What are glaciers?

The glacier is a large, slowly moving ice river, made up of many layers of compacted snow. The speed of movement varies greatly depending on the ambient temperature, the depth of ice, the basic slope and other factors. Movement ranges from several meters per hour to several meters per century. Sometimes when the conditions are correct, glaciers experience an increase and accelerate their movement up to 100 times. When the glaciers of tension can be a danger to humans and induce avalanches of rocks and snow.

The glaciers can be found on each continent and in approximately 47 countries. Most mountains higher than 4,500 meters (14,800 ft) have them because the temperature tends to drop rapidly with altitude. There are two main categories of glaciers: alpine glaciers, mountains and continental glaciers, on a flat ground where it is very cold. Continental glaciers almost completely cover Greenland, parts of Iceland, North Siberia and Canada and most of Antarctica. About 70%of fresh water on the planet can only be found in the Antarctic ice surface.

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glaciers are present throughout the year, but differ in their melting speed. In order to qualify as a glacier to pack ice, they exist rather than seasonally. For reasons that are not entirely clear, the planet experienced several main ice ages in its history when glaciers spread to the south like New York, the US and Paris in France. So many glaciers accumulated that the sea level was reduced by 100 m (328 ft), opening large areas of land, such as the North Sea, Bering's Strait and connecting the New Guinea with Southeast Asia.

At one point of the distant past, about 700 million years ago, during the cryogenic period, some scientists believe that the crazy could be so serious than the whole planet was covered with an ice dish. This is called the hypothesis of Snowball Earth, the IS controversial, especially among scientists who doubt the geophysical feasibility of a completely frozen ocean. It is known that glaciers at this time were at this timeExtremely large and reached the equator in at least some areas. Interestingly, the first comprehensive multicellular organisms, Edicaran Biot, appear in a fossil record almost immediately after cryogenic glaciation.