A glacier is a persistent body of dense ice that is constantly moving under its own weight. The “ Glacier” term originated from the French word glace (glah-SAY), which means ice. Glaciers are often called “rivers of ice”. Glaciers fall into two groups: alpine glaciers & ice sheets.
How Glaciers Form ?
Glaciers begin forming in places where more snow piles up each year than melts. After falling, the snow begins to compress or become denser & tightly packed. New snow falls and buries this granular snow. It becomes a dense, grainy ice called firn. As years go by, layers of firn build on top of each other. When the ice grows thick enough- about 50 meters (160 feet) – the firn grains fuse into a huge mass of solid ice. The glacier is so heavy & exerts so much pressure that the firn and snow melt without any increase in temperature. An ice sheet spreads out from its center. The different speeds at which the glaciers move, causes tension to build within the brittles upper part of the ice.
People and Glaciers
Glaciers provide people with many useful resources.
The most important resource provided by glaciers is freshwater. This melting ice of glaciers feds many rivers. One of the largest glaciers in the Himalayan Mountain, is the Gangotri Glacier. It is source of the Ganges River. The Ganges is the most important source of freshwater & electricity in India & Bangladesh. Electricity is created by dams & hydroelectric power plant along the Ganges. Water has been trapped in the glacier for so long, many people believe it has not been exposed to pollutants that liquid water is exposed to. Because of this some companies link glacial water to clean, fresh and taste.
Threats to Glaciers
1. The process called ablation means removal of snow, ice and moraine from a glacier or ice sheet. Ablation includes melting, evaporation, erosion and calving.
2. Earth’s average temperature has been increasing dramatically for more than a century. Glaciers are important indicators of global warming and climate change in several ways.
3. Melting ice sheets contribute to rising sea levels. As ice sheets in Antarctica and Greenland melt, they raise the level of the ocean. Tons of fresh water are added to the ocean every day.
4. Large additions of fresh water also change the ocean ecosystem. Different type of habitat are present in fresh water and salt water. Organisms, such as many types of corals, depend on salt water for survival. Some corals may not be able to adjust to a more freshwater habitat.
Sea life - corals
5. The loss of glacial ice also reduces the amount of fresh water available for plant & animals that needs fresh water to survive.
6. Glaciers near the Equator, such as those on the tropical island in South America are especially at risk. A few glaciers may actually be benefiting from global warming. Although winter temperature are rising, so is the amount of snowfall in areas like Pakistan’s Upper Indus River basin. Glaciers are growing quickly there.
If temperatures rose by 4c above pre-indistrial levels, which some predictions say is possible if the world fails to reduce greenhouse gas emissions quickly, then the sea level rise would be 6.5 meters from the Antarctic alone, not counting the contribution from Greenland & other glaciers.