Earth during the ice age from space. Interesting Ice Age Facts
Climatic changes were most clearly expressed in periodically advancing ice ages, which had a significant impact on the transformation of the land surface under the body of the glacier, water bodies and biological objects that are in the zone of influence of the glacier.
According to the latest scientific data, the duration of glacial eras on Earth is at least a third of the entire time of its evolution over the past 2.5 billion years. And if we take into account the long initial phases of the genesis of glaciation and its gradual degradation, then the epochs of glaciation will take almost as much time as warm, ice-free conditions. The last of the ice ages began almost a million years ago, in the Quaternary, and was marked by an 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 Siberia as well, were under thick ice sheets. In the Southern Hemisphere, under the ice, as now, was the entire Antarctic continent.
The main causes of glaciation are:
space;
astronomical;
geographical.
Cosmic Cause Groups:
change in the amount of heat on Earth due to the passage solar system 1 time/186 million years through the cold zones of the Galaxy;
change in the amount of heat received by the Earth due to a decrease in solar activity.
Astronomical groups of causes:
change in the position of the poles;
the inclination of the earth's axis to the plane of the ecliptic;
change in the eccentricity of the Earth's orbit.
Geological and geographical groups of causes:
climate change and the amount of carbon dioxide in the atmosphere (increase in carbon dioxide - warming; decrease - cooling);
change in the direction of ocean and air currents;
intensive process of mountain building.
Conditions for the manifestation of glaciation on Earth include:
snowfall in the form of precipitation at low temperatures with its accumulation as a material for building up a glacier;
negative temperatures in areas where there are no glaciations;
periods of intense volcanism due to the huge amount of ash emitted by volcanoes, which leads to a sharp decrease in the flow of heat (sun rays) to the earth's surface and causes global temperature decreases by 1.5-2ºС.
The oldest glaciation is the Proterozoic (2300-2000 million years ago) in South Africa, North America, Western Australia. In Canada, 12 km of sedimentary rocks were deposited, in which three thick strata of glacial origin are distinguished.
Established ancient glaciations (Fig. 23):
on the border of the Cambrian-Proterozoic (about 600 million years ago);
late Ordovician (about 400 million years ago);
Permian and Carboniferous periods (about 300 million years ago).
The duration of ice ages is tens to hundreds of thousands of years.
Rice. 23. Geochronological scale of geological epochs and ancient glaciations
During the period of maximum distribution 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. Under the ice sheet up to 2.5 km thick was the whole of northern Europe. Having reached the greatest development 250 thousand years ago, the Quaternary glaciers of the Northern Hemisphere began to gradually shrink.
Before Neogene period throughout the Earth - an even warm climate - in the area of \u200b\u200bthe islands of Svalbard and Franz Josef Land (according to paleobotanical finds of subtropical plants) at that time there were subtropics.
Reasons for the cooling of the climate:
the formation of mountain ranges (Cordillera, Andes), which isolated the Arctic region from warm currents and winds (uplift of mountains by 1 km - cooling by 6ºС);
creation of a cold microclimate in the Arctic region;
cessation of heat supply to the Arctic region from warm equatorial regions.
By the end of the Neogene period, North and South America joined, which created obstacles for the free flow of ocean waters, as a result of which:
equatorial waters turned the current to the north;
the warm waters of the Gulf Stream, cooling sharply in northern waters, created a steam effect;
precipitation of a large amount of precipitation in the form of rain and snow has increased sharply;
a decrease in temperature by 5-6ºС led to the glaciation of vast territories (North America, Europe);
a new period of glaciation began, lasting about 300 thousand years (the frequency of glacier-interglacial periods from the end of the Neogene to the Anthropogen (4 glaciations) is 100 thousand years).
Glaciation was not continuous throughout the Quaternary period. There is geological, paleobotanical and other evidence that during this time the glaciers completely disappeared at least three times, giving way to interglacial epochs when the climate was warmer than the present. However, these warm epochs were replaced by cooling periods, and glaciers spread again. At present, the Earth is at the end of the fourth era of the Quaternary glaciation, and, according to geological forecasts, our descendants in a few hundred-thousand years will again find themselves in the conditions of an ice age, and not warming.
The Quaternary glaciation of Antarctica developed along a different path. It arose many millions of years before the time when glaciers appeared in North America and Europe. In addition to climatic conditions, this was facilitated by the high mainland that existed here for a long time. Unlike the ancient ice sheets of the Northern Hemisphere, which disappeared and reappeared, the Antarctic ice sheet has changed little in its size. The maximum glaciation of Antarctica was only one and a half times greater than the current one in terms of volume and not much more in area.
The culmination of the last ice age on Earth was 21-17 thousand years ago (Fig. 24), when the volume of ice increased to approximately 100 million km3. In Antarctica, glaciation at that time captured the entire continental shelf. The volume of ice in the ice sheet, apparently, reached 40 million km 3, that is, it was about 40% more than its present volume. The boundary of the pack ice shifted to the north by approximately 10°. In the Northern Hemisphere 20 thousand years ago, a giant Panarctic 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 km3, and the level of the World Ocean dropped by at least 125m.
The degradation of the Panarctic cover began 17 thousand years ago with the destruction of the ice shelves that were part of it. After that, the "marine" parts of the Eurasian and North American ice sheets, which lost their stability, began to disintegrate catastrophically. The disintegration of the glaciation occurred in just a few thousand years (Fig. 25).
Huge masses of water flowed from the edge of the ice sheets at that time, giant dammed lakes arose, and their breakthroughs were many times larger than modern ones. In nature, spontaneous processes dominated, immeasurably more active than now. This resulted in a significant update natural environment, a partial change in the animal and plant world, the beginning of human dominance on Earth.
The last retreat of the glaciers, which began over 14 thousand years ago, remains in the memory of people. Apparently, it is the process of melting glaciers and raising the water level in the ocean with extensive flooding of territories that is described in the Bible as a global flood.
12 thousand years ago the Holocene began - the modern geological epoch. The air temperature in temperate latitudes increased by 6° compared to the cold Late Pleistocene. Glaciation took on modern dimensions.
In the historical epoch - for about 3 thousand years - the advance of glaciers occurred in separate centuries with low air temperature and increased humidity and were called small ice ages. 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 are covered with glaciers, in the Mediterranean and Black Sea countries on the verge new era the climate was colder and wetter than now. In the Alps in the 1st millennium BC. e. glaciers moved to lower levels, cluttered mountain passes with ice and destroyed some high-lying villages. This epoch is marked by a major advance of the Caucasian glaciers.
The climate at the turn of the 1st and 2nd millennium AD was quite different. Warmer conditions and the lack of ice in the northern seas allowed the navigators of Northern Europe to penetrate far north. From 870, the colonization of Iceland began, where at that time there were fewer glaciers than now.
In the 10th century, the Normans, led by Eirik the Red, discovered the southern tip of a huge island, the shores of which were overgrown with dense grass and tall shrubs, they founded the first European colony here, and this land was called Greenland, or “green land” (which is by no means now say about the harsh lands of modern Greenland).
By the end of the 1st millennium, mountain glaciers in the Alps, the Caucasus, Scandinavia, and Iceland also retreated strongly.
The climate began to seriously change again in the 14th century. Glaciers began to advance in Greenland, the summer thawing of soils became more and more short-lived, and by the end of the century, permafrost was firmly established here. The ice cover of the northern seas increased, and attempts made in subsequent centuries to reach Greenland by the usual route 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 came, which were called the Little Ice Age. In the south of Europe, severe and long winters often repeated, in 1621 and 1669 the Bosphorus froze, and in 1709 the Adriatic Sea froze along the shores.
AT 
about the second half of the 19th century, the small ice Age and a relatively warm era began, which continues to this day.
Rice. 24. The boundaries of the last glaciation
Rice. 25. Scheme of the formation and melting of the glacier (along the profile of the Arctic Ocean - Kola Peninsula - Russian Platform)
Ecology
The ice ages that have taken place more than once on our planet have always been covered in a mass of mysteries. We know that they shrouded entire continents in cold, turning them into uninhabited tundra.
Also known about 11 such periods, and all of them took place with regular constancy. However, we still don't know much about them. We invite you to get acquainted with the most interesting facts about the ice ages of our past.
giant animals
By the time the last ice age arrived, evolution had already mammals appeared. Animals that could survive the harsh climatic conditions, were quite large, their bodies were covered with a thick layer of fur.
Scientists have named these creatures "megafauna", which was able to survive low temperatures in areas covered with ice, for example, in the area of \u200b\u200bmodern Tibet. Smaller animals couldn't adjust to new conditions of glaciation and perished.
Herbivorous representatives of the megafauna have learned to find their food even under layers of ice and have been able to adapt to the environment in different ways: for example, rhinos ice age had spatulate horns, with the help of which they dug up snowdrifts.
Predatory animals, for example, saber-toothed cats, giant short-faced bears and dire wolves, perfectly survived in the new conditions. Although their prey could sometimes fight back due to their large size, it was in abundance.
ice age people
Although modern man Homo sapiens couldn't brag at the time large sizes and wool, he was able to survive in the cold tundra of the ice ages for many millennia.
Living conditions were harsh, but people were resourceful. For example, 15 thousand years ago they lived in tribes that were engaged in hunting and gathering, built original dwellings from mammoth bones, sewed warm clothes from animal skins. When food was plentiful, they stocked up in the permafrost - natural freezer.
Mostly for hunting, such tools as stone knives and arrows were used. To catch and kill the large animals of the Ice Age, it was necessary to use special traps. When the beast fell into such traps, a group of people attacked him and beat him to death.
Little Ice Age
Between major ice ages, there were sometimes small periods. It cannot be said that they were destructive, but they also caused famine, disease due to crop failure, and other problems.
The most recent of the Little Ice Ages began around 12th-14th centuries. The most difficult time can be called the period from 1500 to 1850. At this time in the Northern Hemisphere, a fairly low temperature was observed.
In Europe, it was common when the seas froze, and in mountainous areas, for example, in the territory of modern Switzerland, the snow did not melt even in summer. Cold weather influenced every aspect of life and culture. Probably, the Middle Ages remained in history, as "Time of Troubles" also because the planet was dominated by a small ice age.
periods of warming
Some ice ages actually turned out to be quite warm. Despite the fact that the surface of the earth was shrouded in ice, the weather was relatively warm.
Sometimes in the atmosphere of the planet accumulated enough a large number of carbon dioxide, which is the cause of greenhouse effect when heat is trapped in the atmosphere and warms the planet. In this case, the ice continues to form and reflect the sun's rays back into space.
According to experts, this phenomenon led to the formation giant desert with ice on the surface but quite warm weather.
When will the next ice age start?
The theory that ice ages occur on our planet at regular intervals goes against theories about global warming. There's no doubt about what's happening today global warming which may help prevent the next ice age.
Human activities release carbon dioxide, which for the most part guilty of the problem global warming. However, this gas has another strange side effect. According to researchers from University of Cambridge, the release of CO2 could stop the next ice age.
According to the planetary cycle of our planet, the next ice age should come soon, but it can take place only if the level of carbon dioxide in the atmosphere will be relatively low. However, CO2 levels are currently so high that no ice age is out of the question anytime soon.
Even if a person abruptly stops emitting carbon dioxide into the atmosphere (which is unlikely), existing quantity enough to prevent the onset of the ice age at least another thousand years.
Plants of the Ice Age
The easiest way to live in the Ice Age predators: they could always find food for themselves. But what do herbivores actually eat?
It turns out that there was enough food for these animals. During the ice ages on the planet many plants grew that could survive in harsh conditions. The steppe area was covered with shrubs and grass, which fed mammoths and other herbivores.
More large plants you could also meet a great variety: for example, grew in abundance firs and pines. Found in warmer regions birches and willows. That is, the climate by and large in many modern southern regions resembled the one that exists today in Siberia.
However, the plants of the Ice Age were somewhat different from modern ones. Of course, with the onset of cold weather many plants died. If a plant was not able to adapt to a new climate, it had two options: either move to more southern zones or die.
For example, the present-day state of Victoria in southern Australia had the richest variety of plant species on the planet until the Ice Age most of the species died.
Cause of the Ice Age in the Himalayas?
It turns out that the Himalayas, the highest mountain system of our planet, directly related with the onset of the ice age.
40-50 million years ago the land masses where China and India are today collided to form the highest mountains. As a result of the collision, huge volumes of "fresh" rocks from the bowels of the earth.
These rocks eroded, and as a result chemical reactions carbon dioxide began to be removed from the atmosphere. The climate on the planet began to become colder, the ice age began.
snowball earth
During different ice ages, our planet was mostly shrouded in ice and snow. only partially. Even during the most severe ice age, ice covered only one-third the globe.
However, there is a hypothesis that at certain periods the Earth was still completely covered in snow, which made her look like a giant snowball. Life still managed to survive thanks to the rare islands with relatively little ice and with enough light for plant photosynthesis.
According to this theory, our planet turned into a snowball at least once, more precisely 716 million years ago.
Garden of Eden
Some scientists are convinced that garden of eden described in the Bible actually existed. It is believed that he was in Africa, and it is thanks to him that our distant ancestors survived the ice age.
About 200 thousand years ago came a severe ice age, which put an end to many forms of life. Fortunately, a small group of people were able to survive the period of severe cold. These people moved to the area where South Africa is today.
Despite the fact that almost the entire planet was covered with ice, this area remained ice-free. A large number of living beings lived here. The soils of this area were rich nutrients so there was abundance of plants. Caves created by nature were used by people and animals as shelters. For living beings, it was a real paradise.
According to some scientists, in the "Garden of Eden" lived no more than a hundred people, which is why humans do not have as much genetic diversity as most other species. However, this theory has not found scientific evidence.
During the Paleogene, the northern hemisphere was warm and humid climate, but in the Neogene (25 - 3 million years ago) it became much colder and drier. Changes environment associated with cooling and the appearance of glaciations are a feature of the Quaternary period. This is why it is sometimes called the Ice Age.
Ice ages have happened many times in the history of the Earth. Traces of continental glaciations were found in the layers of the Carboniferous and Permian (300-250 million years), Vendian (680-650 million years), Riphean (850-800 million years). The oldest glacial deposits found on Earth are over 2 billion years old.
No single planetary or cosmic factor has been found to cause glaciation. Glaciations are the result of a combination of several events, some of which play the main role, while others play the role of a "trigger" mechanism. It has been noted that all the great glaciations of our planet coincided with major mountain-building epochs, when the relief of the earth's surface was the most contrasting. The area of the seas has decreased. Under these conditions, climate fluctuations have become more dramatic. Mountains up to 2000 m high, which arose in Antarctica, i.e. directly at the South Pole of the Earth, became the first focus of the formation of sheet glaciers. The glaciation of Antarctica began more than 30 million years ago. The appearance of a glacier there greatly increased the reflectivity, which in turn led to a decrease in temperature. Gradually, the glacier of Antarctica grew both in area and in thickness, and its influence on the thermal regime of the Earth was increasing. The temperature of the ice slowly decreased. The Antarctic continent has become the largest accumulator of cold on the planet. The formation of huge plateaus in Tibet and in the western part of the North American continent has made a great contribution to climate change in the Northern Hemisphere.
It got colder and colder, and about 3 million years ago, the climate of the Earth as a whole became so cold that ice ages periodically began to set in, during which ice sheets captured most of the northern hemisphere. Mountain-building processes are a necessary but still insufficient condition for the occurrence of glaciation. The average heights of the mountains are now not lower, and perhaps even higher than those that were during the glaciation. However, now the area of glaciers is relatively small. Some additional reason is needed directly causing the cooling.
It should be emphasized that any significant decrease in temperature is not required for the occurrence of a major glaciation of the planet. Calculations show that the total average annual decrease in temperature on Earth by 2 - 4? C will cause spontaneous development of glaciers, which in turn will lower the temperature on Earth. As a result, the ice shell will cover a significant part of the Earth's area.
Carbon dioxide plays a huge role in the regulation of the temperature of the near-surface air layers. Carbon dioxide freely passes the sun's rays to the earth's surface, but absorbs most of the planet's thermal radiation. It is a colossal screen that prevents the cooling of our planet. Now the content of carbon dioxide in the atmosphere does not exceed 0.03%. If this figure is halved, then the average annual temperatures in the middle latitudes will decrease by 4–5 ° C, which may lead to the onset of an ice age. According to some data, the concentration of CO2 in the atmosphere during the ice ages was about a third less than in the interglacials and sea water contained 60 times more carbon dioxide than the atmosphere.
The decrease in the CO2 content in the atmosphere can be explained by the following mechanisms. If the rate of spreading (pushing apart) and, accordingly, subduction significantly decreased in some periods, then this should have led to the release of a smaller amount of carbon dioxide into the atmosphere. In fact, global average spreading rates show little change over the past 40 million years. If the rate of CO2 replacement was practically unchanged, then the rate of its removal from the atmosphere due to the chemical weathering of rocks increased significantly with the appearance of giant plateaus. In Tibet and America, carbon dioxide combines with rainwater and groundwater to form carbon dioxide, which reacts with silicate minerals in rocks. The resulting bicarbonate ions are transported to the oceans, where they are consumed by organisms such as plankton and corals, and then deposited on the ocean floor. Of course, these sediments will fall into the subduction zone, melt, and CO2 will again enter the atmosphere as a result of volcanic activity, but this process takes a long time, from tens to hundreds of millions of years.
It may seem that as a result of volcanic activity, the CO2 content in the atmosphere will increase and therefore it will be warmer, but this is not entirely true.
The study of modern and ancient volcanic activity allowed the volcanologist I. V. Melekestsev to connect the cooling and the glaciation that caused it with an increase in the intensity of volcanism. It is well known that volcanism has a marked effect on earth's atmosphere, changing its gas composition, temperature, and also polluting it with finely divided material of volcanic ash. Huge masses of ash, measured in billions of tons, are ejected by volcanoes into the upper atmosphere, and then carried by jet streams around the globe. A few days after the 1956 eruption of the Bezymyanny volcano, its ash was found in the upper troposphere above London. North America and Australia. Pollution of the atmosphere with volcanic ash causes a significant decrease in its transparency and, consequently, weakening solar radiation 10-20% against the norm. In addition, ash particles serve as condensation nuclei, contributing to great development cloudiness. An increase in cloudiness, in turn, significantly reduces the amount of solar radiation. According to Brooks' calculations, an increase in cloudiness from 50 (typical for the present) to 60% would lead to a decrease average annual temperature on the globe at 2°C.
State educational institution higher vocational education Moscow region
International University of Nature, Society and Man "Dubna"
Faculty of Natural and Engineering Sciences
Department of Ecology and Earth Sciences
COURSE WORK
By discipline
Geology
Scientific adviser:
Candidate of G.M.S., Associate Professor Anisimova O.V.
Dubna, 2011
Introduction
1. Ice Age
1.1 Ice Ages in Earth's History
1.2 Proterozoic Ice Age
1.3 Paleozoic Ice Age
1.4 Cenozoic Ice Age
1.5 Tertiary period
1.6 Quaternary
2. The Last Ice Age
2.2 Flora and fauna
2.3Rivers and lakes
2.4 West Siberian lake
2.5Oceans
2.6 Great Glacier
3. Quaternary glaciations in the European part of Russia
4. Causes of Ice Ages
Conclusion
Bibliography
Introduction
Target:
To study the main ice ages in the history of the Earth and their role in shaping the modern landscape.
Relevance:
The relevance and significance of this topic is determined by the fact that the glacial epochs are not so well studied to fully confirm the existence on our Earth.
Tasks:
- spend literature review;
- establish the main ice ages;
– obtaining detailed data on the last Quaternary glaciations;
Establish the main causes of glaciation in the history of the Earth.
At present, there is still little data that confirms the distribution of frozen rock strata on our planet in ancient epochs. The proof is mainly the discovery of ancient continental glaciations in their moraine deposits and the establishment of the phenomena of mechanical separation of the rocks of the glacier bed, the transfer and processing of detrital material and its deposition after ice melting. Compacted and cemented ancient moraines, the density of which is close to sandstone-type rocks, are called tillites. Detection of such formations different ages in various regions of the globe clearly indicates the repeated emergence, existence and disappearance of ice sheets, and, consequently, frozen strata. The development of ice sheets and frozen strata can occur asynchronously, i.e. the maximum development over the area of glaciation and cryolithozone may not coincide in phase. However, in any case, the presence of large ice sheets indicates the existence and development of frozen strata, which should occupy much larger areas than the ice sheets themselves.
According to N.M. Chumakov, as well as V.B. Harland and M.J. Hambry, the time intervals during which glacial deposits were formed are called glacial eras (lasting the first hundreds of millions of years), ice ages (millions - the first tens of millions of years), ice ages (the first millions of years). In the history of the Earth, the following glacial eras can be distinguished: Early Proterozoic, Late Proterozoic, Paleozoic and Cenozoic.
1. Ice Age
Are there ice ages? Of course yes. The evidence for this is incomplete, but it is well defined, and some of this evidence extends to large areas. Evidence for the existence of the Permian Ice Age is present on several continents, and in addition, traces of glaciers have been found on the continents dating back to other epochs of the Paleozoic era up to its beginning, the Early Cambrian time. Even in much older rocks, pre-Phanerozoic, we find traces left by glaciers and glacial deposits. Some of these footprints are over two billion years old, perhaps half the age of the Earth as a planet.
Glacial epoch of glaciations (glacials) - time interval geological history Earth, characterized by a strong cooling of the climate and the development of vast continental ice not only in the polar, but also in temperate latitudes.
Peculiarities:
It is characterized by a long, continuous and severe cooling of the climate, the growth of ice sheets in the polar and temperate latitudes.
· Glacial epochs are accompanied by a decrease in the level of the World Ocean by 100 m or more, due to the fact that water accumulates in the form of ice sheets on land.
·During glacial epochs, the areas occupied by permafrost are expanding, soil and vegetation zones are shifting towards the equator.
It has been established that over the past 800 thousand years there have been eight glacial epochs, each of which lasted from 70 to 90 thousand years.
Fig.1 Ice age
1.1 Ice Ages in Earth's History
Periods of climate cooling, accompanied by the formation of continental ice sheets, are recurring events in the history of the Earth. The intervals of cold climate during which extensive continental ice sheets and sediments lasting hundreds of millions of years are formed are called ice ages; in glacial eras, glacial periods lasting tens of millions of years are distinguished, which, in turn, consist of glacial epochs - glaciations (glacials) alternating with interglacials (interglacials).
Geological studies have proved that there was a periodic process of climate change on Earth, covering the time from the late Proterozoic to the present.
These are relatively long ice ages that lasted for almost half of the history of the Earth. The following ice ages are distinguished in the history of the Earth:
Early Proterozoic - 2.5-2 billion years ago
Late Proterozoic - 900-630 million years ago
Paleozoic - 460-230 million years ago
Cenozoic - 30 million years ago - present
Let's consider each of them in more detail.
1.2 Proterozoic Ice Age
Proterozoic - from the Greek. the words proteros - primary, zoe - life. The Proterozoic era is a geological period in the history of the Earth, including the history of the formation of rocks of various origins from 2.6 to 1.6 billion years. A period in the history of the Earth, which was characterized by the development of the simplest forms of life of unicellular living organisms from prokaryotes to eukaryotes, which later evolved into multicellular organisms as a result of the so-called Ediacaran "explosion".
Early Proterozoic Ice Age
This is the oldest glaciation recorded in geological history at the end of the Proterozoic on the border with the Vendian, and according to the Snowball Earth hypothesis, the glacier covered most of the continents at equatorial latitudes. In fact, it was not one, but a series of glaciations and interglacial periods. Since it is believed that nothing can prevent the spread of glaciation due to the growth of albedo (reflection solar radiation from the white surface of glaciers), it is believed that the subsequent warming may be caused, for example, by an increase in the amount of greenhouse gases due to the increase in volcanic activity, accompanied, as you know, by the release of a huge amount of gases.
Late Proterozoic Ice Age
It was distinguished under the name of the Lapland glaciation at the level of the Vendian glacial deposits 670-630 million years ago. These deposits are found in Europe, Asia, West Africa, Greenland and Australia. The paleoclimatic reconstruction of the glacial formations of this time suggests that the European and African ice continents of that time were a single ice sheet.
Fig.2 Vend. Ulytau during the Ice Age Snowball
1.3 Paleozoic Ice Age
Paleozoic - from the word paleos - ancient, zoe - life. Palaeozoic. Geological time in the history of the Earth covering 320-325 million years. With an age of glacial deposits of 460-230 million years, it includes the Late Ordovician - Early Silurian (460-420 million years), Late Devonian (370-355 million years) and Carboniferous-Permian ice ages (275 - 230 million years). The interglacial period of these periods is characterized by a warm climate, which contributed to the rapid development of vegetation. Large and unique coal basins and horizons of oil and gas fields later formed in the places of their distribution.
Late Ordovician - Early Silurian Ice Age.
Glacial deposits of this time, called the Saharan (after the name of the modern Sahara). They were distributed in what is now Africa. South America, eastern North America and Western Europe. This period is characterized by the formation of an ice sheet over much of northern, northwestern, and western Africa, including the Arabian Peninsula. Paleoclimatic reconstructions suggest that the thickness of the Saharan ice sheet reached at least 3 km and is similar in area to the modern glacier of Antarctica.
Late Devonian Ice Age
Glacial deposits of this period were found on the territory of modern Brazil. The glacial region extended from the modern mouth of the river. Amazons to the east coast of Brazil, capturing the Niger region in Africa. In Africa, in Northern Niger, tillites (glacial deposits) occur, which are comparable to those in Brazil. In general, glacial regions stretched from the border of Peru with Brazil to northern Niger, the diameter of the region was more than 5000 km. South Pole in the late Devonian, according to the reconstruction of P. Morel and E. Irving, was in the center of Gondwana in Central Africa. Glacial basins are located on the oceanic margin of the paleocontinent, mainly at high latitudes (not north of the 65th parallel). Judging by the then high-latitude continental position of Africa, one can assume the possible widespread development of frozen rocks on this continent and, moreover, in the northwest of South America.
Over the past million years, an ice age has occurred on Earth about every 100,000 years. This cycle actually exists, and different groups scientists in different time tried to find the reason for its existence. True, there is no prevailing point of view on this issue yet.
Over a million years ago, the cycle was different. The ice age was replaced by climate warming about once every 40 thousand years. But then the periodicity of the onset of glaciers changed from 40 thousand years to 100 thousand years. Why did this happen?
Experts from Cardiff University offered their own explanation for this change. The results of the work of scientists were published in the authoritative publication Geology. According to experts, the main reason for the change in the frequency of the onset of ice ages is the oceans, or rather, their ability to absorb carbon dioxide from the atmosphere.
By studying the sediments that make up the bottom of the oceans, the team found that the concentration of CO 2 varies from layer to layer of sediments with a period of just 100,000 years. It is likely, scientists say, that excess carbon dioxide was removed from the atmosphere by the surface of the ocean with further binding of this gas. As a result, the average annual temperature gradually decreases, and another ice age begins. And it so happened that the duration of the ice age more than a million years ago increased, and the cycle "heat-cold" became longer.
“It is likely that the oceans absorb and release carbon dioxide, and when there is more ice, the oceans absorb more carbon dioxide from the atmosphere, making the planet colder. When there is little ice, the oceans release carbon dioxide, so the climate gets warmer,” says Professor Carrie Lear. “By studying the concentration of carbon dioxide in the remains of tiny creatures (here we mean sedimentary rocks - ed.), we learned that during periods when the area of \u200b\u200bglaciers increased, the oceans absorbed more carbon dioxide, so we can assume that there is less of it in the atmosphere.
Seaweeds are said to have played a major role in the uptake of CO 2 since carbon dioxide is an essential component of the photosynthesis process.
Carbon dioxide enters the atmosphere from the ocean through upwelling. Upwelling (English upwelling) or rise is a process in which deep waters oceans rise to the surface. It is most often observed at the western borders of the continents, where it moves colder, nutrient-rich waters from the depths of the ocean to the surface, replacing warmer, nutrient-poor surface waters. It can also be found in almost any area of the oceans.
A layer of ice on the surface of the water prevents carbon dioxide from entering the atmosphere, so if a large part of the ocean freezes, this prolongs the duration of the ice age. “If we believe that the oceans emit and absorb carbon dioxide, then we must understand that a large amount of ice prevents this process. It's like a lid on the surface of the ocean,” says Professor Liar.
With an increase in the area of glaciers on the ice surface, not only does the concentration of “warming” CO 2 decrease, but the albedo of those regions that are covered with ice also increases. As a result, the planet receives less energy, which means it cools even faster.
Now the Earth is in the interglacial warm period. The last ice age ended about 11,000 years ago. Since then, the average annual temperature and sea level have been constantly rising, and the amount of ice on the surface of the oceans has been decreasing. As a result, according to scientists, a large amount of CO 2 enters the atmosphere. In addition, humans also produce carbon dioxide, and in huge quantities.
All this led to the fact that in September the concentration of carbon dioxide in the Earth's atmosphere increased to 400 parts per million. This figure has increased from 280 to 400 parts per million in just 200 years of industrial development. Most likely, CO 2 in the atmosphere will not decrease in the foreseeable future. All this should lead to an increase in the average annual temperature on Earth by about + 5 ° C in the next thousand years.
Specialists from the Department of Climate Studies at the Potsdam Observatory have recently built a model of the Earth's climate, taking into account the global carbon cycle. As the model showed, even with minimal carbon dioxide emissions into the atmosphere, the Northern Hemisphere ice sheet will not be able to increase. This means that the onset of the next ice age can move forward by at least 50-100 thousand years. So we have another change in the glacier-warm cycle ahead of us, this time man is responsible for it.
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