The Alleghanian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957.
The Alleghanian orogeny, a result of three separate continental collisions. USGS
Major fault at the dividing line between the Allegheny Plateau and the true Appalachian Mountains (Williamsport, Pennsylvania).
The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain. The general definition used is one followed by the United States Geological Survey and the Geological Survey of Canada to describe the respective countries' physiographic regions. The U.S. uses the term Appalachian Highlands and Canada uses the term Appalachian Uplands; the Appalachian Mountains are not synonymous with the Appalachian Plateau, which is one of the provinces of the Appalachian Highlands.
The Appalachian Mountains in the background with Penns Valley in Pennsylvania in the foreground in October 2021
Appalachian Mountains broken down by physiographic division, provinces, and sections
Appalachian Highlands physiographic provinces
Appalachian Uplands of Canada's 13 divisions
