Geology
When traveling the parkway one is exposed to a dramatic geological history that some geologists believe included at least four mountain-building episodes. The most recent episode, known as the Alleghanian Orogeny, was responsible for creating the mountain chain that runs from Canada to Alabama. During this period North America collided with the supercontinent known as Gondwanaland. It is believed that the Blue Ridge Mountains were at one time as high as the Rocky Mountains but as a result of weathering and erosion the mountains have been worn down to their present size (Graham,104). Immense portions of the mountains have undergone no less than three cycles of erosion and uplifting with each cycle of erosion to the level of peneplain. The current uplift is still occurring at a rate of approximately 1.5 inches every 1,000 years (Logue, 3 ).
The main factor contributing to the erosion process is water. In general, the further you go south on the parkway rainfall amounts increase. However, the exact amount of precipitation is considerably affected by local topography, direction and moisture content of prevailing winds and rain-shadow effects. Precipitation amounts vary from as much as 85 inches per year to as little as 40 inches per year. Water’s handiwork is seen all along the parkway. Three major rivers—the James, the Roanoke and the French Broad—have forever left their indelible mark on the parkway’s landscape.
Not to be out done, the Linville River has yielded one of the most impressive sights of water’s mighty power that can be viewed from the parkway. The river is the architect of the parkway’s most popular waterfall, Linville Falls, and the commanding 1500-foot-deep trench below the falls, Linville Gorge. In similar manner, gaps mark the spot where water has reshaped the landscape by attacking a rock’s weak spot. As water flows into and through a joint or fault, freezes and thaws, and leaches out minerals it enlarges the gap slowly but surely. Twenty four sections of the Blue Ridge Parkway are named after this phenomenon including Tuggle Gap and Big Witch Gap (Graham, 104).
Glaciers never reached the Blue Ridge and Southern Appalachians and consequently there is a noteworthy absence of lakes and ponds in the parkway region. Consequently, Stan Abbott designed many artificial impoundments such as Abbott Lake at Peaks of Otter to enhance the parkway’s recreational offerings (Blue Ridge Parkway – America’s Favorite Journey, pg104). Nonetheless, Ice Age glaciers had a dramatic affect on the biodiversity of the Central and Southern Appalachians. As the glaciers pushed southward, northern plants and animals were forced to retreat ahead of the ice sheets and eventually found refuge in the Blue Ridge and Southern Appalachians. At the highest elevations spruce-fir forests provide a sanctuary for plants and animals whose closest relatives live in the forests of New England and Canada (Graham, 107).
Among those animals found in the midst of the red spruce and Fraser fir are Black-capped chickadees, northern flying squirrels and saw-whet owls. From start to finish the parkway passes through a half-dozen forest types. Lowland vegetation common to the piedmont and coastal plain can be found in the floodplain forest of the James River. In between the spruce-fir forests and the floodplain forests are northern hardwood, oak-hickory, pine-oak and Appalachian Cove forests—the most species-rich forest type (Graham, 110).
Works Cited
Graham, Scott J., and Elizabeth C. Hunter. Blue Ridge Parkway: America’s Favorite
Journey.
2003.
Logue, Victoria, Frank Logue, and Nicole Blouin. Guide to the Blue Ridge
Parkway. 2nd ed. Birmingham: Menasha Ridge, 2003.