Nebraska Soils Field Trip - Virginia Tech

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4th IUSS Soil Classification Conference <strong>Field</strong> Tour Guidebook Hitchcock Nature Center The Hitchcock Nature Center exists to develop and foster appreciation and understanding of the Loess Hills as a globally significant landform through land management, environmental education and lowimpact recreation. Acquired by Pottawattamie County in 1991, Hitchcock Nature Center (HNC) currently consists of 1274 acres located in the heart of the globally significant Loess Hills. The Loess Hills harbor some of the largest remaining prairie remnants in Iowa and provide refuge for plants and animals found nowhere else in the state. Hitchcock is open every day of the year for hiking, camping, picnicking, bird watching, snow sledding, star gazing, or simply enjoying nature. Hitchcock Nature Center is also the headquarters of two county-wide conservation programs: Environmental Education and Natural Areas Management. Hitchcock Nature Center 27792 Ski Hill Loop Honey Creek, IA 51542 Phone: (712) 545-3283 58
4th IUSS Soil Classification Conference <strong>Field</strong> Tour Guidebook Overview of the Loess Hills By Richard Lensch Soil Scientist (Retired) Iowa Loess Hills The loess hills of western Iowa are divided into two Major Land Resource areas-MLRA 107A and MLRA 107B. MLRA107A is located on the Northern Iowa drift plane and MLRA107B is located on the Southern Iowa drift plane. The Northern Iowa drift plane, which occupies Northwestern Iowa, was covered by the Tazewell ice sheet approximately 40,000 BP. Little modification of the landscape occurred between the recession of the early Wisconsin ice sheet and the beginning of Wisconsin loess deposition about 31,000 years BP. It is characterized by broad loess covered flats with glacial till at depths of 1 and 8 meters. In stark contrast to the Northern Iowa drift plane, the Southern Iowa drift plane is a much more mature landscape that is heavily dissected by geologic erosion. Erosion began on the Southern Iowa drift plane in Pre-Illinoian time, and is characterized by hills with narrower interfluves and steeper side slopes than the Northern Iowa drift plane. Loess thickness ranges from more than 22 meters to 2 meters on the Southern Iowa drift plane. Loess deposition started approximately 159,000 yeas BP on the Southern Iowa drift plane. The Loess Hills are comprised of three major layers. From oldest to youngest, the layers are known as the Loveland Loess, (120,000 to 159,000 years old), the Pisgah Loess (25,000 to 31,000 years old), and the Peoria Loess (12,500-25,000 years old). (1) Thickness of the loess, in MLRA 107B, ranges in from more than 22 meters at the bluffs to about 5 meters at the eastern boundary. As the loess thickness thins with the distance from the source area, sand content and coarse silt to fine silt ratios decrease, and clay content increases, within the solum. Soil solums show increased weathering and maturity as the distance increases from the source area. Erosion has exposed other geologic formations beneath the loess, such as glacial deposits of sand and gravel, glacial till, and paleosols. Limestone and shale bedrock can be observed in deep quarries along the western edge of the loess hills. A thin layer of volcanic ash can be seen in some road cuts. This ash layer is the result of eruption of a mega volcano near Yellowstone National Park in Wyoming more than 640,000 years ago. In MLRA 107B, gullies are an integral part of the landscape. Loess is eroded from the side hills and deposits this sediment in drainage ways and on floodplains. Many gullies can be many miles long and pose a serious problem. Some gullies in the Monona-Ida association, near the loess bluffs can be more than 100 feet wide, and as deep as 80 feet. Bridges and roads can collapse as the gullies widen restricting travel. 59 (1) U.S. Department of the Interior; U.S. Geological Survey Information Handout, July 1999. This page is http://pubs.usgs.gov/info-handout/loess/. Maintained by Eastern Publications Web Team. Last revised 8-18-99
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Soil Taxonomy Fine-loamy, mixed, ac
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Nebraska Soils Field Trip - Virginia Tech

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