Mountain Building and Crustal Deformation

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Mountain Building and Crustal Deformation
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Economic Consequences of Geologic Structures

• Tracing Coal Seams, Aquifers, etc.
• Ore Deposits are often localized along faults and
  folds
• Petroleum Traps

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Isostasy
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Thickness and Density
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Isostatic Rebound in Canada
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Mountain Building (Orogeny)

• Orogeny is the variety of processes that occur
  during mountain-building, including
• Distinctive Patterns of Deposition
• Deformation
• Metamorphism
• Intrusions
• Volcanic Activity
• Oceanic Trenches
• Seismic Activity

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A Subduction Zone
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Metamorphism and Orogeny
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Why Mountains are High
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How Fast Can Folds Form?
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Huttons Unconformity, Scotland
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Large Fold, Turkey
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Eroded Fold, Pennsylvania
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Fold in Glacier, Antarctica
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Anticlines and Synclines
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Folds, Pennsylvania
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Which Way was Up?

• Sedimentary Structures are governed by
• Gravity
• Exposure to the Surface
• They all have a right way up

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Foliation

• Foliation is a sheetlike structure that forms
  when rocks are deformed.

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Foliation

• In every case, the foliation is
• In the direction of least resistance
• at right angles to the direction of greatest
  compression.

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Axial Plane
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Folds and Foliation
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Folds and Foliation

• On a small scale (microscopic to centimeters),
  foliation forms
• On a large scale (centimeters to kilometers),
  rocks fold.
• Both foliation and the axial plane of the fold
  are at right angles to the direction of greatest
  compression.

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Fold And Foliation
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Growth of Minerals
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The Importance of Minor Folds
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Minor Folds and Foliation Are Clues to Much
Larger Structures
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How Geologists Use These Clues

• Here's an outcrop that might be seen in the
  field.

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How Geologists Use These Clues

• We can mentally fill out the rest of the fold.
• Note that we still have no idea how big the fold
  is, only what kind it is.

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Complex Folds, Scotland
Complex Folds, Scotland
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Complex Folds, Scotland
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Faults, Appalachians
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Thrust Faults in Snow
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Domes and Basins