structural geology deformation and mountain building n.
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Structural Geology: Deformation and Mountain Building. Inner core: Solid iron Outer core : Liquid iron, convecting (magnetic field) Mantle ( Asthenosphere ) : Solid iron-magnesium silicate, plastic, convecting Crust (Lithosphere): Rigid, thin 5-30km.

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tectonic stresses large scale s train of the crust geologic structures
Inner core: Solid iron

Outer core: Liquid iron, convecting(magnetic field)

Mantle (Asthenosphere): Solid iron-magnesium silicate, plastic, convecting

Crust (Lithosphere):Rigid, thin 5-30km

Tectonic Stresses Large Scale Strain of the Crust - Geologic Structures

Crust: Rigid, Thin

Mantle: Plastic, Convecting

tectonics and structural geology

Tectonic Stresses resulting from Internal Energy (heat driving convection) Strains (deforms) the Mantle and Crust

Bends Rocks

ductile strain (Folds)

Breaks Rock

brittle strain (Joints)

Moves large blocks

Faults

Releases energyEarthquakes

Tectonics and Structural Geology
stresses at plate boundaries
Divergent

(Tensional)

|

Convergent

(Compressional)

|

Transform

(Shear)

e.g., Pacific NW

Stresses at Plate Boundaries
geological structures
Geological Structures
  • Different stresses result in various forms of strain (geologic structures)
    • Folds (compressive stresses may cause ductile strain)
    • Faults (Any type of stress may cause brittle strain. The type of fault depends on the type of stress)
geological structures1
Geological Structures
  • Fault: a discontinuity surface across which there has been shear displacement
  • Hangingwall: the wall and body of rock above an inclined fault
  • Footwall: the wall and body of rock beneath an inclined fault
geological structures2
Geological Structures
  • Normal Fault: hanging wall moved downwards compared to the footwall
  • Reverse Fault: hanging wall moved upwards compared to the footwall
  • Thrust fault: low angle reverse fault
geological structures3
Geological Structures
  • Strike Slip Fault: displacement parallel to the fault plane.
  • Can be left or right handed!
strike and dip
Strike and Dip
  • Define and map the orientation of planar features
    • Bedding planes (sedimentary rocks)
    • Foliation
    • Joints
    • Faults
    • Dikes
    • Sills
    • Ore Veins

Fig. 10-4, p. 221

strike and dip1
Strike and Dip

Strike and Dip Map Symbol

  • Strike: The line of intersection between the plane and a horizontal surface
  • Dip: Angle that the plane makes with that horizontal plane

Fig. 10-4, p. 221

fold terminology
Fold Terminology
  • Hinge: the greatest curvature of a folded surface
  • Axial plane: a planar surface defined by the successive positions of fold hinges
  • Plunge

Axis Axis

brittle strain joints
Brittle Strain  Joints
  • When shallow crust is strained rocks tend to exhibit brittle strain
defining fault orientation
Defining Fault Orientation
  • Strike of fault plane parallels the
    • fault trace
    • fault scarp
  • Direction of Dip of the fault plane indicates the Hanging wall block
fault
Fault:
  • Movement occurring along a discontinuity
  • Brittle strain and subsequent movement as a result of stress
  • Fault terminology
faults
Fault: When movement occurs along a discontinuity

Fault type depends on the type of stress

Faults
horsts and grabens
Horsts and Grabens
  • Older Rocks are exposed along the ridges formed by the horsts
  • Younger rocks lie beneath the grabens
  • Sediment fills in the linear valleys

Horst

Horst

Graben

Graben

nevada
Nevada
  • “Washboard topography” is the result of Horsts and Grabens
  • A.k.a, Basin and Range
  • E.g., Humbolt Range
  • E.g., Death Valley (Graben)
horst and graben nevada
Horst and Graben, Nevada

Horst

Graben

Humboldt Range, Northern Nevada

horst and graben nevada1
Horst and Graben, Nevada

Horst

Graben

Humboldt Range, Northern Nevada

reverse and thrust faults
Reverse and Thrust Faults
  • Compressive stress causes the hanging wall to move upward relative to the foot wall  Reverse Fault
  • At convergent plate boundaries ancient rocks can be thrust over younger rocks  Thrust Fault
strike slip faults
Strike Slip Faults
  • Physiographic Features