Ihe dị ka ijeri afọ 2.7 gara aga, lava basaltic wụsara site na cracks na ala nke oké osimiri oge ochie; ihe fọdụrụ nke nkume mgbawa a kpụrụ Canadian Shield na n'ebe ugwu ọwụwa anyanwụ Minnesota. Mgbọrọgwụ nke ugwu mgbawa ndị a na ihe omume nke oké osimiri Precambrian kpụrụ Iron Range nke ebe ugwu Minnesota. Mgbe oge nke mgbawa ugwu nke 1.1 ijeri afọ gara aga, ọrụ geological nke Minnesota dịwanye ala, na-enweghị mgbawa ugwu ma ọ bụ ugwu ugwu, ma na-enweghị oke osimiri ugboro ugboro, nke hapụrụ ọtụtụ ọkwa nke sedimentary sedimentary. N'oge na-adịbeghị anya, ice sheets dịkarịa ala otu kilomita na-emebi ala ọdịda anyanwụ nke ala ma kpụọ ala ya.
Afọ 12,000 gara aga