The Taconic orogeny
The first of the Appalachians' three risings
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An orogeny is what happens when two landmasses are pressed together and the rocks between them fold and are thrust upward. Mountain ranges are rarely built in one event. The Appalachians are the product of three separate collisions across 250 million years — Taconic, Acadian and Alleghanian — each leaving its own set of rocks and faults. Debris eroded from the Taconic mountains filled the inland sea to the west and forms the thick sedimentary layers beneath much of Ohio and Pennsylvania.
For children
A chain of volcanic islands, rather like Japan today, drifted into North America's eastern edge and was shoved up onto it. It was the first of three great collisions that together built the Appalachians.
Sources
- Encyclopædia Britannica: «Taconic orogeny»
- USGS: Geology of the Appalachian Highlands
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