Broad geologic features can be seen underlying farm fields, forests, roads and towns. Geological forces have modified these landscapes for thousands of years, while human activity is a recent, but also significant agent of change. Blue and green represent bare soils with varying degrees of moisture. Pink and red indicate healthy pastures and forests.
Open water is black, while roads and towns are white and magenta.
The Mississippi River flows through a narrow valley between Davenport and Rock Island-Moline. Streaked deposits of wind-blown sand and silt cross the landscape between the Mississippi and its tributary, the Wapsipinicon River. The wide Missouri River valley in Fremont County was excavated by glacial meltwaters. Since then, the river has meandered from side to side, leaving the scour marks evident here. Today the river is confined to a narrow portion of its floodplain by engineered levees, but the Flood of '93 again covered much of the area between the bluffs.