When we talk about land here, we are referring to the actual ground under our feet — the soil, land formations, and rocks that make up our valleys. Scientifically, we are talking about the geology and topography of the land. The Catawba Valley is part of a larger region with similar features — the Ridge and Valley province of the Appalachians.
JMU Geologists Lynn Fichter and Steve Baedke begin their story of the formation of Virginia with an important hint — “no rock is accidental.”1 The rocks, soils, peaks, and sinkholes that make up the Catawba Valley tells a story of a complicated geologic process that has been going on for hundreds of millions of years.
It’s strange to think that the ground we stand on in this valley was once the bottom of a vast sea, or that the gentle rolling hills are actually the result of crashing and lifting continents. The Appalachian Mountains were formed an estimated 480 million years ago, when the planet’s continents were colliding to form Pangaea. Prior to this, the area we now call SW Virginia was a low-lying area frequently covered by a shallow sea. As a seabed, layer upon layer of organic material accumulated, which came to form the sedimentary rock including limestone and dolomite which are so prevalent in the valley floors today. 2
Imagine kicking the edge of a rug and the ridges and bunches that rise across the rug. When the tectonic plates that make up the earth’s crust starting shifting, colliding, and pulling apart hundreds of millions of years ago, it was like that rug.3 The pushing of plates together formed volcanoes and jagged mountains in the area of SW Virginia — mountains that looked more like the Rockies than the rolling terrain we see today today. This colliding of plates created a lot of friction and heat, which formed hard igneous types of rocks — the kind of rock which forms the ridges we see today. As the plates slowly pulled apart, erosion began wearing down the mountain peaks. The plates continued to push and pull for millions of years, creating the different geologic provinces of the Appalachians we see today (for a much more detailed explanation, see Sandra Clark’s Birth of the Mountains).4
Standing in the Catawba Valley and looking around, you get a very clear idea of what the Ridge and Valley province of the Appalachians is supposed to look like. Low parallel ridges with steep rocky slopes are separated by narrow, relatively flat valleys. These formations are the result of millions of years worth of the tectonic activity described above followed by erosion, which wore down the softer sedimentary rocks including limestone, dolomite, and shale from the ridges, down into the valleys. The soils on the valley floors are based on these parent materials. Because of weathering effects and terrain, the soil tends to be thin and rocky, though there are certainly richer pockets scattered throughout. A good way to find out about soil quality in a particular spot is to check the NRCS soil survey database or conduct a soil test through Virginia Cooperative Extension.
The combination of the kinds of rock that make up this section of the Appalachians and the process of their erosion has resulted in two other features so distinctive about the valley — namely the prominent rivers and streams running parallel to the ridges, and the karst landscape underground. Though the two are connected, we will discuss the rivers in the Water section, but we will explore the issue of karst here.
Remembering that large portions of the area were underwater for long periods of time, it is not surprising that sedimentary rocks in the region are mostly based on carbonate — the same material that makes shells. Limestone and dolomite are two common types of carbonate sedimentary rock types that we find in the region. The same weathering elements which have eroded the mountains have worn away and even dissolved underground pockets of this carbonate sedimentary rock, creating caves, sinkholes, and sinking creeks. As a result, you end up with a vast underground drainage network which can impact surface land use, but also creates a direct link between surface activity and the quality of the groundwater we rely on to drink. 5
Karst is the reason springs are so plentiful in the area. Much of the region’s groundwater travels through this network of underground caves and aquifers, emerging at the surface through springs and then sometimes sinking back underground further downstream. Sinkholes are where the ground has collapsed because of the deterioration of the bedrock, and they create a direct links into these groundwater systems. That means that whatever goes into a sinkhole goes almost directly into the water supply for the region.
The caves that are formed as a result of karst also make the region quite a special place. Caves are home to a huge variety of unique species of bats, salamanders, and all sorts of invertebrates which will be discussed further in the Plants and Animals section.
To learn more about the wonders and challenges of living in a karst landscape, read Living on Karst, published by the Cave Conservancy of Virginia. Virginia DCR also has a number of resources available on karst management and conservation.
Based on our understanding of the land itself, we can see why certain uses of the land are more productive or make more sense than others. The Catawba Valley is not an abundant crop-producing area because the terrain and the soils are not well-suited for that use. That is not to say however that these lands are not productive. Abundant forests cover the slopes and ridges; rich pastureland, open fields, residences, small businesses, and gardens meander down the valleys. Cattle production is the predominant agricultural activity, with small herds grazing on the rocky hillsides. Threading through these various land-uses up and down the valley are two main tributaries, Catawba Creek and the North Fork of the Roanoke River, which will discussed in the Water section.