Mountain Building

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Mountain Building

• The most extreme form of cructal deformation

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TYPES of MOUNTAINS

• Folded Mountains at continental convergent
  boundaries, they contain the highest mountains in
  the world (Himalayas, Alps, Appalachians, Urals.
• Fault Block Mountains Where the earths crust
  has been stretched and broken into blocks usually
  associated with continental divergent boundaries
  (Sierra Navada Range in California)

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TYPES of MOUNTAINS CONT

• Dome Mountains a rare type of mountain when
  magma at hotspots or continental/ocean convergent
  boundaries pushes up through the crust. (Black
  Hills of So Dakota and the Adirondack Mountains
  of New York )

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TYPES OF MOUNTAINS CONT

• Volcanic Mountains Mountains that form when
  magma erupts onto the earths surface, commonly
  formed at convergent plate boundaries and are
  associated with subduction zones. (Mid-Ocean
  Ridges, Azores, Andes, Cascades in Oregon and
  Washington)
• Hot Spots in the ocean floor form Hawaiian
  Islands, Aleutians in Alaska)

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Types and processes of mountain-building
(Orogenesis)

• 1. Volcanic mountains
• 2. Fold-and-thrust mountains
• 3. Fault-block mountains
• 4. Upwarped mountains

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Convergent Plate Boundaries and Folding
Continent-Continent collision forms Folded
Mountain BeltAlps, Himalayans, Appalachians
Ocean-Ocean collision forms Island Arc
Japan, Aleutians, Cent. Am.
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Types of Mountains

• 2. Fold-and-thrust mountains
• Formed by Continent-Continent Collisions

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Appalachian Mountain System
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Model for the Evolution of the Southern
Appalachians
Supercontinent breaks up, rifts apart.
Another Rift Over here somewhere
rift
Another rift starts moving Africa west. The ocean
floor breaks and one side subducts, starting a
new island arc.
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Model for the Evolution of the Southern
Appalachians (contd)
The ocean floor breaks again, new subduction adds
volcanics to an existing microcontinent
Weak rifts
Net westward movement pushes the ridge,
subduction zone and fragment into
N.America Rifting restarts to the East
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Model for the Evolution of the Southern
Appalachians (contd)
Arc and subduction zone collide w/ N.Am.,
westward subduction starts
The continents collide
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Model for the Evolution of the Southern
Appalachians (contd)
Rifting Restarts
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Fault-block mountains

• Rift Valleys, Mid Ocean Ridges
• Basin and Range province ???
• Normal Fault Blocks as in East Africa
• Divergent Margins?
• Paradigm Shifts

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Origin of the Basin and Range Southwestern North
AmericaLooks different
Paradigm Shifts
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Upwarped mountains

• a) Gently bent without much deformation
• b) Ascent of buoyant mantle material
• c) Far from plate boundaries
• d) Adirondack Mountains Uplift of deep
  PreCambrian Igneous and Metamorphic rocks

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The Adirondack Mountains of Northern New York
Source Clyde H. Smith/Allstock/Tony Stone Images
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Collisional Mountains ??? (The Grand Tetons in
Wyoming)
Source Peter French/DRK Photo
Paradigm shifts What is wrong with our model?
More on this later
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Lewis Thrust Fault (cont'd)
Source Breck P. Kent
PreCambrian Limestone over Cretaceous
Shales
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Graben in Iceland
Source Simon Fraser/Science Photo Library/Photo
Researchers, Inc.
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Rock Distortion
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Evidence of Lateral Compression

• Formerly horizontal layers are twisted, bent, or
  broken.
• Some folded rocks are pushed over on their sides,
  or even upside down.

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Folded Sandstone
Source Martin Bond/Science Photo Library/Photo
Researchers, Inc.
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Folded Rocks, Hwy 23 Newfoundland, New Jersey
Note highest point
Source Breck P. Kent
Adjacent Anticline and Syncline
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Folded Rocks (Dorset, England)Center has
overturned area
Older
Overturned Area
Younger
Lucky we have ways of recognizing right side
up What are they?
Source Tom Bean
Older
Younger