| Loess Hills | |
|---|---|
 Loess Hills east ofMondamin, Iowa. | |
 Interactive map of Loess Hills | |
| Location | WesternIowa andMissouri, EasternNebraska andKansas, U.S. |
| Coordinates | 41°48′05″N95°59′42″W / 41.8013°N 95.995°W /41.8013; -95.995 |
| Designated | 1986 |
TheLoess Hills are a formation of wind-depositedloess soil in the westernmost parts ofIowa andMissouri, and the easternmost parts ofNebraska andKansas, along theMissouri River.
The Loess (/ˈloʊ.əs/,/ˈlʌs/, or/ˈlɛs/) Hills are generally located between 1 and 15 miles (2 and 24 km) east of theMissouri River channel. The Loess Hills rise 200 feet (60 m) above the flat plains forming a narrow band running north–south 200 miles (320 km) along the Missouri River.[1] These hills are the first rise in land beyond thefloodplain, forming something of a "front range" for Iowa, and parts of Missouri and Nebraska adjacent to the Missouri River. The Loess land formations of Iowa extend north into South Dakota and is a feature of three state Parks in South Eastern South Dakota. Union Grove State Park, Newton Hills State Park and Blood Run State Park.
During thelast Ice Age,glaciers advanced into the middle of North America, grinding underlying rock into dust-like "glacial flour." As temperatures warmed, the glaciers retreated and vast amounts of meltwater and sediment flooded theMissouri River Valley. The sediment was deposited on the flood plain, creating hugemud flats. When meltwaters receded, these mud flats were exposed. As they dried, the fine-grainedsilt was picked up by strongprevailing westerly winds. Huge dust clouds were moved and redeposited over broad areas. The heavier, coarser silt was deposited close to the Missouri River flood plain, forming vastdune fields. The dune fields were eventually stabilized by grass. Due to the erosive nature of loess soil and its ability to stand in vertical columns when dry, the stabilized dunes were eroded into the corrugated, sharply dissected bluffs we see today.
The dominant features of this landscape are "peak and saddle" topography, "razor ridges" (narrow ridges, often less than 10 feet (3 m) wide, which fall off at near ninety-degree angles on either side for 60 feet (18 m) or more), and "cat-step" terraces (caused by the constant slumping and vertical shearing of the loess soil). The soil has a characteristic yellow hue and is generally broken down into several units based on the period of deposition (Loveland, Pisgah, Peoria). Loess is known locally as "sugar clay" because it can be extremely hard when dry, but when wet, loses all cohesion. The Loess Hills of Iowa are remarkable for the depth of the drift layer, often more than 90 feet (27 m) deep. The only comparable deposits of loess to such an extent are located inShaanxi,China.[1]
Today, the hills stretch from theBlood Run Site in South Dakota in the north toMound City, Missouri in the south. Loess topography can be found at various points in extreme eastern portions of Nebraska and Kansas along the Missouri River valley, particularly near the Nebraska cities ofBrownville,Rulo,Plattsmouth,Fort Calhoun, andPonca, and the Iowa cities of Hamburg and Sidney. Southeastern South Dakota has three state parks that feature the loess formations: Union Grove State Park, Newton Hills State Park and Blood Run State Park, all of which are south of Sioux Falls. The Big Sioux River separates the South Dakota Loess Hills from the Iowa Loess Hills; in South Dakota, the Loess Hills follow the eastern edge of Brule Creek. The hills are usually no more than 200 feet (61 m) above the Missouri River bottoms. However, in some areas, such as Murray Hill in Harrison County, Iowa, the Loess Hills can rise over 350 feet (110 m) above the adjacent Missouri River floodplain.[2]
The Loess Hills have abundant oak-hickory hardwood forests and some of the last remaining stands ofprairie grass in the region. The invasion of prairie and oak savanna areas by woodland species such as red cedar (not native to the Hills) is threatening the stability of the fragile soils, as well as diminishing the native ecosystems found there. The areas of native prairie comprisebig bluestem andlittle bluestem,Indian grass,sideoats grama, andforbs such asyucca,pasque flower (the South Dakota state flower) andlead plant (false indigo). Many of the prairie species found in the Loess Hills are outside of their normal range of distribution, with plants like spiny-leafed yucca and prickly pear cactus being more common further west, in theSandhills of central Nebraska. In 1984, a previously undiscovered fern, the Prairie Moonwort, was discovered in the Hills and is thought to be endemic to the Hills.
Common fauna of the modern Loess Hills includewhite-tail deer,coyote,wild turkey,badger,bobcat,red andgray fox,ringneck pheasant,bobwhite, andred-tailed hawk, some of which were introduced or encouraged by Euro-American settlers. Woodland species are also on the rise in the Loess Hills as the suppression of fire has led to an increase in habitat for forest-dwelling species. Fauna more typical of the pre-settlement Loess Hills, such as theprairie rattlesnake,great plains skink,plains pocket mouse,ornate box turtle andspadefoot toad, are becoming rare and even endangered due tohabitat fragmentation as a result of increased development and suppression of fire in prairie remnants and oak savannas. Species such as bobcat have been rebounding, andmountain lions have been recorded in Southwest Iowa in the last decade. Historically, fauna also includedAmerican bison,prairie chicken,mule deer,elk, andgray wolf; these were extirpated by the late nineteenth century.
The Missouri River valley had historically been a major migration corridor for birds, however, the channelization of the river and destruction ofwetlands has led to a marked decline. The corridor still boasts one of the best areas to view raptor migrations on the continent. As air masses move off the Great Plains, they sink into the Missouri River valley. The prevailing winds across the floodplain then hit the sharp rise of the Loess Hills, creating thermal updrafts that raptors use to make their way to and from breeding grounds. Raptors can often be viewed forming "kettles", where many birds will create a funnel-like formation as they utilize the same thermal. Typical species found during the months from September to December includered-tailed hawk,sharp-shinned hawk,peregrine falcon,ferruginous hawk,Swainson's hawk,Cooper's hawk,osprey,northern harrier,American kestrel, andbald eagle. In all, 20 species of raptor have been identified in a single season since theHitchcock Nature Center HawkWatch started, with a record count of 16,000 birds in one season in 2005.
Broken Kettle Grasslands Preserve in the northern Loess Hills is home to Iowa's only population of nestingblack-billed magpies and home to the last remaining known population of prairie rattlesnake in Iowa.[3]
The Loess Hills Scenic Byway affords many scenic views fromWestfield, Iowa, and toHamburg. While much of the landscape is held in private ownership, thousands of acres of public land exist in state and county parks, wildlife areas and preserves.The Nature Conservancy also owns several preserve areas in the Hills which are open to the public, including Broken Kettle Grasslands Preserve—the largest contiguous tract of native prairie left in Iowa.[4] TheLoess Hills State Forest is located in west-central Iowa inHarrison andMonona counties. It comprises four units totaling 10,600 acres (43 km2), and offers hiking, backpacking, picnicking, and fishing opportunities. Preparation Canyon State Park, located nearPisgah inMonona County, is a less developed park in the middle of the Loess Hills State Forest. It has 344 acres (1.4 km2) including what was once the Mormon village ofPreparation. Backpacking trails lead to hike-in campsites. Two major state parks anchor the north and south end of the range—Waubonsie in the south and Stone in the north, both offer camping and a variety of other amenities.Hitchcock Nature Center is operated by thePottawattamie County Conservation Board and features a lodge with raptor viewing platform and observation tower, from which one has striking views of the Hills, theMissouri River valley, and the skyline of downtownOmaha, Nebraska. Hike-in camping is also available at this location.TwoNational Natural Landmarks are located in the Loess Hills. The Little Sioux/Smith Lake Site contains 2,980 acres (12 km2) and is perhaps the best example of the unique topography produced by large deposits of loess soil. The 7,440-acre (30 km2) Turin Site of the Loess Hills National Natural Landmark is located just outside Turin and also contains the Turin Man prehistoric archeological site.[5]
The Loess Hills have a rich archaeological heritage. The hills aroundGlenwood, inMills County, were inhabited by theGlenwood culture, an eastern extension of the Nebraska Phase of theWoodland period. The Glenwood Culture lived in the area from roughly 900 A.D. to 1300 A.D. and built hundreds of earth lodges in the region, farming the rich valley bottoms and cultivating native plants from the surrounding hills. An earth lodge replica has been reconstructed in Glenwood Lake Park, and the Mills County Museum, also located at the park, houses an excellent collection of artifacts collected by renowned amateur archeologist Paul Rowe.
The city ofCouncil Bluffs, Iowa (originally "Kanesville") derives its name from the hills based on theLewis and Clark first formal "council", or meeting, withNative Americans in 1804, although the meeting with theOto andMissouri tribe actually took place on the Nebraska side of the Missouri River atFort Atkinson.Sgt. Charles Floyd, the only fatality of the Lewis and Clark Expedition, is buried on a bluff in the Loess Hills in what is nowSioux City, Iowa.
In 1853,MormonelderCharles B. Thompson split off from the mainwagon train toUtah. He initially led 50 to 60 Mormon families toKanesville. Thompson and a few other men then chose an area called Monona ("peaceful valley"), where they founded the town ofPreparation, named for "School of Preparation for theLife Beyond." Realizing the valley's wealth as afarming region, Thompson used hisnewspaper to report a message "from a spirit" directing the Mormon people to turn over all deeds and possessions to Thompson, who changed his name to "Father Ephraim". In 1856, the people asked for the return of their property; Thompson refused and they decided tolynch him. Thompson escaped the mob by hiding in an attic inOnawa. He then fled Iowa.[6]
On August 12, 1859,Abraham Lincoln ascended the hills at Cemetery Hill at Fairview Cemetery in Council Bluffs while being briefed on possible locations for theFirst transcontinental railroad.
Loess soil also forms theArikaree Breaks in northwest Kansas, and the Mississippi-Yazoo "Bluff Hills" nearVicksburg, Mississippi. A large region ofNebraska to the south and east of theSandhills is covered with loess. Deep loess deposits are also found in theRhine River valley inGermany.Crowley's Ridge in southeasternMissouri and northeastern and easternArkansas is made up of loess soil. The wordloess is derived from the German for "loose or crumbly."
