The continental rifting process

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The continental rifting process. a. q. Kk. Continental Crust. Rifting. Spreading Center. Trench. Subduction. Basalt. Volcanic Arc. Granite. Accretionary Prism. Oceanic Crust. Partial melting occurs when some minerals melt - PowerPoint PPT Presentation

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The continental rifting process a

q

Kk

SubductionContinentalCrustOceanicCrustAccretionaryPrismVolcanicArcTrenchRiftingSpreadingCenterGraniteBasalt

The role of partial melting

Granite

BasaltPartial melting occurs when some minerals meltwhile others remain solid because their melting point has not been reached

3 Types of PlateBoundariesCONVERGENTOne plate dives beneath another (subduction) or two plates collide without either subducting.DIVERGENTNew lithosphere forms as plates pull apart.

TRANSFORMPlates grind past each other. No change in Lithosphere4

Main Types of Plate MotionConvergentDivergentTransformMODERN CONTINENTS EVOLVED FROM PANGAEA

Linked on this slide is the animation:Continents Form over Timehttp://www.edugen.com:30120/geodiscoveries/resources/ch14/print/continents_form/index.htm

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Divergent BoundarySeafloor spreading leads to the formation of new crust that, compared to continental crust, is relatively enriched in iron and magnesium and depleted in silica (SiO2) (because it reflects thechemistry of the mantle).

As two plates continue to move apart, the rock in the seafloor grows older as its distance from the rift zone increases, and as it ages, it cools and becomes denser and is buried under marine sediments that are deposited on the seafloor.

Mid-Ocean RidgeSpreading Center

Transform boundary (side-to-side plate movement)Fault a place where the crust is broken and the broken edgesare offset relative to each other(either vertically or horizontally)Suggested tips to give students: Lots more about FAULTS coming up later in the course!10Transform Boundaries Connect Two Spreading CentersOccur where two plates slide past each other.Motion called shearing.Connect two spreading centers (less commonly, two subduction zones).Probably the most famous transform boundary in the world is the San Andreas Fault.

Suggested tips to give students: A Hotspot is a volcanic center located within a lithospheric plate that is thought to be caused by a plume of hot mantle material rising from depth. The Hawaiian Islands are created by a hotspot. J. Tuzon Wilson proposed both the Hotspot Hypothesis and that Transform Boundaries connect two spreading centers. 11oceanic fracture zone Transform Boundary with inactive (fracture zone) and active (transform fault) portions.

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