Many of the most scenic area of West Virginia are found in the eastern and southeastern parts of the state where carbonate rocks (limestone and dolomite) are exposed to the surface. The limestone below where you are standing and visible throughout the valley was laid down when the area that is now the eastern United States was covered by shallow, tropical seas. The Greenbrier limestone formation dominates the landscape of northern Monroe County covering over 70 square miles.
Monroe County karstland is one of the world's densest sinkhole plains, with an average of 18 sinkholes per square kilometer. This limestone also hosts the largest, deepest, and most complex caves, the largest karst basins, the largest number of caves, and one of the largest karst springs in West Virginia.
Limestone is relatively impermeable. Water cannot flow through it like it flows through sandstone. Over time, groundwater, slightly acidified by organic material in the soil, seeped into cracks in the limestone dissolving it and carving caves, conduits, pipes, and channels. Water flows through the dissolved openings in the rock.
The landscape formed by the slow chemical dissolution of soluble rocks is called "karst". The results of chemical weathering of rocks are expressed by the formation of sinkholes (dolines), sinking streams ('lost rivers"), large springs, and caves. The most characteristic feature of a karst is the lack of surface streams; most of the water in these areas is flowing in underground channels through caves. The sinking streams and drainage through the bottoms of the numerous sinkholes divert most of the rainfall to underground routes where the water may travel for several miles before returning to the surface at large springs.
The most entensive karst features in West Virginia may be found in the Greenbrier valley of Greenbrier, Monroe, and Pocahontas counties. The town of Union is situated on karst sinkhole plains and includes where you are standing at the posted coordinates. The scenic course of U.S. 219 from the Virginia state line in Monroe County north through Greenbrier County transverses a mature sinkhole plain, where ribbons of exposed carbonate rocks called karren are evident in the fields and pastures of the area. While visiting this Earthcache and on the drive to it, you will be able to see these "ribbons" or karrens.
Karren, also called lapies, furrows (from several cm to 1–2 m and more in depth) are characteristic for areas where denuded karst has developed. The karren lie in parallel rows or as branching labyrinths and are usually separated by narrow sharp-pointed crests. Karren occur as a result of the leaching of the surface of limestones and other soluble rock by rain, thawing snow, and more rarely sea and river water. Frequently the karren develop along cracks (crack karren). On steep rocky surfaces the karren are not related to cracks (fluted or wall karren). Often the karren occupy large areas, forming karren fields (karrenfeld).
To qualify for the this Earthcache, email me the answers to the following questions. You will see signs at the posted coordinates that will help.
1. Can you see any "ribbons" or karrens from the posted coordinates? If so, in what direction are they? If not, do you remember seeing any on the hills just before here?
2. The 1925 West Virginia Geological Survey listed 49 caves in Monroe County. Hundreds are known today in this limestone region, including the extensive Scott Hollow cave system. When was it discovered?(look at the sign)
3. How long do you estimate the covered bridge to be in feet?
4. (Optional) Take a photo of you (or your group) and/or your GPS with the covered bridge or with a karren in the background.