Iowa's
Sesquicentennial
by Jean Cutler Prior
In 1996 Iowa celebrated 150 years of statehood. Sesquicentennials are historical milestones, and comparisons between "then" and "now" are inevitable. Geological perspectives on 150 years of human history may seem like a mismatch of time scales. People tend to think of the landscape as a permanent, unchanging feature of our lives, with modifications during such a geologically brief span of time as being almost insignificant -- but that is not true. Geologists recognize that Iowa's floodplains, hillslopes, gullies, and karst regions are dynamic, naturally changing portions of today's landscape. People, however, are also part of the landscape, and their mechanized earth-moving ability also makes them a major force altering the land surface.
Photo by
George Hallberg.
In just 150 years, people have imprinted a variety of cultural patterns across the state's terrain. Glacial boulders stranded in Iowa thousands of years ago have been moved by generations of farmers from fields to fence rows (photo above). Plows and planters annually turn over the upper few inches of most of rural Iowa, loosening the soil in furrows to the forces of wind and rain. A grid of roads intersecting on one-mile squares helps us navigate the countryside. Hay is mowed and bailed, seasonally scoring Iowa's hillslopes with intricate webbed patterns (photo below). Dams and levees regulate the flow of water through the state's lowlands, while artificial ponds and reservoirs hold water in place among the rolling hills. Terraces are bulldozed into place across the steeper hillsides to slow the loss of soil and moisture from the land. Meandering river channels have been straightened and confined between narrow embankments, forcing rivers to erode deeper courses, in turn lowering local water tables and draining adjacent wetland. Miles of clay tiles and plastic tubing have been laid beneath acres of landscape to redirect infiltrating rainwater and hasten drying of the land surface. Deposits of non-renewable minerals, stone, sand and gravel that were geologically stored for thousands or millions of years have been mined and quarried from the earth. Urban lands are excavated and rearranged to suit builders and conform to legal regulations. The leftovers of our daily lives are buried in landfills. And the quality of one of our most basic needs -- the drinking water supplied by underground geologic strata -- can be compromised by this human activity, sometimes in unexpected ways and over long periods of time. In few other states having rural, dispersed populations does the impact of 150 years of human activity dominate the landscape as completely as it does here in Iowa.
Photo by
Drake Hokanson.