Lakes occupy the glacially scoured depressions in the bedrock. Lawrence and boreal forest regions due to the presence of white pine and red pine along with boreal tree species. There are also iron formation and metasediments. Middle Proterozoic bedrock includes basalt, rhyolite, gabbro, diabase, anorthosite, granite, sandstone, and shale. Soils are derived from a mantle of acid, cobbly and gravelly glacial till of variable depth.
Sandy loam is the predominant soil texture, along with loamy sands.
Soils of the outwash plains are sand. Fire dependence characterizes all these forest types. Jack pine is most prevalent in the two areas where the landscape is least dissected by small lakes, north of Vermilion Lake and within and north of the Sawbill outwash plain. White pine-red pine forests are most common in areas most dissected by lakes, probably as a result of partial fire protection. Heinselman's work indicated that major fires occurred during drought years.