Folding Ductile (Plastic) Deformation

Identify the foot wall block. Identify the hanging wall block. Is this a strike-slip or dip-slip fault? Is this fault caused by tensional or compressional forces? Is this a normal or reverse fault?

Earthquakes (elastic strain) Folds (ductile strain) Stress (a compressional, tensional, or shear force) Elastic Limit point Fracture point Deformation Region Elastic Ductile Brittle Earthquakes occur in this region due to Elastic Rebound There is NO permanent deformation This does not create a break in the Earth. The earth is already broken. This is just slippage along the break. Earthquakes (elastic strain) Folds (ductile strain) Faults (brittle strain) All of the folds occur in this region as the Earth is bent but not broken. Anticlines, Synclines, Monoclines, Basins, Domes Normal, Reverse, and Strike-slip faults All of the faults occur in this region as the Earth is broken.

Folded Structures Anticlines Synclines Monoclines Basins Domes

Anticlines

Anticline - oldest rock formation in the middle.

Syncline - youngest rock formation in the middle.

Syncline in Eastern Tennessee

Fold Geometry Symmetrical Asymmetrical Overturned

Plunge Measured from a horizontal line.

Plunge - the inclination of the fold axis

Fold Geometry

Anticlines and Synclines

Monocline

Monocline Peru Monocline – caused by basement-block faulting

Domes Oldest rock in center Basins Youngest rock in center

Map view of structures Map Symbols

Horizontal Strata

Inclined Strata

Dome

Black Hills Dome

Black Hills Geology

Basin

Plunging Anticlines And Synclines

Sheep Mountain Anticline, Wyoming

What causes folding and faulting Anticlines and synclines – compression Basins – subsidence, the sinking of the ground due to crustal thinning. Monoclines – basement block faulting Domes – intrusions Normal Faults – tension Reverse Faults – compression Strike-Slip Faults – shear stress

1. Name this structure. Which is older A or B 1. Name this structure. Which is older A or B? Do the layer dip away from or towards the center? Is this structure caused by tension, compression, or shear stress? Name this structure. Do the layers dip away from or toward the center of this structure? Is this structure caused by tension, compression, subsidence, or an intrusion? 3. ID the foot wall. ID the hanging wall. Is this a dip-slip or strike-slip fault? Is this a normal, reverse, left-lateral, or right lateral fault? What caused this fault, tension, compression, or shear stress? 4. Is this a dip-slip or strike-slip fault? Is it caused by tension, compression, or shear stress. Name this fault. 5. ID axis D and E. Label points F and G. Label areas A, B, and C.

Wisconsin Arch Mich. Basin Cincinnati Arch Nashville Dome Ozark Dome Forest City Basin Kankakee Arch Illinois Basin Mississippi Rvr. Arch