Glaciers are an extraordinary miracle of nature that slowly moves across the surface of the Earth. This cluster eternal ice on its way it captures and transports rocks, forming unique landscapes such as moraines and cirques. Sometimes the glacier stops moving and the so-called dead ice forms.
Some glaciers, moving a short distance into large lakes or seas, form an area where they break up and, as a result, drift icebergs.
Geographical feature (meaning)
Glaciers appear in places where the accumulated mass of snow and ice significantly exceeds the mass of melting snow. And after many years, a glacier will form in such a region.
Glaciers are the largest reservoirs of fresh water on Earth. Most glaciers accumulate water in winter season and give it away as melt water. Such waters are especially useful in mountainous regions of the planet, where such water is used by people who live in areas where there is little precipitation. Glacier meltwater is also a source for the existence of flora and fauna.
Characteristics and types of glaciers
According to the method of movement and visual outlines, glaciers are classified into two types: cover (continental) and mountain. Ice sheet glaciers occupy 98% of the total area of planetary glaciation, and mountain glaciers occupy almost 1.5%
Continental glaciers are giant ice sheets located in Antarctica and Greenland. Glaciers of this type have flat-convex outlines that do not depend on the typical topography. Snow accumulates in the center of the glacier, and consumption occurs mainly on the outskirts. The ice of the cover glacier moves in a radial direction - from the center to the periphery, where the ice that is afloat breaks off.
Mountain-type glaciers are small in size, but different forms, which depend on their content. All glaciers of this type areas of feeding, transportation and melting are clearly visible. Nutrition is carried out with the help of snow, avalanches, a little sublimation of water vapor and snow transfer by the wind.
The largest glaciers
The largest glacier in the world is the Lambert Glacier, which is located in Antarctica. The length is 515 kilometers, and the width ranges from 30 to 120 kilometers, the depth of the glacier is 2.5 km. The entire surface of the glacier is cut by a large number of cracks. The glacier was discovered in the 50s of the twentieth century by the Australian cartographer Lambert.
In Norway (Svalbard archipelago) there is the Austfonna glacier, which leads the list of the largest glaciers in the Old Continent by area (8200 km2).
(Vatnajökull Glacier and Grimsuod Volcano)
In Iceland there is the Vatnajökull glacier, which ranks second in Europe in terms of area (8100 km2). The largest in mainland Europe is the Jostedalsbreen glacier (1230 km2), which is a wide plateau with numerous ice branches.
Melting glaciers - causes and consequences
The most dangerous of all modern natural processes is the melting of glaciers. Why is this happening? The planet is currently heating up - this is the result of the release of greenhouse gases into the atmosphere that are produced by humanity. As a result, the average temperature on Earth also rises. Since ice is the repository of fresh water on the planet, its reserves will sooner or later run out with intense global warming. Glaciers are also climate stabilizers on the planet. Due to the amount of ice that has melted, salt water is evenly diluted with fresh water, which has a special impact on the level of air humidity, precipitation, and temperature indicators in both the summer and winter seasons.
Vatnajökull Vatnajökull is the largest ice cap in Iceland, covering 8% of the island. Vatnajökull Glacier is located in southwest Iceland and is a popular destination for glacier walking tours and ice caves.
Interesting facts about the Vatanjökull glacier
- Surface: 8,100 km2
- Average thickness: 400 - 600 m
- Maximum thickness: 1000 m
- Altitude: 1400 - 1800 m
- Highest peak: 2,200 m (Hvannadalshnjúkur)
Information about the Vatanjökull glacier Vatnajökull
The Vatnajökull Glacier lies within the larger Vatnájökull National Park, which covers the former national parks of Skaftafell, in the southwest, and Jökulsárgljúfur, in the north. The highest point of the Vatnajökull glacier is Hvannadalsnjökull, which lies on top of a stratovolcano known as Öræfajökull.
Beneath the glacier are some of the most active volcanoes in the country, the most notable of which are Grímsvötn, Öræfajökull and Bárðabunga. Volcanic activity in the region has occurred for centuries, and many geologists believe that this will continue in the near future. If their calculations are correct, this means significant volcanic activity for Vatnajökull over the next half century.
The glacier boasts more than 30 glacier tongues that flow from the ice caps but remain confined to the sides of the valley. The main tongues of the Vatnajökull glacier are Dingujökull in the north, Breidramerkurhökull and Skiarrajökull in the south. In the west the languages Síðujökull, Skaftárjökull and Tungnaárjökull can be found.
Glaciers are in constant motion under the weight of the ice. Every year, due to the melting and movement of ice, new ice caves appear, which soon disappear.
Ice caves in Vatnajökull
Anyone who has seen photographs of ice caves knows that it is worth seeing. Since Vatnajökull is the largest glacier in Europe, it is one of the best places to see this natural wonder - ice caves. Every year, visitors get the chance to see a natural ice cave in Vatnajökull National Park.
Ice caves only form in winter, when glacial rivers disappear and the water freezes. Their locations, shapes and sizes are constantly changing, making them a distinctive and unique spectacle.
If you are planning to try your luck and see an ice cave in Iceland, please do so under professional guidance - the weather and circumstances can pose a big risk!
Vatnajokull Glacier Tours
There are many companies running tours to the Vatnajökull Glacier, many of them departing from the Skaftafell National Park Visitor Centre.
Some glaciers represent one of the most impressive sights in the world, in fact, we will tell you about them today.
Austfonna, Norway
This glacier is located on the Spitsbergen archipelago, and ranks first in size on the entire Old Continent. Its area is 8200 square kilometers.
Vatnajökull, Iceland
Slightly smaller area – 8100 sq. km - occupies the Vatnaekul glacier in Iceland. This glacier is the second largest in Europe. If we take the volume of the glacier as a criterion, then only the part protruding to the surface will be 3100 cubic kilometers.
Jostedalsbreen, Norway
It is the largest glacier in continental Europe. It covers an area of 487 square kilometers, however, unfortunately, the glacier is shrinking very quickly and there is a danger of its complete destruction.
Aletsch, Switzerland
The largest Alpine glacier is located in Switzerland, on the Valais. The total area of this glacier is 117.6 square kilometers, and its length is more than 20 km. The Aletsch Glacier, as well as the nearby Jungfrau Mountains, have been declared a UNESCO World Heritage Site.
Schneeferner, Germany
In the region of the Bavarian Alps there is the largest glacier in Germany, which is also the northernmost Alpine glacier. It is located in the Zugspitze massif (the most high mountain in the country), on the Zugspitzplatt plateau and its area covers about 3 hectares.
Pastors, Austria
The Austrian Shepherd Glacier lies in the Grossglockner massif, and is the largest glacier in the country. It is noteworthy that the name “pastors” is of Slavic origin and means a place for grazing sheep.
Southern Patagonian Ice Sheet, Chile and Argentina
It occupies a surface area of 16,800 square kilometers of the South Patagonian Shield and is considered the largest glacier in South America. Most of its territory is located in Chile - 14,200 square meters. km, and only 2600 belongs to Argentina. Streams diverge from the glacier. 50 km long, thus creating a huge lake.
Lambert Glacier, Antarctica
The largest and longest glacier in the world is the Lambert Glacier, which is located in East Antarctica. The glacier was discovered in 1956 and is estimated to be 400 miles long and 50 kilometers wide, which occupies approximately 10% of the entire ice continent.
Malaspina, USA
The glacier covers an area of 4275 square kilometers, located at the foot of Mount St. Elias in Alaska.
Fedchenko Glacier, Tajikistan
Fedchenko Glacier in Tajikistan is the longest glacier outside the polar zones. It is located at an altitude of 6000 meters above sea level. In addition, it is the largest glacier in the Pamir Mountains and among all Asian continents. The glacier is so huge that the size of its “tributaries” far exceeds the most powerful European glaciers.
One of the mysteries of the Earth, along with the emergence of Life on it and the extinction of dinosaurs at the end of the Cretaceous period, is - Great Glaciations.
It is believed that glaciations repeat on Earth regularly every 180-200 million years. Traces of glaciations are known in sediments that are billions and hundreds of millions of years old - in the Cambrian, Carboniferous, Triassic-Permian. That they could be is “said” by the so-called tillites, breeds very similar to moraine the latter, more precisely last glaciations. These are the remains of ancient glacial deposits, consisting of a clayey mass with inclusions of large and small boulders scratched by movement (hatched).
Separate layers tillites, found even in equatorial Africa, can reach thickness of tens and even hundreds of meters!
Signs of glaciations were found on different continents - in Australia, South America, Africa and India, which is used by scientists for reconstruction of paleocontinents and is often cited as confirmation plate tectonics theories.
Traces of ancient glaciations indicate that glaciations on a continental scale– this is not a random phenomenon at all, it is a natural natural phenomenon that occurs under certain conditions.
The last of the ice ages began almost million years ago, in Quaternary time, or the Quaternary period, the Pleistocene and was marked by the extensive spread of glaciers - The Great Glaciation of the Earth.
Under thick, many-kilometer-long covers of ice they found themselves Northern part North American continent - the North American ice sheet, reaching a thickness of up to 3.5 km and extending to approximately 38° north latitude and a significant part of Europe, to which (an ice sheet up to 2.5-3 km thick). On the territory of Russia, the glacier descended in two huge tongues along the ancient valleys of the Dnieper and Don.
Partial glaciation also covered Siberia - there was mainly the so-called “mountain-valley glaciation”, when glaciers did not cover the entire area with a thick cover, but were only in the mountains and foothill valleys, which is associated with the sharply continental climate and low temperatures in Eastern Siberia . But almost all of Western Siberia, due to the fact that the rivers were dammed and their flow into the Arctic Ocean stopped, found itself under water, and was a huge sea-lake.
In the Southern Hemisphere, the entire Antarctic continent was under ice, as it is 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.
Having reached their greatest development about 250 thousand years ago, the Quaternary glaciers of the Northern Hemisphere began to gradually shrink as the glaciation period was not continuous throughout the Quaternary period.
There is geological, paleobotanical and other evidence that glaciers disappeared several times, giving way to epochs interglacial when the climate was even warmer than today. However, the warm eras were replaced by cold snaps again, and the glaciers spread again.
We now live, apparently, at the end of the fourth epoch of the Quaternary glaciation.
But in Antarctica, glaciation arose millions of years before the time when glaciers appeared in North America and Europe. In addition to the climatic conditions, this was facilitated by the high continent that had existed here for a long time. By the way, now, due to the fact that the thickness of the Antarctic glacier is enormous, the continental bed of the “ice continent” is in some places below sea level...
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 than the modern one in volume, and not much larger in area.
Now about the hypotheses... There are hundreds, if not thousands, of hypotheses about why glaciations occur, and whether there were any at all!
The following main ones are usually put forward: scientific hypotheses:
- Volcanic eruptions leading to a decrease in the transparency of the atmosphere and cooling throughout the Earth;
- Epochs of orogenesis (mountain building);
- Reducing the amount of carbon dioxide in the atmosphere, which reduces the “greenhouse effect” and leads to cooling;
- Cyclicity of solar activity;
- Changes in the position of the Earth relative to the Sun.
But, nevertheless, the causes of glaciations have not been fully elucidated!
It is assumed, for example, that glaciation begins when, with an increase in the distance between the Earth and the Sun, around which it rotates in a slightly elongated orbit, the amount of solar heat received by our planet decreases, i.e. glaciation occurs when the Earth passes the point of its orbit that is farthest from the Sun.
However, astronomers believe that changes in the amount of solar radiation hitting the Earth alone are not enough to trigger an ice age. Apparently, fluctuations in the activity of the Sun itself also matter, which is a periodic, cyclical process, and changes every 11-12 years, with a cyclicity of 2-3 years and 5-6 years. And the largest cycles of activity, as established by the Soviet geographer A.V. Shnitnikov - approximately 1800-2000 years old.
There is also a hypothesis that the emergence of glaciers is associated with certain areas of the Universe through which our Solar System passes, moving with the entire Galaxy, either filled with gas or “clouds” of cosmic dust. And it is likely that “cosmic winter” on Earth occurs when Earth is located at the point furthest from the center of our Galaxy, where there are accumulations of “cosmic dust” and gas.
It should be noted that usually before epochs of cooling there are always epochs of warming, and there is, for example, a hypothesis that the Arctic Ocean, due to warming, at times is completely freed from ice (by the way, this is still happening), and there is increased evaporation from the surface of the ocean , streams of moist air are directed to the polar regions of America and Eurasia, and snow falls over the cold surface of the Earth, which does not have time to melt during the short and cold summer. This is how ice sheets appear on continents.
But when, as a result of the transformation of part of the water into ice, the level of the World Ocean drops by tens of meters, the warm Atlantic Ocean ceases to communicate with the Arctic Ocean, and it gradually becomes covered with ice again, evaporation from its surface abruptly stops, less and less snow falls on the continents and less, the “feeding” of the glaciers deteriorates, and the ice sheets begin to melt, and the level of the World Ocean rises again. And again the Arctic Ocean connects with the Atlantic, and again the ice cover began to gradually disappear, i.e. the development cycle of the next glaciation begins anew.
Yes, all these hypotheses quite possible, but so far none of them can be confirmed by serious scientific facts.
Therefore, one of the main, fundamental hypotheses is climate change on the Earth itself, which is associated with the above-mentioned hypotheses.
But it is quite possible that glaciation processes are associated with combined influence of various natural factors, which could act together and replace each other, and the important thing is that, having begun, glaciations, like a “wound clock,” already develop independently, according to their own laws, sometimes even “ignoring” some climatic conditions and patterns.
And the ice age that began in the Northern Hemisphere about 1 million years back, not finished yet, and we, as already mentioned, live in a warmer period of time, in interglacial.
Throughout the era of the Great Glaciations of the Earth, the ice either retreated or advanced again. On the territory of both America and Europe there were, apparently, four global ice ages, between which there were relatively warm periods.
But the complete retreat of the ice occurred only about 20 - 25 thousand years ago, but in some areas the ice lingered even longer. The glacier retreated from the area of modern St. Petersburg only 16 thousand years ago, and in some places in the North small remnants of ancient glaciation have survived to this day.
Let us note that modern glaciers cannot be compared with the ancient glaciation of our planet - they occupy only about 15 million square meters. km, i.e. less than one-thirtieth earth's surface.
How can one determine whether there was glaciation in a given place on Earth or not? This is usually quite easy to determine by the peculiar forms of geographical relief and rocks.
In the fields and forests of Russia there are often large accumulations of huge boulders, pebbles, blocks, sands and clays. They usually lie directly on the surface, but they can also be seen in the cliffs of ravines and on the slopes of river valleys.
By the way, one of the first who tried to explain how these deposits were formed was the outstanding geographer and anarchist theorist, Prince Peter Alekseevich Kropotkin. In his work “Research on the Ice Age” (1876), he argued that the territory of Russia was once covered by huge ice fields.
If we look at the physiographic map European Russia, then in the location of hills, hills, basins and valleys of large rivers one can notice some patterns. So, for example, the Leningrad and Novgorod regions from the south and east are, as it were, limited Valdai Upland shaped like an arc. This is exactly the line where in the distant past a huge glacier, advancing from the north, stopped.
To the southeast of the Valdai Upland is the slightly winding Smolensk-Moscow Upland, stretching from Smolensk to Pereslavl-Zalessky. This is another of the boundaries of the distribution of cover glaciers.
Numerous hilly, winding hills are also visible on the West Siberian Plain - "manes" also evidence of the activity of ancient glaciers, or rather glacial waters. Many traces of stopping moving glaciers flowing down the mountain slopes into large basins were discovered in Central and Eastern Siberia.
It is difficult to imagine ice several kilometers thick on the site of current cities, rivers and lakes, but, nevertheless, the glacial plateaus were not inferior in height to the Urals, the Carpathians or the Scandinavian mountains. These gigantic and, moreover, moving masses of ice influenced the entire natural environment– relief, landscapes, river flow, soils, vegetation and fauna.
It should be noted that on the territory of Europe and the European part of Russia, practically no rocks have been preserved from the geological eras preceding the Quaternary period - Paleogene (66-25 million years) and Neogene (25-1.8 million years), they were completely eroded and redeposited during the Quaternary period, or as it is often called, Pleistocene.
Glaciers originated and moved from Scandinavia, the Kola Peninsula, the Polar Urals (Pai-Khoi) and the islands of the Arctic Ocean. And almost all the geological deposits that we see on the territory of Moscow - moraine, more precisely moraine loams, sands of various origins (aquaglacial, lake, river), huge boulders, as well as cover loams - all this is evidence of the powerful influence of the glacier.
On the territory of Moscow, traces of three glaciations can be identified (although there are many more of them - different researchers identify from 5 to several dozen periods of ice advances and retreats):
- Oka (about 1 million years ago),
- Dnieper (about 300 thousand years ago),
- Moscow (about 150 thousand years ago).
Valdai the glacier (disappeared only 10 - 12 thousand years ago) “did not reach Moscow”, and the deposits of this period are characterized by hydroglacial (fluvio-glacial) deposits - mainly the sands of the Meshchera Lowland.
And the names of the glaciers themselves correspond to the names of those places to which the glaciers reached - the Oka, Dnieper and Don, the Moscow River, Valdai, etc.
Since the thickness of the glaciers reached almost 3 km, one can imagine what colossal work he performed! Some hills and hills on the territory of Moscow and the Moscow region are thick (up to 100 meters!) deposits that were “brought” by the glacier.
The best known are, for example Klinsko-Dmitrovskaya moraine ridge, individual hills on the territory of Moscow ( Sparrow Hills and Teplostanskaya Upland). Huge boulders weighing up to several tons (for example, the Maiden Stone in Kolomenskoye) are also the result of the glacier.
Glaciers smoothed out the unevenness of the relief: they destroyed hills and ridges, and with the resulting rock fragments they filled depressions - river valleys and lake basins, transporting huge masses of stone fragments over a distance of more than 2 thousand km.
However, huge masses of ice (given its colossal thickness) put so much pressure on the underlying rocks that even the strongest of them could not stand it and collapsed.
Their fragments were frozen into the body of the moving glacier and, like sandpaper, for tens of thousands of years they scratched rocks composed of granites, gneisses, sandstones and other rocks, creating depressions in them. Numerous glacial grooves, “scars” and glacial polishing on granite rocks, as well as long hollows in the earth’s crust, subsequently occupied by lakes and swamps, are still preserved. An example is the countless depressions of the lakes of Karelia and the Kola Peninsula.
But the glaciers did not plow up all the rocks on their way. The destruction was mainly carried out in those areas where the ice sheets originated, grew, reached a thickness of more than 3 km and from where they began their movement. The main center of glaciation in Europe was Fennoscandia, which included the Scandinavian mountains, the plateaus of the Kola Peninsula, as well as the plateaus and plains of Finland and Karelia.
Along the way, the ice became saturated with fragments of destroyed rocks, and they gradually accumulated both inside the glacier and under it. When the ice melted, masses of debris, sand and clay remained on the surface. This process was especially active when the movement of the glacier stopped and the melting of its fragments began.
At the edge of glaciers, as a rule, water flows arose, moving along the surface of the ice, in the body of the glacier and under the ice thickness. Gradually they merged, forming entire rivers, which over thousands of years formed narrow valleys and washed away a lot of debris.
As already mentioned, the forms of glacial relief are very diverse. For moraine plains characterized by many ridges and shafts, marking places where moving ice stops, and the main form of relief among them is shafts of terminal moraines, usually these are low arched ridges composed of sand and clay mixed with boulders and pebbles. The depressions between the ridges are often occupied by lakes. Sometimes among the moraine plains you can see outcasts- blocks hundreds of meters in size and weighing tens of tons, giant pieces of the glacier bed, transported by it over enormous distances.
Glaciers often blocked river flows and near such “dams” huge lakes arose, filling depressions in river valleys and depressions, which often changed the direction of river flow. And although such lakes existed for a relatively short time (from a thousand to three thousand years), at their bottom they managed to accumulate lacustrine clays, layered sediments, by counting the layers of which, one can clearly distinguish the periods of winter and summer, as well as how many years these sediments have accumulated.
In the era of the last Valdai glaciation arose Upper Volga periglacial lakes(Mologo-Sheksninskoye, Tverskoye, Verkhne-Molozhskoye, etc.). At first their waters flowed to the southwest, but with the retreat of the glacier they were able to flow to the north. Traces of Mologo-Sheksninsky Lake remain in the form of terraces and shorelines at an altitude of about 100 m.
There are very numerous traces of ancient glaciers in the mountains of Siberia, the Urals, and the Far East. As a result of ancient glaciation, 135-280 thousand years ago, sharp mountain peaks - “gendarmes” - appeared in Altai, the Sayans, the Baikal region and Transbaikalia, on the Stanovoi Highlands. The so-called “net type of glaciation” prevailed here, i.e. If you could look from a bird's eye view, you could see how ice-free plateaus and mountain peaks rise against the background of glaciers.
It should be noted that during the ice ages, quite large ice massifs were located on part of the territory of Siberia, for example on archipelago Severnaya Zemlya, in the Byrranga mountains (Taimyr Peninsula), as well as on the Putorana plateau in northern Siberia.
Extensive mountain-valley glaciation was 270-310 thousand years ago Verkhoyansk Range, Okhotsk-Kolyma Plateau and Chukotka Mountains. These areas are considered centers of glaciations in Siberia.
Traces of these glaciations are numerous bowl-shaped depressions of mountain peaks - circuses or punishments, huge moraine ridges and lake plains in place of melted ice.
In the mountains, as well as on the plains, lakes arose near ice dams, periodically the lakes overflowed, and gigantic masses of water through low watersheds rushed with incredible speed into neighboring valleys, crashing into them and forming huge canyons and gorges. For example, in Altai, in the Chuya-Kurai depression, “giant ripples”, “drilling boilers”, gorges and canyons, huge outlier boulders, “dry waterfalls” and other traces of water flows escaping from ancient lakes “only” are still preserved. just” 12-14 thousand years ago.
“Invading” the plains of Northern Eurasia from the north, the ice sheets either penetrated far to the south along relief depressions, or stopped at some obstacles, for example, hills.
It is probably not yet possible to accurately determine which of the glaciations was the “greatest,” however, it is known, for example, that the Valdai glacier was sharply smaller in area than the Dnieper glacier.
The landscapes at the boundaries of the cover glaciers also differed. Thus, during the Oka glaciation era (500-400 thousand years ago), to the south of them there was a strip of Arctic deserts about 700 km wide - from the Carpathians in the west to the Verkhoyansk Range in the east. Even further, 400-450 km to the south, stretched cold forest-steppe, where only such unpretentious trees as larches, birches and pines could grow. And only at the latitude of the Northern Black Sea region and Eastern Kazakhstan did comparatively warm steppes and semi-deserts begin.
During the era of the Dnieper glaciation, glaciers were significantly larger. Along the edge of the ice sheet stretched the tundra-steppe (dry tundra) with a very harsh climate. The average annual temperature was approaching minus 6°C (for comparison: in the Moscow region the average annual temperature is currently about +2.5°C).
The open space of the tundra, where there was little snow in winter and stood very coldy, cracked, forming the so-called “permafrost polygons”, which in plan resemble a wedge in shape. They are called “ice wedges,” and in Siberia they often reach a height of ten meters! Traces of these “ice wedges” in ancient glacial deposits “speak” of a harsh climate. Traces of permafrost, or cryogenic effects, are also noticeable in sands; these are often disturbed, as if “torn” layers, often with a high content of iron minerals.
Fluvio-glacial deposits with traces of cryogenic impact
The last “Great Glaciation” has been studied for more than 100 years. Many decades of hard work by outstanding researchers went into collecting data on its distribution on the plains and in the mountains, mapping end-moraine complexes and traces of glacial-dammed lakes, glacial scars, drumlins, and areas of “hilly moraine.”
True, there are also researchers who generally deny ancient glaciations and consider the glacial theory to be erroneous. In their opinion, there was no glaciation at all, but there was a “cold sea on which icebergs floated,” and all glacial deposits are just bottom sediments of this shallow sea!
Other researchers, “recognizing the general validity of the theory of glaciations,” nevertheless doubt the correctness of the conclusion about the grandiose scale of glaciations of the past, and they are especially distrustful of the conclusion about ice sheets that overlapped the polar continental shelves; they believe that there were “small ice caps of the Arctic archipelagos”, “bare tundra” or “cold seas”, and in North America, where the largest “Laurentian ice sheet” in the Northern Hemisphere has long been restored, there were only “groups of glaciers merged at the bases of the domes”.
For Northern Eurasia, these researchers recognize only the Scandinavian ice sheet and isolated “ice caps” of the Polar Urals, Taimyr and the Putorana Plateau, and in the mountains of temperate latitudes and Siberia - only valley glaciers.
And some scientists, on the contrary, are “reconstructing” “giant ice sheets” in Siberia, which are not inferior in size and structure to the Antarctic.
As we have already noted, in the Southern Hemisphere, the Antarctic ice sheet extended over the entire continent, including its underwater margins, in particular the areas of the Ross and Weddell seas.
The maximum height of the Antarctic ice sheet was 4 km, i.e. was close to modern (now about 3.5 km), the ice area increased to almost 17 million square kilometers, and the total volume of ice reached 35-36 million cubic kilometers.
Two more large ice sheets were in South America and New Zealand.
The Patagonian Ice Sheet was located in the Patagonian Andes, their foothills and on the adjacent continental shelf. Today it is reminded of by the picturesque fjord topography of the Chilean coast and the residual ice sheets of the Andes.
"South Alpine complex" of New Zealand– was a smaller copy of Patagonian. It had the same shape and extended onto the shelf in the same way; on the coast it developed a system of similar fjords.
In the Northern Hemisphere, during periods of maximum glaciation, we would see huge Arctic ice sheet, which arose as a result of the merger North American and Eurasian covers into a single glacial system, and important role played by floating ice shelves, especially the Central Arctic, which covered the entire deep-sea part of the Arctic Ocean.
The largest elements of the Arctic ice sheet were the Laurentian Shield of North America and the Kara Shield of Arctic Eurasia, they were shaped like giant flat-convex domes. The center of the first of them was located over the southwestern part of Hudson Bay, the peak rose to a height of more than 3 km, and its eastern edge extended to the outer edge of the continental shelf.
The Kara ice sheet occupied the entire area of the modern Barents and Kara seas, its center lay over the Kara Sea, and the southern marginal zone covered the entire north of the Russian Plain, Western and Central Siberia.
Of the other elements of the Arctic cover, it deserves special attention East Siberian Ice Sheet, which spread on the shelves of the Laptev, East Siberian and Chukchi seas and was larger than the Greenland ice sheet. He left traces in the form of large glaciodislocations New Siberian Islands and Tiksi region, are also associated with it grandiose glacial-erosive forms of Wrangel Island and the Chukotka Peninsula.
So, the last ice sheet of the Northern Hemisphere consisted of more than a dozen large ice sheets and many smaller ones, as well as the ice shelves that united them, floating in the deep ocean.
The periods of time during which glaciers disappeared, or were reduced by 80-90%, are called interglacials. Landscapes freed from ice in a relatively warm climate were transformed: the tundra retreated to the northern coast of Eurasia, and the taiga and deciduous forests, forest-steppes and steppes occupied a position close to the modern one.
Thus, over the past million years, the nature of Northern Eurasia and North America has repeatedly changed its appearance.
Boulders, crushed stone and sand, frozen into the bottom layers of a moving glacier, acting as a giant “file”, smoothed, polished, scratched granites and gneisses, and under the ice, peculiar layers of boulder loams and sands were formed, characterized by high density associated with the influence of glacial load - main, or bottom moraine.
Since the size of the glacier is determined balance between the amount of snow that falls on it annually, which turns into firn, and then into ice, and what does not have time to melt and evaporate during the warm seasons, then with climate warming, the edges of the glaciers retreat to new, “equilibrium boundaries.” The end parts of the glacial tongues stop moving and gradually melt, and boulders, sand and loam included in the ice are released, forming a shaft that follows the contours of the glacier - terminal moraine; the other part of the clastic material (mainly sand and clay particles) is carried away by meltwater flows and deposited around in the form fluvioglacial sandy plains (Zandrov).
Similar flows also operate deep in glaciers, filling cracks and intraglacial caverns with fluvioglacial material. After the melting of glacial tongues with such filled voids on the earth's surface, chaotic piles of hills remain on top of the melted bottom moraine various shapes and composition: ovoid (viewed from above) drumlins, elongated, like railway embankments (along the axis of the glacier and perpendicular to the terminal moraines) oz And irregular shape kama.
All these forms of glacial landscape are very clearly represented in North America: the boundary of ancient glaciation here is marked by a terminal moraine ridge with heights of up to fifty meters, stretching across the entire continent from its eastern coast to the western. To the north of this “Great Glacial Wall” the glacial deposits are represented mainly by moraine, and to the south of it they are represented by a “cloak” of fluvioglacial sands and pebbles.
Just as four glacial epochs have been identified for the territory of the European part of Russia, four glacial epochs have also been identified for Central Europe, named after the corresponding Alpine rivers - Günz, Mindel, Riess and Würm, and in North America - Nebraska, Kansas, Illinois and Wisconsin glaciations.
Climate periglacial The areas (surrounding the glacier) were cold and dry, which is fully confirmed by paleontological data. In these landscapes a very specific fauna appears with a combination cryophilic (cold-loving) and xerophilic (dry-loving) plants – tundra-steppe.
Now similar natural areas, similar to periglacial ones, are preserved in the form of so-called relict steppes– islands among the taiga and forest-tundra landscapes, for example, the so-called alasy Yakutia, the southern slopes of the mountains of northeastern Siberia and Alaska, as well as the cold, dry highlands of Central Asia.
Tundra-steppe was different in that her the herbaceous layer was formed mainly not by mosses (as in the tundra), but by grasses, and it was here that it took shape cryophilic option herbaceous vegetation with a very high biomass of grazing ungulates and predators – the so-called “mammoth fauna”.
It contained a bizarre mixture of different kinds animals as characteristic of tundra – reindeer, caribou, muskox, lemmings, For steppes - saiga, horse, camel, bison, gophers, and mammoths and woolly rhinoceroses, saber-toothed tiger - Smilodon, and giant hyena.
It should be noted that many climate changes have been repeated, as it were, “in miniature” within the memory of mankind. These are the so-called “Little Ice Ages” and “Interglacials”.
For example, during the so-called “Little Ice Age” from 1450 to 1850, glaciers advanced everywhere, and their sizes exceeded modern ones (snow cover appeared, for example, in the mountains of Ethiopia, where there is none now).
And in the period preceding the Little Ice Age Atlantic optimum(900-1300) glaciers, on the contrary, shrank, and the climate was noticeably milder than the present one. Let us remember that it was during these times that the Vikings called Greenland the “Green Land”, and even settled it, and also reached the coast of North America and the island of Newfoundland in their boats. And the Novgorod merchants-ushkuiniki passed through the “Northern by sea"to the Gulf of Ob, founding the city of Mangazeya there.
And the last retreat of glaciers, which began over 10 thousand years ago, is well remembered by people, hence the legends about the Great Flood, as a huge amount of meltwater rushed down to the south, rains and floods became frequent.
In the distant past, glaciers grew in epochs from low temperature air and increased humidity, the same conditions developed in the last centuries of the last era, and in the middle of the last millennium.
And 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 at the turn of the era the climate was colder and wetter than 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. It was during this era that glaciers in the Caucasus sharply intensified and grew.
But by the end of the 1st millennium, climate warming began again, and mountain glaciers in the Alps, Caucasus, Scandinavia and Iceland retreated.
The climate began to change seriously again only in the 14th century; glaciers began to grow rapidly in Greenland, summer thawing of the soil became increasingly short-lived, and by the end of the century permafrost was firmly established here.
From the end of the 15th century, glaciers began to grow in many mountainous countries and polar regions, and after the relatively warm 16th century, harsh centuries began, which were 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. But the “Little Ice Age” ended in the second half of the 19th century and a relatively warm era began, which continues to this day.
Note that the warming of the 20th century is especially pronounced in the polar latitudes of the Northern Hemisphere, and fluctuations in glacial systems are characterized by the percentage 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 of the 20th century was close to zero, then in the mid-60s of the 20th century about 30%, and at the end of the 70s of the 20th century, 65-70% of the surveyed glaciers were advancing here.
Their similar state indicates that the anthropogenic (technogenic) increase in the content of carbon dioxide, methane and other gases and aerosols in the atmosphere in the 20th century did not in any way affect the normal course of global atmospheric and glacial processes. However, at the end of the last, twentieth century, glaciers began to retreat everywhere in the mountains, and the ice of Greenland began to melt, which is associated with climate warming, and which especially intensified in the 1990s.
It is known that the currently increased man-made emissions of carbon dioxide, methane, freon and various aerosols into the atmosphere seem to help reduce solar radiation. In this regard, “voices” appeared, first from journalists, then from politicians, and then from scientists about the beginning of a “new ice age.” Environmentalists have “sounded the alarm”, fearing “the coming anthropogenic warming” due to the constant increase in carbon dioxide and other impurities in the atmosphere.
Yes, it is well known that an increase in CO 2 leads to an increase in the amount of retained heat and thereby increases the air temperature at the Earth’s surface, forming the notorious “greenhouse effect”.
Some other gases of technogenic origin have the same effect: freons, nitrogen oxides and sulfur oxides, methane, ammonia. But, nevertheless, not all carbon dioxide remains in the atmosphere: 50-60% of industrial CO 2 emissions end up in the ocean, where they are quickly absorbed by animals (corals in the first place), and of course they are also absorbed by plants–Let's remember the process of photosynthesis: plants absorb carbon dioxide and release oxygen! Those. the more carbon dioxide, the better, the higher the percentage of oxygen in the atmosphere! By the way, this already happened in the history of the Earth, in the Carboniferous period... Therefore, even a multiple increase in the concentration of CO 2 in the atmosphere cannot lead to the same multiple increase in temperature, since there is a certain natural regulation mechanism that sharply slows down the greenhouse effect at high concentrations of CO 2.
So all the numerous “scientific hypotheses” about the “greenhouse effect”, “rising sea levels”, “changes in the Gulf Stream”, and naturally the “coming Apocalypse” are mostly imposed on us “from above”, by politicians, incompetent scientists, illiterate journalists or simply science scammers. The more you intimidate the population, the easier it is to sell goods and manage...
But in fact, an ordinary natural process is taking place - one stage, one climatic epoch gives way to another, and there is nothing strange about it... But the fact that natural disasters occur, and that there are supposedly more of them - tornadoes, floods, etc. - is another 100-200 years ago, vast areas of the Earth were simply uninhabited! And now there are more than 7 billion people, and they often live where floods and tornadoes are possible - along the banks of rivers and oceans, in the deserts of America! Moreover, let us remember that natural disasters have always existed, and even destroyed entire civilizations!
As for the opinions of scientists, which both politicians and journalists love to refer to... Back in 1983, American sociologists Randall Collins and Sal Restivo, in their famous article “Pirates and Politicians in Mathematics,” wrote openly: “...There is no immutable set of norms that guide the behavior of scientists. What remains constant is the activity of scientists (and related other types of intellectuals), aimed at acquiring wealth and fame, as well as gaining the ability to control the flow of ideas and impose their own ideas on others... The ideals of science do not predetermine scientific behavior, but arise from the struggle for individual success under various competition conditions...”
And a little more about science... Various large companies often provide grants for so-called “scientific research” in certain areas, but the question arises - how competent is the person conducting the research in this area? Why was he chosen out of hundreds of scientists?
And if a certain scientist, “a certain organization” orders, for example, “a certain research on the safety of nuclear energy,” then, it goes without saying that this scientist will be forced to “listen” to the customer, since he has “well-defined interests,” and it is understandable , that he will most likely “adjust” “his conclusions” to the customer, since the main question is already not a question of scientific research–and what does the customer want to receive, what is the result?. And if the customer's result won't suit, then this scientist won't invite you anymore, and not in any “serious project”, i.e. “monetary”, he will no longer participate, since they will invite another scientist, more “amenable”... Much, of course, depends on his civic position, professionalism, and reputation as a scientist... But let’s not forget how much they “get” in Russia scientists... Yes, in the world, in Europe and the USA, a scientist lives mainly on grants... And any scientist also “wants to eat.”
In addition, the data and opinions of one scientist, albeit a major specialist in his field, are not a fact! But if research is confirmed by any scientific groups, institutes, laboratories, t o only then can research be worthy of serious attention.
Unless, of course, these “groups”, “institutes” or “laboratories” were funded by the customer this study or project...
A.A. Kazdym,
Candidate of Geological and Mineralogical Sciences, member of MOIP
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1,603 ViewsGlobal warming threatens to melt glaciers. The news keeps talking about the threat of disappearance of one or another ice river. In the meantime, until they melt away, you should hurry and see a selection of the most beautiful glaciers in the world.
1. Biafo Glacier, Pakistan
Thanks to its secluded location in the heart of the highlands of northern Pakistan, the Biafo Glacier has remained virtually untouched by civilization. The journey to the huge “Snow Lake” along the edge of the icy plain will take several days, which, due to the splendor of the surrounding flora and fauna, will not seem boring. It is better to go hiking if you are in good physical shape. Otherwise, there is a great possibility instead of contemplation pristine beauty nature, admiring only the earth under your feet.
2. Perito Moreno Glacier, Argentina
There are as many as 13 glaciers in the Lago Argentino National Park, but the Perito Moreno Glacier is considered the most beautiful of them. The icy river, which is 60 meters high, divides the high-altitude Lake Argentino into 2 parts: the Rich Sea and the Southern Sea. Making their way through the glacier along the canal, the waters of these seas gradually destroy it, and thanks to this tourists can admire the view of huge blocks of ice falling into the water. On the territory of the reserve you can meet guanacos, rhea ostriches and even the condor - the largest bird in the world.
3. Glacier Bay, Alaska
Glacier Bay is gigantic national park, which is located on the southeastern coast of Alaska and is protected by UNESCO. There are practically no walking tours in the reserve; glaciers are inspected from an airplane or helicopter. However, you can watch the sparkling ice without leaving the hotel, which is located right in the park. In addition, icebergs that have broken off from the edge of the glacier and rearing ice blocks can be admired by taking a cruise along the coast. In the surrounding waters of the reserve you can stumble upon whales, walruses and even dolphins, and the coastal forests are home to bears and deer.
4. Furtwängler Glacier, Tanzania
Since the beginning of the century, the glacier located almost at the equator has been gradually melting and, according to scientists, by 2020 it will completely disappear. Furtwängler is located at an altitude of more than 5000 meters, on the northern side of Kilimanjaro, near its summit
5. Pasterze Glacier, Austria
The largest of Austria's 925 glaciers, the Pasterze is also gradually disappearing and is predicted to be less than half its current size by 2100. In the meantime, this 9-kilometer-long, seemingly motionless river of ice slowly descends from an altitude of 3,500 meters to the foot of Mount Glosgrokner.
6. Vatnajokull Glacier, Iceland
Iceland's largest glacier makes up approximately 80 percent of the island's total ice cover, which gets its name from the frozen water. Its huge fields, riddled with cracks, stretch over 8,300 square kilometers. The cold beauty of the ice is rivaled by the lava frozen in the intricate curves of the nearby volcanic landscape. Favorite activities for tourists: descending into ice crevices, rock climbing on a glacier, snow rafting and swimming in the thermal springs of ice caves.
7. Yulong Glacier, China
Scientists have more than once predicted the disappearance of China's southernmost glacier, but systematic observations of its movement, which have been carried out since 1982, refute pessimistic forecasts: depending on climate fluctuations, the glacier retreats several hundred meters upward, then descends again. The lower boundary of the glacier is currently located at an altitude of about 4200 meters above sea level, and getting to it is not so easy due to the very rarefied air.
8. Fox and Franz Joseph Glaciers, New Zealand
The glaciers flowing like a frozen waterfall from the western slope of the Southern Alps come so close to the subtropical evergreen forests that their proximity seems completely unnatural.
9. Athabasca Glacier, Canada
Another rapidly melting glacier, considered the most beautiful in North America, has recently lost almost half of its volume. Currently it is only about 6 kilometers long. Such rapid melting has resulted in the fact that the glacier is constantly in motion and therefore it is strictly forbidden to walk along it alone, without a guide.
10. Antarctic
And, of course, the most ice and snow can be seen in Antarctica, which probably became the reason for the increased popularity of the continent due to global warming. If in the 90s 6-7 thousand people came here during the season, then last year the number of tourists reached 45,000, and therefore the number of incidents harming the ecology of the region increased. Therefore, quite recently, 28 countries conducting scientific activities in Antarctica signed an agreement to limit tourism to the mainland.
2016-06-22
