|This map is compiled from a number of data sources of
The northern third of the state and some eastern counties were mapped by subtracting depth to bedrock as shown on the map of thickness of unconsolidated deposits. The thickness map was used as a mask to isolate portions of the digital elevation map. The isolated portions were then reduced by 0, 50, 100, or 200 feet as required. The resulting layers were then recombined to create the map above. More reliable data from published sources were overlain on top, superseding the estimated bedrock elevation.
The overall result is surprisingly seamless. Small-scale features in the digitally-estimated areas must be taken with caution, because small hills of glacial origin and some valleys cut entirely into glacial deposits may show up. Also, there may be artifacts at county lines and mapped boundaries of different drift depths. However, large features of substantial relief are almost surely real. For example, it's not clear from the unconsolidated-deposit map whether some areas of thick deposits in Barron, Shawano, and Marinette counties are moraines or extensions of nearby filled valley systems. Subtracting the drift thickness from the digital elevation reveals features so low they are certainly real valleys.
Created 1 November 2000, Last Update 1 November 2000
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