Welcome to the Flint Hills

by Lanny Massey

November 13, 2007

created in requirement for ES 546

Field Geomorphology, Emporia State University

Clickable Kansas map

Figure 1: taken from the Kansas Geological Survey

Table of Contents

Introduction

Climate

Geology

Economics

Topography

References


Introduction:

"Although the Flint Hills region is known for its rolling grasslands, it is named for flint, a type of rock that is found embedded in the limestone that forms the hills. Flint, also called chert, does not erode as easily as the softer limestone. When the limestone at the surface is eroded by wind and water, it eventually breaks down into soil. The exposed flint is broken down into gravel which mixes with the soil and makes the ground rocky." (Kansas Geological Survey, 1997)

The Flint Hills are a range of hills which bisect the state in a general north-south direction from Marshall county in the north to Cowley county in the south. This trend continues south into Oklahoma, where the hills are named the Osage Hills.  This physiographic region varies in width from 30 to 80 miles wide. The Flint Hills are capped by westward-dipping limestone strata that are separated by less erosion resistant shale beds (Adams, 1899). The height of the Flint Hills is controlled by the vertical distance between beds of the weather resistant limestone, that are strong enough to hold benches or plateaus. The approximate 350 foot relief of the Flint Hills is, therefore, due to the presence of a few hundred feet of shale and softer limestone beneath intermittent layers of resistant limestone that will hold benches against the weathering of Kansas' varied climate (Bass 1929).

The Flint Hills follow in position a range of buried mountains called the Nemaha Mountains. This positioning is more by chance then actual result of the Nemaha Uplift that produce this once mountain range. Little of the ruggedness of the Flint Hills is due to effects of the uplift (Moore and Haynes, 1917). A few surface folds from the Nemaha Uplift do appear in the Flint Hills of Butler county (Aber, J.S., 1991). The hills are grass-covered and only slightly forested in the creek and river valleys. The Flint Hills represent some of the richest grazing in United States. The Flint Hills exhibit, arguably, the most beautiful natural scenery in the state of Kansas.

Figure 2: Photo taken by Lanny Massey, at the scenic overlook south of Manhattan.
 

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Geology: 


Figure 3.

 

Geologic map of Kansas.
Image taken from the Kansas Geological Survey.

 Ancient Kansas was once a shallow body of water called the Permian Sea. Throughout the Permian Period the earth's oceans rose and fell many times creating different types of aquatic environments with the rising and falling of the sea level. “The shallow warm seas supported enormous numbers of invertebrates, fishes, and amphibians. Many animals and plants (such as oysters, corals, some sponges, sea urchins, plankton, and algae) take calcium carbonate (CaCO3) out of the water and secrete it to form shells or skeletons. As these organisms die, they drop to the ocean floor. Over time, the organic parts decay and the calcium carbonate accumulates to form limestone. Fossil remains of these aquatic animals can often be found in limestone.”(US Dept. of Interior, 2007 ) Limestone can also form when calcium carbonate falls out of solution, and settles to the bottom.

Figure 4

Limestone and Shale Map

Image taken from the US Dept. of Interior

 

Limestone layers, as do shale layers that form between them, vary in width, color, and durability due to the many variables in the layers creation. In many of the cut banks of the creeks and rivers of the Flint Hills region, alternating layers of limestone and shales are seen in figure 4 (US Dept. of Interior, 2007). These are the cyclothems of the Lower Permian (Aber, J.S., 2002).  Regular deposition of alternating shale and limestone can be seen throughout the Pennsylvanian and Permian systems of eastern Kansas.

R. C. Moore (1936) described the cyclothemic cycles of Pennsylvanian layers, in Stratigraphic classification of the Pennsylvanian rocks of Kansas. He described an ideal cyclothem, as “a series of rocks composed of sandstone, shale, underclay, coal, shale, limestone, shale, limestone, shale, limestone, and shale”.  The shales seen in the Flinthills, while Permian and not Pennsylvanian in age, show a similar cyclothem pattern without the presence of coal.

Figure 5: Ideal major and minor cyclothems for Council Grove and Chase Groups, Lower Permian, Butler County, Kansas

Image taken from  Surficial Geology of Butler County

Lithologies of individual units within Lower Permian cyclothems differ considerably, however, from Upper Pennsylvanian cyclothems. Red beds, cherty limestone, and evaporites (subsurface) are common in Lower Permian strata; whereas coal, sandstone, and black shale are scarce or absent (Aber, J.S., 1991)”.

The shale beds vary in color from red to a dark gray green color.  Some theories explain that seas deposited red shales, where they were shallow. Limestones where they were deeper, and black to gray shales at intermediate depth. As sea levels rose and fell, they repeated the limestone/shale sequences over and over. This pattern is recognized throughout the rock strata in the Flint Hills area. (US Dept. of Interior, 2007)

In the figure 6, both the gray and red shale examples can be seen. The Flint Hills geology indicates that the area experienced many periods of rising and falling sea levels, land movement, and crust shifts (US Dept. of Interior, 2007). Sea level changes may have occurred in response to glaciations. When water is frozen to form the glaciers, lower sea levels worldwide would result. When temperatures warmed, ice would melt, glaciers would retreat and sea level would then again rise (Aber, S. W. et al)

Chert is common in many Kansas limestones as mineral deposits often formed in the cracks and pores. An example of these chert deposits can be seen in the figure to the right. One of the more predominant chert deposits in the limestone layers is flint, from which the hills receive their name (US Dept. of Interior, 2007). Weathered chert terraces can be seen on the north side of east-west running streams and on the west of north-south running streams. A regional observation that east-west creeks and rivers migrate to the south, while north-south running creeks and rivers migrate to the east was made by Dr. James Aber, during Emporia State's field geology class (Aber, J.S., 2007).  This would account for the chert beds location to the rivers and creeks of the region.

 

 

Figure 6: Photo taken by Lanny Massey, in a creek bed west of Lake Kahola. Figure 7: Photo taken by Lanny Massey, east of the Lake Kahola Spillway.

 

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Topography:

The rocky hill region of the Flint Hills is the largest remaining tall grass prairie ecosystem on the North American continent."The Flint Hills form a prominent erosional massif that stands well above lower plains of the east and west" (Aber,  J.S., 2002). The area is consider to be within the Central Lowlands because of its geologic similarities to the Osage Cuesta Plains to the east (Frye, 1952). The region displays ridges that are flat and have shallow, rocky soils resistant to plowing. The ridge slopes are moderate to steep in inclination (U.S. Department of Agriculture, 1975b). Limestone layers are exposed on steep-sided hills above stream and creek valleys (Knapp et al, 1998). The upland soils are silty clay loams which are well drained because of the ridge slopes. These residual upland soils are generally produced by the weathering of shales and limestones. This creates a residual soil that is rocky and poorly suited to row crop agriculture. 

During the Tertiary period, the Flint Hills became a major divide of two distinct drainage provinces. River erosion has been greatest in the western portion of the Flint Hills. Significant down cutting patterns are also seen immediately east of the Flint Hills in the Osage Cuestas. This pattern suggests that the Flint Hills may have emerged gradually, while terrains on either side were lowered by erosion (Aber, J.S. 1997). The drainage west of the Flint Hills discharges southward from Kansas into Oklahoma. The drainage east of the Flint Hills discharges eastward into Missouri.  The Kansas River is the only through-flowing river that managed to cross-cut the Flint Hills Upland. It is believed this event occurred as a result of glaciation in northeastern Kansas. The Cottonwood River has managed to erode through the crest of the Flint Hills but has yet to cross cut the region (Frye, 1952). Crop land can be found in the numerous creek and river valleys of the region. The flood plain soils of the creeks and rivers are deep and stratified with silty, clay loams with little or no slope; limestone and chert fragments can be found in the subsoils (U.S. Department of Agriculture, 1975b, US Dept. of Interior).

The eastern portion of the Flint Hills landscape has flat hilltops, with gentle slopes dropping to lower benches on the hillside. The shale layers erode into gentle slopes between the benches of the more weather resistant limestone layers. These layers are seen as flat hilltops and hillside benches. This terraced topography is seen in the Flinthills region (US Dept. of Interior, 2007). Figures 8 and 9 are examples of this topography. The western portion of the Flint Hills displays a less prominent series of dip slopes and is relatively smooth, compared to the eastern portion of the region (Frye, 1952,Aber, J.S., 2007). The contrast between fall and late spring/early summer can be seen in figures 2 and 3, as well.

Figure 8: Photo taken by Lanny Massey, at the scenic overlook south of Manhattan. Figure 9: Photo taken by Lanny Massey, on the Nations ranch in Chase County. 

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Climate:

The climate of the Flint Hills is one of extremes. It ranges from extreme heat and drought in late July through early September, to bitter cold winters locked in ice and frigid winds during from late December to early February. Summer highs range from 80-110 degrees Fahrenheit( 26-43 degrees Celsius), while winter lows reach -21 degrees Fahrenheit (-29 degrees Celsius). Average precipitation for the region is approximately 33 inches (84 cm).  The amount of rainfall varies greatly from year to year and occasional droughts are experienced. The amount of rainfall varies greatly from year to year, and occasional droughts and floods are experienced. Large portions of the precipitation come from thunderstorms in late spring and cold drizzle in early fall. (US Dept. of Interior, 2007).  The table below shows the average monthly temperature and precipitation for the Manhattan, Kansas area.

Table 1--Normal monthly and annual temperature and precipitation at Manhattan, Kansas, taken from Kansas Geological Survey. Figure 10: Photo taken by Lanny Massey, south of Manhattan, near my grandfather's farm.

Month

Temp (°F)

Precip.
(inches)

January

31.0

0.75

February

26.6

1.13

March

42.6

1.35

April

55.3

2.73

May

66.8

4.32

June

74.7

4.42

July

79.5

4.67

August

79.2

3.58

September

69.0

3.04

October

61.1

2.24

November

44.1

1.28

December

31.2

0.85

Year

 

30.36

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Economics:

The major economic resource in the Flint Hills is agricultural grazing. Since the Flint Hills is the largest tall grass ecosystem on the North American continent, it lends itself to the widespread grazing of cattle. Much like the buffalo of yesteryear, cattle can be found grazing the uplands in pastures that range to thousands of acres, in size. Row crops and wheat are found as staple agriculture in the river bottoms and tributary flood plains. Commercialization and large metropolitan communities are largely missing in the region.

Butler county, in the western portion of the Flint Hills, and Greenwood county is the eastern portion of the region, are important petroleum and oil production regions. In the early 1900's, the petroleum and oil region of Butler county were discovered, giving this portion of the Flint Hills an economic boom (Aber, 1991). The petroleum and oil deposits in this area could correlate with several anticline, syncline structures in the area. These structures lend themselves to the trapping of oil reseviors (Jewett, 1941,Gerhard, 2004).  Butler county is also a region of larger population and commercialization near Wichita. The northern portion of the Flint Hills also has its larger population base in the Manhattan-Junction City area. This population bed is centered around Kansas State University and the Fort Riley military base.

Abundant limestone suitable for building stone is also available. Only a small amounts are currently being quarried. The Cottonwood, Fort Riley, and Neva limestones have been principal players in building construction in the past. "Most of the buildings of Kansas State [University] are made of these rocks, principally of the Cottonwood limestone. At Junction City and at Fort Riley much Fort Riley limestone has been used in buildings" (Jewett, 1941). I am proud to say that my great-great grandfather was one of the principal architects and stone masons in the building of the limestone structures on the base at Fort Riley.

Recently new economic interest has developers looking to the Flint Hills as a source of wind farm development. "Unlike the vast stretches of farmland in western Kansas where wind farms are generally welcomed, the environmentally sensitive Flint Hills have seen stiff opposition to wind-farm development" (Kansas Geological Survey, 2003) .

In conclusion, the Flint Hills are a scenic venue with limited regional development. The Flint Hills provide an vista in which to escape from the day to day routine and allow one to take a step back in time, away from busy streets and city lights. The rural populace of the Flint Hills would prefer to preserve the tranquility and beauty of the region and limit economic infringement (Kansas Geological Survey, 2003).

Figure 11: Photo taken by Lanny Massey, on the Nations ranch in Chase County.  Figure 12: Photo taken by Lanny Massey, near Lake Kahola .

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References:

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L.L. Massey,  November 13, 2007. Created in requirement for ES 546 Field Geomorphology, Emporia State University.