Скачать презентацию Classroom presentations to accompany Understanding Earth 3 rd Скачать презентацию Classroom presentations to accompany Understanding Earth 3 rd

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Classroom presentations to accompany Understanding Earth, 3 rd edition prepared by Peter Copeland William Classroom presentations to accompany Understanding Earth, 3 rd edition prepared by Peter Copeland William Dupré University of Houston Chapter 10 Folds, Faults, and Other Records of Rock Deformation

Deformation of Rocks Deformation of Rocks

Deformation of rocks • Folds and faults are geologic structures. • Structural geology is Deformation of rocks • Folds and faults are geologic structures. • Structural geology is the study of the deformation of rocks and the effects of this movement.

Small-scale Folds Phil Dombrowski Fig. 10. 1 Small-scale Folds Phil Dombrowski Fig. 10. 1

Small-scale Faults Tom Bean Fig. 10. 2 Small-scale Faults Tom Bean Fig. 10. 2

Orientation of deformed rocks We need some way to describe the distribution of geologic Orientation of deformed rocks We need some way to describe the distribution of geologic structures. Strike: bearing of a line defined by Strike the intersection of the plane in question and the horizontal Dip: acute angle between the plane Dip and the horizontal, measured perpendicular to strike.

Fig. 10. 4 Fig. 10. 4

Fig. 10. 4 Fig. 10. 4

Dipping Sedimentary Beds Chris Pellant Fig. 10. 3 Dipping Sedimentary Beds Chris Pellant Fig. 10. 3

Cockscomb Ridge, S. Utah P. L. Kresan Cockscomb Ridge, S. Utah P. L. Kresan

Cockscomb Ridge, S. Utah Strike Dip P. L. Kresan Cockscomb Ridge, S. Utah Strike Dip P. L. Kresan

Geologic Map and Cross Section Fig. 10. 5 Geologic Map and Cross Section Fig. 10. 5

Stress (force per unit area) Types of directed stresses include: • Compression • Extension Stress (force per unit area) Types of directed stresses include: • Compression • Extension • Shear

Compression Action of coincident oppositely directed forces acting towards each other Compression Action of coincident oppositely directed forces acting towards each other

Tension Action of coincident oppositely directed forces acting away from each other Tension Action of coincident oppositely directed forces acting away from each other

Shear Action of coincident oppositely directed forces acting parallel to each other across a Shear Action of coincident oppositely directed forces acting parallel to each other across a surface in a couple

Strength • Ability of an object to resist deformation • Compressive or tensile Strength • Ability of an object to resist deformation • Compressive or tensile

Strain Any change in original shape or size of an object in response to Strain Any change in original shape or size of an object in response to stress acting on the object

Types of deformation • Elastic • Ductile (plastic) • Brittle (rupture) Types of deformation • Elastic • Ductile (plastic) • Brittle (rupture)

Elastic deformation Temporary change in shape or size that is recovered when the deforming Elastic deformation Temporary change in shape or size that is recovered when the deforming force is removed

Ductile (plastic) deformation • Permanent change in shape or size that is not recovered Ductile (plastic) deformation • Permanent change in shape or size that is not recovered when the stress is removed • Occurs by the slippage of atoms or small groups of atoms past each other in the deforming material, without loss of cohesion

Brittle deformation (rupture) • Loss of cohesion of a body under the influence of Brittle deformation (rupture) • Loss of cohesion of a body under the influence of deforming stress • Usually occurs along sub-planar surfaces that separate zones of coherent material

Factors that affect deformation • Temperature • Pressure • Strain rate • Rock type Factors that affect deformation • Temperature • Pressure • Strain rate • Rock type The variation of these factors determines if a rock will fault or fold.

Effects of rock type on deformation Some rocks are stronger than others. competent: rocks Effects of rock type on deformation Some rocks are stronger than others. competent: rocks that deform only under great stresses incompetent: rocks that deform under moderate to low stresses

Tectonic Forces and Resulting Deformation Fig. 10. 6 Tectonic Forces and Resulting Deformation Fig. 10. 6

Experimental Deformation of Marble Brittle Deformation Ductile Deformation Fig. 10. 7 M. S. Patterson Experimental Deformation of Marble Brittle Deformation Ductile Deformation Fig. 10. 7 M. S. Patterson

Types of folds (bent planar structures) anticline: older rocks on the inside anticline syncline: Types of folds (bent planar structures) anticline: older rocks on the inside anticline syncline: older rocks on the outside syncline (scale - from mm to tens of km)

Anticlines and Synclines Fig. 10. 9 Anticlines and Synclines Fig. 10. 9

Fold terms • axial Plane: the plane of mirror symmetry dividing the fold into Fold terms • axial Plane: the plane of mirror symmetry dividing the fold into two limbs • axis: line formed by the intersection of the axial plane and a bedding plane • horizontal fold: where the fold axis is horizontal • plunging fold: where the fold axis is not horizontal

Fold Terminology Fig. 10 Fold Terminology Fig. 10

Bill Evarts Fig. 10. 11 Bill Evarts Fig. 10. 11

Symmetrical, Asymmetrical and Overturned Folds Fig. 10. 12 Symmetrical, Asymmetrical and Overturned Folds Fig. 10. 12

Anticline Axial plane Bill Evarts Fig. 10. 11 Anticline Axial plane Bill Evarts Fig. 10. 11

Asymmetric Folds Antiform Breck Kent Synform Asymmetric Folds Antiform Breck Kent Synform

Overturned Folds Phil Dombrowski Fig. 10. 1 Overturned Folds Phil Dombrowski Fig. 10. 1

Overturned Syncline, Israel Geological Survey of Israel Fig. 10. 13 Overturned Syncline, Israel Geological Survey of Israel Fig. 10. 13

Map View of Plunging Folds Fig. 10. 14 Map View of Plunging Folds Fig. 10. 14

Oil Field at crest of Plunging Anticline Kurt N. Coonstenius Oil Field at crest of Plunging Anticline Kurt N. Coonstenius

Axial Trace of Plunging Anticline* * Note Landers Oil Field on crest of anticline Axial Trace of Plunging Anticline* * Note Landers Oil Field on crest of anticline Kurt N. Coonstenius

Valley and Ridge Province P. L. Kresan Valley and Ridge Province P. L. Kresan

Plunging Folds in the Valley and Ridge J. Shelton, Geology illustrated Fig. 10. 15 Plunging Folds in the Valley and Ridge J. Shelton, Geology illustrated Fig. 10. 15

Valley and Ridge Province of the Appalachian Mountains Fig. 10. 19 Valley and Ridge Province of the Appalachian Mountains Fig. 10. 19

Raplee Anticline, S. E. Utah Raplee Anticline, S. E. Utah

Raplee Anticline on the San Juan River, Utah Raplee Anticline on the San Juan River, Utah

Domes and Basins Fig. 10. 16 Domes and Basins Fig. 10. 16

Sinclair Dome, Wyoming John S. Shelton Fig. 10. 17 Sinclair Dome, Wyoming John S. Shelton Fig. 10. 17

Syncline Fig. 10. 18 Syncline Fig. 10. 18

Drape Fold over Reverse Fault, WY George Davis Drape Fold over Reverse Fault, WY George Davis

Columns Formed by Jointcontrolled Weathering Terry Englander Fig. 10. 20 Columns Formed by Jointcontrolled Weathering Terry Englander Fig. 10. 20

Joint-controlled Landscape, S. E. Utah Joint-controlled Landscape, S. E. Utah

Faults Fractures in rocks created by earthquakes (hanging wall, footwall, displacement) • Dip-slip faults Faults Fractures in rocks created by earthquakes (hanging wall, footwall, displacement) • Dip-slip faults — normal — reverse • Strike-slip faults • Oblique-slip faults

Faults may be Faults may be "reactivated" History of a fault may be very long. Previously developed weakness is the most likely place to break. Reactivation may have opposite sense as before. Active = 10, 000 to 100, 000 years Very important for dams and reactors

Dip-slip faults Motion of the fault blocks, parallel to the dip direction. Dip-slip faults Motion of the fault blocks, parallel to the dip direction.

Classification of Faults hanging wall footwall cross section Classification of Faults hanging wall footwall cross section

Classification of Faults hanging wall footwall cross section Classification of Faults hanging wall footwall cross section

Normal Fault hanging wall footwall cross section Normal Fault hanging wall footwall cross section

Reverse Fault hanging wall footwall cross section Reverse Fault hanging wall footwall cross section

Thrust Fault Thrust faults are low-angle reverse faults. hanging wall footwall cross section Thrust Fault Thrust faults are low-angle reverse faults. hanging wall footwall cross section

Fig. 10. 22 Fig. 10. 22

Fig. 10. 22 a Fig. 10. 22 a

Normal Dip-slip Fault Normal Dip-slip Fault

Fig. 10. 22 b Fig. 10. 22 b

Reverse Dip-slip Fault Reverse Dip-slip Fault

Strike-slip faults Motion of the fault blocks, parallel to the strike direction. Strike-slip faults Motion of the fault blocks, parallel to the strike direction.

Left-lateral Strike Slip Fault map view Left-lateral Strike Slip Fault map view

Right-lateral Strike Slip Fault map view Right-lateral Strike Slip Fault map view

Fig. 10. 22 c Fig. 10. 22 c

Strikeslip Fault Gudmundar E. Sigvaldason Fig. 10. 21 Strikeslip Fault Gudmundar E. Sigvaldason Fig. 10. 21

Fig. 10. 22 d Fig. 10. 22 d

Large-scale Overthrust Sheet Fig. 10. 23 Large-scale Overthrust Sheet Fig. 10. 23

Keystone Thrust Fault, S. Nevada Cambrian Limestone Jurassic Sandstone John S. . Shelton Fig. Keystone Thrust Fault, S. Nevada Cambrian Limestone Jurassic Sandstone John S. . Shelton Fig. 10. 24

Lewis Thrust, Sawtooth Range, Wyoming Kurt N. Coonstenius Lewis Thrust, Sawtooth Range, Wyoming Kurt N. Coonstenius

French Thrust, Wyoming Mississippian Limestone Cretaceous Shale Kurt N. Coonstenius French Thrust, Wyoming Mississippian Limestone Cretaceous Shale Kurt N. Coonstenius

Rift Valley Formed by Extension Fig. 10. 25 Rift Valley Formed by Extension Fig. 10. 25

Wildrose Graben, Southern California Wildrose Graben, Southern California

NASA/TSADO/Tom Stack Fig. 10. 26 NASA/TSADO/Tom Stack Fig. 10. 26

Stages in the Development of the Basin and Range Province in Nevada and Utah Stages in the Development of the Basin and Range Province in Nevada and Utah Fig. 10. 27

Stages in the Development of the Basin and Range Province in Nevada and Utah Stages in the Development of the Basin and Range Province in Nevada and Utah Fig. 10. 27

1872 Fault Scarp, Southern California 1872 Fault Scarp, Southern California

1988 Armenian Earthquake Fault Scarp Armando Cisternas Fig. 10. 28 1988 Armenian Earthquake Fault Scarp Armando Cisternas Fig. 10. 28

1992 Landers Earthquake Fault Scarp 1992 Landers Earthquake Fault Scarp

Dating the order of deformation Use geometry: Inclusions Cross-cutting relationships Combine with fossils and Dating the order of deformation Use geometry: Inclusions Cross-cutting relationships Combine with fossils and radiometric dating