What is a glacier?
So what exactly is a glacier? Seeing as I have never studied glaciers, the first thing that springs to my mind is vast amounts of ice in high up mountainous areas, or huge iced areas in the Arctic and Antarctic.
So what exactly is a glacier? Seeing as I have never studied glaciers, the first thing that springs to my mind is vast amounts of ice in high up mountainous areas, or huge iced areas in the Arctic and Antarctic.
As a student when studying for mt GCSEs, I found BBC bitesize was always a great place to start when looking for definitions, explanations, diagrams and videos. An easy way to learn, using step by step processes. Using BBC bitesize, an old text book and other various websites (listed at the end of the post) I have found out the following:
A glacier is made up of compact ice that forms over a long period of time in high up mountainous areas. The size of glaciers can vary from the size of a field to expanding for hundreds of kilometres long. Some glaciers can be thought as remnants from the last Ice Age, this was when ice covered nearly 32 percent of the land, and 30 percent of the oceans. Today however, glaciers take up about 10 percent of the total land area.
A glacier is made up of compact ice that forms over a long period of time in high up mountainous areas. The size of glaciers can vary from the size of a field to expanding for hundreds of kilometres long. Some glaciers can be thought as remnants from the last Ice Age, this was when ice covered nearly 32 percent of the land, and 30 percent of the oceans. Today however, glaciers take up about 10 percent of the total land area. Glaciers are seen as unique due to their ability to move and are often referred to as being ‘like rivers’ due to holding similar qualities such as:
- - Starting in highland areas
- - Having the ability to flow
- - Having distinctive cross profiles and long profiles
- - Having processes in which they erode highland areas but deposit in low land areas.
Up until 10,000 years ago, glaciers covered nearly the whole of the UK as a result of the last ice age (see image). Today, glacial erosion has played a significant part in the way in which our landscapes have formed. So how are glaciers formed and what are their processes?
The best way to explain how a glacier is formed is by the glacier system (also known as a glacial budget and is shown in the diagrams). This system is made up of inputs, storage, flows and outputs.
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| Basic diagram of glacial system |
Glaciers form when snow remains in one location long enough to transform into ice. Inputs come from precipitation (snow) and avalanches from the glacier sides. The majority of the snow falls in highland areas; this is known as the zone of accumulation where snow is stored. As snow continues to fall, layers build up with the underlying layers being compressed. This compression squeezes the air out of the snow resulting in ice formation. Over time this mass begins to slowly move downhill under the force of gravity. It is estimated that glaciers move between 7 and 10km per year. This movement (flow) causes the land to undergo erosion such as abrasion and plucking. In the lowlands, the glacier begins to slowly melt, known and ablation, and evaporation will take place to a certain extent. These are the glaciers outputs.
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| Advanced diagram of glacial system |
These processes can be very complex with a source stating:
'Usually inputs (accumulation) are likely to exceed outputs (ablation) near to the head of a glacier and in winter. Ablation will exceed accumulation in summer and in lower altitudes where temperatures are higher. If, over a period of time, the annual rate of accumulation exceeds ablation, then the glacier will advance. If ablation exceeds accumulation, the glacier will retreat'.
At present the majority of the world’s remaining glaciers are retreating.
Students can benefit from the links mentioned below and particularly BBC bitesize when trying to grasp what a glacier is and what their processes are. I feel group or class discussions can enhance a students understanding whilst reflecting on the key words (in italics) and their definitions. I think students would benefit by sketching and labelling the glacial system shown in the diagrams above, I have shown a basic and more advanced diagram, one for higher and one for lower years of study.
Key links:
Thx Emma ur work was sooo helpful
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