The Anatomy of a Glacier

Similarly to that of the last post, this one should also have come closer to the beginning of the blog as it is focussing on the anatomy of a glacier. 

There are two main parts to the glacier, they being the accumulation zone and the ablation zone.

Accumulation Zone

Ablation Zone

·         This zone is in the upper part of the glacier at higher altitudes. ·         More snow accumulates than is lost each year, with the lower layers of snow transforming into ice. ·         As the glacier is always in constant motion the ice in this zone flows down to lower altitudes. ·         The area of the glacier in lower altitude is known as the ablation zone. ·         The accumulation zone has three main layers, these are: o   Top layer – fresh snow o   Middle layer – snow that is transforming into ice (known as firn) o   Bottom layer - ice

·         Located in the lower part of the glacier at a lower altitude. ·         More snow is lost than accumulates. ·         Bare ice becomes exposed in this zone when snow melts away each summer.

Accumulation and ablation zones can be found in all glaciers, with there being a boundary that marks where one zone changes into the next. This boundary is known as the equilibrium line and is where accumulation equals ablation.

The end of the glacier is known as the terminus.

Many glaciers also have streams which flow from them. These streams are created from rain and meltwater which work their way from the surface of the glacier through small crevasses. Another way of water entering the glacier can be through moulins which are circular shafts that descend vertically from the surface into the glacier. Whichever way the water enters the glacier, it travels through cracks or tunnels down to the ground where it then flows through rock and ice, working its way into further tunnels that appear as streams at the end of the glacier. Occasionally, the areas in which the streams exit the glacier can form into large but thin ice caves (which have a high possibility of collapsing). Once these streams have left the glacier/ice cave they travel further to outwash plains, with the streams themselves often appearing milky due to fine sediment known as glacial flour (created by rocks carried along the bottom of the glacier grinding down other rocks). Outwash plains are large areas of glacial sediment such as gravel, sand and clay deposited by meltwater streams, with the smallest particles being located furthest away from the glacial snout. New streams are also able to sort and transport older sediment from previous streams and glacial activity, therefore sometimes carrying sediment further than the original glacial boundary. Outwash plains from large or previously large glaciers can grow to over 50 metres thick.

Although everything noted above is for my personal information, the diagrams could easily be used in a classroom to provide a colourful and informative visual diagram for students, with the table providing easily accessibly information on the accumulation and ablation zones.