After the Ice Age. How people survived the Ice Age

The Ice Age has always been a mystery. We know he could shrink entire continents to the size of frozen tundra. We know there have been eleven or so, and they seem to happen on a regular basis. We definitely know that there was an extreme amount of ice. However, there is much more to the Ice Ages than meets the eye.

By the time the last one came glacial period, evolution has already “invented” mammals. The animals that decided to breed and reproduce during the Ice Age were quite large and covered in fur. Scientists have given them common name"megafauna" because it managed to survive the Ice Age. However, since other, less cold-resistant species could not survive it, the megafauna felt quite good.

Megafauna herbivores are accustomed to foraging in icy environments, adapting to their surroundings different ways. For example, Ice Age rhinoceroses may have had a shovel-shaped horn for removing snow. Predators like saber-toothed tigers, short-faced bears and direwolves (yes, the wolves from Game of Thrones actually once existed) also adapted to their environment. Although times were cruel, and the prey could very well turn predator into prey, there was plenty of meat in it.

Ice Age people

Despite their relatively small size and little hair, Homo sapiens survived in the cold tundras of ice ages for thousands of years. Life was cold and difficult, but people were resourceful. For example, 15,000 years ago, Ice Age people lived in hunter-gatherer tribes, building comfortable homes from mammoth bones and making warm clothing from animal fur. When there was plenty of food, they stored it in the natural refrigerators of permafrost.

Since hunting tools at that time consisted mainly of stone knives and arrowheads, sophisticated weapons were rare. People used traps to capture and kill the huge Ice Age animals. When an animal fell into a trap, people attacked it in a group and beat it to death.

Little Ice Ages

Sometimes small ice ages occurred between large and long ones. They were not as destructive, but could still cause famine and disease due to failed harvests and other side effects.

The most recent of these small ice ages began sometime between the 12th and 14th centuries and peaked between 1500 and 1850. For hundreds of years in the northern hemisphere, the cold weather. In Europe, the seas regularly froze, and mountainous countries (for example, Switzerland) could only watch as glaciers moved, destroying villages. There were years without summer, but nasty ones weather influenced every aspect of life and culture (perhaps this is why the Middle Ages seem dark to us).

Science is still trying to figure out what caused this minor ice age. Among possible reasons- a combination of severe volcanic activity and a temporary decrease in solar energy from the Sun.

Warm Ice Age

Some ice ages may have been quite warm. The ground was covered with a huge amount of ice, but in fact the weather was quite pleasant.

Sometimes the events that lead to an ice age are so severe that even if the atmosphere is full of greenhouse gases (which trap heat from the sun in the atmosphere, warming the planet), ice still continues to form because if there is a thick enough layer of pollution it will reflect the sun's rays back into the atmosphere. space. Experts say this would turn the Earth into a giant Baked Alaska dessert - cold on the inside (ice on the surface) and warm on the outside (warm atmosphere).

The man whose name recalls the famous tennis player was in fact a respected scientist, one of the geniuses who defined the scientific milieu of the 19th century. He is considered one of the founding fathers of American science, although he was French.

Among many other achievements, it is thanks to Agassiz that we know at least something about the ice ages. Although this idea had been touched upon by many before, in 1837 the scientist became the first person to seriously introduce ice ages into science. His theories and publications on the ice fields that covered most of the earth were foolishly rejected when the author first presented them. Nevertheless, he did not renounce his words, and further research ultimately led to the recognition of his “crazy theories.”

It is noteworthy that his pioneering work on ice ages and glacial activity was a simple hobby. By occupation he was an ichthyologist (studying fish).

Man-made pollution prevented the next ice age

Theories that ice ages recur on a semi-regular basis, no matter what we do, often conflict with theories about global warming. While the latter are certainly authoritative, some believe that it is global warming that may be useful in the future fight against glaciers.

Carbon dioxide emissions caused by human activities are considered a significant part of the global warming problem. However they have one strange one by-effect. According to researchers from the University of Cambridge, CO2 emissions may be able to stop the next ice age. How? Although the planetary cycle of the Earth is constantly trying to start an ice age, it will only begin if the level carbon dioxide in the atmosphere will be extremely low. By pumping CO2 into the atmosphere, humans may have inadvertently made ice ages temporarily unavailable.

And even if concerns about global warming (which is also very bad) force people to reduce CO2 emissions, there is still time. We've currently sent so much carbon dioxide into the sky that an ice age won't start for at least another 1,000 years.

Ice Age Plants

Predators had it relatively easy during the Ice Ages. After all, they could always eat someone else. But what did the herbivores eat?

It turns out that everything they wanted. In those days there were many plants that could survive the Ice Age. Even in the coldest times, steppe-meadow and tree-shrub areas remained, which allowed mammoths and other herbivores not to die of hunger. These pastures were full of plant species that thrive in cold, dry weather - such as spruce and pine. In warmer areas, birch and willow trees were abundant. In general, the climate at that time was very similar to Siberian. Although the plants were most likely seriously different from their modern counterparts.

All of the above does not mean that the ice ages did not destroy some of the vegetation. If a plant could not adapt to the climate, it could only migrate through seeds or disappear. Australia once had the longest lists of diverse plants, until glaciers destroyed a good portion of them.

The Himalayas may have caused an ice age

Mountains, as a rule, are not famous for actively causing anything other than occasional collapses - they just stand there and stand there. The Himalayas may disprove this belief. They may be directly responsible for causing the Ice Age.

When the landmasses of India and Asia collided 40-50 million years ago, the collision grew massive rock ridges into the Himalaya mountain range. This brought out a huge amount of “fresh” stone. Then the process of chemical erosion began, which removes significant amounts of carbon dioxide from the atmosphere over time. And this, in turn, could affect the planet's climate. The atmosphere "cooled" and caused an ice age.

Snowball Earth

During most ice ages, ice sheets cover only part of the world. Even a particularly severe ice age is believed to have covered only about one-third of the globe.

What is “Snowball Earth”? The so-called Snowball Earth.

Snowball Earth is the chilling granddaddy of ice ages. It's a complete freezer that literally froze every bit of the planet's surface until the Earth froze into a huge snowball flying through space. The little that was able to survive complete freezing, or clung to rare places with relatively a small amount ice, or, in the case of plants, got caught in places where there was enough sunlight for photosynthesis.

According to some sources, this event occurred at least once, 716 million years ago. But there could have been more than one such period.

Garden of Eden

Some scientists seriously believe that that same Garden of Eden was real. They say it was in Africa and was the only reason our ancestors survived the Ice Age.

Just under 200,000 years ago, a particularly hostile Ice Age was killing off species left and right. Fortunately, a small group of early humans were able to survive the terrible cold. They came across the coast that is now South Africa. Even though ice was taking its toll all over the world, this zone remained ice-free and completely habitable. Her soil was rich nutrients and gave me a lot of food. There were many natural caves that could be used for shelter. For a young species struggling to survive, it was nothing short of paradise.

The human population of the "Garden of Eden" numbered only a few hundred individuals. This theory is supported by many experts, but it still lacks conclusive evidence, including studies that show that humans have much less genetic diversity than most other species.

The Pleistocene Epoch began about 2.6 million years ago and ended 11,700 years ago. At the end of this era, the last ice age to date passed, when glaciers covered vast areas of the Earth's continents. Since the formation of the Earth 4.6 billion years ago, there have been at least five documented major ice ages. The Pleistocene is the first era in which Homo sapiens evolved: by the end of the era, people settled almost throughout the planet. What was the last ice age like?

Ice skating rink as big as the world

It was during the Pleistocene that the continents were located on Earth in the way we are used to. At some point during the Ice Age, sheets of ice covered all of Antarctica, much of Europe, North and South America, and small parts of Asia. In North America they extended across Greenland and Canada and parts of the northern United States. Remnants of glaciers from this period can still be seen in some parts of the world, including Greenland and Antarctica. But the glaciers did not just “stand still.” Scientists note about 20 cycles when glaciers advanced and retreated, when they melted and grew again.

In general, the climate then was much colder and drier than it is today. Because most of the water on the Earth's surface was frozen, there was little precipitation—about half what it is today. During peak periods, when most water was frozen, global average temperatures were 5 -10°C below today's temperature norms. However, winter and summer still replaced each other. True, you wouldn’t have been able to sunbathe in those summer days.

Life during the Ice Age

While Homo sapiens, in the dire situation of perpetual cold temperatures, began to develop brains to survive, many vertebrates, especially large mammals, also courageously endured the harsh climatic conditions of this period. In addition to the well-known woolly mammoths, saber-toothed cats, giant ground sloths and mastodons roamed the Earth during this period. Although many vertebrates went extinct during this period, the Earth was home to mammals that can still be found today, including monkeys, cattle, deer, rabbits, kangaroos, bears, and members of the canine and feline families.

There were no dinosaurs, except for a few early birds, during the Ice Age: they became extinct at the end Cretaceous period, more than 60 million years before the start of the Pleistocene era. But the birds themselves did well during that period, including relatives of ducks, geese, hawks and eagles. The birds had to compete with mammals and other creatures for limited supplies of food and water, since much of it was frozen. Also during the Pleistocene period there were crocodiles, lizards, turtles, pythons and other reptiles.

The vegetation was worse: in many areas it was difficult to find dense forests. More common were individual coniferous trees, such as pines, cypresses and yews, as well as some broad-leaved trees, such as beeches and oaks.

Mass extinction

Unfortunately, about 13,000 years ago, more than three-quarters of the large Ice Age animals, including woolly mammoths, mastodons, saber-tooth tigers and giant bears, went extinct. Scientists have been arguing for many years about the reasons for their disappearance. There are two main hypotheses: human resourcefulness and climate change, but both cannot explain the planet-scale extinction.

Some researchers believe that, like the dinosaurs, there was some extraterrestrial intervention: recent studies show that an extraterrestrial object, perhaps a comet about 3-4 kilometers wide, could have exploded over southern Canada, almost destroying ancient culture Stone Age, as well as megafauna like mammoths and mastodons.

Based on materials from Livescience.com

There have been long periods in Earth's history when the entire planet was warm, from the equator to the poles. But there were also such cold times that glaciations reached those regions that currently belong to 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 character 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 of 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 deluvial because they were considered evidence 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.

Because of 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 pronounced 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 zonation, orbital changes may 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, the climatic conditions are relatively warm. This is the essence of the interglacial: high sea level, warm temperature conditions and generally a 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 may 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 on South Pole, and the Arctic Ocean to 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 of the continental shelf that are now submerged. This would mean, for example, that one day it would 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. Under natural conditions, many of the animals and plants we see today have a long history and survive the Ice Age well, although there are those that evolve only 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 urgent and exciting question. 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 population. 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.

Sometimes you can hear the statement that the Ice Age is already behind us and people will not have to deal with this phenomenon in the future. This would be true if we were sure that modern glaciation on the globe is just a remnant of the Great Quaternary glaciation of the Earth and should inevitably soon disappear. In fact, glaciers continue to be one of the leading components of the environment and make an important contribution to the life of our planet.

Formation of mountain glaciers

As you ascend into the mountains, the air becomes colder. At some height winter snow does not have time to melt over the summer; from year to year it accumulates and gives rise to glaciers. A glacier is a mass multi-year ice mainly atmospheric origin, which moves under the influence of gravity and takes the form of a stream, dome or floating slab (if we are talking about cover and shelf glaciers).

In the upper part of the glacier there is an accumulation area where sediment accumulates, which is gradually converted into ice. Constant replenishment of snow reserves, its compaction, and recrystallization lead to the fact that it turns into a coarse-grained mass of ice grains - firn, and then, under the pressure of the overlying layers, into massive glacier ice.

From the accumulation area, ice flows to the lower part - the so-called ablation area, where it is consumed mainly by melting. Top part a mountain glacier is usually a firn basin. It occupies a car (or cirque - the extended upper reaches of the valley) and has a concave surface. When leaving the cirque, the glacier often crosses a high mouth step - a crossbar; Here the ice is cut through deep transverse cracks and an icefall occurs. Then the glacier descends in a relatively narrow tongue down the valley. The life of a glacier is largely determined by the balance of its mass. With a positive balance, when the flow of matter on the glacier exceeds its flow, the mass of ice increases, the glacier becomes more active, moves forward, and captures new areas. If negative, it becomes passive, retreats, freeing the valley and slopes from under the ice.

Perpetual motion

Majestic and calm, glaciers are in fact in constant movement. The so-called cirque and valley glaciers flow slowly down the slopes, and ice sheets and domes spread from the center to the periphery. This movement is determined by the force of gravity and becomes possible due to the property of ice to deform under stress. Brittle in individual fragments, in vast massifs the ice acquires plastic properties, like frozen pitch, which cracks if you hit it, but slowly flows along the surface, being “loaded” In one place. There are also frequent cases when ice with almost its entire mass slides along the bed or other layers of ice - this is the so-called block sliding of glaciers. Cracks form in the same places on the glacier, but since new ice masses are involved in this process each time, the old cracks, as the ice moves from the place of their formation, gradually “heal”, that is, they close. Individual cracks stretch across the glacier from several tens to many hundreds of meters, their depth reaches 20-30, and sometimes 50 meters or more.

The movement of thousand-ton ice masses, although very slowly, does a tremendous amount of work - over many thousands of years it transforms the face of the planet beyond recognition. Centimeter by centimeter, ice creeps along solid rocks, leaving grooves and scars on them, breaking them and carrying them with it. Glaciers annually remove layers from the surface of the Antarctic continent. rocks thickness on average 0.05 mm. This apparent microscopic value already grows to 50 m if we take into account the entire million years of the Quaternary period, when the Antarctic continent was probably covered with ice. Many glaciers in the Alps and Caucasus have an ice movement speed of about 100 m per year. In the larger glaciers of the Tien Shan and Pamir, the ice moves 150-300 m per year, and on some Himalayan glaciers - up to 1 km, that is, 2-3 m per day.

Glaciers have a variety of sizes: from 1 km in length for small cirque glaciers, to tens of kilometers in large valley glaciers. The largest glacier in Asia, Fedchenko glacier, reaches a length of 77 km. In their movement, glaciers carry over many tens, or even hundreds of kilometers, blocks of rock that have fallen from mountain slopes onto their surface. Such blocks are called erratic, that is, “wandering” boulders, the composition of which differs from the local rocks.

Thousands of such boulders are found on the plains of Europe and North America, in the valleys at their exit from the mountains. The volume of some of them reaches several thousand cubic meters. Known, for example, is the giant Ermolovsky stone in the riverbed of the Terek, at the exit from the Daryal gorge of the Caucasus. The length of the stone exceeds 28 m, and the height is about 17 m. The source of their appearance is the places where the corresponding rocks come to the surface. In America these are the Cordillera and Labrador, in Europe - Scandinavia, Finland, Karelia. And they were brought here from afar, from where huge ice sheets once existed, a reminder of which is the modern ice sheet of Antarctica.

The mystery of their pulsation

In the middle of the 20th century, people were faced with another problem - pulsating glaciers, characterized by sudden advances of their ends, without any apparent connection with climate change. Hundreds of pulsating glaciers are now known in many glacial regions. Most of them are in Alaska, Iceland and Spitsbergen, in the mountains Central Asia, in the Pamirs.

The general cause of glacial movements is the accumulation of ice in conditions where its flow is hampered by the narrowness of the valley, moraine cover, mutual damming of the main trunk and side tributaries, etc. Such accumulation creates conditions of instability that cause ice runoff: large chips, heating of the ice with the release of water during internal melting, the appearance of water and water-clay lubricant on the bed and chips. On September 20, 2002, a disaster occurred in the valley of the Genaldon River in North Ossetia. Huge masses of ice, mixed with water and stone material, burst out from the upper reaches of the valley, quickly swept down the valley, destroying everything in its path, and formed a blockage, spreading across the entire Karmadon basin in front of the ridge of the Rocky Range. The culprit of the disaster was the pulsating Kolka glacier, the movements of which occurred several times in the past.

The Kolka glacier, like many other pulsating glaciers, has difficulty draining ice. Over the course of many years, ice accumulates in front of an obstacle, increases its mass to a certain critical volume, and when the braking forces cannot resist the shear forces, a sharp release of tension occurs and the glacier advances. In the past, movements of the Kolka glacier occurred around 1835, in 1902 and 1969. They arose when the glacier accumulated a mass of 1-1.3 million tons. The Genaldon disaster of 1902 guide occurred on July 3, at the height of the hot summer. The air temperature during this period exceeded the norm by 2.7°C, and there were heavy downpours. Having turned into a pulp of ice, water and moraine, the ice ejection transformed into a crushing high-speed mudflow that rushed through in a matter of minutes. The 1969 movement developed gradually, reaching its greatest development in winter, when the amount of meltwater in the basin was minimal. This determined the relatively calm course of events. In 2002, a huge amount of water accumulated in the glacier, which became the trigger for movement. Obviously, the water “teared” the glacier from its bed and a powerful water-ice-rock mudflow formed. The fact that the movement was triggered ahead of time and reached a colossal scale was due to the existing complex of factors: the unstable dynamic state of the glacier, which had already accumulated a mass close to critical; powerful accumulation of water in the glacier and under the glacier; landslides of ice and rock, which created an overload in the rear part of the glacier.

A world without glaciers

The total volume of ice on Earth is almost 26 million km 3, or about 2% of all Earth's water. This mass of ice is equal to the flow of all the rivers of the globe over 700 years.

If the existing ice were evenly distributed over the surface of our planet, it would cover it with a layer 53 m thick. And if this ice suddenly melted, the level of the World Ocean would rise by 64 m. At the same time, densely populated fertile coastal plains over an area of ​​about 15 million would be flooded. . km 2 2 . Such a sudden melting cannot occur, but throughout geological epochs, when ice sheets arose and then gradually melted, sea level fluctuations were even greater.

Direct dependency

The influence of glaciers on the Earth's climate is enormous. In winter, extremely little solar radiation comes to the polar regions, since the Sun does not appear over the horizon and the polar night prevails here. And in the summer, due to the long duration of the polar day, the amount of radiant energy coming from the Sun is greater than even in the equator region. However, temperatures remain low as up to 80% of the incoming energy is reflected back by snow and ice. The picture would have been completely different if there had been no ice cover. In this case, almost all the heat that comes in summer would be absorbed and the temperature in the polar regions would differ from the tropical one to a much lesser extent. So, if there were no continental ice sheets of Antarctica and the North Ice Sheet around the earth's poles Arctic Ocean, on Earth there would not be the usual division into natural zones and the entire climate would be much more uniform. Once the ice masses at the poles melt, the polar regions will become much warmer, and rich vegetation will appear on the shores of the former Arctic Ocean and on the surface of ice-free Antarctica. This is exactly what happened on Earth in the Neogene period - just a few million years ago it had a smooth, mild climate. However, one can imagine another state of the planet, when it is completely covered with a shell of ice. After all, once formed under certain conditions, glaciers are able to grow on their own, since they lower the surrounding temperature and grow in height, thereby spreading into higher and colder layers of the atmosphere. Icebergs breaking off from large ice sheets are carried across the ocean and end up in tropical waters, where their melting also helps to cool the water and air.

If nothing prevents the formation of glaciers, then the thickness of the ice layer could increase to several kilometers due to water from the oceans, the level of which would continuously decrease. In this way, gradually all the continents would be under ice, the temperature on the surface of the Earth would drop to about -90 ° C and organic life on it would cease. Fortunately, this has not happened throughout the entire geological history of the Earth, and there is no reason to think that such glaciation could occur in the future. Currently, the Earth is experiencing a state of partial glaciation, when only a tenth of its surface is covered by glaciers. This state is unstable: glaciers either shrink or increase in size and very rarely remain unchanged.

White cover of the "blue planet"

If you look at our planet from space, you can see that some of its parts look completely white - this is the snow cover that is so familiar to the inhabitants of temperate zones.

Snow is nearby amazing properties, making it an indispensable component in the “kitchen” of Nature. The Earth's snow cover reflects more than half of the radiant energy coming to us from the Sun, the same one that covers the polar glaciers (the cleanest and driest) - in general, up to 90% of the sun's rays! However, snow also has another phenomenal property. It is known that thermal energy All bodies radiate, and the darker they are, the greater the heat loss from their surface. But snow, being dazzlingly white, is capable of emitting thermal energy almost like a completely black body. The differences between them do not reach even 1%. So, even the slight heat that the snow cover has is quickly radiated into the atmosphere. As a result, the snow cools even more, and the areas of the globe covered by it become a source of cooling for the entire planet.

Features of the sixth continent

Antarctica is the highest continent on the planet, with an average height of 2,350 m (the average height of Europe is 340 m, Asia is 960 m). This altitude anomaly is explained by the fact that most of the mass of the continent is composed of ice, which is almost three times lighter than rocks. Once it was free of ice and did not differ much in height from other continents, but gradually a powerful ice shell covered the entire continent, and the earth’s crust began to bend under colossal load. Over the past millions of years, this excess load has been “isostatically compensated”, in other words, the earth’s crust has bent, but traces of it are still reflected in the Earth’s topography. Oceanographic studies of coastal Antarctic waters showed that the continental shelf (shelf), which borders all continents with a shallow strip with depths of no more than 200 m, turned out to be 200-300 m deeper off the coast of Antarctica. The reason for this is the lowering of the earth's crust under the weight of the ice that previously covered the continental shelf 600-700 m thick. Relatively recently, the ice retreated from here, but the earth's crust has not yet had time to “unbend” and, in addition, it is held in place by ice lying to the south. The unrestricted expansion of the Antarctic ice sheet has always been hampered by the sea.

Any expansion of glaciers beyond the land is possible only under the condition that the sea near the coast is not deep, otherwise sea currents and waves will sooner or later destroy the ice that has extended far into the sea. Therefore, the boundary of maximum glaciation ran along the outer edge of the continental shelf. Antarctic glaciation in general is greatly influenced by sea level changes. When the level of the World Ocean falls, the ice sheet of the sixth continent begins to advance; when it rises, it retreats. It is known that over the past 100 years, sea level has risen by 18 cm, and continues to rise now. Apparently, the destruction of some Antarctic ice shelves, accompanied by the calving of huge table icebergs up to 150 km long, is associated with this process. At the same time, there is every reason to believe that the mass of Antarctic glaciation is increasing in the modern era, and this may also be associated with ongoing global warming. Indeed, climate warming is causing increased atmospheric circulation and strengthening of interlatitudinal exchange air masses. Warmer and humid air enters the Antarctic continent. However, an increase in temperature of several degrees does not cause any melting inland, where frosts are now 40-60 ° C, while an increase in the amount of moisture leads to heavier snowfalls. This means that warming causes an increase in nutrition and an increase in glaciation in Antarctica.

Last Maximum Glaciation

The culmination of the last ice age on Earth was 21-17 thousand years ago, when the volume of ice increased to approximately 100 million km 3. In Antarctica, glaciation at this time covered the entire continental shelf. The volume of ice in the ice sheet apparently reached 40 million km 3, that is, it was approximately 40% more than its modern volume. The pack ice boundary shifted northward by approximately 10°. In the Northern Hemisphere, 20 thousand years ago, a gigantic Pan-Arctic ancient ice sheet was formed, uniting the Eurasian, Greenland, Laurentian and a number of smaller shields, as well as extensive floating ice shelves. The total volume of the shield exceeded 50 million km 3, and the level of the World Ocean dropped by no less than 125 m.

The degradation of the Panarctic cover began 17 thousand years ago with the destruction of the ice shelves that were part of it. After this, the “sea” parts of the Eurasian and North American ice sheets, which had lost stability, began to collapse catastrophically. The collapse of glaciation occurred in just a few thousand years. At that time, huge masses of water flowed from the edge of the ice sheets, giant dammed lakes arose, and their breakthroughs were many times larger than today. Natural processes dominated in nature, immeasurably more active than now. This led to a significant renewal of the natural environment, a partial change of animals and flora, the beginning of human domination on Earth.

12 thousand years ago, the Holocene began - the modern geological era. Air temperature in temperate latitudes ax increased by 6° compared to the cold late Pleistocene. Glaciation has taken on modern proportions.

Ancient glaciations...

Ideas about ancient glaciations of mountains were expressed at the end of the 18th century, and about past glaciations of the plains of temperate latitudes - in the first half of the 19th century. The theory of ancient glaciation did not immediately gain recognition among scientists. Also in early XIX centuries, in many places around the globe, streaked boulders of rocks that were clearly not of local origin were found, but scientists did not know what could have brought them. IN

In 1830, the English explorer Charles Lyell came up with his theory, in which he attributed both the spreading of boulders and the shading of rocks to the action of floating sea ​​ice. Lyell's hypothesis met with serious objections. During his famous voyage on the Beagle ship (1831-1835), Charles Darwin lived for some time on Tierra del Fuego, where he saw with his own eyes the glaciers and the icebergs they generate. He subsequently wrote that boulders can be carried across the sea by icebergs, especially during periods of greater glacial development. And after his trip to the Alps in 1857, Lyell himself doubted the correctness of his theory. In 1837, the Swiss explorer L. Agassiz was the first to explain the polishing of rocks, the transport of boulders, and the deposition of moraine by the influence of glaciers. A significant contribution to the development of the glacial theory was made by Russian scientists, and above all P.A. Kropotkin. Traveling through Siberia in 1866, he discovered many boulders, glacial sediments, and smooth polished rocks on the Patom Highlands and connected these finds with the activity of ancient glaciers. In 1871 Russian geographical society sent him to Finland, a country with bright traces of recently retreated glaciers. This trip finally shaped his views. When studying ancient geological deposits, we often find tillites - coarse fossilized moraines and glacial-marine sediments. They were found on all continents in sediments of different ages, and they are used to reconstruct the glacial history of the Earth for 2.5 billion years, during which the planet experienced 4 glacial eras that lasted from many tens to 200 million years. Each such era consisted of ice ages comparable in duration to the Pleistocene, or Quaternary period, and each period - of large number ice ages.

The duration of glacial eras on Earth is at least a third of the total time of its evolution over the past 2.5 billion years. And if we take into account the long initial phases of the origin of glaciation and its gradual degradation, then the glaciation eras will take almost as much time as warm, ice-free conditions. The last of the ice ages began almost a million years ago, in Quaternary time, and was marked by the extensive spread of glaciers - the Great Glaciation of the Earth. The northern part of the North American continent, a significant part of Europe, and possibly also Siberia were under thick covers of ice. In the Southern Hemisphere, the entire Antarctic continent was under ice, as now. During the period of maximum expansion of the Quaternary glaciation, glaciers covered over 40 million km 2 - about a quarter of the entire surface of the continents. The largest in the Northern Hemisphere was the North American ice sheet, reaching a thickness of 3.5 km. All of northern Europe was under an ice sheet up to 2.5 km thick. Having reached their greatest development 250 thousand years ago, the Quaternary glaciers of the Northern Hemisphere began to gradually shrink. Glaciation was not continuous throughout the Quaternary period. There is geological, paleobotanical and other evidence that during this time glaciers completely disappeared at least three times, giving way to interglacial eras when the climate was warmer than today. However, these warm eras were replaced by cold snaps, and the glaciers spread again. We now live, apparently, at the end of the fourth epoch of the Quaternary glaciation. The Quaternary glaciation of Antarctica developed quite differently than in the Northern Hemisphere. It arose many millions of years before glaciers appeared in North America and Europe. Besides climatic conditions This was facilitated by the high continent that had existed here for a long time. Unlike the ancient ice sheets of the Northern Hemisphere, which disappeared and then reappeared, the Antarctic ice sheet has changed little in its size. The maximum glaciation of Antarctica was only one and a half times larger in volume than the modern one and not much larger in area.

...and their possible causes

The cause of major climate changes and the occurrence of the great glaciations of the Earth still remains a mystery. All hypotheses expressed on this subject can be combined into three groups - the cause of periodic changes in the earth’s climate was sought either outside solar system, either in the activity of the Sun itself, or in the processes occurring on Earth.

Galaxy
Cosmic hypotheses include assumptions about the influence on the cooling of the Earth of various parts of the Universe that the Earth passes through, moving in space along with the Galaxy. Some believe that cooling occurs when the Earth passes through areas of global space filled with gas. Others attribute the same effects to the effects of clouds of cosmic dust. According to another hypothesis, the Earth as a whole should experience great changes when, moving along with the Sun, it moves from the star-saturated part of the Galaxy to its outer, rarefied regions. When the globe approaches the apogalactium - the point furthest from the part of our Galaxy where the greatest number stars, it enters the “cosmic winter” zone and the Ice Age begins on it.

Sun
The development of glaciations is also associated with fluctuations in the activity of the Sun itself. Heliophysicists have long figured out the periodicity of the appearance of dark spots, flares, prominences and learned to predict these phenomena. It turned out that solar activity changes periodically. There are periods of different durations: 2-3, 5-6, 11, 22 and about 100 years. It may happen that the culminations of several periods of different durations coincide and solar activity will be especially high. But it may also be the other way around - several periods of reduced solar activity will coincide, and this will cause the development of glaciation. Such changes in solar activity, of course, are reflected in the fluctuations of glaciers, but are unlikely to cause a great glaciation of the Earth.

CO 2
An increase or decrease in temperature on Earth can also occur if the composition of the atmosphere changes. Thus, carbon dioxide, which freely transmits the sun's rays to the Earth, but absorbs most of its thermal radiation, serves as a colossal screen that prevents the cooling of our planet. Now the content of CO 2 in the atmosphere does not exceed 0.03%. If this figure is halved, then average annual temperatures in temperate zones will decrease by 4-5°, which could lead to the onset of an ice age.

Volcanoes
Volcanic dust emitted during large eruptions up to a height of 40 km can also serve as unique screens. Clouds of volcanic dust, on the one hand, block the sun's rays, and on the other hand, do not allow the earth's radiation to pass through. But the first process is stronger than the second, so periods of increased volcanism should cause the Earth to cool.

Mountains
The idea of ​​a connection between glaciation on our planet and mountain building is also widely known. During the eras of mountain building, the rising large masses of the continents fell into higher layers of the atmosphere, cooled and served as places for the birth of glaciers.

Ocean
According to many researchers, glaciation can also occur as a result of a change in the direction of sea currents. For example, the Gulf Stream was previously diverted by a ridge of land extending from Newfoundland to the Cape Verde Islands, helping to cool the Arctic compared to modern conditions.

Atmosphere
IN Lately scientists began to connect the development of glaciation with a restructuring of atmospheric circulation - when certain areas of the planet receive significantly more precipitation and, if there is enough high mountains This is where glaciation occurs.

Antarctica
Perhaps the rise of the Antarctic continent contributed to the emergence of glaciation. As a result of the expansion of the Antarctic ice sheet, the temperature of the entire Earth decreased by several degrees and the level of the World Ocean dropped by several tens of meters, which contributed to the development of glaciation in the north.

"Recent History"

The last retreat of glaciers, which began over 10 thousand years ago, remains in human memory. IN historical era- over about 3 thousand years - the advance of glaciers occurred in centuries with lower air temperatures and increased humidity. The same conditions developed in the last centuries of the last era and in the middle of the last millennium. About 2.5 thousand years ago, a significant cooling of the climate began. The Arctic islands were covered with glaciers; in the Mediterranean and Black Sea countries, on the verge of a new era, the climate was colder and wetter than it is now. In the Alps in the 1st millennium BC. e. glaciers moved to lower levels, blocked mountain passes with ice and destroyed some high-lying villages. This era saw a major advance of the Caucasian glaciers. The climate was completely different at the turn of the 1st and 2nd millennia.

Warmer conditions and the absence of ice in the northern seas allowed sailors Northern Europe penetrate far to the north. In 870, the colonization of Iceland began, where there were fewer glaciers at that time than now.

In the 10th century, the Normans, led by Eirik the Red, discovered the southern tip huge island, the banks of which were overgrown with thick grass and tall bushes, they founded the first European colony here, and this land was called Greenland.

By the end of the 1st millennium there was a strong retreat and mountain glaciers in the Alps, the Caucasus, Scandinavia and Iceland. The climate began to change seriously again in the 14th century. Glaciers began to advance in Greenland, summer thawing of soil became increasingly short-lived, and by the end of the century permafrost was firmly established here. Ice cover has increased northern seas, and attempts made in subsequent centuries to reach Greenland usually ended in failure. Since the end of the 15th century, the advance of glaciers began in many mountainous countries and polar regions. After the relatively warm 16th century, harsh centuries began, called the Little Ice Age. In the south of Europe, severe and long winters often recurred; in 1621 and 1669, the Bosporus Strait froze, and in 1709, the Adriatic Sea froze off the coast. In the second half of the 19th century, the Little Ice Age ended and a relatively warm era began, which continues to this day.

What awaits us?

The warming of the 20th century was especially pronounced in the polar latitudes of the Northern Hemisphere. Fluctuations in glacial systems are characterized by the proportion of advancing, stationary, and retreating glaciers. For example, for the Alps there is data covering the entire past century. If the share of advancing alpine glaciers in the 40-50s was close to zero, then in the mid-60s about 30%, and in the late 70s - 65-70% of the surveyed glaciers, advanced here. Their similar state indicated that the anthropogenic increase in the content of carbon dioxide, other gases and aerosols in the atmosphere in the 20th century did not affect the normal course of global atmospheric and glacial processes. However, at the end of the last century, glaciers throughout the mountains began to retreat, which was a reaction to global warming, the trend of which especially intensified in the 1990s.

It is known that the currently increased amount of aerosol emissions of anthropogenic origin into the atmosphere helps to reduce the influx of solar radiation. In this regard, voices appeared about the beginning of the Ice Age, but they were lost in a powerful wave of fears of impending anthropogenic warming due to the constant increase in CO 2 and other gaseous impurities in the atmosphere.

An increase in CO2 leads to an increase in the amount of retained heat and thereby increases the temperature. Some small gas impurities entering the atmosphere have the same effect: freons, nitrogen oxides, methane, ammonia, and so on. But nevertheless, not the entire mass of carbon dioxide formed during combustion remains in the atmosphere: 50-60% of industrial CO 2 emissions end up in the ocean or are absorbed by plants. A multiple increase in the concentration of CO 2 in the atmosphere does not lead to the same multiple increase in temperature. Obviously, there is a natural regulatory mechanism that sharply slows down Greenhouse effect at concentrations of CO 2 exceeding two or three times.

It is difficult to say with certainty what the prospects for an increase in the CO2 content in the atmosphere are in the coming decades and how the temperature will rise as a result of this. Some scientists suggest its increase in the first quarter of the 21st century by 1-1.5°, and in the future even more. However, this position has not been proven; there are many reasons to believe that modern warming is part of a natural cycle of climate fluctuations and will be replaced by cooling in the near future. In any case, the Holocene, which has lasted for more than 11 thousand years, turns out to be the longest interglacial in the last 420 thousand years and will obviously end soon. And while we are concerned about the consequences of the current warming, we must not forget about the possible future cooling on Earth.

Vladimir Kotlyakov, academician, director of the Institute of Geography of the Russian Academy of Sciences

We are in the grip of autumn and it is getting colder. Are we heading towards an ice age, one reader wonders.
The fleeting Danish summer is over. The leaves are falling from the trees, the birds are flying south, it is getting darker and, of course, colder too.
Our reader Lars Petersen from Copenhagen has started preparing for the cold days. And he wants to know how seriously he needs to prepare.
“When does the next ice age start? I learned that glacial and interglacial periods follow each other regularly. Since we are living in an interglacial period, it is logical to assume that the next ice age is ahead of us, isn’t it?” - he writes in a letter to the section “Ask Science” (Spørg Videnskaben).
We in the editorial office shudder at the thought of cold winter, which lies in wait for us at the 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 a long way off
Therefore, we addressed Sune Olander Rasmussen, a lecturer at the Center for Fundamental Research on Ice and Climate at the University of Copenhagen.
Sune Rasmussen studies cold and obtains information about past weather by storming Greenland glaciers and icebergs. In addition, he can use his knowledge to act as an "ice age predictor."
“In order for an ice age to occur, several conditions must coincide. We cannot predict exactly when the ice age will begin, but even if humanity had no further influence on the climate, our forecast is that the conditions for it will develop in 40 to 50 thousand years at best,” Sune Rasmussen reassures us.
Since we are talking to the “ice age predictor” anyway, we can get some more information about what “conditions” these are about. we're talking about, to understand a little more about what the Ice Age actually was.
This is what an ice age is
Sune Rasmussen says that during the last ice age the average temperature on earth was several degrees lower than today, and that the climate at higher latitudes was colder.
Most of northern hemisphere was covered by massive ice sheets. For example, Scandinavia, Canada and some other parts of North America were covered with a three-kilometer ice shell.
The enormous weight of the ice sheet pressed earth's crust a kilometer inside the Earth.
Ice ages are longer than interglacials
However, 19 thousand years ago changes in climate began to occur.
This meant that the Earth gradually became warmer, and over the next 7,000 years freed itself from the cold grip of the Ice Age. After this, the interglacial period began, in which we now find ourselves.
In Greenland, the last remnants of the shell came off very abruptly 11,700 years ago, or 11,715 years ago to be precise. This is evidenced by research by Sune Rasmussen and his colleagues.
This means that 11,715 years have passed since the last ice age, and this is a completely normal length of an interglacial.
“It’s funny that we usually think of the Ice Age as an “event,” when in fact it’s just the opposite. The average 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 interglacial periods only lasted about 10,000 years, which explains the widespread but erroneous belief that our current interglacial period is coming to an 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 slight variations in the Earth's orbit around the Sun. The variations determine how much sunlight reaches which latitudes, thereby influencing how warm or cold it is.
This discovery was made by Serbian geophysicist Milutin Milankovic almost 100 years ago, and is therefore known as the Milankovitch Cycles.
Milankovitch cycles are:
1. The Earth’s orbit around the Sun, which changes cyclically approximately once every 100,000 years. The orbit changes from almost circular to more elliptical, and then back again. Because of this, the distance to the Sun changes. The further the Earth is from the Sun, the less solar radiation our planet receives. In addition, when the shape of the orbit changes, the length of the seasons also changes.
2. The tilt of the earth's axis, which varies between 22 and 24.5 degrees relative to the orbit around the Sun. This cycle spans approximately 41,000 years. 22 or 24.5 degrees does not seem to be such a significant difference, but the tilt of the axis greatly affects the severity of the different seasons. The more the Earth is tilted, the greater the difference between winter and summer. The Earth's axial tilt is currently 23.5 and decreasing, meaning the differences between winter and summer will decrease over the next thousands of 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 onset of an 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 certain latitudes receive in certain time years, as well as received in the past and will receive in the future,” says Sune Rasmussen.
Snow in summer leads to ice age
Temperatures in summer play a particularly important role in this context.
Milanković realized that for there to be a prerequisite for the onset of an ice age, summers in the northern hemisphere must be cold.
If winters are snowy and much of the northern hemisphere is covered in snow, then temperatures and the number of hours of sunshine in the summer determine whether snow is allowed to remain throughout the summer.
“If the snow does not melt in the summer, then little sunlight penetrates into the Earth. The rest is reflected back into space by a snow-white blanket. This exacerbates the cooling that began due to a change in the Earth’s orbit around the Sun,” says Sune Rasmussen.
“Further cooling brings more snow, which further reduces the amount of heat absorbed, and so on, until the ice age begins,” he continues.
Likewise, a period of hot summers causes the Ice Age to end. Then the hot sun melts the ice enough to sunlight could again fall on dark surfaces, such as soil or sea, which absorb it and heat the Earth.
People are delaying the next ice age
Another factor that matters for the possibility of the onset of an ice age is the amount of carbon dioxide in the atmosphere.
Just as snow reflecting light enhances ice formation or speeds up its melting, a rise in atmospheric carbon dioxide from 180 ppm to 280 ppm (parts per million) helped bring the Earth out of the last ice age.
However, since industrialization began, people have been constantly increasing the proportion of carbon dioxide, so that now it is almost 400 ppm.
“It took nature 7,000 years to raise the share of carbon dioxide by 100 ppm after the end of the Ice Age. Humans managed to do the same thing in just 150 years. It has great importance to see if the Earth could enter a new ice age. This is a very significant influence, which not only means that an ice age cannot begin at the moment,” says Sune Rasmussen.
We thank Lars Petersen for the good question and send a winter gray T-shirt to Copenhagen. We also thank Sune Rasmussen for his good answer.
We also encourage our readers to send more scientific questions to [email protected].
Did you know?
Scientists always talk about an ice age only in the northern hemisphere of the planet. The reason is that there is too little land in the southern hemisphere to support massive layers of snow and ice.
Excluding 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.