Geomorphic Features of Kansas: Chalk Buttes

By: Tyler Ringler

Field Geomorphology: Fall 2007

Source: http://www.kgs.ku.edu/Extension/smoky/places.html

Introduction
The Chalk Buttes Physiographic Region

The Chalk Buttes Physiographic Region
Geologic and Environmental Reasoning
Paleontological Aspects
Methodology: Small Format Aerial Photography
Interpretations and Conclusions

The Chalk Buttes Physiographic Region

The Chalk Buttes Physiographic region is located in north central Kansas and spans across sections of Smith, Jewell, Phillips, Rooks, Osborne, Ellis, Gove,and Trego counties (Figure 1) and has a regional elevation of around 1500 feet above sea level. This region is characterized by towering chalk "monument" rocks that jut out of the earth like statues from a distance (Figure 2). The area is underlain, geologically, by Upper Cretaceous chalk bedrock with surface sediment consisting of loess and alluvium in valleys. The surrounding region can also be characterized, topographically, by gentle hills and badland features making for moderate elevational relief. Surrounding vegetation involves mixed brush and short prairie grasses with mixed agriculture. The region is famous for the abundance of vertebrate marine fossils (Aber, 2007).

Figure 1; Physiographic Regions of Kansas
Picture from Kansas Physiographic Regions ; James S. Aber ; Modified by: Tyler Ringler
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Figure 2; Side view of chalk monument, Gove County
Picture from Geokansas ; Modified by: Tyler Ringler
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Chalk Buttes Physiographic Region

Geologic and Environmental Reasoning

This region of Kansas was submerged during the western interior seaway during the Cretaceous which placed tremendous pressure on the underlying strata which now is represented by these chalk monuments (Figure 2). The structures were developed over time as the surrounding strata slowly eroded away leaving the more resistant chalk beds exposed. The resistance to erosion of this particular chalk is due to the regional aridity of the environment, especially towards the western portion of the area. These chalk beds are part of the Niobrara Formation. The Niobrara is exposed extremely well in bluffs of the Solomon, Saline, and Smoky Hill rivers and has a thickness of around 600 feet (Buchanan 1984).

Erosional processes in this region responsible for the disappearance of the surrounding strata are dependant on several variables that determine the denudation of this land surface. These include the amount and severity of weathering (wind, rain, etc), relative age of the terrain, thickness, and the formations ability to resist these factors (Charlton and Merriam 2003). Erosional rates are generally higher in younger topography and lower in older ones. However, there are other factors that aid or inhibit erosional processes such as tilling or plowing of the land, or lack thereof, which could further break apart upper soil horizons and hasten erosion. Areas of mid-continent location, like Kansas, are mature physiographic regions and tend to have steady erosional rates, when ignoring significant accelerated times of erosion such as floods or wind storms. The ersosional process here is cumbered by something else; a cap rock which is found cemented to the top of these monuments. This cap rock protects the structures over time from direct erosional contact. However, once the cap rock has been eroded, natural erosional processes are quick to work on the soft chalk. The cap rock is residual rock from the once overlying limestone formation. Typical measurements of erosional rates are reported in centimeters per millennium (Charlton and Merriam 2003).

Initial estimates of uniform erosion of the chalk buttes were made by H.T.U. Smith in the 1940s at some three to seven thousand years. This estimate described the time he thought it would take until the towers of chalk would be eroded to ground level. This figure had to be altered due to the massive alteration of the ground cover and a significant increase in precipitation over the last few decades. These two variables are codependent; the increase in localized precipitation has changed the ground cover from sagebrush to dense prairie grasses due to grazing and cultivation (Charlton and Merriam 2003).

Figure 2; Chalk Monument Structure.
Picture courtesy of Kallie Moore. Modified by: Tyler Ringler
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Paleontological Aspects

Chalk is formed from the presence of an open ocean abundant in sea life including marine plants and animals. Chalk forms as these organisms die then sink to the sea floor creating a slime of limy organic remains. Over time, this layer builds until the bed is formed. Consequently, the Niobrara Formation is littered with the remains of fossilized skeletons of these extinct fishes and reptiles, as well as various bivalves. The fossils are abundant as seen below (Figures 3 and 4).

Figure 3; Remains of giant clam shell rim (where top and bottom shell meet)
Image courtesy of Kallie Moore. Modified by Tyler Ringler
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Figure 4; Remnants of a fossilized giant clam shell
Image courtesy of Kallie Moore. Modified by Tyler Ringler
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Methodology: Small Format Aerial Photography

To fully evaluate and analyze the various geomorphological features of Kansas, small format aerial photography (SFAP) was used. More specifically, kite aerial photography was used to get a "bird's eye" view of the landscape. This process seems extremely simple, but is rather complex. KAP involves a lifting mechanism (wind) to send a suitable kite (Figure 5) airborne with a camera rig attached to the string (Figure 6). Cameras used were all digital, which eases transfer time to a viewing mechanism, as well as maximizing image storage when compared to a typical film camera. The camera rig is adjustable, via remote control, to angle of tilt as well as a full 360 degree circle. There are environmental variables that determine the type of kite and consequential camera and rigging system to use. If wind conditions are favorable, larger kites and heavier cameras can be supported. However, under light wind conditions, smaller kites are utilized and the lightest camera is preferred such as the Cannon Elph (Aber and Aber, 2007).

Figure 5; Kite supporting camera rig
Picture courtesy of Kallie Moore; Modified by: Tyler Ringler
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Figure 6; KAP camera rigging system
Picture from Kite Aerial Photography, Cameras and Rigs; James S. and Susan W. Aber ; Modified by: Tyler Ringler
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Wind conditions this year at the chalk buttes were brutal, with gusts greater than 45 mph. Though KAP could not be used during this expedition, below is an aerial photograph from a previous field geomorphology class comparing topographical relief of the butte structures from an oblique angle (Figure 7), as well as a vertical angle (Figure 8).

Figure 7; Oblique aerial photograph using KAP
Picture from Kansas Physiographic Regions ; James S. Aber ; Modified by: Tyler Ringler
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Figure 8; Vertical aerial photograph using KAP
Picture from Kansas Physiographic Regions ; James S. Aber ; Modified by: Tyler Ringler
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Interpretations and Conclusions

The chalk buttes physiographic region in north central kansas is unique when compared to the surrounding regions. This area shows the extreme impact of long-term erosional processes on the distinctive Niobrara Formation. The resistant chalk layering in the region shows a strong resistance to these processes when compared to the surrounding strata, creating these towering structures that stick out on the topographical outlay of the surrounding region (Figure 9). These massive features are an excellent location for investigations of paleoclimate, paleontology, and geomorphological processes that topographically distinguish the midwest from other parts of the country. By utilizing SFAP, students are more apt to visualize the regional elevational relief, thus providing a deeper understanding as to the extent of these processes creating the geomorphology.

Figure 9; Chalk butte with archway
Picture courtesy of Kallie Moore; Modified by: Tyler Ringler
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References:

Aber, James S. (2007) ES 546 Project Summary: Kansas Physiographic Regions. Public Information. World Wide Web, http://academic.emporia.edu/aberjame/geomorph/project/summary.htm [Retrieved 26, Oct. 2007].

Aber, James S. and Aber, Susan W. (2007) Kite Aerial Photography Cameras and Rigs. Public Information. World Wide Web, http://www.geospectra.net/kite/equip/camera_rigs.htm [Retrieved 26, Oct. 2007].

Brosius, Liz. (2005) Geokansas: A place to learn about Kansas geology. Public Information. World Wide Web, http://www.kgs.ku.edu/Extension/smoky/places.html [Retrieved 26, Oct. 2007].

Buchanan, Rex. Kansas Geology. University Press of Kansas. 1984.

Charlton, J. and Merriam, D. 2003. Ever changing landscape: Recent topographic landmark erosion in Kansas. Kansas Academy of Science, Transactions 106, p. 29-39.

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Webpage for public use created for term project requirement for Field Geomorphology (ES 546), Emporia State University