For the last 200 million years, since the end of the mountain-building era, water, wind, and ice have been wearing the Appalachians down. During the Devonian period, roughly 380 million years ago, a second major mountain-building episode occurred known as the Acadian Orogeny.
Ancient Volcanoes Shaping the Appalachian Mountain Origin
The initial building phase began roughly 480 million years ago during the Ordovician period, in an event known as the Taconic Orogeny. By this time, the continents were moving toward each other again, eventually merging into the supercontinent of Pangaea.
At that time, what is now the eastern coast of North America was the edge of a passive continental margin, similar to today’s Atlantic coastline. This phase was characterized by the collision of the ancestral North American continent, often referred to as Laurentia, with a massive landmass that would eventually become parts of Europe.
Ancient Volcanoes Fueled the Appalachian Mountains' Birth
A chain of volcanic islands, located near the equator, began to collide with the North American continent. Rainwater seeped into cracks in the rock, freezing and expanding during winter cycles in a process called frost wedging.
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