Glaciers And Glaciations
Glaciers are made up of fallen snow that, after long time, is compressed into large, thick ice masses.
Glaciers form when snow remains in one location long enough to transform into ice. What makes glaciers is their ability to move. Because of their mass, glaciers flow like very slow rivers.
Glaciers occupy more less the 10% of the world's total land area, and most of them are located in Polar Regions like Antarctica and Greenland.
Glaciers are residues of the Ice Age, when ice nearly covered the 32% of the land, and 30% of the oceans.
An Ice Age can occur if cool temperatures are constants for long periods of time, allowing polar ice to advance into lower latitudes. Within the past 750,000 years, scientists realized that there have been at least eight Ice Age cycles, separated by warm periods (interglacial periods). Currently, the Earth is reaching the end of an interglacial period, so this means that in a few thousand years there will be another ice age. This is part of the normal climate variation cycle.
As said before, glaciers begin to form when snow remains in the same area for long periods of time, where enough snow accumulates to transform into ice. Each year, new layers of snow cover and compress the previous layers. This compression makes the snow to re-crystallize. Slowly, the grains grow larger and the air pockets between the grains get smaller, causing the snow to slowly compact and increase density.
After two winters, the snow turns into "firn" (firn is the middle state between snow and glacier ice). At this point, snow is half dense than water.
Glaciers live a dynamic existence. Many elements help the glacier to form and growth. When snow falls in the accumulation area, it adds to the glacier some mass. As the snow slowly turns to ice, the glacier increases in weight, forcing glacial movement. Down the glacier there is the ablation area, where most of the melting and evaporation occur. Between these two areas a balance is reached, so here the glacier is in equilibrium. If the equilibrium is disturbed, either by increased snowfall or even by excessive melting, the glacier moves at until he reaches its normal position.
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Glaciers live a dynamic existence. Many elements help the glacier to form and growth. When snow falls in the accumulation area, it adds to the glacier some mass. As the snow slowly turns to ice, the glacier increases in weight, forcing glacial movement. Down the glacier there is the ablation area, where most of the melting and evaporation occur. Between these two areas a balance is reached, so here the glacier is in equilibrium. If the equilibrium is disturbed, either by increased snowfall or even by excessive melting, the glacier moves at until he reaches its normal position.
Several features are common to most glaciers. The strength of the glacier's movement causes it to deform, sometimes creating huge cracks in the ice called crevasses, which may make travel across a glacier. Underneath the glacier, where the glacier's ice meets the ground, large amounts of rock and soil are ground up by the enormous weight of the glacier.
This hanging glacier above Lyman Lake in Washington State may look simply like a mass of snow, but the crevasses are evidence that it really is a glacier.
Glacial most common features are moraines, created when the glacier pushes or carries the rocky debris as it moves. These long, dark bands of debris are visible on top and along the edges of glaciers. Medial moraines run down the middle of a glacier, lateral moraines along the sides, and terminal moraines are found at the end (also called snout) of a glacier. Sometimes one glacier flows into another, also creating moraines.
Barnard Glacier shows several medial moraines. In this case, the thickest medial moraines occur where additional glaciers flow into Barnard Glacier.
Types Of Glaciers
Ice Sheets They are found only in Antarctica and Greenland. Ice sheets are huge masses of glacial ice and snow expanding over 50,000 square kilometers.
Ice Caps Ice caps are miniature ice sheets, covering less than 50,000 square kilometers. They form particularly in polar and sub-polar regions that are relatively flat and high in elevation.
Ice Fields Ice fields are similar to ice caps, except that their flow is influenced by the underlying topography.
Kalstenius Ice Field, located on Ellesmere Island, Canada, shows vast stretches of ice. The ice field produces multiple outlet glaciers that flow into a larger valley glacier. The glacier in this photograph is three miles wide.
Mountain Glaciers These types of glaciers develop in mountainous regions; the largest mountain glaciers are found in Arctic Canada, Alaska, in South America, the Himalayas and in Asia.
In this undated photograph, Variegated Glacier winds through the Saint Elias Mountains in Alaska, terminating near Yakutat Bay. An ice field is visible in the upper left hand corner of the photograph.
Cirque Glaciers Cirque Glaciers are named because of the "bowl" hollows they occupy, and they are found typically on high mountainsides, and they tend to be wider than longer.
Hanging Glaciers They are also called ice aprons; these glaciers approach to steep mountainsides. Like cirques glaciers, they tend to be wider than longer. Hanging glaciers are common in the Alps, where they often cause avalanches.
Do glaciers affect people?
Glaciers Provide Drinking Water People living in the city of La Paz, Bolivia, trust on glacial melting from a nearby ice cap to provide water during the significant dry spells that they experience. Even if parts of Japan receive huge amounts of snow, there are no glaciers. Because the Japanese must endure frequent droughts, scientists are examining ways to create artificial glaciers that could provide more water for people when the weather is dry.
Glaciers Irrigate Crops Some researchers have recently tried to spray carbon dust onto glaciers, hoping that the melting will provide water to the drought-stricken countries of India, Afghanistan, and Pakistan. However, the experiment proved to be too expensive, so they have left the idea. In Switzerland, farmers have irrigated their crops by channeling melt water from glaciers to their fields.
Glaciers Help Generate Hydroelectric Power Scientists and engineers in Norway, Canada and New Zealand have worked together to goal into glacial resources by using electricity that has been generated in part by damming glacial melt water.
Are glaciers dangerous?
Flooding Caused by a Glacier In Peru, in 1941, 6000 people were terrorized when a glacial lake suddenly exploded, flooding the town of Huaraz below it. Since then, another lake has formed at the base of the glacier, but engineers have created artificial channels to prevent future flooding.
Avalanches from Glaciers Ice avalanches from glaciers have been recorded in the Swiss Alps. In 1965 Switzerland was constructing a dam for a hydroelectric plant above the town of Mattmark. Without warning, a huge mass of ice from the tongue of Allalingletscher broke off. In few seconds, the avalanche rushed down the slopes and buried much of the construction camp, killing 88 workers.