Why was there an ice age? Interesting facts about the Ice Age

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

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

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

Rice. 1 - Ice Age

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

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

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

Last Ice Age

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

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

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

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

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

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

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

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

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

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

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

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

Hominids had the most natural resources to adapt to changing conditions. They were able to move to areas with the largest number food resources, where the slow process of their evolution began.
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1.8 million years ago the Quaternary (anthropogenic) period began geological history land that continues to this day.

River basins expanded. There was a rapid development of the mammal fauna, especially mastodons (which would later become extinct, like many other ancient animal species), ungulates and great apes. During this geological period in the history of the earth, man appears (hence the word anthropogenic in the name of this geological period).

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

The Oksky glacier with its southern edge covered the territory of the modern Kashira region, including our region. The first glaciation was the coldest; tree 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 “Oka glaciation”. The glacier left moraine deposits dominated by boulders of local sedimentary rocks.

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

Mammoth fauna

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

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

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

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

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

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

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

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

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

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

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

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

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

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

GLACIAL PERIOD

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

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

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

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

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

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

When did the Ice Age end?

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

About 25 thousand years ago, the peoples who inhabited 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 Pole itself. This was during the final stages of the Ice Age, when all of Canada, most of the United States and northwestern Europe were covered in a layer of ice more than one kilometer thick.

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

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

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

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

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

Why do glaciers still exist today?

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

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

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

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

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

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

There were long periods in the history of the Earth when the entire planet was warm - from the equator to the poles. But there were also times so cold that glaciations reached those regions that currently belong to the temperate zones. Most likely, the change of these periods was cyclical. During warm times, ice could be relatively scarce and found only in polar regions or on mountain tops. An important feature of ice ages is that they change the nature of the earth's surface: each glaciation affects the appearance of the earth. These changes themselves may be small and insignificant, but they are permanent.

History of Ice Ages

We don't know exactly how many ice ages there have been throughout Earth's history. We know of at least five, possibly seven ice ages, starting with the Precambrian, in particular: 700 million years ago, 450 million years ago (Ordovician period), 300 million years ago - Permian-Carboniferous glaciation, one of the largest ice ages, affecting the southern continents. The southern continents mean the so-called Gondwana - an ancient supercontinent that included Antarctica, Australia, South America, India and Africa.

The most recent glaciation refers to the period in which we live. The Quaternary period of the Cenozoic era began about 2.5 million years ago, when the glaciers of the Northern Hemisphere reached the sea. But the first signs of this glaciation date back to 50 million years ago in Antarctica.

The structure of each ice age is periodic: there are relatively short warm periods, and there are longer periods of icing. Naturally, cold periods are not the result of glaciation alone. Glaciation is the most obvious consequence of cold periods. However, there are quite long intervals that are very cold, despite the absence of glaciations. Today, examples of such regions are Alaska or Siberia, where it is very cold in winter, but there is no glaciation because there is not enough precipitation to provide enough water for the formation of glaciers.

Discovery of Ice Ages

We have known that there are ice ages on Earth since the mid-19th century. Among the many names associated with the discovery of this phenomenon, the first is usually the name of Louis Agassiz, a Swiss geologist who lived in the mid-19th century. He studied the glaciers of the Alps and realized that they were once much more extensive than they are today. He wasn't the only one who noticed this. In particular, Jean de Charpentier, another Swiss, also noted this fact.

It is not surprising that these discoveries were made mainly in Switzerland, since glaciers still exist in the Alps, although they are melting quite quickly. It is easy to see that glaciers were once much larger - just look at the Swiss landscape, troughs (glacial valleys) and so on. However, it was Agassiz who first put forward this theory in 1840, publishing it in the book “Étude sur les glaciers”, and later, in 1844, he developed this idea in the book “Système glaciare”. Despite initial skepticism, over time people began to realize that this was indeed true.

With the advent of geological mapping, especially in Northern Europe, it became clear that glaciers used to be on an enormous scale. There was considerable discussion at the time about how this information related to the Flood because there was a conflict between geological evidence and biblical teachings. Initially, glacial deposits were called colluvial because they were considered evidence of the Great Flood. Only later did it become known that this explanation was not suitable: these deposits were evidence of a cold climate and extensive glaciations. By the beginning of the twentieth century, it became clear that there were many glaciations, not just one, and from that moment this field of science began to develop.

Ice Age Research

Geological evidence of ice ages is known. The main evidence for glaciations comes from the characteristic deposits formed by glaciers. They are preserved in the geological section in the form of thick ordered layers of special sediments (sediments) - diamicton. These are simply glacial accumulations, but they include not only the deposits of a glacier, but also deposits of meltwater formed by meltwater streams, glacial lakes or glaciers moving out to sea.

There are several forms of glacial lakes. Their main difference is that they are a body of water surrounded by ice. For example, if we have a glacier that rises into a river valley, then it blocks the valley, like a cork in a bottle. Naturally, when ice blocks a valley, the river will still flow and the water level will rise until it overflows. Thus, a glacial lake is formed through direct contact with ice. There are certain sediments that are contained in such lakes that we can identify.

Due to the way glaciers melt, which depends on seasonal temperature changes, ice melts occur annually. This leads to an annual increase in minor sediments that fall from under the ice into the lake. If we then look into the lake, we see stratification (rhythmic layered sediments), which are also known by the Swedish name “varve”, which means “annual accumulation”. So we can actually see annual layering in glacial lakes. We can even count these varves and find out how long this lake existed. In general, with the help of this material we can get a lot of information.

In Antarctica we can see huge ice shelves that flow from the land into the sea. And naturally, ice is buoyant, so it floats on water. As it floats, it carries pebbles and minor sediments with it. The thermal effects of the water cause the ice to melt and shed this material. This leads to the formation of a process called rafting of rocks that go into the ocean. When we see fossil deposits from this period, we can find out where the glacier was, how far it extended, and so on.

Causes of glaciations

Researchers believe that ice ages occur because the Earth's climate depends on the uneven heating of its surface by the Sun. For example, the equatorial regions, where the Sun is almost vertically overhead, are the warmest zones, and the polar regions, where it is at a large angle to the surface, are the coldest. This means that differences in heating of different parts of the Earth's surface drive the ocean-atmospheric machine, which is constantly trying to transfer heat from the equatorial regions to the poles.

If the Earth were an ordinary sphere, this transfer would be very efficient, and the contrast between the equator and the poles would be very small. This has happened in the past. But since there are now continents, they stand in the way of this circulation, and the structure of its flows becomes very complex. Simple currents are constrained and modified - largely by mountains - leading to the circulation patterns we see today that control the trade winds and ocean currents. For example, one theory about why the ice age began 2.5 million years ago links this phenomenon to the emergence of the Himalayan mountains. The Himalayas are still growing very quickly, and it turns out that the existence of these mountains in a very warm part of the Earth controls things like the monsoon system. The onset of the Quaternary Ice Age is also associated with the closure of the Isthmus of Panama, which connects north and south America, which prevented heat transfer from equatorial zone Pacific Ocean to Atlantic.

If the location of the continents relative to each other and relative to the equator allowed circulation to work effectively, then it would be warm at the poles, and relatively warm conditions would persist throughout the earth's surface. The amount of heat received by the Earth would be constant and vary only slightly. But since our continents create serious barriers to circulation between north and south, we have distinct climatic zones. This means that the poles are relatively cold and the equatorial regions are warm. When things are as they are now, the Earth can change due to variations in the amount of solar heat it receives.

These variations are almost completely constant. The reason for this is that over time, the earth's axis changes, as does the earth's orbit. Given this complex climate zoning, orbital changes could contribute to long-term changes in climate, leading to climate fluctuations. Because of this, we do not have continuous icing, but periods of icing, interrupted by warm periods. This occurs under the influence of orbital changes. The latest orbital changes are considered as three separate events: one lasting 20 thousand years, the second lasting 40 thousand years, and the third lasting 100 thousand years.

This led to deviations in the pattern of cyclical climate changes during the Ice Age. The icing most likely occurred during this cyclic period of 100 thousand years. The last interglacial period, which was as warm as the current one, lasted about 125 thousand years, and then came the long ice age, which took about 100 thousand years. We are now living in another interglacial era. This period will not last forever, so another ice age awaits us in the future.

Why do ice ages end?

Orbital changes change the climate, and it turns out that ice ages are characterized by alternating cold periods, which can last up to 100 thousand years, and warm periods. We call them the glacial (glacial) and interglacial (interglacial) eras. The interglacial era is usually characterized by approximately the same conditions that we observe today: high sea levels, limited areas of glaciation, and so on. Naturally, glaciations still exist in Antarctica, Greenland and other similar places. But in general climatic conditions relatively warm. This is the essence of the interglacial: high sea levels, warm temperature conditions and a generally fairly even climate.

But during the Ice Age average annual temperature changes significantly, vegetative zones are forced to shift north or south depending on the hemisphere. Regions like Moscow or Cambridge are becoming uninhabited, at least in winter. Although they can be inhabited in summer due to the strong contrast between the seasons. But what actually happens is that the cold zones expand significantly, the average annual temperature decreases, and overall climate conditions become very cold. While the largest glacial events are relatively limited in time (perhaps about 10 thousand years), the entire Long Cold Period can last 100 thousand years or even more. This is what glacial-interglacial cyclicity looks like.

Due to the length of each period, it is difficult to say when we will exit the current era. This is due to plate tectonics, the location of continents on the surface of the Earth. Currently North Pole and the South Pole are isolated: Antarctica is at the South Pole and the North Pole Arctic Ocean in the north. Because of this, there is a problem with heat circulation. Until the position of the continents changes, this ice age will continue. Based on long-term tectonic changes, it can be assumed that it will take another 50 million years in the future until significant changes occur that allow the Earth to emerge from the Ice Age.

Geological consequences

This frees up huge areas continental shelf which are flooded today. This will mean, for example, that one day it will be possible to walk from Britain to France, from New Guinea to Southeast Asia. One of the most critical places is the Bering Strait, which connects Alaska with Eastern Siberia. It is quite shallow, about 40 meters, so if the sea level drops to one hundred meters, this area will become dry land. This is also important because plants and animals will be able to migrate through these places and enter regions that they cannot reach today. Thus, the colonization of North America depends on the so-called Beringia.

Animals and the Ice Age

It's important to remember that we ourselves are "products" of the Ice Age: we evolved during it, so we can survive it. However, this is not a matter of individuals - it is a matter of the entire population. The problem today is that there are too many of us and our activities have significantly changed natural conditions. IN natural conditions many animals and plants we see today have long story and survive the ice age very well, although there are those that evolve slightly. They migrate and adapt. There are areas in which animals and plants survived the Ice Age. These so-called refugia were located further north or south from their current distribution.

But as a result human activity Some species died or became extinct. This happened on every continent, perhaps with the exception of Africa. A huge number of large vertebrates, namely mammals, as well as marsupials in Australia, were exterminated by humans. This was caused either directly by our activities, such as hunting, or indirectly by the destruction of their habitat. Animals living in northern latitudes today, in the past they lived in the Mediterranean. We have destroyed this region so much that it will likely be very difficult for these animals and plants to colonize it again.

Consequences of global warming

Under normal conditions by geological standards, we would return to the Ice Age fairly soon. But due to global warming, which is a consequence of human activity, we are delaying it. We will not be able to completely prevent it, since the reasons that caused it in the past still exist. Human activity, an element unintended by nature, is influencing atmospheric warming, which may already have caused a delay in the next glacial.

Today, climate change is a very pressing and exciting issue. If the Greenland ice sheet melts, sea levels will rise by six meters. In the past, during the previous interglacial epoch, which was approximately 125 thousand years ago, the Greenland ice sheet melted profusely, and sea levels became 4-6 meters higher than today. This, of course, is not the end of the world, but it is not a temporary difficulty either. After all, the Earth has recovered from disasters before, and it will be able to survive this one too.

The long-term forecast for the planet is not bad, but for people it is a different matter. The more research we do, the more we understand how the Earth is changing and where it is leading, the better we understand the planet we live on. This is important because people are finally starting to think about sea level change, global warming, and the impact of all these things on agriculture and populations. Much of this has to do with the study of ice ages. Through this research we are learning about the mechanisms of glaciations, and we can use this knowledge proactively to try to mitigate some of these changes that we are causing. This is one of the main results and one of the goals of ice age research.
Of course, the main consequence of the Ice Age is the huge ice sheets. Where does water come from? From the oceans, of course. What happens during ice ages? Glaciers form as a result of precipitation on land. Because water is not returned to the ocean, sea levels are falling. During the most intense glaciations, sea level can drop by more than a hundred meters.

The periods of the geological history of the Earth are epochs, the successive changes of which shaped it as a planet. At this time, mountains were formed and destroyed, seas appeared and dried up, ice ages succeeded each other, and the evolution of the animal world took place. The study of the geological history of the Earth is carried out through sections rocks, which have preserved the mineral composition of the period that formed them.

Cenozoic period

The current period of Earth's geological history is the Cenozoic. It began sixty-six million years ago and is still going on. The conditional boundary was drawn by geologists at the end Cretaceous period when there was a mass extinction of species.

The term was proposed by the English geologist Phillips back in the mid-nineteenth century. Its literal translation sounds like “new life.” The era is divided into three periods, each of which, in turn, is divided into eras.

Geological periods

Any geological era is divided into periods. IN Cenozoic era There are three periods:

Paleogene;

The Quaternary period of the Cenozoic era, or Anthropocene.

In earlier terminology, the first two periods were combined under the name "Tertiary period".

On land, which had not yet completely divided into separate continents, mammals reigned. Rodents and insectivores, early primates, appeared. Reptiles have been replaced in the seas predatory fish and sharks, new species of mollusks and algae appeared. Thirty-eight million years ago, the diversity of species on Earth was amazing, and the evolutionary process affected representatives of all kingdoms.

Just five million years ago, the first apes began to walk on land. Another three million years later, in the territory belonging to modern Africa, Homo erectus began to gather in tribes, collecting roots and mushrooms. Ten thousand years ago, modern man appeared and began to reshape the Earth to suit his needs.

Paleography

The Paleogene lasted forty-three million years. Continents in their modern form were still part of Gondwana, which was beginning to split into separate fragments. South America was the first to float freely, becoming a reservoir for unique plants and animals. In the Eocene era, the continents gradually occupied their current position. Antarctica separates from South America, and India moves closer to Asia. A body of water appeared between North America and Eurasia.

During the Oligocene epoch, the climate becomes cool, India finally consolidates below the equator, and Australia drifts between Asia and Antarctica, moving away from both. Due to temperature changes, ice caps form at the South Pole, causing sea levels to drop.

During the Neogene period, the continents begin to collide with each other. Africa “rams” Europe, as a result of which the Alps appear, India and Asia form the Himalayan mountains. The Andes and rocky mountains appear in the same way. In the Pliocene era, the world becomes even colder, forests die out, giving way to steppes.

Two million years ago, a period of glaciation began, sea levels fluctuated, and the white caps at the poles either grew or melted again. Animal and vegetable world is being tested. Today, humanity is experiencing one of the stages of warming, but on a global scale the ice age continues to last.

Life in the Cenozoic

The Cenozoic periods cover a relatively short period of time. If you put the entire geological history of the earth on a dial, then the last two minutes will be reserved for the Cenozoic.

The extinction event that marked the end of the Cretaceous period and the beginning new era, wiped out from the face of the Earth all the animals that were larger than a crocodile. Those who managed to survive were able to adapt to new conditions or evolved. The drift of the continents continued until the advent of people, and on those of them that were isolated, a unique animal and plant world was able to survive.

The Cenozoic era was distinguished by great species diversity flora and fauna. It is called the time of mammals and angiosperms. In addition, this era can be called the era of steppes, savannas, insects and flowering plants. The emergence of Homo sapiens can be considered the crown of the evolutionary process on Earth.

Quaternary period

Modern humanity lives in the Quaternary epoch of the Cenozoic era. It began two and a half million years ago, when in Africa, great apes began to form tribes and obtain food by collecting berries and digging up roots.

The Quaternary period was marked by the formation of mountains and seas and the movement of continents. The earth acquired the appearance it has now. For geological researchers, this period is simply a stumbling block, since its duration is so short that radioisotope scanning methods of rocks are simply not sensitive enough and produce large errors.

The characteristics of the Quaternary period are based on materials obtained using radiocarbon dating. This method is based on measuring the amounts of rapidly decaying isotopes in soil and rock, as well as the bones and tissues of extinct animals. The entire period of time can be divided into two eras: the Pleistocene and the Holocene. Humanity is now in the second era. There are no exact estimates yet of when it will end, but scientists continue to build hypotheses.

Pleistocene era

The Quaternary period opens the Pleistocene. It began two and a half million years ago and ended only twelve thousand years ago. It was a time of glaciation. Long ice ages were interspersed with short warming periods.

One hundred thousand years ago in the area of ​​modern Northern Europe a thick ice cap appeared, which began to spread in different directions, absorbing more and more new territories. Animals and plants were forced to either adapt to new conditions or die. The frozen desert stretches from Asia to North America. In some places the ice thickness reached two kilometers.

The beginning of the Quaternary period turned out to be too harsh for the creatures that inhabited the earth. They are used to the warmth temperate climate. In addition, ancient people began to hunt animals, who had already invented the stone ax and other hand tools. Entire species of mammals, birds and marine fauna are disappearing from the face of the Earth. Could not resist harsh conditions and Neanderthal. Cro-Magnons were more resilient, successful in hunting, and it was their genetic material that should have survived.

Holocene era

The second half of the Quaternary period began twelve thousand years ago and continues to this day. It is characterized by relative warming and climate stabilization. The beginning of the era was marked by the mass extinction of animals, and it continued with the development of human civilization and its technological flourishing.

Animal changes and plant composition throughout the era were insignificant. Mammoths finally became extinct, and some species of birds and marine mammals ceased to exist. About seventy years ago the general temperature of the earth increased. Scientists attribute this to the fact that industrial activity humans cause global warming. In this regard, glaciers in North America and Eurasia have melted, and the Arctic ice cover is disintegrating.

glacial period

An ice age is a stage in the geological history of the planet that lasts several million years, during which there is a decrease in temperature and an increase in the number of continental glaciers. As a rule, glaciations alternate with warming periods. Now the Earth is in a period of relative temperature rise, but this does not mean that in half a millennium the situation cannot change dramatically.

At the end of the nineteenth century, geologist Kropotkin visited the Lena gold mines with an expedition and discovered signs of ancient glaciation there. He was so interested in the findings that he began large-scale international work in this direction. First of all, he visited Finland and Sweden, as he assumed that it was from there that the ice caps spread to Eastern Europe and Asia. Kropotkin's reports and his hypotheses regarding the modern Ice Age formed the basis of modern ideas about this time period.

History of the Earth

The ice age the Earth is currently in is far from the first in our history. Cooling of the climate has happened before. It was accompanied by significant changes in the relief of the continents and their movement, and also influenced species composition flora and fauna. There could be gaps of hundreds of thousands or millions of years between glaciations. Each ice age is divided into ice ages or glacials, which during the period alternate with interglacials - interglacials.

There are four glacial eras in the history of the Earth:

Early Proterozoic.

Late Proterozoic.

Paleozoic.

Cenozoic.

Each of them lasted from 400 million to 2 billion years. This suggests that our ice age has not even reached its equator yet.

Cenozoic Ice Age

Animals of the Quaternary period were forced to grow additional fur or seek shelter from ice and snow. The climate on the planet has changed again.

The first epoch of the Quaternary period was characterized by cooling, and in the second there was relative warming, but even now, in the most extreme latitudes and at the poles, ice cover remains. It covers the Arctic, Antarctic and Greenland. The thickness of the ice varies from two thousand meters to five thousand.

The Pleistocene Ice Age is considered to be the strongest in the entire Cenozoic era, when the temperature dropped so much that three of the five oceans on the planet froze.

Chronology of Cenozoic glaciations

The glaciation of the Quaternary period began recently, if we consider this phenomenon in relation to the history of the Earth as a whole. It is possible to identify individual epochs during which the temperature dropped especially low.

1. The end of the Eocene (38 million years ago) - glaciation of Antarctica.
2. The entire Oligocene.
3. Middle Miocene.
4. Mid-Pliocene.
5. Glacial Gilbert, freezing of the seas.
6. Continental Pleistocene.
7. Late Upper Pleistocene (about ten thousand years ago).

This was the last major period when, due to climate cooling, animals and humans had to adapt to new conditions in order to survive.

Paleozoic Ice Age

During the Paleozoic era, the Earth froze so much that ice caps reached Africa and South America in the south, and also covered the entire North America and Europe. Two glaciers almost converge along the equator. The peak is considered to be the moment when a three-kilometer layer of ice rose above the territory of northern and western Africa.

Scientists have discovered the remains and effects of glacial deposits in studies in Brazil, Africa (in Nigeria) and the mouth of the Amazon River. Thanks to radioisotope analysis, it was found that age and chemical composition of these finds is the same. This means that it can be argued that the rock layers were formed as a result of one global process that affected several continents at once.

Planet Earth is still very young by cosmic standards. She is just beginning her journey in the Universe. It is unknown whether it will continue with us or whether humanity will simply become an insignificant episode in successive geological eras. If you look at the calendar, we have spent a negligible amount of time on this planet, and it is quite simple to destroy us with the help of another cold snap. People need to remember this and not exaggerate their role in biological system Earth.

Consequences of warming

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

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

Major periods of glaciation in the history of the planet

The answer to the first question depends on whether you are talking about large glaciations or small ones that occur during these long periods. Throughout history, the Earth has experienced five major periods of glaciation, some of which lasted for hundreds of millions of years. In fact, even now the Earth is experiencing a large period of glaciation, and this explains why it has polar ice caps.

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 glaciation (450-420 million years ago), and the Late Paleozoic glaciation (335-260 million years ago). million years ago) and 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 thousand years. However, in the last 800 thousand years, significant ice ages have occurred less frequently - approximately every 100 thousand years.

How does the 100,000 year cycle work?

The ice sheets grow for about 90 thousand years and then begin to melt during the 10 thousand 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 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 also how much carbon dioxide we emit into the atmosphere, the next ice age won't start for at least 100,000 years.

What causes an ice age?

The hypothesis put forward by Serbian astronomer Milutin Milanković explains why cycles of glacial and interglacial periods exist on Earth.

As a planet orbits 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 on a 41,000-year cycle), its eccentricity (the change in the shape of its orbit around of the Sun, which fluctuates from the near circle to oval shape) and its wobble (one full 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 the history of the planet. If the Earth is experiencing an ice age, it will be covered with more or less ice, depending on these orbital cycles. But if the Earth is too warm, no change will occur, at least in terms of increasing amounts of ice.

What can affect the warming of the planet?

The first gas that comes to mind is carbon dioxide. Over the past 800 thousand years, carbon dioxide levels have ranged from 170 to 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 results in glacial and interglacial periods. But carbon dioxide levels are significantly higher today than in past periods of fluctuation. In May 2016, carbon dioxide levels over Antarctica reached 400 parts per million.

The Earth has warmed up this much before. For example, during the time of dinosaurs the air temperature was even higher than it is now. But the problem is that in the modern world it is growing at a record pace, since we have emitted too much carbon dioxide into the atmosphere over the past a short time. Moreover, given that the rate of emissions is not currently decreasing, we can conclude that the situation is unlikely to change in the near future.

Consequences of warming

The warming caused by this carbon dioxide will have large consequences because even a small increase average temperature 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 led to a significant change in regional temperatures, the disappearance of huge parts of flora and fauna, and the emergence of new species.

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

What causes major 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 colder temperatures.

For example, according to the uplift and weathering hypothesis, when plate tectonics causes mountain ranges to grow, new exposed rock appears on the surface. It easily weathers and disintegrates when it ends up in 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.