New observations on the geomorphology and origins of Mountain Lake, Virginia

Abstract

Mountain Lake is the only natural lake of significance in the unglaciated southern Appalachian Highlands. It is located near the summit of Salt Pond Mountain, Giles County Virginia, at an elevation of 1177 m. It is underlain by Ordovician and Silurian non-calcareous shale and sandstone of the Martinsburg, Juniata and Clinch formations. Historical (250 years) and sediment (6000 years) records suggest that the size of the lake has varied periodically. In the 1930s lake origin was proposed as due to valley damming by a lateral landslide (Hutchinson and Pickford, 1932) or damming by scree (Sharp, 1933). A later theory modified the landslide hypothesis to the primarily vertical collapse of a canyon feature in the Clinch (Parker et al., 1975). Fracture trace analysis now reveals a regional lineation feature associated with the lake. This feature is present surficially both downgradient from the lake to the northwest, and upgradient to the southeast. Sonar bathymetry and diver reconnaissance show it expressed as a (relatively sediment-free) narrow open crevice in the deepest (33 m) portion of the lake, probably a fault. Hydrologic observation and resistivity suggest preferential water movement along this fracture, as well as leakage directly from the lake. The present study suggests conduit erosion within this feature and periodic vertical downsettling of overlying Clinch material as the primary mechanism of lake origin and water-level fluctuations through time.

Investigating the potential and mechanism of soil piping causing water-level drops in Mountain Lake, Giles County, Virginia

“…Seepage through the dam material has been observed to occur in previous studies by Sharp (1933), Marland (1967), andParker et al (1975). Although Cawley (1999) and Cawley et al (2001b) claim that the water loss is associated with the northwest trending fracture lineation, they also state the possibility of seepage through the dam material. These two studies, as well as Parker et al (1975), suggest that earthquakes may affect water levels by adjusting the Tuscarora blocks making up the landslide dam.…”

“…lake is full), water seeps out of the lake basin through subterranean pathways at the northern end of the lake (Marland, 1967;Parker et al, 1975;Cawley, 1999;Cawley et al, 2001b;Jansons et al, 2004;Roningen, 2011;Joyce, 2012). Water budget studies have estimated a net groundwater outflow of about 44-49 liters/second (Jansons et al, 2004;Roningen, 2011), channeled through piping holes within the four lake-bottom depressions (Figures 4 and 6).…”

“…By far the most popular explanation has been that seepage at the northern end of the lake occurs through the mass of colluvial deposits from the Tuscarora Sandstone, which forms the presumed natural landslide dam (Sharp, 1933;Marland, 1967;Parker et al, 1975). Cawley et al (2001b) suggested that the seepage occurs along a SE-NW lineation feature, identified by Cawley (1999), which was interpreted as a "fracture feature and probable fault". These authors support this hypothesis by explaining that a steep walled crevice-like feature at the northeastern margin of the lake and the two deeper …”

“…When full, the lake has a total surface area of about 0.21 km 2 and a maximum water depth of 33 m at the northern end, which shallows towards the south (Williams, 1930;Cawley et al, 2001b;Roningen, 2011;). Mountain Lake occupies a small watershed (1.3 km 2 ) within the Ohio Hydrologic Unit and is fed by precipitation, surface runoff, and a line of lake-bottom springs found at the contact between the Reedsville-Trenton Formation and the Juniata Formation (Cawley et al, 2001b). The headwaters of three major streams lie close to the Lake: Sartain…”

The Lago Cardiel Basin, Argentina (49°S): Origin and evolution revealed by high-resolution multichannel seismic reflection studies

“…However, studies of other lakes throughout the world show that water can leak through the lake bottom if it has zones of high permeability. This permeability can result from karst development (Fernandes et al, 2001;Crilley and Torak, 2003) or seismic activity that periodically readjusts bedrock positions along shallow faults and produces an alternation of sediment deposition and erosion (Cawley et al, 2001).…”