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APPALACHIAN GEOLOGY |
Making Mountains
Geology and Ecology
The geology of the Appalachian
mountains can best be summed
up in two words: creation and destruction.
From Milepost 0 at Rockfish Gap, VA to Milepost 355 near Mount Mitchell State Park, NC,
the Parkway lives up to its name by following the crest of the Blue Ridge Mountains
averaging about 3,000 feet in elevation, occasionally dipping down into the coves and
hollows or crossing low-elevation water gaps. At Mount Mitchell, the Parkway veers
westward through the Black Mountains, then into the Craggies before descending toward
Asheville. From there, the road climbs to elevations over 6,000 feet in the Balsam
Mountains before entering the Great Smoky Mountains National Park near Cherokee.
The mountain-building process here is one of both creation and destruction. This creation, perhaps hundreds of millions of years in the geologic past, was both violent and dramatic. The destruction goes on before our very eyes today, at a seemingly slow and steady pace.
Geologists tell us that sections of huge plates forming the crust of the earth have collided violently on numerous occasions in the past. The results are folded-up slabs of crust piled up like a deck of cards or a wrinkled throw rug. This mass of mostly igneous (cooled, molten material) and metamorphic (formed under heat and pressure) rock is the geological foundation of the Appalachians that we see today.
Perhaps of more interest to visitors today
is the other half of the mountain-building story, their gradual destruction. The slow,
steady forces of wind, water, and chemical decomposition have reduced the Blue Ridge from
Sierra-like proportions to the low profile of the world's oldest mountain range. The
almost constant wind that blows across the exposed ridgetops of the Appalachians plays an
important role in the weathering and eroding processes. Summer thunderstorms bring
torrents of rain. In the winter, freezing and thawing water in crevices brings occasional
rock slides that bear witness to the erosional processes in these mountains. Occasional
catastrophic events like floods, hurricane force winds, blizzards and ice storms can
change the face of the mountains overnight.
The geological history of the mountains is a determining factor in all of the flora (plant life) and fauna (animal life) protected in the park. Plant and animal communities can change dramatically depending on the direction a particular ridge is facing, the elevation, soil type, and exposure to the elements. The eastern edge of the Blue Ridge is consistently more rugged and steep than the western edge due to the direction of uplift during the creation of the mountains. Because of this, the eastern slopes of the Blue Ridge have more rugged river drainage, evidenced by Linville Gorge (MP 316) and Rockcastle Gorge (MP 169).
