1 Structural Geology – Review Questions and Practice Exam Short Answer Definition (use drawings where necessary) 13. Slickensides (3 pts) 14. En echelon fractures (3 pts) 15. Vein (3 pts) 16. Normal Fault (3 pts) 17. Thrust Fault (3 pts) 18. Cataclasis (3 pts) 19. Listric (3 pts) 20. Graben (3 pts) 1. What is structural geology? What are the essential questions that are asked in this scientific specialty? (5 Pts) 2. Explain the statement that "structural systems commonly display fractal behavior". (5 pts)2 3. Discuss, with examples, the difference between primary and secondary rock structure (examples are required). (5 pts) 4. What is the difference between "stress" and "strain"? (5 Pts) 5. Differentiate between Mode I, II and III fractures (drawings are required). (6 Pts) 6. In each of the map sketches below, draw a line showing the anticipated strike of the mode I fractures that would likely develop. (5 Pts) 7. In each of the cross-sections below, draw arrows on each side of the faults to show the relative sense of displacement. (5 pts) 8. Discuss the net stratigraphic effect commonly produced by a thrust fault (a diagram is required) (5 Pts) 9. List 5 pieces of evidence commonly used to identify faults in the field. (5 Pts) 10. Draw and label a diagram depicting the difference between synthetic and antithetic faults. (5 Pts)3 11. Draw and label a geologic map depicting the difference between sinistral and dextral wrench faults. (5 Pts) Lecture Part I. Short Answer: define the following terms using 1-2 sentences and diagrams where appropriate (remember a picture is worth a thousand words) (2 pts each x 11 = 22 pts total). 1. Cylindrical fold- 2. Overturned anticline 3. Monocline 4. Dip isogon 5. Kink fold 6. Penetrative Rock Fabric 7. Crenulation 8. Boudinage 9. Force 10. Stress 11. Negative normal stress4 4. List three geometric elements that can be used to describe fold patterns in rock. (3 pts) 5. Compare and contrast between ductile deformation and brittle deformation (discuss processes and products of each). (3 pts) 6. Discuss the difference in meaning that is implied between the terms "antiform" and "anticline". Diagrams are required. (3 pts) 7. What are the two primary geometric components that form the basis for Ramsay's fold classification scheme? (2 Pts) 8. Discuss the difference between the fold processes of "bending" and "buckling". (4 pts) 9. Discuss the difference between flexure slip folding and flow folding processes. (2pts) A. What is the difference between a similar and parallel fold (Ramsay's fold type 2 and 1B respectively)? (2 Pts) B. Which type of the above fold processes and fold types would be dominant in the deformation of a shale layer vs. a sandstone layer? AND WHY? (2 Pts)5 10. Discuss (with examples) the difference between foliation and lineation rock fabric. (4 pts) 11. Draw a 2-D diagram of an upright, non-plunging antiformal structure with several layers. With a colored pencil, draw a series of lines throughout the folded layers depicting the likely orientation of axial plane cleavage, if developed. (3 Pts) 12. What is the difference between a slickenside and a slickenline? Discuss the process of forming slickenlines on a fault plane. (4 pts) 13. What is the difference between a scalar quantity and a vector quantity?(3 pts) 14. Draw a 2-D diagram depicting a fault plane with a dip of 45 degrees. Draw an arrow representing a positive, vertical maximum principle stress (σ1 ) acting on the fault plane. Perform a visual, generalized stress resolution showing the components of shear stress (σs) and normal stress (σn) operating on the fault plane (i.e. draw arrows and label the orientations of shear and normal stress). (4 pts) 15. Draw a generalized 2-D diagram of the stress "ellipse" with σ1 >σ3. (2 pts) 16. Draw a generalized 2-D diagram of the stress "ellipse" with σ1 = σ3. (2 Pts) 17. Draw a generalized schematic of the Mohr diagram. Label the axes of the diagram.6 Draw an example Mohr circle on the diagram, labeling the points at σ1 and σ3 (depict σ3 as negative and σ1 as positive). (2.5 Pts) Drawing Here Based on your diagram, answer the following: A. Is σ1 compressional or tensional? (0.5 Pt) B. Is σ3 tensional or compressional? (0.5 Pt) C. By definition, what is the value of shear stress at σ1 and σ3 on the Mohr circle? (0.5 Pt) D. In terms of shear stress, is a clockwise sense of rotation positive or negative? (0.5 Pt) E. In terms of shear stress, is a counterclockwise sense of rotation negative or positive? (0.5 Pt) Matching. Match the phrase on the right with the term on the left (25 Pts). ___ 1. Columnar joints A. Ratio: stress/strain ___ 2. Pure shear strain B. Term meaning perpendicular to ___ 3. Pi diagrams C. Thermal contraction fractures ___ 4. Positive σs D. Non-rotational, homogeneous deformation ___ 5. Paleomagnetism E. Change in shape per unit time ___ 6. Hydrostatic Pressure F. Active tension perpendicular to a surface ___ 7. North magnetic pole G. Erosion / release fractures ___ 8. Young's Modulus H. Involves plot of poles to beds on folds ___ 9. σ1 I. Example: a cube deformed into a rhombohedron ___ 10. Sheet Joints J. Magnetic inclination = 90 degrees upward. ___ 11. Beta diagram K. Force oriented parallel to axis of rock core ___ 12.Orthogonal L. Ratio: extension/shortening ___ 13. Positive σn M. Stress beyond which=permanent deformation. ___ 14. Brittle Failure N. Active compression perpendicular to surface ___ 15. Simple shear strain O. Magnetic inclination = 90 degrees downward. ___ 16. Negative σs P. Deformation by loss of cohesion ___ 17. σ3 Q. Equal to σn, defines right edge of Mohr circle ___ 18. Ductile Failure R. Counterclockwise shear sense ___ 19. South magnetic pole S. Involves plot of great circles to beds on folds ___ 20. yield stress T. Permanent deformation without loss of cohesion ___ 21. Polar wandering U. Tectonic reconstruction in which plate = static ___ 22. Radial Stress V. ratio: (L2/L1) - 17 ___ 23. strain rate W. σ1= σ2= σ3 ___ 24. negative σn X. Fossil magnetism acquired by rock at origin ___ 25. Axial stress Y. Clockwise shear sense Z. Equal to σn, defines left edge of Mohr circle AA. Force oriented