Tarns of the Lake District: Difference between revisions
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The typical characteristics of cirque tarns resemble a pudding bowl, some definitely more circular than others. This bowl will have a single deep point, usually in or near the centre, some of which are very deep for their size. A prime example of this is [[Blea Water]], just north of the [[Kentmere]] valley and west of [[Haweswater]] Reservoir. It has a depth of 63 metres (206 feet), almost twice the depth of [[Grisedale Tarn]] at 33 metres (108 feet). The next deepest is [[Red Tarn]] at 26 metres (85 feet), and [[Easedale Tarn]] at 22.5 metres (74 feet).<ref>Smith, ''Smaller Lakes and Tarns'', p.27</ref> The moraine can also affect how deep the tarn is, depending on how much debris was moved during the "ice action" of its excavation.
Cirque tarns do come in a variety of shapes and sizes, not all of these being the typical shape one would expect to see. Those that stand out, mentioned above, were formed because the land under the ice dome during the last glacial period, paired with the radial (outward) flow of ice, meant that certain geological processes made the shaping of them possible. There are upwards of 200 cirque type features, yet, one would be surprised to see that of this large number, only 19 hold water.<ref name="smith24"/> Some cirque basins did, historically, hold water but have now
At the end of the last glacial period, the landscape would have looked very different, scarred, barren, devoid of life, and the number of cirque tarns would have been greater. In the last 13,000 years, these have been reduced dramatically and lost to history. Yet the evidence of infilling is still very much apparent as seen at [[Blind Tarn Moss]] near [[Grasmere]], and at [[Dry Cove Moss]] near [[Weatherlam]],<ref>Smith, ''Smaller Lakes and Tarns'', p.36</ref> where the outline of the cirques now reveal a peaty wetland. It is only a matter of time before the tarns will all but disappear because of the same infill process. That is, unless human intervention disrupts that natural progression by damming or creating fishing ponds!
These mountainous tarns are unlike their lower altitude relatives found in the outlying fells (and various other locations in the northwest) where they look more like large ponds. While a number of these will be natural, others will be man-made, once serving different industrial purposes.
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