proved that many of his works really have a basis.

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 an ice mass. If large-scale ice sheets have already formed on the surface of the Earth, then they will cause a sharp cooling by reflecting sunlight, and therefore heat. Another reason for the formation of glaciers could be a change in the level of greenhouse effects. The presence of large Arctic massifs and the rapid spread of plants eliminates the 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 remoteness 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 only one third of the entire area. There are suggestions that ice ages also took place, when the entire surface of our planet was covered with ice. But this fact is still controversial in the world of geological research.

To date, the most significant glacial massif is the Antarctic. The thickness of the ice 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. Approximately seventy percent of this island is occupied by glaciers, and this is one tenth of the ice of our entire planet. At this point in time, scientists believe that the ice age will not be able to start for at least another thousand years. The thing is that in the modern world there is a colossal release 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 mankind - global warming, which can be no less massive than the beginning of the ice age.