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Ice sheets do not appear to have covered the present land of the Southwest Region to any important extent during any of the major cold episodes of the Ice Age. In the Isles of Scilly, material deposited directly from a grounded ice sheet has been recognised and is thought to be Devensian (last cold phase) in age (Fig. 49). Various giant boulders derived from metamorphic sources are a notable feature of some localities on the North Devon coast, some of which appear to have come from Scotland. However, it is not clear whether they were transported to their present locations by a large ice sheet or by floating ice.

In spite of the lack of an actual ice sheet, the repeated cold episodes of the Ice Age must have had a considerable effect upon the weathering style of the bedrock, for example influencing the granite tors, mobilising material to move down slopes and changing drainage patterns and the surface blanket of soft materials.

FIG 49. Map showing the greatest extent of the last main (Devensian) ice sheet across England and Wales.