The Unique Geology and Biological Diversity of Southern Boone County and The Philips Farm Tract

By Randal Clark

Boone County owes much of its rugged beauty to its location at the juncture of two distinctive and beautiful geological regions: the prairies and the Ozark hills. Those two landscapes merge in South Boone County.  One prime location where the sinkholes, caves and springs of the Ozarks blends with the savannah landscape of the prairies is just south of Columbia near Highway 63 at a special place known as the Philips Farm.

The landscape of southern Boone County has evolved over millions of years. The limestone bedrock was created in warm shallow oceans about 250 million years ago. It consists of the fossilized remains of the many sea creatures that lived in the area. About 100 million years ago the area rose out of the ocean for the last time as a swampy, flat plain with slow–moving, winding streams running through it. The Missouri River actually ran north of Boone County, through northern Missouri. The Ozark landscape was first created about 50 million years ago, when southern Missouri started to slowly rise like a bubble. The streams of the area tried to maintain their same elevation and started to cut into the landscape, forming the Ozark-like valleys we now have. Starting when the land first arose from the oceans, the karst features of the area (sinkholes, losing streams, caves, and springs) were formed. Karst features are formed when rainwater at the surface combines with carbon dioxide given off from decaying plants and makes a weak carbonic acid solution. This mildly acidic water finds its way down through cracks and joints in the bedrock and dissolves the surrounding limestone.  

Over millions of years, these enlarged chambers are what formed the caves, spring and sinkholes of the area.  About a million years ago, glaciers entered this part of Missouri for the last time and put the final geological touch on the area.  At the northern border of Missouri, the glaciers were two miles thick. They plowed over the landscape, flattening everything in front of them and even changing the course of the Missouri River by pushing it southward to its current course.  By the time the glaciers reached southern Boone County, they had greatly diminished. They no longer had the strength to flatten the land as they did in northern Missouri, and so the Ozark-like characteristics of the area were retained. After the glaciers retreated, Northern Missouri became a vast prairie dotted with wooded streams. That is why the northern half of Boone County is more prairie-like, while the southern half marks the beginning of Ozark topography, with its many creeks and bluffs.  

Perhaps the most significant geological characteristic of this area is its karst topography, characterized by sinkholes and losing streams.  A sinkhole can be described as a collapsed underground cave; some can be bowl-shaped or elongated, while others are steep-sided natural funnels that may lead directly to cave passages and underground streams. Regardless of their shape, all sinkholes provide a direct connection between surface water and groundwater. A losing stream has many cracks in its streambed so that water from the stream leaves the surface and enters the groundwater. The groundwater from sinkholes and losing streams may reappear on the surface at another location. The presence of either sinkholes or losing streams in an area indicates karst topography. Since the area just south of Columbia, called the Pierpont Sinkhole Plain, has both features, and it has several major caves, it is considered one of the major karst areas of the state.

The Philips Farm Tract lies in the watershed of Clear and Gans Creek, both losing streams.  Most of the area (about two-thirds) lies in the Clear Creek watershed, which would be the stream most impacted by development. The southeast corner of the tract (about a third) lies in the Gans Creek watershed.

As Boone County streams go, Clear Creek is one of the smaller ones.   Therefore, the impact of development on the stream could be greater and faster than most other streams in the area.  Also, because of the groundwater pumped into it by the USGS Columbia Environmental Research Center at its headwaters, it is the only permanently flowing stream in the area.  Because of this, its biological diversity is potentially very high.  

Gans Creek runs just south of Clear Creek, but has a much larger watershed.  Gans Creek starts in eastern Boone County just north of Route WW and flows southwest until it ends at Rock Bridge State Park, when Clear Creek enters it.  When Gans and Clear Creek come together, they become Little Bonne Femme Creek.

Gans Creek is one of the highest quality streams in Missouri. It has a high biological diversity because of its rural, less developed watershed and because of the many different types of habitats that occur in the watershed (high quality streams, springs, caves, bottomland forest, bluffs, glades and upland forest and fields). Gans Creek runs through the northern portion of the Pierpont Sinkhole Plain. The watersheds of Gans Creek and the Bonne Femme Creek to the south have one of the highest densities of sinkholes and caves in the state.  The Devil’s Icebox Cave, the longest cave in the state north of the Missouri River and the sixth longest cave in Missouri, runs under their watersheds.  

Because of the karst structures (sinkholes, caves and springs) and because of its high biological diversity, Gans Creek was designated as an Outstanding State Resource Water in the 1980s by DNR’s Water Quality Division. The water quality of these streams are not to be degraded from the quality at the time of the law. To assure the antidegradation policy, exceptionally stringent water quality management requirements will be required for these streams. Therefore, under state law, no degradation of Gans Creek is allowed due to urban development or any other use in its watershed.

For an excellent description of karst features in Missouri, see the March 2000 issue of the Missouri Conservationist, especially the article by Tom Aley called “Karst Groundwater” (www.conservation.state.mo.us/conmag/2000/03/02.htm).  The following information is from this article.

“Whatever goes down in a karst area, comes back up. About three quarters of the water that reaches major rivers (Missouri River in this case) in Missouri Karstlands (Gans, Clear and Little Bonne Femme Creek) has passed through the groundwater systems for at least some distance. In many cases the underground openings are larger than bacteria or parasites that cause waterborne illnesses in people and animals. Some recharge areas cannot even filter out large materials such as acorns, walnuts, cans and pieces of Styrofoam.”

Sinkholes can accept water faster than a fire hose could deliver it.  So during storm events, even the seven-mile-long Devil’s Icebox Cave fills completely with water from the sinkholes in the area.

As stated earlier, a losing stream, such as Gans or Clear Creek, is a stream that has many cracks in its course, which causes it to lose a good portion of its surface water to the local groundwater and caves. Therefore any contaminants that get into these streams will also contaminate the groundwater and caves.  A fascinating characteristic of karst groundwater movement is the great speed with which much of the water moves. Karst groundwater travel rates in Missouri are often in the range of a mile per day. In non-karst areas, groundwater travel rates are commonly only a few feet per year.

Surface water that enters the groundwater in one watershed may reappear in another. The Pierpont Sinkhole Plain provides a classic example of this. Dye tracing in the 1980s determined that water from the Bonne Femme Creek near the Highway 163 Bridge enters the groundwater through a losing section and is the main source of water coming out of the Devil’s Icebox Cave in the Little Bonne Femme Watershed. Therefore any contamination in the upper Bonne Femme Creek not only affects that creek, but also the Devil’s Icebox Cave and Little Bonne Femme Creek. In other words, contamination in the losing sections of Gans and Clear Creek could rapidly affect the groundwater, caves, and other watersheds of the area.

As losing streams, Clear, Gans Creek, and Bonne Femme Creek are perhaps  the most sensitive to urban development of any streams in Boone County. Any contaminants that get into the streams will not only end up in Rock Bridge State Park, where many people use the stream for recreational purposes, but also in the local groundwater and caves with little or no filtration. Once groundwater is contaminated, because turnover rates are so small and it covers such large areas, it is almost impossible to clean up! Protection of water quality in Clear and Gans Creeks is critical for the protection of groundwater quality in wells and springs of the area.

Most streams in Southern Boone County were once the home of the Topeka Shiner (Notropis topeka) fish, which is now a federally listed endangered species.  Although it has not officially been located in Clear or Gans Creek in recent years, the fish still occurs in Bonne Femme Creek, Turkey, and Bass Creeks (Three Creeks Conservation Area), just south of the area. This prairie/forest stream fish is very sensitive to habitat loss due to disturbed watersheds and has died out in many Midwestern streams. Boone County streams have some of the largest remaining populations.

Another endangered species that requires forested, high quality streams is the federal and state-listed endangered Gray Bat (Myotis grisescens). This bat lives in caves in the area and comes out at night in the summer to eat insects along local streams. Its numbers have declined when the trees along the streams have been cut and when large amounts of pesticides and herbicides are used in the area.  Its Boone County population had crashed, but is slowly rising again. For a summertime wildlife thrill, you can go out to the bluffs of Gans Creeks in Rock Bridge Memorial State Park at sundown to watch the Gray Bats fly up and down the streams.

The Devil’s Ice Box Cave (in the Gans and Bonne Femme Watershed) is home to the endangered Pink Planarian (Kenkia glandulosa). This is a one-inch long pink flatworm that occurs nowhere else in the world other than the Devil’s Icebox Cave.  Its populations are known to be sensitive to groundwater contaminants.  Current research is ongoing at the University of Missouri on the status and requirements of this species.  Any increase in the contaminants in the watershed of Clear, Gans, Little Bonne Femme and Bonne Femme creeks would have a potential impact on this unique species and could render it extinct.

Any sizable development of the Philips farm area would have the potential to degrade the unique biological diversity and water quality of those creeks, Devil’s Icebox Cave, Rock Bridge Memorial State Park, and the groundwater and caves of the area.  Because of the high biological diversity, unique sensitivity, and recreational value of this area, it is crucial that the development of this area and the surrounding watersheds must be kept to a minimum.