Diastrophism ko


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Diastrophism ko

  1. 1. OBJECTIVES: At the end of the presentation, you should be able to know about the following: • Definition of Diastrophism • Theories explaining Diastrophism • Stress and Strain • Faults and Folds
  2. 2. Defining DIASTROPHISM:Tectonismdeformation of Earth’s crust by natural processes (movements)leads to the formation of continents and ocean basins, mountain systems, plateaus, rift valleys, and other features.
  3. 3. TRIVIA:Do you know that?Due to Earth’s gravity it is impossiblefor mountains to be higher than49, 000 feet (15,000 metres).
  4. 4. How does Diastrophism occur?
  5. 5. 1.) Isostasy Theory state of gravitational equilibrium between the Earths lithosphere and asthenosphere tectonic plates "float" at an elevation which depends on their thickness and density.
  6. 6. Simple Analogy:
  7. 7. Example:North Greenland fjord cliffs
  8. 8. TRIVIA: Thegeneral term isostasy was coined in 1889 by the American geologist Clarence Edward Dutton.
  9. 9. 2.) Contraction TheoryEarth is SHRINKING.Gravity draws the crust inward causing it to bend, buckle and trench.
  10. 10.  Shrinking resulted in a reduction in the Earth’s diameter while the circumference remained unchanged due to folding and buckling of the crust
  11. 11. 3.) Convection Current Theory convection within the Earths mantle pushes the plates movement of a fluid, caused by differences in temperature
  12. 12. According to this theory: Theplate is the cooled surface layer of a convection current in upper mantle.
  13. 13. 4.) Continental Drift Theory Continents were joined in a super-continent, called Pangaea (all lands). Over a vast period of time, the continents drifted apart to their current locations.
  14. 14. Some Evidences: The jigsaw fit of the outline of the continental margins.
  15. 15. Fossils
  16. 16.  Numerous geological similarities between South America and Africa.
  17. 17. TRIVIA: Continental Drift theory was first presented by Alfred Wegener who died two days after his 50th birthday.
  18. 18. 5.) Expansion Theory Earth is physically expanding in diameter, mass, or both.
  19. 19. 6.) Plate Tectonics Theory Earths outer layer is fragmented into plates that are in constant motion.
  20. 20. Plate Boundaries and Their Motions Divergent Convergent Transform/ Thrust
  21. 21. Major Earth Movements Uplift Subsidence
  22. 22. TRIVIA:Do you knowthat?On everycontinentthere is a citycalled Rome.
  23. 23. STRESS AND STRAIN3 main concepts about stress and strain:rocks deform,stress causes strain and strain results in structures,different physical conditions create different structures
  24. 24. STRESS is a Force acting on some areas
  25. 25. 3 BASIC TYPES OF STRESS Compressional Stress Tensional Stress Shear Stress
  26. 26. STRESS AND STRAIN Strain is a change in size, shape, or volume of a material. Response to stress
  27. 27. 3 BASIC TYPES OF STRAINElastic StrainPlastic StrainFracture Strain
  28. 28. NOTE : Stresscan happen with out strain, but strain cannot happen without stress.
  29. 29. 2 Major Types ofStructural Deformation  Fault  Fold
  30. 30. Fault rocksbreak due to force 4 types:Normal FaultReverse FaultStrike-Slip FaultThrust Fault
  31. 31. Fold Rocks bend due to forceTypes of Fold: Symmetrical Folds Assymetrical Folds Isoclinal Folds Overturned Folds Recumbant Folds Chevron Folds
  33. 33. Syncline youngestrocks occur in the core of a fold Caused by compressional stress U-shaped
  34. 34. Anticline oldest rocks occur in the core of a fold Caused by compressional stress A-shaped
  35. 35. Compressional Stress two plates move together or one moves and applies a force on another one that is not moving.
  36. 36. Tensional Stress one part of a plate moves away from another part of a plate.
  37. 37. Shear Stress two plates slide past one another
  38. 38. Elastic Strainrocks recover to their original shape.
  39. 39. Plastic or Ductile Strain Rocks do not return to their original shape.
  40. 40. Fracture or Brittle Strainrocks crack or break under the stress.