Many mountain ranges are formed by the collision of tectonic plates. The compression of land that occurs as a result forces land upward creating the range. While this is the same basic process that created the Appalachian Mountains, there were some other complex aspects involved. Between the two continents colliding was an ocean filled with multiple island chains. These island chains were formed by subduction zones, areas where one plate goes beneath the other. The plate then melts and rises to the surface creating volcanoes. When this happens in the middle of the ocean we are left with island chains like Japan.
As the two continents began to drift towards each other, the volcanic island chains became trapped in between. Also between the continents were other “micro continents” which were not formed by subduction. This meant there was far more earthen material between the two continents leading to even more uplift. The resulting mountain range not only reached towering heights because of the excess material, but it also had distinct features throughout the range of the normal uplift, the islands chains, and the microcontinents involved.
This process of tectonic plates colliding, and later diverging, is called the Wilson Cycle. It is a continuing process that has been happening for eons and will continue to shape the face of the Earth for eons.