This simplified geologic map shows the general distribution of rock types underlying Minnesota's landscape. Some of the rocks are 3.6 billion years old- the oldest found so far in the United States. The map is modified from Morey, G.B., compiler, 1996, Geologic map of Minnesota, bedrock geology: MGS state Map Series S-20, scale 1:1,000,000. Digital compilation by R.G. Tipping and B.A. Lusardi.