Mountain building and crustal deformation
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Mountain Building and Crustal Deformation . Economic Consequences of Geologic Structures. Tracing Coal Seams, Aquifers, etc. Ore Deposits are often localized along faults and folds Petroleum Traps. Isostasy . Thickness and Density. Isostatic Rebound in Canada .

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Mountain Building and Crustal Deformation

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Mountain Building and Crustal Deformation


Economic Consequences of Geologic Structures

  • Tracing Coal Seams, Aquifers, etc.

  • Ore Deposits are often localized along faults and folds

  • Petroleum Traps


Isostasy


Thickness and Density


Isostatic Rebound in Canada


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


A Subduction Zone


Metamorphism and Orogeny


Why Mountains are High


How Fast Can Folds Form?


Hutton’s Unconformity, Scotland


Large Fold, Turkey


Eroded Fold, Pennsylvania


Fold in Glacier, Antarctica


Anticlines and Synclines


Folds, Pennsylvania


Which Way was Up?

Sedimentary Structures are governed by:

  • Gravity

  • Exposure to the Surface

    They all have a “right way up”


Foliation

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


Foliation

In every case, the foliation is:

  • In the direction of least resistance

  • at right angles to the direction of greatest compression.


Axial Plane


Folds and Foliation


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.


Fold And Foliation


Growth of Minerals


The Importance of Minor Folds


Minor Folds and Foliation Are Clues to Much Larger Structures


How Geologists Use These Clues

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


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.


Complex Folds, Scotland

Complex Folds, Scotland


Complex Folds, Scotland


Faults, Appalachians


Thrust Faults in Snow


Domes and Basins


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