Study Notes

Glacial Systems - Introduction to The Glacial System

AS, A-Level
AQA, Edexcel, OCR, IB, Eduqas, WJEC

Last updated 22 Mar 2021

The glacial system consists of inputs, stores, transfers and outputs. Understanding the connections and relationships between the different components of the system helps indicate how a change in one component results in consequential changes throughout the system.


The main input to the glacier system is through precipitation in the form of snow. Ice and snow can also be inputted to the glacial system through avalanches which can occur both naturally and due to human activity in mountain areas. Inputs to a glacier result in accumulation.


The mass of ice within a glacier is a store that can be added to (accumulation) or lost (ablation). Material that is carried by the glacier is also known as a store.


The transfer is the movement of a glacier due to gravity, gradient and increasing accumulation at the glacier source. In mountainous areas this movement is much quicker than that of ice sheets, which are often on a flatter surface. The main movement is downhill although, unlike water, ice has the capacity to move uphill if the ice pressure behind is great enough, resulting in the over-deepening of glaciated valleys.


The main output is the loss of water vapour from the evaporation of water from the glacier’s surface. If, under certain circumstances, snow and ice converts directly to water vapour without going through the liquid water stage it is known as sublimation.

Another output is calving which is where blocks of ice break off at a glacier’s snout. Usually this occurs where glaciers end in lakes or the sea, but it can also occur when ice falls off the end of a hanging valley glacier.

The other main water output from a glacier is where water leaves the snout of the glacier in liquid form as meltwater streams.

All these outputs from a glacier’s ice store are known as ablation. Solid material leaving the glacier can also be included as an output. As a glacier retreats (melts towards its source), rocky material will be washed out of the glacier, known as moraine.

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