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The preservation of this soil implies that the ice has been nonerosive and frozen to the bed for much of that time, that there was no substantial exposure of central Greenland once the ice sheet became fully established, and that preglacial landscapes can remain preserved for long periods under continental ice sheets.

The great gap in the main quartzite range, a part of which is occupied by Devil's lake, was a narrows in a preglacial valley.

The course and relations of this stream suggest the following explanation: Before the ice came into the region, Skillett creek probably flowed in a general northeasterly direction to the Baraboo, through a valley comparable in size to the preglacial part of the present valley.

The preglacial valleys of this slope were obliterated by being filled during the glacial epoch.

When preglacial valleys were filled by the drift in spots only, the postglacial streams followed them where they were not filled, only to leave them where the blocking occurred.