Plate techtonics

Plate techtonics -> equivelent of Survival of Fittest in Biology

3 major Boundry Types

1. Ridge
2. Divergent margin
   1. Formation of new oceanic crust by sea floor spreading
   2. Ocean crust -> denser, more mafic, basalt
   3. Extensional Regime, normal faults, shallow seismicity
   4. High Heat flow, decompression melting
   5. Intrusive igneous -> gabbro and basalt (essp. pillow basalts)
   6. Highly fractured rocks -> alot of water goes through -> causes differences in carbon weathering
   7. Tends to fault in three geometric paterns (third often failing to spread)
   8. Tends to also have reafs at shelf slope break
   9. Starts by bowing up, then breaking, finally filling with lakes then ocean
   10. Oceanic crust is much thinner than continental crust
3. Convergent Margin
   1. Recycling of old, cool oceanic crust (subduction)
   2. Older = Colder = less boyant
   3. Reverse or thrust faulting
   4. Deep seismicity
   5. Increaed Temp = Partial melting of mafic crust = felsic magma
   6. Compression leads to deformation, metamorphism and mountain building
   7. Water, accumulated in pourse ocean basin
   8. Water brought down into asthenosphere = decreasing melting point = more rising magma = mountain building
   9. Also, happens in Continent Continent collision (India subducting under Eurasia) -> causes deformation = himalias
   10. Also, happens in Ocean Ocean collision -> causes island arc = japan
   11. When passive margin collides, subduction reverses causing forlorn basin (like western interior basin in N. America)
4. Transform margins
   1. No new crust forms
   2. Shear regime -> strike-slip faults, shallow seimicity
   3. San. Andres
5. Hot spots are fixed points, thus things like Hawaiian islands, show direction and rate of plate movement
6. Magnetic liniations -> lavas on land dated, and reversal history -> reversal history matched to magnetic liniations, giving us time frames

Driving Forces

1. Mantal Convection (differences in heat)
2. Ridge push or slab pull? -> slab pull is thermal model, push is topographic model
3. Subducted material goes down to the core mantel boundry
4. Icehouses and Greenhouses, match up with rates of volcanism
5. The Wilson Cycle (200my cycle), length of ocean basins determains CO2 levels

Implications