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| Great image of ice wedge polygons from physicalgeography.net |
Well... not quite the post rate I'd expected after finishing Uni, but work and life take over and before you know it you've not posted anything in over a month! Before I get stuck in, I graduated last week with a 1st, something I am especially happy with as I had resigned myself to a 2:1 following an uncomfortable feeling after an exam. In other news, I’ve not seen the sun in what feels like months as Britain drowns in the longest intermittent downpour I have ever been subject to. I’m also seriously considering further study/ research; my graduation reminded me how much I miss it already! Enough about me... If I remember rightly, I promised an introduction to the periglacial environment. When I say environment in this context, I mean the specific climatic and geomorphological conditions to allow for a specific suite of processes to operate.
First, (as I'm sure @Dawnitoes will delight in reading) we'll talk about the word "periglacial". The word literally means "near a glacier" and on its inception that is exactly what the word was used for. However, since the processes and features seen in these areas surrounding glaciers were identified in other cold areas in the absence of a glacier, the term eventually evolved. “Periglacial” is now the word used to describe a set of zonal processes that occur in cold environments due to the presence of ice and snow and the repeated freezing and thawing of water. Certain azonal processes can also exhibit distinctive characteristics in periglacial areas. I've visited permafrost before in a previous article (however not formally introduced you... how rude of me). Permafrost – an area of perennially frozen ground – is responsible for many of the processes and landforms associated with periglacial areas; however it is not the defining characteristic of a periglacial area. There is likely to be an article on permafrost in the near future.
So, we have rather hand-wavey, vague explanation of the factors controlling periglacial environments without explaining any processes or resultant landforms associated with places you may term “periglacial”. Or have we? I mentioned in the paragraph above about “the repeated freezing and thawing of water”, which is probably the most important process when we consider most specific periglacial processes and landforms.
In these periglacial environments, the temperature fluctuates about the freezing point of water often diurnally (daily) at the ground surface; and annually (with the seasons) for deeper freezing and thawing. Seasonal snow accumulation and subsequent melting and the movement of groundwater towards a freezing front are also important water processes. As a general statement, these water/ ice processes result in weathering processes acting upon bare rocks and transport processes acting upon sediments.
As I write this, I’m debating whether to name and dissect specific processes and resultant landforms, or whether they warrant their own “brief introductions”... I have an idea. I’ll recommend a reference for you to read (if you wish) and then follow this up, starting with a post on periglacial weathering processes and formations, I’ll formally introduce you to permafrost, finishing with sediment movement processes and distinctive landforms. Anything I don’t catch in either of these will more than likely land in a final summary post...
For your reading, I recommend you read the following book; a comprehensive summary of the processes and landforms typical of periglacial environments:
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