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Tuesday, 7 December 2010

Dartmoor and Exmoor Ice caps


If there ever were true ice-caps on Dartmoor and Exmoor, maybe they would have looked like this.  This is the Barnes Ice Cap on Baffin Island -- widely interpreted as a last remnant of the Laurentide ice sheet.  There are some little glacier tongues around the edges, but they are not very prominent;  the terrain is that of an undulating plateau or hilly area, with radiating river valleys.  Note the dusting of snow, larger snowpatches coalescing towards the ice edge, and also quite large frozen lakes here and there.  This is a zone of continuous permafrost -- but this does not stop glacier thinning, and the Barnes ice Cap is on the way out because of global warming.

Close-ups of the ice cap surface show that it is made up of many thousands of ice layers, each one representing a year of snow accumulation.

At the beginning of a glacial episode, small ice caps like this probably develop widely across the landscape, gradually coalescing and then being incorporated into the ice sheet as it builds up and starts to override the landscape.

At the end of a glacial cycle, these small ice caps may persist in the high arctic, but around the fringes of the British - Irish ice sheet thy probably melted away very rapidly.

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