Valley and Ridge Physiography Topics

1. Regional Setting
2. Extent and Boundaries
3. Characteristic Features
4. Drainage
5. Scenic Tour
Introduction to Physiography
Coastal Plain
Mesozoic Basins
Blue Ridge
Valley and Ridge
Appalachian Plateaus
Virginia's Rivers


Scenic Tour of the Valley and Ridge (Part 4)

Mountain Lake

• Mountain Lake is located high atop Salt Pond Mountain in the Valley and Ridge of eastern Giles County. It is the only natural lake in the Valley and Ridge of the southern Appalachian mountains.

Mountain Lake is the only natural lake in Virginia's Valley and Ridge. It is located in a small valley on a mountain top about 4000 feet above sea level. (Photograph by Lori Combs)

• Mountain Lake is located in the valley formed on a breached anticline where streams have eroded through hard Silurian sandstones into softer Ordovician shales and limestones.

505 to 438 million years ago
438 to 408 million years ago
an anticline that has been deeply eroded in the center, so that it has inward-facing cliffs on both sides

Geologic Map showing the kind of rocks present in the Mountain Lake area. Orem (Reedsville, Eggleston and Mocassin Formations) and j (Juniata Formation) represents Ordovician shale and carbonates. Stu (Tuscarora Formation) and Srh (Rose Hill Formation) are Silurian sandstones that partially underly the lake. The "c" represents "colluvium" or landslide deposits that are very common in the area. (Map courtesy of the Virginia Division of Geology and Mineral Resources, Schultz et. al., 1986, Geologic Map of Giles County, VA, Publication 069.

The photo shows an exposure of the Silurian sandstone. (Photograph by Phyllis Newbill)

438 to 408 million years ago
505 to 438 million years ago

• The origin of the lake is controversial.  Many geologists today believe that it was formed by an ancient landslide.

Many thories about the origin of Mountain Lake have been proposed. Among thse are formation due to solution of rocks, volcanic activity, meteorite impact, cold weather processes during the Pleistocene Ice Age, and even cows stomping around a salt lick on the mountain top. (Above photo by Robert Whisonant, photo below by Phyllis Newbill)

Mountain Lake is drained by a creek at the north end flowing through a natural dam made of large sandtone blocks intermixed with other sediments. The dam probably formed by a rockslide, which may have been caused by earthquake activity in the Giles County seismic zone. (Photograph by Robert Whisonant)

1.6 million years to 10,000 years ago

• Mountain Lake has been a famous resort for many years.  A hotel and recreation facilities are located there.

Mountain Lake, a famous resort, had a hotel as early as the 1860s. In the Civil War, Union soldiers camped here as they retreated back to West Virginia from a battle in the New River Valley. (Photograph by Phyllis Newbill)

• The water level in Mountain Lake has historically fluctuated. In 2008, the lake was nearly completely dry. Researchers determined that water was seeping though 4 depressions in the lake bottom.

This photo, dated December 2012, shows two of the leaky depressions (D-1 and D-2) at the north end of the lake. The former high-water lake level is clearly seen as the edge of the tree line. The white rocks that line the side of the lake are blocks of sandstone from a landslide that blocked a stream that likely caused the formation of the lake. (Photograph by Skip Watts)

Picture taken in 2008 from the dry lake bed, looking toward the north end of the lake. In the distance at the edge of the lake is the Newport House that at one time was at the water's edge. (Photograph by Jolanta Wawrzycka)

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