Editing Appalachian Mountains (section)

===Acadian Orogeny===
The third mountain-building event was the [[Acadian orogeny]] which occurred between 375 and 359 million years ago.<ref>{{Cite journal |last=Hatch |first=N. L. |date=2009 |title=The Acadian orogeny: A review |journal=Geological Society of America Bulletin |volume=121 |issue=5–6 |pages=639–678}}</ref> The Acadian orogeny was caused by a series of collisions of pieces of crust from the Avalonia Terrane, sections broken off from continent of [[Gondwana]], with the North American Plate. The collision initiating this orogeny resulted in the closing of the southern [[Iapetus Ocean]] and the formation of a high mountain belt. After the Acadian collision took place, Gondwana began to retreat from Laurentia with the newly [[Accretion (geology)|accreted]] [[Avalonia]]n [[terrane]]s left behind. As Gondwana moved away, a new ocean opened up, the [[Rheic Ocean]], during the Middle to Late Devonian, and subsequently its closure would result in the formation of the [[Alleghanian orogeny]].