Did you know that our planet is at eleven percent of its territory is covered by ice?Yes, these are visible from space, white areas cover an area of more than 16 million square kilometers.So, despite the alarm environmentalists who keeps talking about global warming, the Earth is still largely icebound.They contain about two thirds of all fresh water - and it is 25 million cubic kilometers of ice.Scientists have calculated that if all of it had melted, global sea levels would rise by tens of meters, which would lead to great destruction and loss of entire nations.But what is the glacier?Can a snow slide, poured water, called this proud name?In this article we will see how glaciers are formed, how they live and where they die.We consider the meaning of terms such as language, firn, Morena.And we learn how the glaciers are classified according to different directories.
What Glacier: determination
Encyclopedias, dictionaries and textbooks for different describe the term.And the same is not clear.For example, the following definition: "The mass of land ice outside of natural origin, which has the independent movement caused by gravity."Let's try to explain in accessible language, what the glacier.It is compressed under its own weight of snow that accumulates over the years in areas with low temperatures (Polar latitude or high-altitude zone), and then, an increase in the volume ramps up to other territories (in the valley to the sea).If this explanation seems incomprehensible to you, then it rastolkuem easier.There are areas where the temperature is always below zero.Precipitation there falls in solid form: snow, frost, frost, the cold clouds.Accumulating, they are compressed under its own weight, and is formed glacier.He begins to live his own life, or open the sliding tongues icebergs.
snow, firn ice
The mountains are often brought to see how over the green valleys rise up shining white peaks.But when winter came into its own in the upper, it does not mean that the glaciers were formed.First snow like icing sugar, priporoshit top, too light and fluffy.Due to its open structure, it is easily exposed to heat.During the day or in the summer (if it is very high or at the poles of the Earth), fluffy snowflakes to melt.Then again, they freeze.But this is not the old fishnet asterisk.Snowflakes are converted into solid balls - firn.This grit accumulated over the years.Under its own weight firn begins ivy again alters its structure.Here we come to an understanding of what the glacier.As for the definition of this term is the third, final phase of the conversion of solid precipitation.
Classification
People have long wondered what is glaciers.The researchers found that each of them has its own geophysical or hydrothermal features.Therefore, there is a need in the labeling ice.Initially, there was some inconsistency in cataloging.In some countries take account of the morphological features, other decisive criteria were hydrothermal characteristics.Now there is the World Service tracking glaciers.This authoritative international body defines what it means to the glacier, and decides to which group in the catalog WGMS it belongs.However, the new project on the classification of natural objects - GLIMS.Our country is still used catalog glaciers of the USSR.
Types glaciers
Depending on the area of education, the mass of hardened snow is divided into ground (coating), mining and offshore.The first type covers the largest area.These glaciers are formed near the poles.The largest is the Antarctic cover.Its area - more than 13 million square kilometers.In fact, the glacier covers the entire continent of Antarctica.The second place on the square is the cover of Greenland - 2.25 million km2.Mountain glaciers are also called Alpine.They are formed in the areas of altitudinal zones.There are not only in the Alps, but also in the Himalayas, the Caucasus and even in Africa (Kilimanjaro was).But the ice shelves - what is this?Frozen to the bottom of the shallow waters of the polar latitudes.Sometimes the glacial tongues slip into the water and there break off, forming icebergs.They can migrate, carried by wind and current, for many hundreds of kilometers from the place of birth.The largest iceberg in the world is located off the east coast of Antarctica.This is Lambert Glacier.Its length is 700 kilometers.
structure glacier
Experts identify in a snow mass two areas: nutrition, or accumulation and ablation.Their shared so-called snow line.Above her the amount of solid precipitation exceeds the sum of evaporation and melting.And below the snow glacier begins, slowly but die.After all, the term "ablation" is translated from Latin as demolition withdrawal.You can even way to describe what a glacier and its structure.This firn field - an area where the snow goes its metamorphosis.From him depart languages.Sliding down in the area with higher temperatures, they melt, feeding the mountain lakes and streams.But as the glacier tongue have a huge mass of land they squeeze box, driven in front of the boulders, rocks dragged.Such products are "running" are called moraines.
Glaciers in motion
Speed languages depends on many factors.Fundamental is the terrain.For example, in the plains Antarctica, where low temperatures turn the whole continent into a vast firn field, the glacier grows only in height.The layer thickness in some places reaches almost five kilometers!But the languages in the Alps slide at fifty meters a year.The fastest is the Columbia Glacier Alaska Peninsula.Its speed is truly amazing - twenty meters per day!Moving tongues of trough valleys, themselves and create, scraping bottom.Sometimes glaciers limited firn field: taking the car - on the northern spur of the hollow mountains, plenty of snow just does not melt in the summer and "survive" until the winter is already compressed.
What pulsating glaciers
times the mass of snow is not going anywhere.Scientists call it a "dead ice".But sometimes in the snow mass start happening turbulent processes associated with the restructuring of the dynamic mode.The total mass of the ice does not change.The friction of the bed is split blocks.This causes periodic (pulsed) changes in the rate of promotion of languages.They begin to "leak" rapidly, causing devastating ice and sat down.There is a certain frequency 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 Caucasus pulses approximately once every 50 years (1902.1969, 2002), and the Pamirs Bear - each decade (1963, 73, 89).
mass balance
This is the main characteristic of the glacier, in addition to its area, long tongue and speed.Mass balance - what is this?The glacier grows in the cold when it receives a large number of solid precipitation and reduced summer.A mass of snow, transformed into firn that fell from the previous surface in August until the end of the cold, the winter is called balance.Accordingly, the summer - this is how much melted ice from the vernal heat until the first snow.But the annual mass balance - the sum of accumulation and ablation.
