- glaciers -A huge mass of ice slowly flowing over a land mass, formed from compacted snow in an area where snow accumulation exceeds melting and sublimation.
Glaciers are formed in high mountains or around the polar region. During the winter the snow piles up and the glacier grows. But during the summer some of the snow melts and evaporates. Year after year the snow piles up in layers. The increasing weight causes the snow crystals under the surface to become compact and turn into grainlike pellets called firn. At depths of 50 feet the firn is compressed further into dense crystals of glacial ice.
As years pass the slab of ice gets bigger and grows thicker and becomes too big to stand still. The ice starts to move down the hill. When the ice moves it is called a glacier.
During the summer some of the snow and ice melts but in some areas of the glacier the temperature doesn’t rise high enough to melt the snow and ice. Glaciers may also increase and decrease in size because of the changes in the climate around the glacier.
icebergs- A massive floating body of ice broken away from a glacier. Only about 10 percent of its mass is above the surface of the water.
Most icebergs come from glaciers that break off into the sea. Glaciers are formed in the polar regions where snow falls almost constantly. This snow does not get the chance to melt completely and the water that does melt turns into compacted ice. Most icebergs in the North Atlantic Sea are formed by the tidewater glaciers of Greenland. As the tide rises and falls it wears through the ice close to the sea and large chucks of ice break free and become icebergs. Some glaciers do not reach the ocean, but rather end in deep sided valleys known as fiords. Large pieces of ice break off the glacier into the fiords and travel down steam into the ocean. The largest icebergs on earth are found around Antarctica where huge chunks of ice as big as Rhode Island have been observed floating in the ocean around the continent.
Parts
The region near the head of the glacier where snow is converted to firn and then ice is called the zone of accumulation. The region near the foot of the glacier is called the zone of ablation; this is where ice is lost by melting, evaporation or calving (to make icebergs). Separating the accumulation zone from the ablation zone is the equilibrium line. The equilibrium line is located at the equilibrium line altitude (ELA).
Classification of glaciers
Glaciers are of four chief types. Valley, or mountain, glaciers are tongues of moving ice sent out by mountain snowfields following valleys originally formed by streams. In the Alps there are more than 1,200 valley glaciers. Piedmont glaciers, which occur only in high latitudes, are formed by the spreading of valley glaciers where they emerge from their valleys or by the confluence of several valley glaciers. Small ice sheets known as ice caps are flattened, somewhat dome-shaped glaciers spreading out horizontally in all directions and cover mountains and valleys. Continental glaciers are huge ice sheets whose margins may break off to form icebergs (see iceberg). The only existing continental glaciers are the ice sheets of Greenland and Antarctica, but during glacial periods they were far more widespread. Glaciers may be classified as warm or cold depending on whether their temperatures are above or below -10°C (14°F).
Classification of icebergs
Non-tabular:
- Dome: An iceberg with a rounded top.
- Pinnacle: An iceberg with one or more spires.
- Wedge: An iceberg with a steep edge on one side and a slope on the opposite side.
- Dry-Dock: An iceberg that has eroded to form a slot or channel.
- Blocky: An iceberg with steep, vertical sides and a flat top. It differs from tabular icebergs in that its shape is more like a block than a flat sheets
Famous glaciers
1.The largest glacier in Europe is the Jostedal Glacier. It covers about 300 sq. miles (780 sq. kilometers).
2.A notable glacier in Asia is the Muzart Glacier. It covers 1,036,000 kilometers (400,000 sq. miles), the size equal to the Rocky Mountains in the United States. It has the length of about 2,414 kilometers (about 1,500 miles). It has the width of 320 to 480 kilometers (about 200 to 300 miles). Major glaciers also cover the region in North America.
3.The largest and most famous glacier is Malaspina Glacier on Yakutat Bay in Alaska. It covers 2,176 kilometers (840 sq. miles). But the biggest glacier in the world is the ice sheet on Antarctica. This glacier covers 13 million sq. kilometers (about 5 million sq. miles). The second biggest glacier in the world is the ice sheet on Greenland. It covers 1.8 million sq. kilometers (about 700,000 sq. miles). It is over 2,700 meters in thickness (more than 9,000 feet). Right now a lot of the glaciers are shrinking because of global warming.
Animals
Penguins
- Penguins are one of the more famous animals that live on glaciers and icebergs. The Emperor penguin lives on the ice in Antarctica, even though it spends a lot of time in the water. Penguins mate and raise their young on land but hunt for fish in the cold Antarctic seas. Their sleek bodies are perfectly suited to swimming, and they have many adaptations such as a dense layer of feathers to conserve their body heat.
Seals
Seals are a sea mammal that lives on ice packs in the frozen seas in the Arctic. Like penguins, seals hunt in the cold seas but have their pups on top of the ice. Seals may gather on large icebergs or on the packed ice around land. Some species of seal such as the Weddell seal blows air under the ice to create air pockets to breathe from so that they can stay under the thick ice longer.
Polar Bears
Polar bears are one of the few mammals that lives on glaciers and ice in arctic regions. The polar bear hunts seals, fish and other sea life. Their thick fur, fat deposits and wide paws make them ideally suited to living in ice and snow.
