XIV. Plate Tectonics

1. Continental Drift
   1. Wegener (1915)
   2. Pangaea (fig. 15.2)
   3. evidence (fig. 15.3, 15.4, 15.6, 15.7)
2. Sea Floor spreading
   1. seafloor data from WWII
   2. mid-ocean ridge volcanoes
3. Plate Tectonics
1. added data from Pacific Ocean
2. 3 types of plate boundaries (fig. 15.9)

1. oceanic spreading centers
   1. create new oceanic crust
   2. surface expression - mid-ocean ridges
   3. volcanism: (fig. 16.13)
      • basalt volcanoes,
      • lava flows,
      • mafic dikes
   4. earthquakes:
      • shallow to intermediate earthquakes;
      • small to medium magnitude
      • modern examples: mid-Atlantic ridge, Iceland
2. continental rifts (fig. 15.11)
   1. break-up continent, earliest stages of ocean formation (fig. 16.15)
   2. surface expression: rift valley and volcanoes
   3. volcanoes:
      • basalt volcanoes,
      • lava flows
   4. earthquakes:
      • shallow to intermediate earthquakes;
      • small to medium magnitude 
        
   5. modern example: Rio Grande Rift, East African Rift

plates move toward each other

1. subduction zones -  requires involvement of at least one ocean plate (fig. 15.14, 15.15)
   1. destroy ocean crust
   2. surface expression:
      • trench,
      • island arc or volcanic arc 
        
   3. volcanoes:
      • explosive composite volcanoes
   4. earthquakes:
      • Benioff zone;
      • small to huge earthquakes,
      • shallow to very deep (700 km)
   5. modern examples: Japan, Philippines, Aleutians, Andes, S. Mexico, Mt. St. Helens
2. continental collisions:  (fig. 15.14, 15.15)
   1. suture continents together, also folding, faulting and metamorphism
      
   2. surface expression: forms huge mountains
   3. volcanoes: none
   4. earthquakes: variable in depth and size
   5. modern example: Himalayas

1. neither create nor destroy crust
2. surface expression: fault which is often hard to identify, subtle landscape variations
3. volcanoes: none
4. earthquakes: variable in depth and magnitude
5. modern example: San Andreas Fault

1. convection  (fig. 15.27)
2. slab-pull, ridge-push (fig. 15.26)