Central Basin

Where We Live - The Central Basin

Conservation begins with understanding.  Understanding leads to caring.  Caring leads to activism.  

We are fortunate to live in one of the most ecologically diverse states in the United States. Murfreesboro is nestled in the dead center of Tennessee in the physiographic region known as the Central Basin, and more specifically, the Inner Basin. This region is informed, as many ecosystems are, by what lies beneath. In other words, the rocks below our feet. Rock formations, caused by mineral deposits, erosion, shifting plates, and other natural events happen over millions of years, and continue to happen.

Millions of years may be tough to think about.  The blink of time which consists of one human life span may not see much in the way of evolutionary changes, but everything is moving, centimeter by centimeter, and while it informs the present, it’s slowly shaping the future.   While we work to preserve the present-day natural systems, we do so with the knowledge that this area will most likely be completely different in a million years.  It is both humbling and exciting to participate in the great natural changes our shared home undergoes. 

Murfreesboro’s Geologic Structure

Information taken from The Geological History of Tennessee by Robert A. Miller

The Central Basin is an enclosed, elliptical depression that curves down into the bare flat limestone outcroppings of the Inner Basin and is surrounded by the Highland Rim.  The Outer Basin is a unique transitional area that features characteristics of both the Highland Rim and the Inner Basin, including oak-hickory forest systems and karst sinkholes and caves.  Beginning in the Ordovician period, roughly 450 million years ago, lateral movements of the earth’s crust (known as orogenic movements) caused pressure to develop that gradually lifted the sedimentary rock structures into a dome and fractured the layers of shale, chert, limestone, and sandstone that had been deposited over time.  The eventual erosion of the upper layer of sedimentary rocks exposed the limestone bedrock underneath after which point, the soluble nature of limestone caused erosion to occur at a quicker rate.  The flat exposed limestone outcroppings associated with cedar glades, the movement of water along cracks in the limestone forming caves and sinkholes, and the bedrock that is exposed along the streams and rivers of this area are all a result of these geologic events over millions of years.  

Murfreesboro sits in the middle of it all. 

Karst Characteristics

Information taken from MTSU’S Center for Cedar Glade Studies

A karst system or topography is defined by the dissolution of limestone over time by slightly acidic water that creates underground fissures, caves, sinking creeks, sinkholes, and/or springs.  Under Murfreesboro is a system of moving water, caves, and other karst features that results in an interesting study of water movement, sinkhole development, and specialized flora and fauna.  In fact, conditions in these areas are so unique that many species have adapted to the dark, cool, and reduced food source conditions, becoming endemic (specialized species specific to very few locations and conditions) and therefore, endangered.  

The movement of water through these systems is much like a plumbing system, whereby water moves through cracks and seams like pipes and is deposited into large caves or caverns.  A strong mature and intact system does a good job of mitigating flooding, filtering water, and slowing the powerful force that is fast-moving water.   

Plant communities of the Inner Basin

Information taken from The Southeastern Grasslands Initiative

Here in Murfreesboro, we are fortunate to have one of the most globally rare systems, and therefore, one of the most globally unique systems called limestone glades.  Characterized by extreme conditions, thin soil if any, and exposed limestone pavement, the plant species that live here have adapted to very hot conditions in summer to very cold conditions in winter.  In addition to extreme fluctuations in temperature, fluctuations in moisture are relatively extreme.  During the rainy season, because drainage is poor, many portions of glades may be in standing water for long durations, while in the dry season, water is nowhere to be found.  These areas are often surrounded by cedar stands and can include other species of trees like post oaks, locust, some maples and other tree species that can exist in these conditions.

Heading toward the outskirts of the city limits, especially to the west and south, rolling hills begin to change the landscape and in these areas, the dominant forest type of Tennessee begin to take shape.  The oak-hickory forest system, which can grow in the relatively dry soils and stone outcroppings of the hilly slopes moving up the Outer Basin, to the low-lying mesic soils of foothills and riparian areas, consists of diverse plant and animal life dominated by a variety of white and red oak species and those of the hickory family.  Interestingly, the dominant forest type was historically Oak-Chestnut, but with the arrival of the chestnut blight and the decline of the American Chestnut tree, Hickories moved in to dominate our area forests. 

Murfreesboro was, as current research has proposed, historically a part of what is called a limestone oak savanna system.  Whereas a forest system consists of many layers, such as the herbaceous, shrub, understory, and canopy layers, savannas are described as open grasslands with scattered trees.  Fire suppression is likely the result of the forestation of these areas, but historical survey records and the study of plants found in open fields suggests that Murfreesboro and the surrounding Inner Basin counties were likely home to extensive Oak Savanna systems.  The dominant tree of this system is the Post Oak.  

Caring for these unique systems

What truly makes Murfreesboro unique can be found at the confluence of rock, water, and plant.  Everything comes together to create systems that are globally rare and endangered.  What is often forgotten and taken for granted is how a healthy, intact, and diverse ecosystem benefits ALL of life.  Clean water, clean air, food, good soil, temperature regulation - all of these factors create an energy that is healing and nourishing to us all.  Visit our Conservation in Action pages to learn how you can help restore our natural areas and work towards gaining an attitude of stewardship.