R a G B R a I Consistent in Material and Size
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RAGBRAI Geo-pedia Day 1 Milestones What is loess? Loess (rhymes with bus) is wind-blown silt that is very R A G B R A I consistent in material and size. Loess is highly erodible when wet, but is surprisingly stable in vertical sections. Learn about the Land Loess is thickest near its source (the Missouri River) and thins in the predominant wind direction, in this case west to east. You’ll see some examples on the land- Sunday, July 19 scape in the first few miles of RAGBRAI (photo below). Start: Council Bluffs Day 1 Loess Hills/loess outcrops: 10 miles Loess terraces: 15.7 miles after Council Bluffs Sioux Quartzite erratic: 3.4 miles after Mineola West Nishnabotna River: 1.8 mi. after Henderson East Nishnabotna River: 8.2 miles after Emerson The origin of loess is usually attributed to glacial activ- Finish: Red Oak – 51 miles ity. Meltwater from glaciers carried abundant material that was deposited in river valleys. Three loess units are recognized in the Loess Hills of Iowa (oldest to young- Iowa Geo-books est): the Loveland, Pisgah, and Peoria. The Loveland Iowa’s Geological Past is associated with the older Illinoian glacial advance by Wayne Anderson, University of Iowa Press, 1998 (300,000 to 130,000 years ago) and the Pisgah and Peoria were deposited during Wisconsinan time (30,000 “The only authoritative overview of Iowa’s geologic re- to 10,500 years ago). The Peoria Formation loess is the cord… [Wayne Anderson’s] coverage is so current, com- prehensive, and authoritative that professionals as well most regionally extensive loess in Iowa and makes up as rock and fossil enthusiasts will each need a copy.” the greatest thickness of the Loess Hills. Brian F. Glenister, A.K. Miller Professor of Geology Iowa DNR – Geological and Water Survey What is a ‘glacial erratic’? Emeritus, University of Iowa 109 Trowbridge Hall Although glaciers are often romanticized as pure snow Iowa City, IA 52242-1319 and ice, they are actually very dirty and carry tons of Landforms of Iowa (319)-335-1575 www.igsb.uiowa.edu soil, stones, and boulders. When a glacier retreats, the by Jean C. Prior, University of Iowa Press, 1991 stones and boulders are usually left behind, scattered US Geological Survey across the landscape. Geologists call these rocks ‘gla- “Jean Prior writes about the glacial geology of Iowa Iowa Water Science Center cial erratics’ due to their random placement on the land. as if it’s an old friend. She knows and cares about her subject and explains Iowa’s geologic attractions with a 400 S. Clinton St. sure hand.” Iowa City, IA 52240 COVER PHOTO: A view looking east across the Missouri River (319) 337-4191 Valley in Monona County. Photo by Mark Engler. Rex Buchanan, Kansas Geological Survey http://ia.water.usgs.gov Like most years, you’ll begin RAGBRAI 2009 in the Missouri River Valley. Draining 1/6 of the United The Nishnabotna River is a States, the Missouri River flows for 2,300 miles before joining the Mississippi River at St. Louis. This tributary of the Missouri River. It makes it the longest river in North America. Like most rivers in Iowa, the Missouri is relatively young by mostly flows through SW Iowa as geologic standards, about 2 million years old. It was created by melt waters from the great continental two parallel streams, called the glaciers, ice sheets that repeatedly advanced into Iowa over the last 2.5 million years. The width of the East and West branches. Both valley, up to 17 miles in Monona County, attests to the huge volumes of water that the ancient branches are about 100 miles Missouri River carried. Today the wide, flat floodplain is prime agricultural land, with virtually long and 20 miles apart. From their confluence, unlimited supplies the Nish flows another 12 miles before join- of irrigation water ing the Missouri River. Sections of both just a few feet below branches have been straightened and the land surface. channelized (photo above). Although RAGBRAI Riding up and down the hills of SW Iowa, usually crosses some you might be surprised to observe how much portion of the Loess of the land is devoted to corn and soybeans, Hills landform region despite the steep hillslopes. In the first half of the every year, 2009 is 20th century, little attention was given to conser- unique in that the route vation, and intensive plowing turned over the soil crosses near the thick- with no consideration given to topography and est loess deposits, il- runoff. Soil erosion occurred at a massive scale lustrating their impres- during this time. Agriculture has come a long way sive relief. Near Council since then to reduce soil loss from cropped fields. Bluffs, loess thickness As you are pedaling across the landscape, note has been known to the many types of conservation practices used exceed 175 feet! Riders to conserve the soil. Common practices include will have numerous op- terracing contour planting (photo below), and con- portunities to see loess servation tillage practices, along with surrounding exposures on the first fields with buffer strips, field borders, and grass day while leaving Coun- waterways. Together, these practices serve to cil Bluffs, including a reduce erosion and protect one of Iowa’s most road cut only a few feet precious natural resources, its soil. from the route. ' USGS streamflow station Parks and Preserves About three miles after Mineola, if you look to the left, you’ll find a wonderful large glacial er- ratic of Sioux Quartzite (photo left). Sioux Quartzite was deposited as sand on the shore of an ocean that stretched from north-central Wisconsin to Arizona about 1.6 billion years ago. It is exposed in far northwest Iowa and adjoining regions of Minnesota and South Dakota. If you look closely, you’ll see that it gives many roads in western Iowa a distinctive pink hue. It is common as rocks and boulders in the glacial tills of western Iowa and can be identified by its uniform pink color and, when closely examined, the presence of rounded quartz grains. Printed on recycled paper. RAGBRAI Geo-pedia Day 2 Milestones Iowa Stream banks / health of a stream The shape and condition of stream banks can pro- R A G B R A I vide insight into the quality of the stream and the aquatic life it supports. Are the banks high crumbling Learn about the Land walls or gently sloping banks with grass, shrubs, and trees growing on them? You can tell much about the Monday, July 20 stream’s long-term stability by looking at the shape and condition of its banks. A stable bank is a sign of a stable stream (photo Start: Red Oak Day 2 right). All streams West Nodaway River: 8.2 miles after Stanton and rivers move Middle Nodaway River: 0.7 miles after Villisca within their floodplains, but East Nodaway River: 3.6 miles after Villisca a mature, stable Lake Binder: 1.5 miles after Corning stream will not Nodaway Lake Park: 1.8 miles after Fontanelle move very rapidly. Greenfield Lake Park: 4 miles after Fontanelle In Iowa, most streams naturally wind or “meander” Finish: Greenfield – 70 miles back and forth across their floodplains. Bank slough- ing, cut banks (shown below in photo of Nodaway River), and high-wall banks without trees or other For more information… plants are signs of bank instability. A sloping bank about Viking Lake, Nodaway River, and other surface covered with vegetation is more stable and indicates water bodies, along with how to improve watersheds a healthier water- or start an improvement project, visit: www.iowadnr. shed. Not only gov/water/watershed) do gently sloping banks offer bet- ter habitats for The Iowa DNR has many online interactive maps Iowa DNR – Geological and Water Survey wildlife near the available for Iowa’s natural and manmade resources. 109 Trowbridge Hall water’s edge, they An index for these maps is at: Iowa City, IA 52242-1319 (319)-335-1575 help to slow and www.iowadnr.gov/mapping/index.html www.igsb.uiowa.edu filter watershed runoff. Iowa’s oil exploration information can be found at: US Geological Survey www.igsb.uiowa.edu/Browse/oilex/oilex.htm Iowa Water Science Center 400 S. Clinton St. Iowa City, IA 52240 COVER PHOTO: The Swedish Heritage Cultural Center (319) 337-4191 in Stanton, Iowa http://ia.water.usgs.gov Today, you will see the landscape change from dominantly corn and soybeans to more extensive grasslands (photo right). Roughly two-thirds of Iowa was covered by grasslands prior to European settlement – that’s roughly 23 million acres! Much of it was tallgrass prairie, with short-grass prairie in some of the drier areas. Most of the grasslands you now see are farm fields enrolled in USDA’s Conservation Reserve Program (CRP). Farmers can choose to enroll their land into 10–15 year CRP contracts, and receive payments throughout the life of their contract. These grasslands hold and store carbon, reduce ero- sion, and slow storm water run-off, while at the same time providing vital habitat for wildlife. Wildlife species that you may see on these grasslands include whitetail deer, pheasants, quail, turkeys, bobolinks, meadowlarks and more! In all of Iowa’s his- tory only 133 oil exploration wells As you bike across the streams and rivers, you have been drilled in will find that many are artificially straightened, the state. Of these, or channelized. Channelization, or stream only three have en- bank straightening, removes the natural me- countered oil. Many anders in the stream path so that the stream geologists believe flows in a straight line.