Do you know that our planet is eleven percent of its territory covered in ice? Yes, these white areas visible from space cover an area of over 16 million square kilometers. So, despite environmentalists worrying about global warming, the Earth is still largely icebound. They contain about two-thirds of all fresh water - and this is 25 million cubic kilometers of ice. Scientists estimate that if all of it melted, the level of the world's oceans would rise by tens of meters, which would lead to great destruction and the death of entire states. But what is a glacier? Can a snow slide watered with water be called that proud name? In this article, we will look at how glaciers form, how they live and where they die. We will consider the meaning of terms such as language, firn, moraine. We also learn how glaciers are classified according to various catalogs.
What is a glacier: definition
Encyclopedias, explanatory dictionaries, and textbooks describe the term differently. And equally incomprehensible. Here, for example, is such a definition: "The mass of terrestrial natural ice of atmospheric origin, which has independent movement caused by gravity." Let us try to explain in plain language what a glacier is. This is snow compacted under its own weight, which accumulates over years in areas with low temperatures (polar latitudes or altitudinal zoning), and then, increasing in volume, slides to other territories (in valleys, in the sea). If this explanation seems incomprehensible to you, then we will explain it more simply. There are areas where the air temperature is always below zero. Precipitation there falls in solid form: snow, hoarfrost, hoarfrost, the passage of cold clouds. Accumulating, they are pressed under their own weight, and a glacier is formed. He begins to live his own life, sliding his tongues or breaking off with icebergs.
Snow, firn, ice
In the mountains, it is often observed that white shining peaks rise above green valleys. But if winter came into its own in the upper reaches, this does not mean that glaciers have formed. The first snowball, like icing sugar that sprinkled peaks, is too light and fluffy. Due to its openwork structure, it is easily exposed to heat. In the afternoon or in the summer (if the matter is very high or near the poles of the Earth) fluffy snowflakes thaw. Then they freeze again. But this is not the old openwork stars. Snowflakes turn into solid balls - firn. This grain accumulates over the years. Under its own weight, the firn begins to flatten, changes its structure again. So we come to understand what a glacier is. The definition of this term refers precisely to the third, final phase of the conversion of solid precipitation.
Classification
People have long been interested in what glaciers are. Researchers have noticed that each of them has its own geophysical or hydrothermal features. Therefore, there was a need for the classification of glaciers. At first, there was a certain disagreement in cataloging. In some countries, morphological features were taken into account, in others, hydrothermal characteristics were the decisive criterion. Now there is a World Glacier Tracking Service. This authoritative international body determines what the glacier means and decides which group in the WGMS catalog it belongs to. However, a new project has been launched to classify these natural objects - GLIMS. The catalog of glaciers of the USSR is still used in our country.
Types of Glaciers
Depending on the region of formation, these hardened snow masses are divided into ground (cover), mountain and shelf. The first species occupies the largest area. Such glaciers formed near the poles. The largest is the Antarctic cover. Its area is more than 13 million square kilometers. In fact, the glacier covers the entire continent of Antarctica. The second largest area is the cover of Greenland - 2.25 million km 2. Mountain glaciers are also called alpine. They are formed in areas of altitudinal zonation. They are found not only in the Alps, but also in the Himalayas, the Caucasus and even in Africa (Kilimanjaro). But what about ice shelves? The shallow water of polar latitudes frozen to the bottom. Sometimes glacial tongues slide into the water and break off there, forming icebergs. They can migrate, carried away by the wind and current, many hundreds of kilometers from the place of birth. The largest iceberg in the world is located on the east coast of Antarctica. This is the Lambert Glacier. Its length is 700 kilometers.
Glacier structure
Specialists distinguish two areas in the snow mass: nutrition, or accumulation, and ablation. They are separated by the so-called snow line. Above it, the amount of solid precipitation exceeds the sum of evaporation and melting. And below the snow line, the glacier begins, albeit slowly, but to die. After all, the term “ablacio” is translated from Latin as demolition, withdrawal. You can also describe what a glacier and its structure are. This firn field is the area where snow passes its metamorphoses. Languages depart from him. Sliding down in an area with higher temperatures, they melt, feeding mountain lakes and streams. But since the tongues of the glacier have a gigantic mass, they squeeze a bed of earth, drive boulders in front of them, drag stones. Such break-in products are called moraines.
Glaciers in motion
The speed of movement of languages depends on many factors. Fundamental is the terrain. For example, in flat Antarctica, where low temperatures turn the entire continent into a huge firn field, the glacier grows only in height. The layer thickness in some places reaches almost five kilometers! But in the Alps, languages crawl at a speed of fifty meters a year. The fastest is the Columbia Glacier on the Alaska Peninsula. Its speed is truly amazing - twenty meters a day! Languages move along the trough valleys, which they themselves create by scraping the foot. Sometimes glaciers are limited only to the firn field: having occupied a car - depression on the northern spur of the mountain, the mass of snow just does not melt in the summer and "survives" until winter is already compressed.
What are pulsating glaciers
Sometimes the mass of snow does not move anywhere. Scientists call it "dead ice." But sometimes violent processes associated with the restructuring of the dynamic regime begin to occur inside the snow mass. In this case, the total mass of the glacier does not change. Friction on the bed causes crushing of blocks. And this causes periodic (pulsating) changes in the speed of advancement of languages. They begin to "flow" rapidly, causing destructive ice mudslides. There is a certain frequency of such sudden changes. Therefore, scientists and coined the term "pulsating glaciers." The frequency of such revolutionary changes may vary. For example, the Caucasian Kolka glacier pulsates approximately once every 50 years (1902.1969, 2002), and in the Pamir Medvezhy every ten years (1963, 73, 89).
