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CONTINENTAL DRIFT AND. PLATE TECTONICS. DRIFT AND PLATES. Continental drift concept Introduction did continents originate at their present locations or did they move to where they are today? - PowerPoint PPT Presentation

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  • CONTINENTAL DRIFT AND PLATE TECTONICS

  • DRIFT AND PLATESContinental drift conceptIntroductiondid continents originate at their present locations or did they move to where they are today?drift concept supplied information to aid in the formulation of rock plate or tectonic plate concepta solid lithosphere floating on top of the asthenosphere gives an idea of how plates can floatAccretion of continental material took place

  • DRIFT AND PLATESconvection cells in Earths interior is the force which split the lithosphere and are the driving force in continental separation

  • DRIFT AND PLATES Accretion of Continental Materials during Drift---Western USA

  • DRIFT AND PLATESwho was the first to observe this map fit? Alfred Wegener was the first to publish a summary of ideas about continental drift in 1912.some ideas in the publication were: 1) the protocontinent or supercontinent was named Pangaea; 2) southern section was named Gondwana or Gondwanaland and northern section, Laurasia; 3) the protocontinent broke in pieces about 150-200 million years ago

  • DRIFT AND PLATESSome important data confirming continental driftmap fit--already mentionedmountain chains formed on continents with longitudinal axes perpendicular to movement of the continents--examples: Himalayan, Rocky Mountain and Andes Mountain chainssame fossils (in rocks),same rocks , mountain ranges, and glacial features located on different continents in areas representing prejoined positions prior to continental drift

  • DRIFT AND PLATESInitial ideas of continental driftjig saw puzzle or map fit of continents

  • Matching of Fossils from Common Locations on Separated Continents

  • Matching of Mountain Chains from Common Locations on Separated Continents

  • Matching of Glacial Deposits from Common Locations on Separated Continents

  • DRIFT AND PLATESpresence and shape of global ocean ridgea ridge is a raised region on ocean basin which is believed to represent prejoined or splitting area of separated continents--the shape of the ridge contours shape of coast lines of separated continents--- this is most evident in the mid Atlantic ocean

  • Global Ocean Ridge

  • DRIFT AND PLATESseafloor spreadingage of rocks located on equivalent positions on both sides of the ridge are the same--rocks progressively increase in age away from the ridgemagnetic intensities in the rocks are found to be the same on equivalent sides of the ridge--on both sides of ridge magnetic intensity alternates between normal(high intensity) and abnormal(low intensity)

  • DRIFT AND PLATES

  • Magnetic Intensities and Sea Floor Spreading

  • DRIFT AND PLATESLithospheric plates and plate tectonicswhere are the spreading continents going?the answer was important in initiating the rock plate conceptrock sections or plates which diverge from spreading zones move towards or converge on subduction zonesRock platesocean basin and continental sections float in the asthenosphere, some plates diverge, some converge and some move parallel (to each other)

  • DRIFT AND PLATESClassification of rock plate boundariesvolcanism and seismic activity are abundantly associated with plate boundariesboundaries are classified as divergent, convergent, or transformed boundariesdivergent boundary--includes all ridges and rifts--tensional forces caused by convection cells drive the plates apart

  • DIVERGENT PLATE BOUNDARY

  • DRIFT AND PLATESkinds of divergent plate boundaries--1)ocean basin to ocean basin boundary;example is the mid ocean ridge

  • DRIFT AND PLATES2) continental to continental boundary

  • DRIFT AND PLATESconvergent boundaries--includes all subduction boundaries--compressional forces caused by convection cells drive plates towards each other--volcanic arcs are associated with convergent boundaries

  • Convergent Plate boundary

  • 3 types of convergent plate boundaries1) Ocean basin to continental boundary(Example is the Cascade Mountain chain)

  • 2) Ocean basin to ocean basin boundary(Examples are Aleutian Islands and Japan)

  • Aleutian Islands and Japan

  • 3) Continental to continental plate boundary(Example is India and Asian continent boundary)

  • DRIFT AND PLATEStransformed boundary--plates move parallel to boundaryExample are those off the Coast of Western U.S.A.

  • DRIFT AND PLATES Major Plates on Earth and Movement RatesMovement rates are about as fast as your fingernails grow

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