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Download Extensional Tectonics Divergent Plate Boundaries
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Divergent Plate Boundaries Oceanic Rifts Continental Rifts Extensional Tectonics Mid Oceanic Ridges 7 km Anatomy of a Mid Oceanic Ridge Generation of new Oceanic Crust Decompression Melting Ophiolites – An ubducted slice of oceanic crust Ocean Sediments Pillow Basalt Sheeted Dikes Layered Gabbro Crystalline Mantle Mid Oceanic Ridges Fast Spreading Ridge •Gradual slopes •No trough •Wide width Slow Spreading Ridge •Steeper sides •Middle trough •Narrow width Continental Rifting Passive Continental Margin Basin and Range Basin and Range Virunga Volcanoes - East African Rift chain on the borders of Rwanda, Zaire and Uganda. Aulacogens -Failed Rifts Convergent Plate Boundary Highest Everest ~ 30,000 ft Marianas ~ -36,000 ft Lowest Convergent Environments Earthquakes and Volcanoes Ocean – Ocean Convergence Japan Island Arc Trench Japan Ocean – Continental Convergence Cascades Ocean – Continental Convergence Cascadian Accretionary Wedge Andes Andes Mountains Ocean-Continent Continent-Continent Continent – Continent Convergence India-Asia Collision Te t hy s Continent – Continent Convergence India-Asia Collision Himalayas Tibet Plateau Average Elevation ~15.000 ft Orogenic Cross-Section Orogenic Cross-Section Fold-Thrust-Belts Canadian Rockies Appalachians Suspect Terranes Magnetic Survey Appalachian Accreted Terranes North American Continental Growth Transform Plate Boundary Transform Plate Boundaries Absolute Plate Velocities GPS GPS Receiver Anotolian Fault Dead Sea Fault Anotolian Fault Alpine Fault Triple Junction Triple Junctions Volcanic Abundance vs. Tectonic Setting Hot Spots Evidence for Mantle Plumes •High heat flow and volcanism occurs far from plate boundary Hotspots and Large Igneous Provinces Evidence for Mantle Plumes •Stationary activity – suggesting a deep root Oceanic Hot Spots Evidence for Mantle Plumes •Recent seismic tomographic evidence Mantle Plumes and Plate Tectonics 2 m/yr Starting Plumes Oceanic Plateaus and Flood Basalts Hotspots and Large Igneous Provinces Oceanic Plateaus and Flood Basalts Ontong – Java Plateau •25 to 43 km thick •36 million cubic km •15-20 km3/yr •Louisville Hotspot Track Continental Hot Spots Geologic Ramifications of Yellowstone Hotspot Continental Hot Spots Iceland Thermal Fragmentation of a Supercontinent Th n Distal Cooling effects Distal Cooling effects Mantle n Mantle Melts Partial Melts Cooling effects Cooling effects Mantle n Mafic Magnetism Flood Basalts Gravity Collapse Gravity Collapse Mantle Melts Partial Melts Divergent Flow Divergent Flow Mantle PANGEA Relative Plate Velocities Absolute Plate Velocities Absolute Plate Velocities - VLBI Absolute Plate Velocities - VLBI What Drives Plate Tectonics ???? Fuel Internal Heat •Primordial heat •Radioactive Decay •K(Potassium),U(Uranium),Th(Thorium) What Drives Plate Tectonics ???? Forces Mantle Crust Plate Driving Forces Slab Pull Ridge Push
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