The Appalachian Mountains (i/ˌæpəˈleɪʃɨn/ or /ˌæpəˈlætʃɨn/), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period, and once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded. The Appalachian chain is a barrier to east-west travel as it forms a series of alternating ridgelines and valleys oriented in opposition to any road running east-west.
Definitions vary on the precise boundaries of the Appalachians. The United States Geological Survey (USGS) defines the Appalachian Highlands physiographic division as consisting of thirteen provinces: the Atlantic Coast Uplands, Eastern Newfoundland Atlantic, Maritime Acadian Highlands, Maritime Plain, Notre Dame and Mégantic Mountains, Western Newfoundland Mountains, Piedmont, Blue Ridge, Valley and Ridge, Saint Lawrence Valley, Appalachian Plateaus, New England province, and the Adirondack provinces. A common variant definition does not include the Adirondack Mountains, which geologically belong to the Grenville Orogeny and have a different geological history to the rest of the Appalachians.
Read more about Appalachian Mountains: Overview, Geology, Influence On History
Famous quotes containing the word mountains:
“The gold-digger in the ravines of the mountains is as much a gambler as his fellow in the saloons of San Francisco. What difference does it make whether you shake dirt or shake dice? If you win, society is the loser.”
—Henry David Thoreau (18171862)