Major Tectonic Events of the Appalachian Region

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Major Tectonic Events of the Appalachian Region

• Grenville Orogeny - 1.1 billion years ago -
  occurred when North America Collides with another
  continent. Forms mountains, but only their roots
  still exist.
• Iapetus Ocean - 650 million years ago - North
  America pulls apart from the rest of Laurasia,
  creating an earlier version of the Atlantic.

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Major Tectonic Events of the Appalachian Region

• Iapetus lasts for about 200 million years. As it
  is closing, a subduction zone and island arc form.

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Major Tectonic Events of the Appalachian Region

• Taconic Orogeny - 445-435 million years ago
  -Iapetus closes, and an off-shore volcanic island
  arc (related to subduction - like Japan today)
  slams into North America, creating more
  mountains. These mountains begin to erode,
  creating thick sediments (4000 feet thick in some
  places - Catskill delta) across the east coast.

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Major Tectonic Events of the Appalachian Region

• Acadian Orogeny - 375-355 million years ago
  -Iapetus begins closing for good, and a new
  mountain range is forced up east of the
  fast-eroding Taconic mountains.

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Major Tectonic Events of the Appalachian Region

• Acadian mountains continue to erode, producing
  tons of sediments across the east coast.
• Alleghenian Orogeny - 320-220 million years ago
  -Iapetus finally closes completely as the
  northwestern part of Africa rams into North
  America (forming part of Pangea). This creates
  our modern Appalachian mountains.

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Major Tectonic Events of the Appalachian Region

• After the orogenies - 220 million years ago to
  the present - Pangea breaks up, forming the new
  Atlantic. The rifting of Africa and North
  America produces pull-apart basins which fill
  with sediments from the new mountains. There is
  also basaltic volcanism as dikes come up through
  the fractures in the rifting crust.