INVESTIGATION OF THE DAMMING OF POND DRAIN AT MOUNTAIN LAKE, VIRGINIA

Mountain Lake, located in Giles County, SW Virginia, is one of only two natural lakes in Virginia and has experienced extreme water-level fluctuations over the past 4200 years. The lake is situated within a broad breach of the northwest limb of a northeast plunging anticline in the Valley and Ridge Province. The lake itself is underlain by four distinct rock units of Ordovician and Silurian age. They are the limestone and calcareous shale of the Martinsburg Fm. along with sandstones of the Juniata Fm., the Tuscarora Sandstone, and the Rose Hill Fm. The lake is hypothesized by previous workers in the area to have formed when colluvium dammed the stream known today as Pond Drain and into which water flows over landslide deposits during full pond stage. Seismic refraction was used in an attempt to estimate depth to bedrock along an ancient head scarp, to quantify source material; and at various locations across the present day stream valley, where hummocky terrain is prevalent, in order to determine the extent of the valley in filling. This preliminary research was done in order to elucidate the topography of the bedrock beneath the dam. The resulting data can be used to better understand the path along which ground water travels. Findings of this survey will be discussed within.