5'3 Mountain Formation

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5.3 Mountain Formation

• Mountain Range a group of adjacent mountains
  with the same general shape and structure
• EX Mt. St. Helens Cascade Mountain Range
• EX Mt. Everest Great Himalayan Range
• Mountain System a group of adjacent mountain
  ranges
• EX Great Smoky Blue Ridge Cumberland Green
  Appalachian Mountain System
• Mountain Belts all the mountain systems in the
  world make up 2 mountain belts
• Eurasian-Melanesian Belt
• Circum-Pacific Belt

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Plate Tectonics and Mountains

• Both belt systems are located on converging
  boundaries
• This leads scientists to believe that most
  mountains are formed when lithosphere plates
  collide
• What about the Appalachians?
• The Appalachians do not occur along convergent
  boundaries
• Do not lie on current converging boundaries but
  geologic evidence shows these ranges were once
  formed by convergence

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Types of Collisions

• Continental vs. Oceanic
• Oceanic is subducted under the continental
• Deformation is great form high mountains
• Subduction causes partial melting of top mantle
  layer
• Produces magma eventually erupt
• Volcanic mountains
• EX Cascades (Pacific Northwest)

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• Mountains also form here by
• As subduction occurs, pieces of the crust break
  off
• The broken pieces become part of the crust
• Stick up and form mountains

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Oceanic vs. Oceanic

• One oceanic crust subducts under another oceanic
  crust
• Water from the subducting plate partially melts
  the mantle
• Magma rises and breaks through the surface
• Form an arc of volcanic mountains on the ocean
  floor
• Mariana Islands Northern Pacific Ocean

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Continental vs. Continental
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Fault block mountains
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Sudden stress near the earth's surface fractures
rock. Faults are fractures along which movement
has occurred. Tensional stress produces normal
faults. In a normal fault, the rock above the
rock plane moves down relative to the rock below.
Complex parallel normal faulting produces fault
block mountains like those of the Great Basin of
California, Nevada, and Utah. Down-dropped blocks
between parallel faults are called grabens.
Up-lifted blocks are horst blocks. Lake Tahoe,
Death Valley, and the Salton Trough lie in
grabens.
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Folded mountains
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Ex. Of folded mountains

• Appalachian Mountains
• Himalayas

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Dome mountains

• Adirondack Mountains
• Black Hills

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Dome mountains

• Made nether by folding or fault-block
• Magma rising but cooling below the surface and
  then the rest of the rock is eroded away.