Karst Terrain

An area of approximately 18,000 acres just east of Catoctin Mountain along the Route 15 corridor north of Leesburg is characterized as karst terrain.

Karst terrain refers to areas where the underlying limestone and other carbonate rocks have been dissolved over time by naturally-occurring mildly acidic water, creating a landscape characterized by underground cavities, sinkholes, and springs. A sinkhole forms when an underground cavity increases in size until it is unable to support the overlying rock and soil and it collapses. The locations of these underground cavities can only be identified before they collapse through geotechnical and geophysical testing.

Karst Terrain


In karst areas, surface water can flow directly into the groundwater system through sinkholes without the beneficial filtering normally provided by the slow percolation of water through soil. Consequently, groundwater in karst areas is more susceptible to pollution. Given the potential hazards of sinkholes and groundwater pollution in karst, land development performance standards, testing, and monitoring are important to help safeguard the public and the environment. View a map of the karst area, and locations of several features related to karst conditions (PDF). Additional information is available from the Loudoun County Health Department.

Certain types of geologic conditions may, either directly or indirectly, provide important beneficial resources upon which business and citizens depend.