Geomorphology: Geology and Ecological Diversity

Minnesota’s geologic history is also evident in the soils and plants that create today’s landscapes. The Ecological

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Classification System (ECS) uses biotic and environmental factors such as climate, geology, topography, soils, hydrology, and vegetation to map, study and classify ever more detailed levels of biological associations.

As a broad example, the Eastern Broadleaf Forest (EBF) Province covers nearly 12 million acres of the central and southeastern parts of the state. The land surface is largely the product of the Pleistocene glacial processes.

The northwestern and central portions have deposits 100-300 feet deep of glacial drift. Huge volumes of meltwater from glacial lakes cut deep valleys along the present course of the Minnesota, St. Croix, and lower Mississippi rivers. The southeast, which was not covered by ice in the last glaciation, experienced headward stream erosion as the Mississippi River valley deepened. This exposed Paleozoic bedrock creating its characteristic bluffs. In the Twin Cities area, channels of pre-glacial rivers cut through rock formations, which later filled with glacial till. Once the till settled, the chains of lakes that now meander through the Twin Cities formed in the depressions.

A wide variety of plant and animal species have adapted to this diverse array of landscape features. And this province is home to the majority of Minnesotans. Human induced changes through activities such as road building and row crop agriculture have become a very significant geomorphic force in more recent times. Managing this rich biological heritage while balancing the needs of an increasing human population will be a long-term challenge.