OCEANIC AND CONTINENTAL CRUST

• Continental crust (~2.7 g/cm³)

  • largely granite

• Ocean Crust (~3.0g/cm³)

  • Largely basalt and gabbro

• Tectonics: the folding and breaking of rocks due to pressure within the earths crust

  • Folding: the bending of crustal rocks, normally due to compression (soft deformation)

  • Faulting: the breaking and resultant displacement of a rock body (brittle deformation)

    

• Continental Drift: Wegeners Pangea

  • Modern reconstruction of Pangea

  • Evidence: geologic, climatic, paleontology, shape

  • Critical point missing: doesn’t mention any processes

SEAFLOOR TOPOGRAPHY - MARIE THARP

• Character of a Divergent margin

  • Plate types: O/O, C/C

  • Applied stress: Extension

  • Resulting strain: Stretching

  • Surface Expression: Low ridge with central trench

  • Seismicity: Low energy, shallow depth

  • Volcanism: Low explosivity, fluid lava

    • Divergent boundary - fast spreading ridge

      • Mid ocean ridge processes:

        • Hot mantle rock risees

        • Melt forms under the lithosphere

        • Magma rises into magma chamber in crust and is injected as dikes forming in new crust

        • law erupts onto ocean floor adding to crust

        • Plates move apart, cool, and thicken

• Character of a transform margin

  • Plate types: O/O, O/C, C/C

  • Applied stress: shear

  • Resulting strain: shearing/twisting laterally

  • Surface expression: offset surface

  • Seismicity: low to moderate energy, shallow

  • Volcanism: not generally present

How do tectonics play a significant role in recycling rocks

• Divergent/transform boundaries

  • Driven by convection currents within the earth

• Different boundaries have different surface expression and geophysical indicators

  • Earthquakes, volcanic activity, trenches, ridges

• Character of a convergent margin

  • Plates locked = stress and deformation

  • Plates release = earthquake and tsunami

    • Platetypes: O/O, O/C (Subduction)

    • Applied stress: Compression

    • Resulting strain: shortening

    • Resulting expression: trench, uplifted mountains

    • Seismicity: high energy, shallow to very deep

    • Volcanism: high explosivity, thick lava

TERRANE ACCRETION