Agenda - Parks and Recreation Commission - 04/10/1997

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APPENDIX A The Geology of Mississippi West Anoka County's geologic history is rich in glacial activity. The most important glacial movement to the present landscape formation of Mississippi West Regional Park was the Grantsburg sublobe (USDA, 1977). The Grantsburg sublobe extended to the northwest bom the southerly expanding Des Moines lobe. As the glacier proceeded it blocked the original Mississippi River channel, which mused the river to flow into the St. Croix River Valley. Eventually, the river began to shift southwesterly until it finally amved at its present course. The Mississippi River deposited sands and gravel across the landscape as its course migrated. Mississippi West Regional Park is located on these river-deposited sands. The Five Soil Forming and Community Typ.e Factors Parent material The parent material is the mineral base that exists upon which the soils form and the vegetation flourishes. The parent material of the soils at Mississippi West is outwash sands. In general, this parent material gives these soils a very low available water holding capacity and natural fertility. These sandy outwash soils are highly susceptible to wind.and water erosion if they are unvegetated. Climate The climate influences the development of the soils in many ways including depth of leaching due to excess precipitation. Vegetative types in this area can only thrive with a cemain temperature and/or rainfall patterns. The climate of Anoka County consists of hot summers and cold winters. The mean winter temperature is 13.3°F and the mean summer temperature is 67.6°F. Precipitation is the greatest in the summer where 21.5 inches is the average. This accounts for about 75% of Anoka County's annual precipitation. Biology Ail of the organisms that live in or on the soil influence its development. Vegetation strongly affects the formation of soil through subsoil to surface nutrient transport, left on the surface as residues or near the surface as roots. The native vegetation of the mainland is primarily tall prairie grasses, oak savannahs, and oak woodlands. The native vegetation on the islands and the shoreline is deciduous 33