Glaciers are one of the worlds’ most mysterious creations- slow moving and cold, their day to day changes can be microscopic while their effects on the environment, the weather, and the ecosystems around them are immense. The melting of glaciers due to global warming has influenced tidal changes, the salinity of the oceans, and changed global weather patterns more drastically than ever before. In this article we will delve deep into the geography of a glacier and what happens when they are gone.
What are Glaciers?
Glaciers are massive ice floes made up of layer upon layer of compacted snow. They can form on sea or land (or a combination of the two) and move very, very slowly- some only an inch or to per year. Glaciers are formed by snowfall that never melts and is packed together with other snowflakes, forming ice sheets that grow upon each other as the freezing temperatures continue. The weight of additional snow and ice on top of the existing layers causes an immense amount of pressure, forcing the layers to become harder and more compact. Glaciers often have layers of blue ice located at their bases- this ice contains no air because the pressure of the glacier has forced it all out. This cycle eventually forms a glacier that acts as a sort of frozen river, slowly but surely moving as the ice continues to grow and build.
Types of Glaciers
Glaciers are located all around the world but behave similarly no matter where they are- from the Andes to the Alps, Greenland to Africa, glaciers move and grow in the same circumstances and leave the same results behind.
Two types of glaciers have been categorized as alpine and continental; alpine glaciers form on or near a mountain and can be subtyped as a cirque (a bowl-shaped glacier near the top of a mountain), a valley (a glacier moving slowly down a valley, reshaping the landscape), a piedmont (the intersection and joining of two or more glaciers into one), or a tidewater (a glacier located on land and ending in the sea, often spawning ice burgs from its edges). Continental glaciers are typically bigger than alpine glaciers and are subtyped as an ice sheet (a glacier that covers a landform, for example in the Arctic), an ice cap (which can be seen on the tops of mountains), or an ice field (a glacier that covers part but not all of a landform).
All of these glaciers to some extent move- some faster than others. The kind of glacial movement that has been named is called ‘sliders’ or ‘creepers’; a slider is the type of glacial movement which describes the movement of the glacier sliding over a thin layer of water located underneath the glacier, and creeping is when the movement of ice crystals against each other at the base of a glacier cause movement because of the anatomy of the glacier- for instance how much it weighs, the pressure it is exacting on the earth below it, and what temperature it is. Most glaciers utilize both of these methods of moving to some extent, and the usual laws of gravity apply: heavier glaciers move faster than lighter ones and glaciers located on a steep mountainside will likely move faster than one on a more tempered plane, and the middle and sides of a glacier will move faster than the bottom is likely to.
This movement serves to carve and shape the geography of the land below the glacier, and as the glacier moves forward or recedes because of melting evidence of the glacier’s path is made visible. Through the slight melting and refreezing of the deep layers of the glacier the rocks and surface below are crushed, torn, and ground down. Steep valleys are carved by the movement of glaciers and, if they fill with melted water, can form fjords. Moraines are another common element left behind by a glacier- they are the piles of rock and assorted debris left behind from the moving or melting of a glacier. Other unique geographical formations are left in the retreat of a glacier allowing geologists and scientists to study the path and behavior of the glacier.
Glaciers will continue to fascinate geologists not only for their current states, but for what they can reveal about the past and the future. Weather anomalies can be detected in the ice of today’s glaciers, giving us clues as to how an older Earth has dealt with the kind of drastic climate change we are seeing in many parts of the world today.
Glacers. National Snow and Ice Center. http://nsidc.org/cryosphere/glaciers
National Geographic Education: Encyclopedic Entry, Glacier. http://education.nationalgeographic.com/education/encyclopedia/glacier/?ar_a=1