General Geology: Crustal deformation

1. General Geology: Crustal deformation • Instructor: Prof. Dr. Boris Natalin

2. Topics: • Forces • Stress • Folds • Faults • Joints (fractures)

3. Force First law of motion, the Law of Inertia: • in the absence of a force a body moves either at constant velocity or is at rest • Acceleration: [a] : [vt–1] : [lt–2][a] is acceleration, m/s2 Second Law of Motion [F] : [ma] : [mlt–2][F] is force, m/s2, called a newton (N) in SI • Force is mass multiplied by acceleration • Force, like velocity, is a vector quantity, meaning that it has both magnitude and direction.

4. Stress Stress, represented by the symbol σ (sigma), is defined as the force per unit area [A]σ = F/A kg/m ⋅ s2 (or N/m2), a pascal (Pa)1 bar = 105 Pa ≈ 1 atmosphere

5. Two-dimensional stress • Traction • Stress tensor • Normal stress, σn • Shear stress, σs

6. Stress ellipsoid fully describes the stress state at a point • Principal stresses: σ1, σ2, and σ3 Properties of stress axes Principal planes of stress

7. Stress States • Isotropic • Anisotropic σ1 ≥ σ2 ≥ σ3 • Differential stress, σd

8. Stress States General triaxial stress: σ1 >σ2 >σ3 ≠0 Biaxial (plane) stress: one axis =0 (e.g., σ1 >0 >σ3) Uniaxial compression: σ1 >0; σ2 =σ3 =0 Uniaxial tension: σ1 =σ2 =0; σ3 <0 Hydrostatic stress (lithostatic pressure): σ1 =σ2 =σ3 Pressure gradient - 27 MPa

9. Deformation consists of three components: • Rotation • Translation • Strain

10. Stress - Change of shape or/and volume - Compressional stress - Tensional stress - Shear stress

11. Deformation: Elastic Behavior • Elastic behavior depends on lattice properties

12. Types of Deformation Plastic deformation • Elastic and plastic deformation Elastic deformation

13. Types of Deformation Brittle failure (faults) Ductile deformation (folds) • Laboratory experiments • Controlling factors:- confining pressure- temperature- time

15. Field studies • Outcrop • Geological mapping • Horizontal versus inclined occurrences of bedding • Strike and dip • Rock structures

17. Orientation of a plane: - Strike - Dip direction - Dip angle Orientation of a line: - Plunge direction - Plunge - Rake (γ)

18. Reconstruction of structures

19. Folds • Fold elements- limb- axis (hinge)- axial plane • Horizontal folds • Inclined folds • Vertical folds

20. Types of folds • Upright (horizontal and plunging) • Inclined (horizontal and plunging) • Recumbent • Vertical folds • Anticline and syncline • Symmetrical and asymmetrical folds • Overturned and recumbent folds

21. Inclined fold

22. Recumbent fold

23. Plunging folds

24. Monoclines

25. Monoclines

26. Domes and basins

27. Domes and basins: Vertical motions

28. Normal faults

29. Faults elements • Footwall block • Hanging wall block

30. Dip-slip fault: normal faults and reverse faults

31. Normal faults

32. Reverse faults and thrusts Cambrian Jurassic The Keystone Thrust

33. Reverse faults and thrusts Lewis Thrust Klippe

34. Strike-slip faults

37. Representation of faults on mapsand cross sections • We use thick (heavy) line for faults on geologic maps • Bars and teeth are on the hanging wall • Bars and teeth do not indicate the direction of movement!

38. Joints A natural, unfilled, planar or curviplanar fracture which forms by tensile loading (i.e., the walls of a joint move apart very slightly as the joint develops). Joint formation does not involve shear displacement.

40. North Anatolian Fault Originated 13-11 Ma Marmara 200 ky Propagates 11 cm/y Seismic activity propagates to the west. Dead Sea and East Anatolian fault (ca. 3 Ma)

41. Strike-slip faults: The North Anatolian fault

42. Strike-slip faults: The North Anatolian fault