4. lecture on structural geology folds
Download as PPTX, PDF1 like191 views
This document discusses structural geology, which deals with the classification, development, and causes of rock structures. It defines primary and secondary rock structures, and basic structural geology terms like outcrops, bedding, strike, and dip. It also describes different types of folds in rocks like anticlines and synclines, and classifications of folds based on parameters like axial plane position, degree of compression, plunge, and mode of occurrence. Finally, it discusses some engineering considerations and the importance of accounting for folds in structures.
4. lecture on structural geology folds
- 1. Structural Geology Amity School of Engineering and Technology
- 2. Structural geology • Branch of geology that deals with classification, mechanism and causes of development of rock structures. Primary structure Structural features that are developed in the body of a rock during its formation stage. Secondary structure Modification of original structures and development of new forms, shapes, alteration of mineral composition induced in rock after rock formation. Amity School of Engineering and Technology
- 3. Basic terms • Outcrop Exposure of a solid rock on the surface of the earth • Bedding or stratification Layered structure of rock • Strike is the direction of the line that is formed by the intersection of the rock’s bedding planes with a horizontal surface.
- 4. Basic terms Dip Max angle of inclination of a layer of a rock with horizontal plane. Measured using clinometer and compass.
- 5. Basic terms Eldorado Canyon, south of Boulder Garden of the Gods, Colorado Springs
- 6. • Outcrop dimension – Width, thickness, depth, dip & strike • Structural form of igneous rock – Intrusions • Injection of magma into pre-existing rock – Flows • Rock structure formed out of solidified lava on the surface of earth – Masses • Enormous bodies of igneous rocks having irregular structural shape Basic terms
- 7. Folds and Folding Folds are undulation or bend developed in rock under stress Process of development of folds in rocks is called folding
- 9. Parts of fold Limbs Sides or flanks of a fold Hinge Point where curvature is max., one limb ends and other limb starts Line joining all hinge points is called hinge line Axial plane Imaginary plane passing through all points of maximum curvature
- 10. Axis of fold Line drawn parallel to hinge line Line represents the intersection of axial plane of a fold with any bed of the fold Plunge of fold Angle of inclination of fold axis with horizontal Crest Highest point in up arched crest Trough Lowest point in an down arched fold
- 11. Classification of folds • Anticlines Up arched strata, convex upward Older rock occupy interior of fold Limbs dip away from axial center • Synclines Down arched strata, convex downward Younger rock is core of fold Limb dip towards a common center
- 13. Parameters for Classification of folds Position of axial plane Degree of compression Behavior with depth Relative curvature of outer & inner arcs Plunge of folds Profile of outer surface Mode of occurrence
- 14. Position of axial plane Symmetrical folds Asymmetrical folds Overturned folds Isoclinal folds Recumbent folds Amity School of Engineering and Technology
- 15. Degree of compression Closed folds Open folds
- 16. Behavior with depth Concentric folds Similar folds Supratenuous folds Amity School of Engineering and Technology
- 17. Relative curvature Class 1 fold Class 2 fold Class 3 fold Amity School of Engineering and Technology
- 18. Plunge as basis Plunging fold Non-plunging fold Amity School of Engineering and Technology
- 19. Profile of fold surface Cheveron folds Conjugate folds Cuspate folds Cylindrical folds Amity School of Engineering and Technology
- 20. Mode of occurrence Anticlinorium Synclinorium Domes and basins Amity School of Engineering and Technology
- 21. Causes of folding Folding due to tangential compression Flexural folding Flowage folding Shear folding Folding due to intrusion Folding due to differential compression Amity School of Engineering and Technology
- 22. Engineering Consideration Presence of fold need to be given due importance in structures Traffic or hydropower tunnels Site selection for dam & reservoirs Fixing alignments of roads, bridges & highways Characteristics of folds Change in attitude Shattering of rock Strained nature Amity School of Engineering and Technology
- 23. Thank You Amity School of Engineering and Technology