What is a glacier? Pulsating glaciers. Where are the glaciers and how are they formed?

Did you know that our planet is covered with ice by eleven percent of its territory? Yes, these white areas visible from space occupy an area of more than 16 million square kilometers. So, despite the worries of ecologists, who talk about global warming, the Earth is still largely icebound. They contain about two thirds of all fresh water - which is 25 million cubic kilometers of ice. Scientists have calculated that if all of it melted, the level of the world's ocean 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 this 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 such terms as language, firn, moraine. And we'll find out how glaciers are classified according to different catalogs.

What is a Glacier: Definition

Encyclopedias, explanatory dictionaries and textbooks describe this term in different ways. And equally incomprehensible. For example, this definition: "The mass of terrestrial natural ice of atmospheric origin, which has an independent movement, caused by gravity." Let's try to explain in an accessible language what a glacier is. This snow is compressed under its own weight, which accumulates over the years in areas with low temperatures (polar latitudes or altitude zonality), and then, increasing in volume, it slides into other territories (into valleys, into the sea). If this explanation seems incomprehensible to you, we will explain it more simply. There are areas where the air temperature is always below zero. Precipitation there falls out in a solid form: snow, frost, hoarfrost, 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 icebergs.

Snow, firn, ice

In the mountains it is often observed how the snow-white shining peaks rise above the green valleys. But if the winter has entered its rights in the upper reaches, this does not mean that the glaciers were formed. The first snowball, like powdered sugar, powdered the top, too light and fluffy. Due to its openwork structure, it easily undergoes heating. Day or summer (if it happens very high or at the poles of the Earth) fluffy snowflakes melt. Then they freeze again. But this is not the old openwork stars. Snowflakes turn into solid balls - firn. This grains accumulate over the years. Under its own weight firn begins to spit, again changes its structure. So we came to understand what a glacier is. The definition of this term refers specifically to the third, final phase of the transformation of solid sediments.

Classification

People have long been interested in what glaciers are. The researchers noticed that each of them has its own geophysical or hydrothermal features. Therefore, there was a need for classification of glaciers. At first there was a certain disparity in cataloging. In some countries, morphological features were taken into account, in others the hydrothermal characteristics were the decisive criterion. Now there is the World Glacier Tracking Service. This authoritative international body determines what the glacier means, and decides which WGMS catalog group it belongs to. However, a new project has been launched to classify these natural objects - GLIMS. Catalog of glaciers of the USSR is still used in our country.

Types of glaciers

Depending on the region of formation, these masses of hardened snow are divided into land (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 place in the area is occupied by the cover of Greenland - 2.25 million km ² . Mountain glaciers are also called Alpine glaciers. They are formed in the areas of altitude zonality. They are found not only in the Alps, but also in the Himalayas, the Caucasus and even in Africa (Kilimanjaro). Well, the ice shelves are what? Frozen to the bottom of the shallow waters of the polar latitudes. Sometimes glacial tongues slip into the water and break off there, forming icebergs. They can migrate, carried away by the wind and current, for many hundreds of kilometers from their birthplace. The largest iceberg in the world is located on the eastern coast of Antarctica. This is the Lambert Glacier. Its length is 700 kilometers.

Structure of the glacier

Specialists distinguish two areas in the snow mass: nutrition, or accumulation, and ablation. They are separated by the so-called line of snows. Above it, the amount of solid precipitation exceeds the sum of evaporation and melting. And below the snow line the glacier begins, even slowly, but to die. After all, the term "ablazio" is translated from Latin as demolition, taking away. It is also possible to describe what a glacier and its structure are. This firn field is the area where the snow passes its metamorphosis. Languages leave from him. Sliding down, in an area with higher temperatures, they melt, fueling mountain lakes and streams. But since the tongues of the glacier have a gigantic mass, they squeeze out a bed of earth, drive boulders before them, drag stones. Such products "break-in" are called moraines.

Glaciers in motion

The speed of the movement of languages depends on many factors. The main thing is the terrain. For example, in the lowland Antarctica, where low temperatures transform the entire continent into a huge firn field, the glacier grows only in height. The thickness of the layer in some places reaches almost five kilometers! But in the Alps, the languages slip at a speed of fifty meters per year. The fastest is the Columbia glacier on the Alaska Peninsula. Its speed is truly amazing - twenty meters a day! Languages are moving along the trough valleys, which they themselves create, scraping the bottom. Sometimes glaciers are limited only to the firn field: after occupying a depression on the northern spur of the mountain, the mass of snow simply does not melt in the summer and "lives out" to the winter already compressed.

What is glacier pulsating

Sometimes the mass of snow does not move anywhere. Scientists call this "dead ice". But sometimes, turbulent processes begin to occur inside the snow mass associated with the restructuring of the dynamic regime. However, the total mass of the glacier does not change. Friction about the bed causes crushing of lumps. And this causes periodic (pulsating) changes in the speed of language advancement. They begin to "leak" swiftly, causing destructive ice mudslides. There is a certain periodicity of such sudden changes. Therefore, the scientists came up with the term "pulsating glaciers". The frequency of such revolutionary changes can be different. For example, the Kolka glacier of the Caucasus pulsates about once every 50 years (1902, 1969, 2002), and on the Pamir Bear - every decade (1963, 73, 89).

Mass balance

This is the main characteristic of the glacier, in addition to its area, the length of the languages and the speed of movement. The balance of mass is what? The glacier grows in cold weather, when it receives a large amount of solid precipitation, and decreases in the summer. The mass of snow, which turned into firn, dropped from the previous surface in August to the end of the cold, is called the winter balance. Accordingly, the summer is how much ice melted from the spring heat to the first snow. Well, the annual mass balance is the sum of accumulation and ablation.