The tectonic event that formed the Appalachian mountain range is the convergence of ancient tectonic plates. The Appalachian mountain range is one of the oldest fold mountain ranges on the planet.
The range was formed when two tectonic plates collides. The resulting collision will cause rocks to become warped into folds and develop cracks called faults.
The resulting folding and faulting at this boundary gave rise to the valley and ridge structure observed.
