Geo 1012 : Planet Earth : lecture outlines
Plate Tectonics IV
Initiation of the Plate Tectonic cycle
Three Zones of volcanism in Plate tectonics
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Spreading Center volcanism
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Creation of new oceanic crust
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Partial melts from mantle
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Basaltic composition
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Subduction Zone volcanism
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Volcanic arcs in the oceans and the continents
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Partial melting of subducted slabs
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Andesitic composition
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Intra-Plate volcanism
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Hot-Spots (Mantle Plumes)
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Fixed with respect to plate motions
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long chains of volcanoes
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Basaltic composition
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Age progression
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Examples: Hawaiian volcanic chain
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Iceland
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Yellowstone
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Origin of mantle plumes
Plate boundaries and earth quake activity
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Earthquakes- contrasts between ridges and subduction zones
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shallow and deep focus earth quake mechanisms
The fate of downgoing lithospheric slabs
Evidence from deep focus earth quakes
Mixing of slabs in the lower mantle
Slabs all the way to the core mantle boundary
Mountain Building
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Volcanic arcs in continental regions
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Island arcs in the ocean basins
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Accretion of exotic blocks
Driving mechanisms- the cause of Plate Tectonics
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Convective motions-pushing lithospheric plates apart
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Cold dense lithosphere sinking and pull of slab
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gravity sliding
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Push by rising plumes
Reconstruction of position of continents through time
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Pangea at ~200 million years ago
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Breakup and motions at 180 million years ago
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Laurasia and Gondwana land
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Ridge system between N. America and Africa
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Birth of the Atlantic
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Northward motion of Africa and India
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Ridge system between Antarctica and northern part of Gondwana land
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Antarctica and Australia together in one piece
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Motions about 135 million years ago
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Splitting of Africa and South America
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Birth of the South Atlantic
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Motions 65 million years ago
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Full fledged Atlantic ocean
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Break up of Madagascar from Africa
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Rift system south of Africa and break up of Australia from Antarctica
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Current configuration
Is it real: Evidence from direct measurements
Satellite Laser Ranging (SLR) techniques
Plate Tectonics - a giant recycling system and a new paradigm
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Explains: Topography and features of the ocean floor (Ridges, Trenches, island chains, etc.
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Motions of plates confirmed by magnetic data
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Formation of various types of mountain chains
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The young age of the oceanic crust
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Different types of volcanism and location
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Different types of earth quakes and their location
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Structural and tectonic features of the continents
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Continental Drift
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