1 / 42

General Geology: Crustal deformation

General Geology: Crustal deformation. Instructor: Prof. Dr. Boris Natalin. Topics: . Forces Stress Folds Faults Joints (fractures). 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

aric
Download Presentation

General Geology: Crustal deformation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

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

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

  16. Reconstruction of structures

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

  18. 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

  19. Inclined fold

  20. Recumbent fold

  21. Plunging folds

  22. Monoclines

  23. Monoclines

  24. Domes and basins

  25. Domes and basins: Vertical motions

  26. Normal faults

  27. Faults elements • Footwall block • Hanging wall block

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

  29. Normal faults

  30. Reverse faults and thrusts Cambrian Jurassic The Keystone Thrust

  31. Reverse faults and thrusts Lewis Thrust Klippe

  32. Strike-slip faults

  33. 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!

  34. 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.

  35. 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)

  36. Strike-slip faults: The North Anatolian fault

  37. Strike-slip faults: The North Anatolian fault

More Related