mountain building and land faults

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Deformation and . Mountain Building A. Plate Tectonics and Stress B. Rock Deformation C. Geologic Structures D. Origin of Mountains E. Continental Crust

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Page 1: Mountain Building and Land Faults

Deformation and . Mountain Building

A. Plate Tectonics and Stress

B. Rock Deformation

C. Geologic Structures

D. Origin of Mountains

E. Continental Crust

Page 2: Mountain Building and Land Faults

Tectonic Stresses Large Scale Strain of the Crust i.e., 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

Crust: Rigid, Thin

Mantle: Plastic, Convecting

Page 3: Mountain Building and Land Faults

Tectonics and Structural Geology

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

Bends Rocks, i.e., ductile strain (Folds)Breaks Rock, i.e., brittle strain (Joints) and Moves large blocks along Faults andReleases energy Earthquakes

Page 4: Mountain Building and Land Faults

Fig. 10-CO, p. 216

Page 5: Mountain Building and Land Faults

Folds and Faults (Palmdale, Ca)

See Fig. 10-2a, p. 219

Page 6: Mountain Building and Land Faults

Eastern Pennsylvania

NorthwesternAfrica

Page 7: Mountain Building and Land Faults

Stresses at Plate

Boundaries Divergent (Tensional)

| Convergent (Compressional) | Transform (Shear)

e.g., Pacific NW

Page 8: Mountain Building and Land Faults

GeoloGic 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)

Page 9: Mountain Building and Land Faults

StikeS and dipS are uSed to identify GeoloGic StructureS

Page 10: Mountain Building and Land Faults

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

Page 11: Mountain Building and Land Faults

Strike and dip

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

Strike and Dip Map Symbol

Page 12: Mountain Building and Land Faults

SippinG BeddinG planeS

Youngest (top)

P: Permian P: Pennsylvanian M: Mississippian D: Devonian S: Silurian O: Ordovician C: Cambrian

Oldest (bottom)

D

S

O

Sedimentary Rocks Dip in the direction of younger rocks

Page 13: Mountain Building and Land Faults

Deciphering the geology of ohio

Using Dipping BeDDing planes

Beds Dip 2o, West Younger rocks,

West Mirror image east of

Sandusky?Sandstone Shale Limestone

M O D2o2o2o

Page 14: Mountain Building and Land Faults

anticline (folD)

Page 15: Mountain Building and Land Faults

anticline (folD)

Page 16: Mountain Building and Land Faults

syncline (folD)

Page 17: Mountain Building and Land Faults
Page 18: Mountain Building and Land Faults

plUnging anticline

Page 19: Mountain Building and Land Faults

folD terminology

Axis Axial Plane Plunging Age of rocks

and outcrops

Axis Axis

Page 20: Mountain Building and Land Faults

plUnging anticline, coloraDo

Page 21: Mountain Building and Land Faults

eastern pennsylvania Folds and faults resulting from

compressive stresses Anticlines (many plunging) Synclines (many plunging) Reverse faults Thrust faults

Page 22: Mountain Building and Land Faults

Domes anD Basins

Page 23: Mountain Building and Land Faults
Page 24: Mountain Building and Land Faults

BeDrock geology of the michigan Basin During and after the

deposition of Michigan’s sedimentary rocks

The crust warped downward

Exposing younger rocks in the center and

Older rocks on the rim (e.g. Toledo)

Page 25: Mountain Building and Land Faults

When shallow crust is strained rocks tend to exhibit brittle strain

Brittle Strain JointS

Page 26: Mountain Building and Land Faults

Sheet JointS

Page 27: Mountain Building and Land Faults

Defining fault orientation

Strike of fault plane parallels the fault trace and fault scarp

Direction of Dip of the fault plane indicates the Hanging wall block

Fig. 10-11a, p. 227

Page 28: Mountain Building and Land Faults

fault: Movement

occurring along a discontinuity

Brittle strain and subsequent movement as a result of stress

Fault

terminology

Page 29: Mountain Building and Land Faults

faultS

Fault: When movement occurs along a discontinuity

Fault type depends on the type of stress

Page 30: Mountain Building and Land Faults

normal faultS

Page 31: Mountain Building and Land Faults

normal faultS, horStS anD graBenS

Page 32: Mountain Building and Land Faults

StructureS at Divergent BounDarieS

Tensional Stresses cause brittle strain and formation of sets of normal faults

i.e., Horsts and Grabens

Page 33: Mountain Building and Land Faults

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 GrabenHorst

Graben

Page 34: Mountain Building and Land Faults

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)

Page 35: Mountain Building and Land Faults

horSt anD graBen, nevaDa

Humboldt Range, Northern Nevada Fig. 10-15b, p. 233

Graben

Horst

Page 36: Mountain Building and Land Faults

horSt anD graBen, nevaDa

Humboldt Range, Northern Nevada

Graben

Horst

Page 37: Mountain Building and Land 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

Page 38: Mountain Building and Land Faults

sTRucTuRes aT a Passive conTinenTal MaRgin

Resulting from continental breakup E.g., The Americas and Africa

Page 39: Mountain Building and Land Faults

salT doMes: e.g., Texas

Rising of less dense salt

Stretches overlying crust

Forming normal faults and

Oil traps

Page 40: Mountain Building and Land Faults

sTRucTuRal oil TRaPs

Page 41: Mountain Building and Land Faults

ThRusT FaulT: glacieR nP, MonTana

Old

Younger

Page 42: Mountain Building and Land Faults

sTRucTuRes aT a conveRgenT BoundaRy

Page 43: Mountain Building and Land Faults

Structures within Mountain Belts

Page 44: Mountain Building and Land Faults

Compressional and TensionalStructures

Page 45: Mountain Building and Land Faults

e.g., The aPls

Intense folding and thrusting of sedimentary rocks

Page 46: Mountain Building and Land Faults

sTRike sliP FaulTs

Physiographic Features

Page 47: Mountain Building and Land Faults

san andReas FaulT

What type of fault is this? What other features are

associated with the fault?

Page 48: Mountain Building and Land Faults

san andReas FaulT