- OROGENY:
An Orogeny is a period of major regional episode of mountain building.
During an orogeny, portions of the Earth's surface are uplifted. Energy for this uplift usually comes from the colliosion of tectonic plates.
The Himalayas in Asia and the Andes in South America are currently undergoing such uplift:
Himalayas: The Indian Plate is pushing north, colliding with the Eurasian Plate.
Andes: The Pacific Plate is pushing east, colliding with the South American Plate.
- Eastern U.S. Orogenies, in chronological order:
- Grenville Orogeny (about 1.3 to 1.0 billion years ago):
Formation of Adirondack Mountains in N.Y. and Laurentian (or Laurentide) Mountains in Canada.
Very intense metamorphism over a very long time. Mountainous terrain has lasted ever since.
- Taconic Orogeny: (about 550 to 440 million years ago, =early phase of Appalachian Orogeny):
Mostly in New England, but also further south into Piedmont region and foothills along east coast.
Includes formation of Taconic Mountains along eastern edge of N.Y. State., also Green Mountain in Vermont,
White Mountains in New Hampshire, and various mountains in Maine.
- Acadian Orogeny (mid to late Devonian, around 375-325 million years ago, =middle phase of Appalachian Orogeny):
Mostly in easternmost Canada (Maritime region) and eastern Maine.
- Alleghenian Orogeny (Carboniferous to Permian, about 300-250 million years ago, =late phase of Appalachian Orogeny)
Widespread mountain-building from Alabama to New York State, including most mountainous parts of Eastern U.S.
- Major Western U.S. Orogenies, in chronological order:
- Nevadan Orogeny (mid Jurassic to early Cretaceous, about 160-140 million years ago):
Formation of Sierra Nevada in California and Nevada.
- Laramide Orogeny (mostly late Cretaceous, 80-65 million years ago):
Formation of northern Rocky Mountains
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