As many people hear the word glacier they immediately think about the Titanic and how it sank because it ran into a glacier. What many people do not know is the history of glaciers. There are a couple different types of glaciers, for instance the type that the titanic ran into is a Tidewater glacier, which is a glacier that flows in the sea. There are also alpine glaciers which are glaciers that are found in the mountains, and there are Continental glaciers which are associated with the ice ages, and that covers most of the contents at one time; including Indiana. Glacier ice is the largest amount of fresh water in the world only second to the oceans as the largest reservoir of water total. Glaciers are found on every continent except Australia.
Glaciers are more or less permanent bodies of ice and compacted snow that have become deep enough and heavy enough to flow under their own weight. Glaciers require very specific climatic conditions. Glaciers develop where the temperatures are cold enough to allow the snow to accumulate and compacted. Most are found in regions of high snowfall in winter and cool temperatures in summer.
These conditions ensure that the snow that accumulates in the winter isn’t lost (by melt, evaporation, or calving) during the summer. Such conditions typically prevail in polar and high alpine regions. There are two main types of glaciers: valley glaciers and continental glaciers (Armstrong).
When it comes to the snow lasting all year long, it has to be enough that it will survive in the warmer months without melting. If a spot on the glacier does melt a little bit it is called a glacier fringe.
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On northern facing slopes it may survive all year, where if it is on a southern facing slope (in the north hemisphere) it may melt because of the sun. If the snow last just one melting season it is considered to be firm. Then the snow accumulates and compacts to become a glacier. The pressure created from the overlying snow compact’s the underlying layers, and the snow grains become larger ice crystals randomly oriented in connected air spaces. These ice crystals can eventually grow to become several centimeters in diameter (Armstrong).
As the air spaces in the ice decrease it shows that compression is continuing and the ice crystals are growing.
Sometimes the dense ice crystals can tend to look blue. When the glacier has pressure and the forces of gravity it will begin to move and flow outwards and downwards moving its own weight. Valley glaciers flow down valleys, and continental glaciers (ice sheets) flow outward in all directions from a central point. Glaciers move by internal deformation and / or by sliding at the base. Internal deformation occurs when the weight and mass of a glacier causes it to spread out due to gravity. Sliding occurs when the glacier slides on a thin layer of water at the bottom of the glacier.
This water may come from glacial melting due to the pressure of the overlying ice, or from water that has worked its way through cracks in the glacier (Armstrong).
When the glacier moves to effects it surroundings in a major way, they can dramatically change the surface area by erosion and the force and mass of the glacier itself. Glaciers erode the rock that is underneath it, and the weight of the glacier is so huge that it can form a valley in the rocks. The glacier pushes this earth and rock forward as it advances, almost like a conveyor belt, and dumps it to the side along the way or at the end of the glacier.
Tidewater glaciers are glaciers that flow into the sea. As the ice reaches the sea pieces break off, or ‘calve’, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous splash as the iceberg strikes the water. If the water is deep glaciers can calve underwater, causing the iceberg to suddenly explode up out of the water. The Hubbard Glacier is the longest tidewater glacier in Alaska and has a calving face over 10 km long (Wikipedia).
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From its source on Mount Logan in the Yukon territory, the Hubbard Glacier stretches 122 km to the sea at Yakutat Bay and Disenchantment Bay. It is the longest tidewater glacier in Alaska, with an open calving face over 10 km wide. Before it reaches the sea, Hubbard is joined by the Valerie Glacier to the west, which, through forward surges of its own ice, has contributed to the advance of the ice flow that experts believe will eventually dam the Russell Fiord from Disenchantment Bay waters (Wikipedia).
The Hubbard Glacier slide forward in May of 1986 blocking Russell Fiord creating “Russell Lake.” The glacier has continued to grow and advance for about a century.
The ice at the end of the Hubbard Glacier is about 400 years old, it takes that long for the ice to be the length of the glacier. It is routine for the glacier to have break offs called ice bergs about the size of 10 story buildings. Where the glacier meets the shore, most of the ice is below the water, and newly calved icebergs can shoot up creating quite a disturbance, so ships must keep their distance from it as they make their way up and down the coast.