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X. 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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Presentation on theme: "X. Deformation and. Mountain Building A.Plate Tectonics and Stress B.Rock Deformation C.Geologic Structures D.Origin of Mountains E.Continental Crust."— Presentation transcript:

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

2 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

3 Tectonics and Structural Geology Tectonic Stresses resulting from Internal 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 and Releases energy  Earthquakes

4 Fig. 10-CO, p. 216

5 Folds and Faults (Palmdale, Ca) See Fig. 10-2a, p. 219

6 Eastern Pennsylvania Northwestern Africa

7 Stresses at Plate Boundaries Divergent (Tensional)  |  Convergent (Compressional)  |  Transform (Shear) e.g., Pacific NW

8 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)

9 Stikes and Dips are used to identify geologic structures

10 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

11 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

12 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

13 Deciphering the Geology of Ohio Using Dipping Bedding Planes Beds Dip 2 o, West Younger rocks, West Mirror image east of Sandusky? Beds Dip 2 o, West Younger rocks, West Mirror image east of Sandusky? Sandstone Shale Limestone M O D 2o2o 2o2o 2o2o

14 Anticline (fold)

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16 Syncline (fold)

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18 Plunging Anticline

19 Fold Terminology Axis Axial Plane Plunging Age of rocks and outcrops Axis

20 Plunging Anticline, Colorado

21 Eastern Pennsylvania Folds and faults resulting from compressive stresses Anticlines (many plunging) Synclines (many plunging) Reverse faults Thrust faults

22 Domes and Basins

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24 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)

25 When shallow crust is strained rocks tend to exhibit brittle strain Brittle Strain  Joints

26 Sheet Joints

27 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 a, p. 227

28 Fault: Movement occurring along a discontinuity Brittle strain and subsequent movement as a result of stress Fault terminology 

29 Faults Fault: When movement occurs along a discontinuity Fault type depends on the type of stress

30 Normal Faults

31 Normal Faults, Horsts and Grabens

32 Structures at Divergent Boundaries Tensional Stresses cause brittle strain and formation of sets of normal faults i.e., Horsts and Grabens

33 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 Graben Horst Graben

34 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)

35 Horst and Graben, Nevada Humboldt Range, Northern Nevada Fig b, p. 233 Graben Horst

36 Horst and Graben, Nevada Humboldt Range, Northern Nevada Graben Horst

37 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

38 Structures at a Passive Continental Margin Resulting from continental breakup E.g., The Americas and Africa

39 Salt Domes: e.g., Texas Rising of less dense salt Stretches overlying crust Forming normal faults and Oil traps

40 Structural Oil Traps

41 Thrust Fault: Glacier NP, Montana Old Younger

42 Structures at a Convergent Boundary

43 Structures within Mountain Belts

44 Compressional and Tensional Structures

45 E.g., The Apls Intense folding and thrusting of sedimentary rocks

46 Strike Slip Faults Physiographic Features

47 San Andreas Fault What type of fault is this? What other features are associated with the fault?

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