Diastrophism ko
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Diastrophism ko






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    Diastrophism ko Diastrophism ko Presentation Transcript

    • 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
    • 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.
    • TRIVIA:Do you know that?Due to Earth’s gravity it is impossiblefor mountains to be higher than49, 000 feet (15,000 metres).
    • How does Diastrophism occur?
    • 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.
    • Simple Analogy:
    • Example:North Greenland fjord cliffs
    • TRIVIA: Thegeneral term isostasy was coined in 1889 by the American geologist Clarence Edward Dutton.
    • 2.) Contraction TheoryEarth is SHRINKING.Gravity draws the crust inward causing it to bend, buckle and trench.
    •  Shrinking resulted in a reduction in the Earth’s diameter while the circumference remained unchanged due to folding and buckling of the crust
    • 3.) Convection Current Theory convection within the Earths mantle pushes the plates movement of a fluid, caused by differences in temperature
    • According to this theory: Theplate is the cooled surface layer of a convection current in upper mantle.
    • 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.
    • Some Evidences: The jigsaw fit of the outline of the continental margins.
    • Fossils
    •  Numerous geological similarities between South America and Africa.
    • TRIVIA: Continental Drift theory was first presented by Alfred Wegener who died two days after his 50th birthday.
    • 5.) Expansion Theory Earth is physically expanding in diameter, mass, or both.
    • 6.) Plate Tectonics Theory Earths outer layer is fragmented into plates that are in constant motion.
    • Plate Boundaries and Their Motions Divergent Convergent Transform/ Thrust
    • Major Earth Movements Uplift Subsidence
    • TRIVIA:Do you knowthat?On everycontinentthere is a citycalled Rome.
    • 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
    • STRESS is a Force acting on some areas
    • 3 BASIC TYPES OF STRESS Compressional Stress Tensional Stress Shear Stress
    • STRESS AND STRAIN Strain is a change in size, shape, or volume of a material. Response to stress
    • 3 BASIC TYPES OF STRAINElastic StrainPlastic StrainFracture Strain
    • NOTE : Stresscan happen with out strain, but strain cannot happen without stress.
    • 2 Major Types ofStructural Deformation  Fault  Fold
    • Fault rocksbreak due to force 4 types:Normal FaultReverse FaultStrike-Slip FaultThrust Fault
    • Fold Rocks bend due to forceTypes of Fold: Symmetrical Folds Assymetrical Folds Isoclinal Folds Overturned Folds Recumbant Folds Chevron Folds
    • Syncline youngestrocks occur in the core of a fold Caused by compressional stress U-shaped
    • Anticline oldest rocks occur in the core of a fold Caused by compressional stress A-shaped
    • Compressional Stress two plates move together or one moves and applies a force on another one that is not moving.
    • Tensional Stress one part of a plate moves away from another part of a plate.
    • Shear Stress two plates slide past one another
    • Elastic Strainrocks recover to their original shape.
    • Plastic or Ductile Strain Rocks do not return to their original shape.
    • Fracture or Brittle Strainrocks crack or break under the stress.