Mount Rogers

Mount Rogers and Whitetop Mountain are the tallest summits on a ridge that forms the border of Smyth, Grayson, and Washington counties
Mount Rogers and Whitetop Mountain are the tallest summits on a ridge that forms the border of Smyth, Grayson, and Washington counties
Source: US Geological Survey (USGS), Abingdon, TN 1:125,000 topographic quadrangle map (1891)

Mount Rogers, at 5,729 feet in elevation, is the highest spot in Virginia. The next four tall peaks are:1

Mount Rogers is on the border of Smyth and Grayson counties, with the tip of the summit in Smyth County
Mount Rogers is on the border of Smyth and Grayson counties, with the tip of the summit in Smyth County
Source: US Geological Survey (USGS), Geographic Names Information System

The creation of Mount Rogers started about a billion years ago during the Grenville Orogeny. Tectonic forces squeezed chunks of continental crust together, forming the supercontinent of Rodinia. The compression pushed up the Grenville Mountains, and simultaneously pushed mountain roots down towards the mantle. The "pluton" of molten rock deep underground cooled slowly. Minerals crystallized at different temperatures and pressures, and crystals aligned in light/dark layers, to create a rock formation now called the Cranberry Gneiss.2

Rodinia started to crack up about 760 million years ago, but in what today is North Carolina/Virginia the rifting failed around 735 million years ago. The rift valley filled with as much as 25,000 feet ofsediments that have since been metamorphosed. Much of the Great Smoky Mountains are formed from the Ocoee Supergroup.

From Cumberland Gap to Grayson County in Virginia, the Crossnore Complex (which includes the Mount Rogers Formation) overlies the Cranbery Gneiss. The Mount Rogers Formation is a mixture of sedimentary and volcanic rocks that accumulated in the valley during the failed rifting 735 million years ago. The rhyolite records the heavy volcanic activity triggered by the thinning crust as the rift valley opened. The sedimentary rocks indicate that erosion was strong, with rivers carrying volcanic material and eroded cobbles/pebbles of Cranberry Gneiss into the valley.

The Konnarock Formation, on top of the Mount Rogers Formation and therefore younger, includes conglomerate with cobbles. The Konnarock Formation is clearly associated with glaciation; in places there are "dropstones" of Cranberry Gneiss which were encased in ice on top of a lake and then deposited when the ice melted. The glaciation occurred at a time when most or perhaps even the entire earth was encased in ice, a "Snowball Earth" period.

The pause in the rifting of Rodinia ended 570 million years ago and the supercontinent broke up. In that process, lava welled up and spread across the surface. In the Blue Ridge north of Charlottesville the lava is known as the Catoctin Formation. After the rifting, the location of Mount Rogers was on the edge of the North American Plate. Marine sediments were deposited for about 100 million years. That changd when the Taconic Orogeny began the process of accreting terranes to the edge of the plate, burying the older formations.3

Heat and pressure from burial and then thrust faulting during orogenies metamorphosed the rock, realigning the cystals to create different minerals. Today Mount Rogers is 300 miles from the shoreline. Erosion has exposed the volcanic and sedimentary bedrock which was deposited over 500 million years ago and then metamorphosed.

In 1966, the US Congress created the Mount Rogers National Recreation Area and included 191,000 acres of National Forest land:4

The area features four Congressionally designated wilderness areas; the Virginia Creeper Trail; the Mount Rogers Scenic Byway which traverses over 50 miles offering views of the National Recreation Area and open rural countryside; the 5,000-acre Crest Zone featuring elevations over 4,000 feet, large rock formations, and a mixture of mountain balds and spruce-fir forests; a herd of wild, free-ranging ponies; and the highest elevated road in the state of Virginia leading to the summit of Whitetop Mountain.

The Mountains of Virginia

Topography of Virginia

Volcanoes in Virginia

Mount Rogers is a feature within the Blue Ridge
Mount Rogers is a feature within the Blue Ridge
Source: ESRI, ArcGIS Online

Links

References

1. "Virginia’s Five Highest Peaks," Virginia Tourism Corporation, https://blog.virginia.org/2014/10/peaks/ (last checked November 22, 2021)
2. "Welcome to the Mount Rogers Field Trip - Cranberry Gneiss," Radord University, https://www.radford.edu/~fldsch/RUFieldschool/formationpages/Cranberry%20Gneiss/Cranberry.html (last checked November 22, 2021)
3. "The Big Picture," Geologic History of the Mount Rogers Area, Radford University, https://www.radford.edu/~fldsch/RUFieldschool/fieldtrips/MountRogers/MtRogersGeolHistory/MtRogersGeoHist.html; "Cranberry Gneiss," Geologic History of the Mount Rogers Area, Radford University, https://www.radford.edu/~fldsch/RUFieldschool/formationpages/Cranberry%20Gneiss/Cranberry.html; "Mount Rogers Formation," Geologic History of the Mount Rogers Area, Radford University, https://www.radford.edu/~fldsch/RUFieldschool/formationpages/Mt.%20Rogers%20Fm/MtRogers.html; "Konnarock Formation," Geologic History of the Mount Rogers Area, Radford University, https://www.radford.edu/~fldsch/RUFieldschool/formationpages/Konnarock%20Fm/Konnarock.html; Scott A. MacLennan, Michael P. Eddy, Arthur J. Merschat, Akshay K. Mehra1, Peter W. Crockford, Adam C. Maloof, C. Scott Southworth, Blair Schoene, "Geologic evidence for an icehouse Earth before the Sturtian global glaciation," Science Advances, Volume 6, Number 24 (June 10, 2020), https://https://doi.org/10.1126/sciadv.aay6647 (last checked November 22, 2021)
4. "Mount Rogers National Recreation Area," US Forest Service, https://www.fs.usda.gov/detail/gwj/specialplaces/?cid=stelprdb5302337 (last checked November 22, 2021)


Rocks and Ridges - The Geology of Virginia
Virginia Places