Landscapes central Great Plains

Landscapes of the
Central Great Plains
Chapter V
Chalk Buttes, Blue Hills,
and Smoky Hills

James S. Aber and Susan W. Aber
Emporia State University Emeritus

V.1 Introduction

The Smoky Hills, Blue Hills, and Chalk Buttes in Kansas are all based on bedrock of Cretaceous age including sandstone, siltstone, shale, chalk and limestone of shallow marine, coastal, and deltaic origins (see geologic maps). Cretaceous strata are widespread in the central Great Plains region, exposed at the surface from northwestern Iowa, across Nebraska and Kansas, to southeastern Colorado, and beyond. Cretaceous strata were once even more extensive, but were reduced by uplift and erosion during the Cenozoic Era.

Cretaceous strata of southeastern Colorado. Gobblers Knob (left) is sandstone eroded into columns and pedestals in the Dakota Sandstone and Purgatorie Formation. Exposure of chalky limestone (right) in the basal Niobrara Formation (NGMDB 2022).

These strata range from well to poorly consolidated, and their susceptibility to erosion is highly variable. Some are resistant and, thus, form hills, ridges, and knobs. Other strata succumb readily to the effects of wind and water and have been reduced to flat plains covered by loess. Land use is primarily agricultural, both for crops and cattle grazing. Oil, natural gas, and wind are major energy resources in some sectors of these regions.

Landscape maps.

V.2 Chalk Buttes

The Chalk Buttes of Kansas form a northeast-trending band between the High Plains and Blue Hills, and a long finger of the Chalk Buttes extends westward into the High Plains along the Smoky Hill River valley. The Chalk Buttes was not recognized earlier as a separate physiographic region. Most previous geologists included the Chalk Buttes as part of the High Plains (Moore 1930; Schoewe 1949; Muilenburg and Swineford 1953). Wilson (1978), however, identified this area as the "Niobrara chalk country" that he included as part of the Smoky Hills. Underlying geology and surficial landforms are considered sufficiently distinct that we treat the Chalk Buttes as a separate landscape region (Aber and Aber 2009).

Lowest elevations are about 1750 feet (535 m) near Mankato in Jewell County, and highest elevation is around 2750 feet (840 m) at its westernmost extension along the Smoky Hill River valley in Logan County. Upland areas comprise subtle hills and undulating plains, in which local relief is generally less than 50 feet (15 m). But where the upland is dissected by small streams, relief may be as much as 100 feet (30 m). Greatest local relief is found along the Smoky Hill River valley, exceeding 300 feet (90 m), where small tributaries have cut numerous steep-sided ravines and eroded badlands along the sides of the main valley in Logan, Gove, Trego and western Ellis counties. In this section, the Smoky Hill River has excavated one of the deepest valleys in the state with little accumulation of alluvial sediment (Haworth 1897).

Little Jerusalem is considered one of the crown jewels of Kansas geology. An area of erosional badlands in the Chalk Buttes on the southern flank of the Smoky Hill River valley, Logan County. Intricate erosion has sculpted a labyrinth of ravines, gullies, and buttes in the Smoky Hill Chalk. High Plains upland surface to left. Panorama assembled from two kite airphotos.

The Chalk Buttes region is characterized by the upper Cretaceous Niobrara Chalk formation, which is composed of chalk, shaly chalk, and chalky limestone beds some 500 to 750 feet (150-230 m) thick (O'Conner 1968). The Niobrara Chalk is world famous for vertebrate and invertebrate fossils, since the late nineteenth century when early collectors scoured the region for spectacular mosasaurs, plesiosaurs, fish, sharks, giant turtles, flying reptiles, aquatic birds, ammonites, squids, and giant clams. In 2014, Kansas adopted two official state fossils, namely the giant mosasaur Tylosaurus and the flying reptile Pteranodon, both found in the Chalk Buttes region. Badlands in the Chalk Buttes region are considered among the most important places in the world for collecting mosasaurs, and the search for remarkable fossils continues today (Everhart 2017).

Where deeply eroded along the Smoky Hill River valley, chalk remnants form buttes, towers, and pinnacles above the valley floor in several places, particularly in Gove and Logan counties. Among the best-known geologic landmarks in Kansas are Castle Rock and Monument Rocks. At Monument Rocks, the residual chalk stands as narrow partitions or walls rising above the surrounding shortgrass prairie like ruins of a prehistoric fortress. This site has been used for movie sets, as it captures the public imagination of the "wild west." Unfortunately the soft chalk is gradually weathering and eroding away, which has led to collapse of several famous landmarks. Both the "Cobra" near Castle Rock and the "Sphynx" at Monument Rocks disappeared in this manner during the past few decades (Charlton and Merriam 2003).

Monument Rocks in the Smoky Hill River valley of western Gove County. Oblique view (left) showing cluster of buttes with an arch. Individual buttes stand 25-30 feet (8-10 m) high. The chalk knob at upper right corner is the eroded stump of the Sphynx, a former pinnacle. Vertical view of butte cluster (right). Note shadows and light coming through the arch in the butte wall. Kite aerial photographs (Aber and Aber 2009).

Groundwater is scarce and surface water in rivers and lakes is subject to recurring drought in the Chalk Buttes region. Cedar Bluffs Reservoir on the Smoky Hill River is the most sizable water body, although it is full only in exceptionally wet years. Other large reservoirs include Webster on the South Fork Solomon River and Kirwin on the North Fork Solomon River. The city of Hays, at the eastern margin of the region, has perennial water shortages, because of insufficient surface water and groundwater supplies. The Chalk Buttes is situated above the Central Kansas Uplift in which numerous oil fields are located.

Oil storage tanks and pump jack in
Ness County, west-central Kansas.

The Chalk Buttes upland is a rolling plain covered by loess. This part of the region is home to the geographic center of the contiguous (48) United States. The U.S. Coast and Geodetic Survey identified this geographic center in 1918 approximately one mile north and one mile west of Lebanon in Smith County. Determining this location was done by balancing a cut-out shape of the United States on a point. The method was considered accurate to within 20 miles. The geographic center of the contiguous U.S. is defined as 39°50' N latitude, 98°35' W longitude. This position is located on private land, so a proxy marker was erected in 1940 by citizens of Lebanon in a small public park about half a mile from the presumed location.

Geographic center of the contiguous (48) United States. View northward (left) showing the actual center (*) and public park (<). View toward east (right) over agricultural fields with Lebanon in the right background. Kite airphotos.

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V.3 Blue Hills

The Blue Hills are found in north-central and west-central Kansas between the Smoky Hills, Chalk Buttes, and High Plains. The Blue Hills area is long recognized as a unique landscape region of the state (Moore 1930; Schoewe 1949; Johnston 1964; Buchanan and McCauley 2010). However, Muilenburg and Swineford (1953) and Muilenburg (1961) combined it into the Smoky Hills. Wilson (1978) considered it a subdivision of the Smoky Hills, which he called the "Fencepost limestone country," but Merriam (2011) included the Blue Hills as part of the Dissected High Plains.

Elevations range from lows about 1440 feet (440 m) in the Saline River valley to more than 2600 feet (790 m) at its boundary with the High Plains in northeastern Finney County. Most of the Blue Hills consists of gently rolling hills and undulating plains with slight local relief; however, a steep escarpment marks the eastern margin of the Blue Hills in places, where local relief exceeds 300 feet (90 m), for example northeast of Ellsworth. Likewise steep slopes and high local relief are found along the edges of some river valleys that are incised into the Blue Hills, such as the Smoky Hill River valley in Russell and Ellsworth counties and Buckner Creek in Hodgeman County.

The Blue Hills are underlain by upper Cretaceous marine shale, chalky shale, and thinly bedded chalky limestone. Formations include from the bottom up the Graneros Shale, Greenhorn Limestone, and Carlile Shale. Blue-gray color of the latter is probably the origin of the name for this region (Buchanan and McCauley 2010). Undoubtedly the most famous geologic feature is the Fence-post limestone bed that marks the top of the Greenhorn Limestone (Muilenburg and Swineford 1975). This thin, chalky limestone bed was widely quarried in the late ninteenth and early twentieth centuries. A similar fossil-rich limestone bed, called the "shell rock," was quarried from the middle Greenhorn Limestone (Wilson 1978). Both were utilized for everything from fenceposts to cathedral-style churches.

Fence-post limestone buildings. Bandstand (left) in Spearville, built by the Works Progress Adminstration in the 1930s. The Cawker City Museum (right) was built in the Kansas venacular style as the Public Library in 1884. It is listed on the National Register of Historic Places.

Traditional hand quarrying of "postrock" came to an end in the early twentieth century, as imported lumber, steel, concrete, and other building materials became readily available. But lately the postrock has become popular again and is being produced mainly for ornamental and decorative purposes. Upper Cretaceous strata of the Blue Hills have yielded many significant fossil specimens, including crocodiles, toothed birds, plesiosaurs, mosasaurs, fish, and large clams (Everhart 2017).

Because of the topographic prominence of the Blue Hills escarpment, several wind farms have been erected during the past two decades to take advantage of the wind-energy potential (Aber and Aber 2020). Like the Chalk Buttes, the Blue Hills spans a buried structure known as the Central Kansas Uplift, which has been a prolific source of oil production since the 1920s.

Overview of Meridian Way Wind Farm on the Blue Hills escarpment in Cloud County. The eastern end seen here is located on the divide between the Solomon River and Republican River drainage basins. Total height of these Vestas V90 3-MW turbines is about 410 feet. Kite airphoto.

The Blue Hills have little groundwater, and surface water resources are limited to the major rivers and streams, which are subject to recurring drought conditions. In north-central Kansas, Wilson Lake and Waconda Lake are large reservoirs with dependable water supplies respectively on the Saline and Solomon rivers.

During the first decade of the twenty-first century, a new reservoir was constructed on Buckner Creek at Horse Thief Canyon in Hodgeman County. After partial filling in 2010, the lake gradually declined during subsequent drought years. Many people believed the lake would never fill. The spring of 2015 was exceptionally wet, however, and repeated heavy rains during May led to significant runoff and local flash flooding that filled the reservoir to full capacity.

Horse Thief Canyon dam (left) under construction in 2009. Original channel of Buckner Creek remains visible along with a chalk outcrop at lower left. Reservoir full (right) following heavy rain and runoff in May 2015. Looking east toward the dam with campground in the foreground. Kite aerial photographs.

On the other hand, Finney State Lake and Wildlife Area is a small reservoir built in the 1930s on a tributary of Pawnee River and located at the southwestern end of the Blue Hills. In wet years, a small puddle of water collects behind the dam that was designed to accommodate a much larger water body; but most years the basin is dry, and wheat or alfalfa may be planted on the lake floor. The unpredictable status of this reservoir is a lesson for water development in western Kansas.

Finney State Lake and Wildlife Area was built in the 1930s for a much larger lake. Upstream groundwater pumping from the High Plains Aquifer and diversion of surface water have rendered this reservoir into a wildlife area in which trees are growing. During wet years, as seen here, a small puddle of water is held behind the high dam on the left, but most years it is completely dry. Kite airphoto.

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V.4 Smoky Hillls

The Smoky Hills form a distinctive region located primarily in north-central Kansas with an extension toward the southwest reaching to the High Plains. The Flint Hills and Glacial Hills lie to the east, Blue Hills is to the west, and the Arkansas River Lowlands bounds the southern limit of the Smoky Hills. Lowest elevations are along the Smoky Hill River valley in Saline County at about 1240 feet (380 m). Highest elevation is along the Ford-Hodgeman county boundary around 2400 feet (730 m). Local relief varies from wide valleys, to gently undulating plains, to rugged hills more than 200 feet (60 m) high. The two most famous vistas are Coronado Heights in Saline County, supposedly visited by Coronado on his expedition in 1541, and Pawnee Rock in Barton County, a key landmark on the Santa Fe Trail.

View northward over Smoky Hill Buttes from Coronado Heights in southern Saline County. The hills in center distance stand more than 200 feet (60 m) above the adjacent terrain. Notice two ponds in the foreground. The near pond trapped suspended yellowish-brown sediment from recent runoff, which prevented the sediment from entering the next pond downstream. Kite aerial photograph.

The Smoky Hills are formed on the Cheyenne, Kiowa, and Dakota formations, which are comprised mainly of shale, siltstone and sandstone that were deposited in coastal, deltaic, and shallow marine environments near the shore of the Western Interior Seaway. A basal Cretaceous conglomerate is found locally and represents gravel transported by rivers from the east and deposited as the sea advanced from the west (Merriam 2007).

Of these formations, the Dakota is most widespread and characteristic of the Smoky Hills. Within the Dakota, sandstone bodies are distributed in various lenses, channels, and sheets, and local lime and iron cementation of the sandstone is highly variable. Well-cemented sandstone is more resistant to erosion than are other poorly consolidated strata and, so, forms the higher mounds and knobs of the region. The patchy distribution of cemented zones in sandstone bodies explains the irregular size, shape, and placement of hills.

Large concretions are among the most distinctive cemented features within the sandstone of the Dakota Formation, as at Mushroom Rock State Park in Ellsworth County and Rock City in Ottawa County. The conventional interpretation is that concretions may have formed around organic matter buried in the sediment, as decay altered the surrounding chemical environment and led to precipitation of calcium-carbonate cement around the organic nucleii (Johnston 1964). More recently, McBride and Milliken (2006) determined that concretions did not grow outward from central nucleii, but rather the cementation took place throughout the spherical bodies, as groundwater from different sources mixed in the formation. Rock City contains about 200 huge spherical concretions that Wilson (1978) likened to giant bowling balls.

	Rock City near Minneapolis in Ottawa County. Superwide-angle overview (left) toward the northeast with Rock City in the foreground and the Solomon River valley in the background. Vertical close-up view (right) of large sandstone concretions on the surface. Most are nearly spherical in shape; some are joined to create double and triple spheres. Helium-blimp aerial photographs
	Ground view of concretions at Rock City. The single spheres in this cluster are 15-25 feet (5-8 m) in diameter.

Fossil sharks and rays, fish, turtles, crocodiles, plesiosaurs, several dinosaur specimens (Liggett 2005), various invertebrates, and thousands of leaf impressions have been found in the Dakota Formation since the mid-1800s. The Kiowa Formation has yielded rare finds of amber, a type of fossil resin now classified in the cedarite group based on its similarity to specimens from Cedar Lake, Alberta, Canada (Aber and Kosmowska-Ceranowicz 2001). Small caves are present in Dakota sandstone, and petroglyphs (rock carvings) made by Native Americans are preserved on cliffs and in caves.

Samples of Kansas amber, known as jelinite, showing typical color variations and texture. Jelenite is the Kansas state gemstone; however, it is quite brittle and cannot be used for jewelry. The jelenite source locality is now underwater in Kanopolis Lake. Penny coin for scale.

Clay and shale of the region have proven excellent raw materials for bricks, tiles, and other ceramic products, and lignite (brown coal) was mined for fuel in the past. Underneath the Cretaceous strata, upper Permian salt beds are mined in the vicinity of Kanopolis and Lyons, and hollowed out caverns in the salt beds are used also for storage of natural gas produced in the Hugoton Gas Area of southwestern Kansas. As for the Chalk Buttes and Blue Hills, the Central Kansas Uplift runs under part of the Smoky Hills, and small oil fields are common.

Oil pumps (left) and storage tanks (center) of a small oil field amid mixed agricultural land use. Rice County; helium-blimp aerial photograph taken by ESU students.

Major rivers cross the Smoky Hills region, namely the Republican, Solomon, Saline, and Smoky Hill. These rivers have migrated back and forth eroding wide valleys as they cut down into relatively soft, shaly bedrock, but steep bluffs and cliffs remain where cemented sandstone is present. Crops are grown in fertile alluvial soils in the valleys and on low terraces; whereas, uplands are utilized mainly for grazing pasture.

Buffalo grazing range in Smoky Hills upland at Maxwell Wildlife Refuge in McPherson County. Trees line small stream valleys, and several ponds are visible in the distance. View toward north; kite airphoto (Aber and Aber 2009).

Surface water is relatively abundant, and Kanopolis Lake is dammed on the Smoky Hill River in Ellsworth County. Groundwater is found in alluvial aquifers of the larger valleys and in uplands where sandstone bodies are present in the shallow subsurface. However, little irrigation is practiced in this region, as summer precipitation is normally adequate for crops. Flooding is a recurring event in the valley bottomlands, as happened at Salina in 2007.

High bluff of resistant sandstone in the Kiowa Formation stands in the Horsethief Canyon area on the north shore of Kanopolis Lake, Ellsworth County.

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Combined references.