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<br />During the Wisconsin ice age, beginning some 75,000 years ago, massive glaciers pushed <br />into Minnesota carrying sands, gravels and rocks from far north with them.. Some 12,000 <br />years ago, the climate of Minnesota became warmer and drier. The glaciers began to melt <br />and as they melted, cracks formed and substantial rivers and streams of melt-water were <br />created. These flows deposit layers of gravel and sand to create the Anoka Sand Plain. Elk <br />River lies within this sand plain as is clearly evident by its very sandy soils and thick deposits <br />of pure sand and gravel. These sandy soils have defined vegetation types and agricultural <br />uses in the area,44 <br /> <br />The environmental setting of Elk River for past peoples has been defined not just by <br />geology, but also by climate, The climate of Minnesota: has experienced minor, but <br />important, variations. in the past 10,000 years, and the importance of these variations is <br />amplified in the Elk River area. Elk River lies within a transitional zone and currently sits on <br />the boundary between prairie, oak. savannah and decidu9us forest habitats. Relatively minor <br />shifts in temperature and wetness cause these habitats to shift, and the vegetation types of <br />Elk River have changed significandy in the past!S <br /> <br />I Date I Elk River Climate and Vegetation I Cultural Periods <br />10,000-6000 B,C. I Open forest with a mix of conifers and Paleoindian <br /> deciduous trees, and substantial sections of <br /> prairie. <br />/6000-2000 B,C. I Prairie during a warmer drier period. Archaic <br />- <br />2000 B.C. - A.D, Oak. Savannah and Deciduous Forest during a Archaic, Initial Woodland <br />300 cooler, wetter period. Some prairie may also <br /> have been present. <br />A.D.300-present Mixture of Oak. Savannah, Deciduous Forest Terminal Woodland, Early <br /> and Prairie. EuroAmerican, <br /> EuroAmerican. <br /> <br />The geology and changing climate of Elk River create limitations in modeling for <br />archaeological sites. The sandy soils and relatively flat terrain allow for and frequent change~ <br />in the course of rivers and streams and the placement of lakes. Changing climate has <br />brought with it changing vegetation. While we are reasonably certain that there have been <br /> <br />20 <br />