Like all mountains, the Blue Ridge Mountains of western North Carolina and Eastern Tennessee are the result of the action of plate tectonics. The crust of our planet is composed of five primary plates, or huge pieces of rock that move very slowly over deeper layers of hot, pliable rock.
Some of the plates are composed of heavy oceanic crust, while others are made of lighter continental crust. At the middle of each oceanic plate, a large crack pours lava out onto the ocean floor. This causes oceanic plates to expand by an inch or two every year. When oceanic crust is forced against continental crust, the oceanic crust is pushed underneath the continental crust. When continental crust is forced against continental crust, huge mountains usually are formed.
The Appalachian Mountains were formed in the remote past, some 200mya, by collision of two continental crusts. During such mountain building, huge sheets of rock are pushed over each other. A rock layer called the Blue Ridge Thrust Sheet was moved over 60 miles to cover what is now Grandfather Mountain.