Depth to Bedrock

Bedrock is the solid rock that underlays the loose material (regolith). Just how far down the bedrock is an important metric. In some areas the soil is deep and fertile, while the bedrock forms outcrops in others. A look at a depth to bedrock maps will show that the Driftless is not like the surrounding areas.

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The map shows the buried path of the Wisconsin River, which at one time flowed from Portage to the Green Bay. This part is now under hundreds of feet of glacial till and invisible to the naked eye. A full description of the eastward flowing Wisconsin / Wyalusing river.

The Kettle Moraines of eastern Wisconsin are shown to be just that, piles of drift up to 300 feet high interspersed with small glacial lakes. These hills, even Holy Hill, are not the result of bedrock outcropping or the underlying bedrock, but are lateral moraines formed when two major glacial lobes sideswiped each other.

The Wisconsin River, which carried a lot of glacial outwash, was much deeper at one point, but has now been mainly buried under sand from glacial outflows. The bedrock in the last 30 miles of the river is 200-300 feet down. The impressive bluffs once overlooked a much lower river bed.

Other rivers stand out, especially the Yahara and Rock rivers in south central Wisconsin.