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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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