a) Outline the conditions under which glaciers are likely to retreat (5)

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The firn line of a glacier moving up the valley signifies that the glacier is retreating, and even though this may take place, it will still move forward down a valley. This retreat occurs when a glacier has a negative mass balance, which is where its outputs, such as sublimation, calving, blow-off, are greater than its inputs such as snowfall and avalanches. Short run seasonal fluctuations such as a decrease in snowfall would ring about a decrease in the level of accumulation and an increase in temperature would lead to an increase in ablation, as the higher temperature would facilitate the melting of the ice. These changes are likely to occur in the summer months and may result in inputs falling and outputs increasing, leading to a negative budget. This would cause the firn line along with the glacier to retreat. However, retreat may also occur in the long run, such as in a post-glacial period where global temperature increases are occurring. b) Examine the impact of retreating glaciers on the formation and modification of landscapes (20) When discussing the impacts of retreating glaciers, one must understand that glaciers are large and dynamic features that have a plethora of significant impacts on the surrounding landscape, which are clear in areas such as Iceland, and in much of the UK. Glacial retreat occurs when there is a negative mass balance brought on by accumulation being surmounted by ablation. The effects of this are more pronounced when the retreat takes place over a longer-term due to deglaciation, rather than just shirt-term seasonal changes. The retreat will result in the deposition of till by the glacier itself forming features such as moraines and drumlins and will also lead to fluvioglacial processes eroding the surrounding landscape and depositing debris. The importance of understanding these impacts is extremely relevant for modern times

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