I always find it quite worry, or maybe daunting is a better word, when I realise there are many aspects of geography where my knowledge is weak or I know very little at all considering I aspire to be a Geography teacher. I nearly missed out periglacial processes and landforms out of my studies, partly because I haven’t studied these before and partly because I underestimated the amount of information there is associated to the topic: glaciation.
However are periglacial aspects included in this topic? Seeing as periglacial areas are those which are not actually glaciated but are exposed to very cold conditions. These freezing conditions result in intense frost action and the development of permanently frozen ground or permafrost.
Periglacial climates can be found in: northern Russia, Alaska and northern Canada and high mountainous areas such as the Alps.
Periglacial regions are subject to persistently low temperatures. Summers are short but can sometimes reach up to 15°C, winters however are long and temperatures remain well below zero and in some cases fall below -50°C at times.
So what is permafrost?
This is where ground remains frozen for two or more years. It is estimated that permafrost currently covers about a quarter of the Earth’s surface and can be up to 5,000 feet thick.
The active layer – this is the uppermost ground layer which thaws from the surface downwards in the summer. The thickness of this layer depends upon local conditions but can extend up to 4m deep. As the ice in this layer melts, large volumes of water are released however are unable to drain through the permafrost layer and the low temperatures do not encourage much evaporation, thus the surface becomes very wet. On some slopes, saturation of this upper layer encourages soil movement downslope. This periglacial process is known as solifluction.
There are three types of permafrost which are:
Continuous permafrost: is found in the coldest regions, reaching deep into the surface layers with little or no melting occurring in the upper layers.
Discontinuous permafrost: occurs in slightly warmer regions where the ground is not frozen to such great depths. Usually these frozen areas extend around 20-30m below ground surface. There are also gaps in the permafrost under rivers, lakes and near the sea.
Sporadic permafrost: is found where annual temperatures are around or just below freezing point. In these places, permafrost only occurs in isolated spots where the local climate is cold enough to prevent complete thawing of the soil during the summer.
For this particular area, I found an old GCSE book of mine very useful when extracting information. This is one of my favourite geography books that I own due to the high usage of diagrams and pictures it contains that helped get me through my geography GCSE. However it is no doubt quite dated by now, but I do believe texts books are very useful sources for information when in the classroom. When students are studying this, they should be able to do the following, using the links below:
• describe the characteristics of periglacial areas
• describe the characteristics of periglacial areas
• explain what permafrost is
• describe the location of past and present periglacial areas (may require internet access for detailed answers)
Links:
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