Blue Ridge Mountains

The Blue Ridge, or Blue Ridge Mountains, is a physiographic province of the larger Appalachian division. The province consists of the Northern and Southern physiographic sections, which divide near the Roanoke River gap. They are a mountain chain in the eastern United States, part of the Appalachian Mountains, forming their eastern front from Georgia to Pennsylvania. 

To the west of the Blue Ridge, between it and the bulk of the Appalachians, lies the Great Valley, bordered on the west by the Ridge and Valley province. The mountains are well known for their bluish color when seen from a distance. Trees put the "blue" in Blue Ridge, from the hydrocarbons released into the atmosphere, thereby contributing to the characteristic haze on the mountains and their distinctive color.

Within the Blue Ridge province, there are two National Parks: the Shenandoah in the northern section and the Great Smoky Mountains in the southern section. The Blue Ridge also contains the Blue Ridge Parkway, a 469-mile long scenic highway that connects the two parks and is located along the ridge crestlines along the Appalachian Trail.

Geography

Most of the rocks that form the Blue Ridge Mountains are ancient granitic charnockites, metamorphosed volcanic formations, and sedimentary limestones. Recent studies completed by Richard Tollo, a professor and geologist at the George Washington University, provide greater insight into the petrologic and geochronologic history of the Blue Ridge basement suites. Modern studies have found that the basement geology of the Blue Ridge is made of compositionally unique gneisses and granitoids, including orthopyroxene-bearing charnockites. Analyses of zircon minerals in the granites completed by John Aleinikoff at the U.S. Geological Survey have provided more detailed emplacement ages.

Many of the features found in the Blue Ridge and documented by Tollo and others have confirmed that the rocks exhibit many similar features in other North American Grenville-age terranes. The lack of a calc-alkaline affinity and zircon ages less than 1,200 Ma suggest that Blue Ridge are unique from the Adirondacks, Green Mountains, and possibly the New York-New Jersey Highlands. 

The petrologic and geochronologic data suggest that the Blue Ridge basement is a composite orogenic crust that was emplaced during several episodes from a crustal magma source. Field relationships further illustrate that rocks emplaced prior to 1,078-1,064 Ma preserve deformational features. Those emplaced post-1,064 Ma generally have a massive texture and missed the main episode of Mesoproterozoic compression.

History

The English who settled Virginia in the early 1600s recorded that the native Powhatan name for the Blue Ridge was Quirank.

At the foot of the Blue Ridge, various tribes including the Siouan Manahoacs, the Iroquois, and the Shawnee hunted and fished. As more settlers moved into Virginia, their economic and at times martial competition pushed the native inhabitants west.

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