Cover glaciers on the world map. How did glaciations appear and why did they move? Pole migration hypothesis

It is known that glaciers are such accumulations of ice that slowly move along the earth's surface. Sometimes the movement stops and a dead cluster forms. Some blocks are capable of passing many tens, hundreds of kilometers across the oceans, seas, inland.

There are several types of glaciers: continental-type covers, ice caps, valley glaciers, foothills. Cover formations occupy about two percent of the area of ​​ice formations, and the rest are continental species.

Glacier formation

What are glaciers and where do they occur? There are many factors that influence the formation of a glacier. Although this is a long process, it depends on the relief and climate whether the surface of the Earth will be covered with ice formation or not.

So what is a glacier and what does it take to form it? For it to begin to form, certain conditions are necessary:

1. The temperature should be negative throughout the year.
2. Precipitation should be in the form of snow.
3. A glacier can form at high altitude: as you know, the higher up the mountain, the colder it is.
4. The formation of ice is influenced by the shape of the relief. For example, glaciers can appear on plains, islands, plateaus, plateaus.

There are formations that can hardly be called mountain glaciers - they cover an entire continent. These are the ice of Antarctica and Greenland, the thickness of which reaches four kilometers. In Antarctica there are mountains, bays, pits and valleys - all covered with a thick layer of ice. And the island of Greenland is a huge glacier that covers the earth.

Scientists have proven that glaciers such as the Antarctic have existed on Earth for over 800,000 years. Although there is an assumption that the ice covered the continent millions of years ago, but so far, scientists have established that the ice here is 800 thousand years old. But even this date suggests that there has been no life in this part of the planet for many millennia.

Glacier classification

There are several classifications of glaciers, among which the main one is the division according to the morphological type, namely, depending on the shape of the glacier. There are cirque, hanging, valley types of boulders. In some areas of ice, several varieties are located at once. For example, you can find hanging and valley varieties.

It is possible to globally divide all accumulations by morphological type into mountain glaciers, cover, transitional ones. The latter are a cross between cover and mountain.

mountain views

Mountain varieties have a variety of forms. Like all types of ice accumulations, this type tends to move: the movement is determined by the slope of the relief and is linear. If we compare this type of formations with integumentary ones in terms of speed, then mountain ones are much faster.

Mountain glaciers have a strongly pronounced area of ​​feeding, transit and melting. The mineral is nourished by snow and water vapor, avalanches, and snow transport during a snowstorm. When moving, ice often descends into the melting zone: alpine forests, meadows. In these territories, the cluster breaks off and can fall into the abyss, intensively begins to melt.

The largest mountain formation is considered to be the Lambert Glacier, located in East Antarctica, with a length of 450 kilometers. It originates in the north in the International Geophysical Year valley and enters the Amery Shelf. Another long glaciers are formations in Alaska - these are Bering and Hubbard.

Mountain cover varieties

We have considered in general what glaciers are. When defining the concept of a mountain cover type, one immediately wants to pay attention to the fact that this is a formation of a mixed type. They were first identified as a separate species by V. Kotlyarov. The glacial formations of the foothills consist of several streams with different types of food. At the foot of the mountains, in the zone of foothills, they merge into a single delta. A representative of such formation is the Malaspina Glacier, located in southern Alaska.

plateau glaciers

When intermountain valleys overflow, at the moments of flow over low ridges, plateau glaciers are formed. And what are glaciers in geography? The definition of the concept of "plateau" is as follows - it is nothing more than a huge chain of islands that merge with each other and arise in place of the ridges.

Formations in the form of a plateau are found on the edges of Antarctica, Greenland.

Sheet glaciers

Integumentary species are represented by the huge shields of Antarctica, the area of ​​which reaches fourteen thousand square kilometers, and the formations of Greenland, the area of ​​which is 1.8 million km2. These glaciers have a flat-convex shape, independent of the relief. The formations are fed by snow and water vapor present on the surface of the glacier.

Cover glaciers move: they are characterized by radial movement, from the center to the periphery, which does not depend on the subglacial bed, where the breaking off of the ends mainly occurs. The detached parts remain afloat.

Scientists have long been trying to figure out what glaciers are and how they form. As a result of the study, it was possible to establish that the Greenland formation was frozen to the very foundation, and the lower layers were frozen with a rocky bed. In Antarctica, the connection between the platforms and the earth's surface is more complex. Scientists managed to establish that there are lakes in the central part of the formations under the ice. They are located at a depth of three or more kilometers. According to the famous scientist V. Kotlyarov, the nature of these lakes can be twofold: they can influence the melting of ice due to the internal heat. The theory of the emergence of lakes as a result of friction of glaciers on the surface of the earth during their movement is not excluded.

Classification of glaciers according to Alman

The Swedish scientist Alman proposed three classes of division of all existing world formations:

1. temperate glaciers. In another way, he called them thermal formations, in which the entire thickness, except for the upper layers, has a melting point.
2. Polar ice. These species are not subject to melting processes.
3. Subpolar. They are characterized by melting processes in the summer.

Avsyuk's classification

Our compatriot proposed another version of the classification. Avsyuk believes that it is most correct to divide glaciers according to the type of temperature distribution in the thickness of the formations. According to this principle, there are:

1. Dry polar species. At times when the temperature in the thickness is below that at which crystallized water melts, dry polar species are formed. Avsyuk refers to such formations on the territory of Greenland, Antarctica, on the mountains of Asia with a height of more than 6 thousand meters, where it is always cold, and even colder in the thickness of the ice than outside.
2. Wet polar view. In this form, in the summer, the temperature rises above zero degrees, and melting processes begin.
3. Wet cold glacier. It is characterized by temperatures above the average annual air temperatures, although they are both negative. Melting of ice is noted only on the surface, even at sub-zero temperatures.
4. Nautical. It is characterized by a temperature at zero in the region of the active layer.
5. Warm ice. Such species are located in the mountains, namely in Central Asia, on the Canadian archipelago.

Dynamic classification

When considering the topic "What are glaciers and what are they like," another question immediately arises: "Is there a division of formations according to the type of movement?" Yes, such a classification exists, and it was proposed by Shumsky, a Soviet glaciologist. This division is based on the main forces that cause the movement of formations: the spreading force and the runoff force. The latter is due to the curvature of the bed and the slope, and the spreading force is due to the sliding process. According to these forces, glaciers are usually divided into runoff blocks, which are also called mountain blocks: in them, the flow force reaches one hundred percent. Spreading formations are represented by ice caps and shields. They do not have any obstacles, so this species can spread in all directions.

The largest glaciers on our planet

It has already been said above what glaciers are in geography and how they are classified. Now it is worth mentioning the most famous glaciers in the world.

In the first place in terms of size is the Lambert Glacier, located in East Antarctica. It was found in 1956. According to preliminary estimates, the length of the formation is about 400 miles, and the width is more than 50 kilometers. This is about ten percent of the area of ​​the entire ice formation.

The largest glacier in the Svalbard archipelago is Austfonna. In terms of its size, it ranks first among all existing formations of the Old World - the area of ​​\u200b\u200bice is more than 8200 square kilometers.

In Iceland, there is a glacier, the size of which is one hundred square kilometers smaller - Vatnaekul.

South America also has a glacier, more specifically the Patagonian Ice Sheet located in Chile and Argentina. Its area is more than fifteen thousand square kilometers. Huge streams of water depart from the glacier, which created the lake.

At the foot of Mount St. Elias in Alaska, there is another giant - Malaspina. Its area is 4200 sq. km. But the longest ice formation located outside the polar zone is Fedchenko, located in Tajikistan. It is located at an altitude of six thousand kilometers above sea level. The glacier is so large that its tributaries exceed the size of the most powerful glaciers in Europe.

There is also an ice mass in Australia - these are Pastors. It is considered the largest formation in this country.

There are many different glaciers in the world, located in various parts of the world, including on warm continents. Many of them have a height of at least three thousand kilometers, and there are objects that are melting at an accelerated pace. It would seem that ice of this size should be only at the poles, but it is on every continent of the world, including in warm countries. Such a scatter of formations indicates the movement of ice and the fact that once the Earth was completely different.

Where can glaciers form?

Glaciers can form in mountains above the snow line. Glaciers can also form on continents and islands in polar latitudes.

What percentage of the hydrosphere is made up of glaciers?

Glaciers account for 1.8%.

What work do glaciers do on the Earth's surface?

Glaciers perform erosive work, leaving scratches, hollows and carrying with them huge masses of detrital material. When melting, glaciers perform accumulative work, leaving ridges, hills, filling the plains.

Find and show on the map areas covered by glaciers.

Antarctica, Greenland, the islands of the Arctic Ocean, Tibet, the Himalayas.

According to Figure 146, determine the boundary of the maximum distribution of icebergs.

The limit of the maximum distribution of icebergs reaches 520 S.l. In the Northern Hemisphere off the coast of North America, floating ice reaches 440 N.L.

Name the continents where permafrost is common.

Permafrost is found on all continents except Australia. It is widely used in Antarctica, Eurasia, North America.

Questions and tasks

1. How are glaciers formed?

Glaciers form in the polar regions and in the mountains, where the air temperature is low all year round. More snow falls here in winter than it melts in summer. With the accumulation of more and more portions of snow, it gradually compacts and turns into ice.

2. How are sheet glaciers different from mountain glaciers? What are the most glaciers on Earth?

Ice sheets that completely hide land areas with mountains and plains located on them are called integumentary glaciers. Mountain glaciers form only on the tops and slopes of mountains. More cover glaciers.

3. Why do solid glaciers move?

Ice is a solid but plastic substance. Therefore, glaciers move slowly - "flow". The lower layers of ice move under the pressure of the upper ones. Movement occurs from the center of glaciers to their marginal parts.

4. On the physical map of the world, give examples of islands and coastal areas that may be flooded when all glaciers melt.

In North America, the entire Atlantic coast of the United States, including Florida and the Gulf of Mexico, will sink into the water. Most of California will also be under water. In Latin America, it will flood the Argentine capital of Buenos Aires, as well as coastal Uruguay and Paraguay. Many parts of Europe will also be destroyed. The British Isles will disappear. Under water will be the Netherlands and most of Denmark.

5. Show the largest ice sheets on a physical map.

The largest ice caps are found in Antarctica, Greenland, Svalbard, Severnaya Zemlya, and the Canadian Arctic Archipelago.

6. What is permafrost?

Permafrost is rock solidified by frozen water.

7. Why are water pipes not buried beyond the Arctic Circle, and why are buildings built on piles - supports driven deep into the ground?

Permafrost sometimes thaws, rocks “float” and at the same time the foundations of buildings, pipelines, railways and roads are destroyed. Therefore, burying pipes and a conventional foundation in permafrost conditions are not safe.

8. Is there permafrost in the area where you live? How does it affect economic activity?

Permafrost has a great impact on human economic activity. It creates significant obstacles to earthworks, the construction and operation of various buildings, etc. Heated buildings erected on permafrost settle over time due to thawing of the soil under them, cracks appear in them, and sometimes they collapse. Permafrost also makes it difficult to supply water to settlements and railways. This required the development of special construction methods in permafrost conditions. Permafrost contributes to the swamping of agricultural lands, as a result of which additional reclamation work is needed, i.e., the removal of excess moisture from the fields. Of the positive factors, two can be distinguished: the creation of natural refrigerators for the storage of perishable products and the saving of fixing material in mines and mines.

Glaciers are an extraordinary miracle of nature that slowly moves along the surface of the Earth. This accumulation of eternal ice captures and transports rocks on its way, forming peculiar landscapes such as moraines and kars. Sometimes the glacier stops moving and the so-called dead ice is formed.

Some glaciers, moving a short distance into large lakes or seas, form a zone where a split occurs and, as a result, drifting icebergs.

Geographic feature (value)

Glaciers form in those 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 during the winter season and release it as melt water. Such waters are especially useful in the mountainous regions of the planet, where such water is used by people who live in areas where there is little precipitation. Also, the melt waters of glaciers are sources 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: integumentary (continental) and mountainous. Cover glaciers occupy 98% of the total area of ​​planetary glaciation, and mountain glaciers - almost 1.5%.

Continental glaciers are gigantic ice sheets located in Antarctica and Greenland. Glaciers of this type have flat-convex outlines that do not depend on the typical relief. Snow accumulates in the center of the glacier, and snow is spent mainly on the outskirts. Ice 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 of different shapes, which depend on their content. All glaciers of this type have pronounced areas of feeding, transportation and melting. Food is provided with the help of snow, avalanches, a little sublimation of water vapor and the transfer of snow by the wind.

The largest glaciers

The largest 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 indented with a large number of cracks. The glacier was discovered in the 1950s by the Australian cartographer Lambert.

In Norway (the Svalbard archipelago) there is the Austfonna glacier, which is the leader in the list of the largest glaciers in the Old Continent (8200 km2).

(Vatnajokull Glacier and Grimswad Volcano)

Iceland is home to 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 outgrowths.

Melting glaciers - causes and consequences

The most dangerous of all modern natural processes is the melting of glaciers. Why is this happening? Currently, the planet is heating up - this is the result of the release of greenhouse gases into the atmosphere, which are produced by mankind. As a result, the average temperature on Earth also rises. Since ice is the storage of fresh water on the planet, its reserves will sooner or later run out with intensive global warming. Also, glaciers are climate stabilizers on the planet. Due to the amount of ice that has melted, there is a uniform dilution of salt water with fresh water, which has a special effect on the level of air humidity, precipitation, temperature in both summer and winter seasons.

A glacier is natural ice formed over many years on land from compressed snow.
Where do glaciers form? If the ice is perennial, it means that it can exist only where the temperature does not rise above 0 ° C for years - near the poles and high in the mountains.

The temperature in the troposphere decreases with height. Climbing the mountains, we eventually find ourselves in an area where the snow does not melt either in summer or in winter. The minimum height at which this happens is called the snowline. In different latitudes, the snow line runs at different heights. In Antarctica, it descends to sea level, in the Caucasus it passes at an altitude of about 3000 m, and in the Himalayas - almost 5000 m above sea level.

The glacier is formed from many years of compressed snow. Solid ice can creep slowly. At the same time, it breaks on bends, forming an icefall, and drags stones behind it - this is how a moraine appears.

What happens to the snow that falls on the mountains above the snow line? On the slopes, it does not linger for a long time, but rolls down in the form of snow avalanches. And on horizontal sections, snow accumulates, compacts and turns into ice.

Ice under the pressure of the upper layers becomes plastic, like resin, and flows down into the valleys. With sharp bends, the glacier breaks, forming cracks. Where a glacier flows down a high step, a zone called an icefall appears. It is as different from a waterfall as a glacier is from a river. The river flows quickly, at a speed of several meters per minute. The glacier creeps very slowly: a few meters a year. The water in the waterfall falls continuously. And in the icefall, the ice, of course, falls, but rarely. Another block of ice can hang for more than one year before it collapses.

In the highest mountains of the world, the Himalayas, everything is gigantic. Such is the Khumbu icefall on the way to Everest.

The ice melts very slowly, so glaciers can sink far below the snow line, peacefully coexisting with lush mountain meadows. Melting, glaciers give rise to mountain rivers.

But the largest glaciers on Earth are not in the high mountains, but at the poles. There is no land at the North Pole. Therefore, glaciers formed only on the islands of the Arctic Ocean. For example, on the largest island of the Earth - Greenland. This glacier is comparable in size to all of Western Europe.
However, the Greenland Glacier is only the second largest on Earth. The largest is in Antarctica. Its area is almost twice the size of Australia and only half the size of Africa. The thickness of the ice here sometimes reaches 4 km. It is in these two glaciers that the main fresh water reserves of the planet are contained.

Sea ice only a few meters thick, pushed by wind and waves, piles on top of each other and forms hummocks. Overcoming them is sometimes no easier than a mountain icefall (a fragment of the painting by K.D. Friedrich “The Death of Nadezhda”).

Crawling to the ocean, the Antarctic glaciers do not stop, but continue to move forward, pushed by the masses of ice pushing from behind. When, under the influence of winds and waves, a block breaks off from the glacier and begins to float in the ocean on its own, they say that an iceberg has formed (translated from German - an ice mountain).

Do not confuse an iceberg with an ice floe. The thickness of the most powerful sea ice is 5-6 m. Iceberg is really a mountain. Its thickness can reach many hundreds of meters, and its length can exceed 100 km. An ice floe forms in the sea. This means that the temperature at least of its lower edge is never below -2°C. An iceberg is a piece of a glacier that arose during severe frosts. The temperature of Antarctic icebergs is up to -50-60°C. Therefore, they do not melt for years. The idea of ​​towing an iceberg to the Sahara as a source of drinking water does not seem so fantastic.

Or mountain valleys.

Glaciers on Earth occupy approximately 10% of the land. This is 16.2 million square meters. km, i.e. almost as much as Russia occupies. If all modern glaciers melted, then the level of the oceans and moraines would rise by 64 m!

Approximately 95% of all glaciers are located in the polar regions, and mainly in Antarctica - this world pantry of cold (Fig. 106). Under the influence of its enormous weight, the ice sheet of Antarctica slowly slides into the ocean, forming icebergs. They sometimes reach a length of 100 km or even more. Above the surface of the ocean, such a floating ice block protrudes by 500 meters, but its underwater part can be up to 3 km.

Glaciers slide along intermountain depressions at a speed in some cases from 1 to 5 m per day. Having reached the snow line, the glaciers melt, giving rise to mountain rivers.

In Russia, glaciers occupy approximately 0.3% of the area. They are found mainly on the islands of the Arctic Ocean: Novaya Zemlya, Franz Josef Land, Severnaya Zemlya, and also in the Caucasus Mountains. In total, there are several thousand large and small glaciers in Russia.

Glaciers and high mountain snows are of great importance for the national economy, because they feed many rivers. And in summer, when the need for irrigation of cotton and rice fields, orchards and vineyards is especially great, these rivers are the most full-flowing, since under the scorching rays of the southern sun the glaciers melt especially intensively at this time.

Such full-flowing rivers of Central Asia as the Amudarya and Syrdarya, as well as hundreds of smaller rivers and streams, owe their existence only to high-mountain glaciers.

The study of glaciers is of exceptional interest for science. That is why great work is being done in Antarctica, Greenland and other areas of modern glaciation.

Pictures (photos, drawings)

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