Appalachian Mountains

The Appalachian , sometimes known as the Appalachians, are a mountain range in eastern to northern .

During the Ordovician Period, the Appalachians initially developed some 480 million years ago.

They formerly reached altitudes comparable to the Alps and the before succumbing to erosion.

The Appalachian are a barrier to east–west movement because they form a sequence of alternating ridgelines and valleys that are angled in opposition to most routes and trains that go east–west.

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