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How tectonics works

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Hence deform elastically until brittle yield strength. Heat flow by diffusion ... Resistance from plate strength. Ridges and rifts: properties. Normal faults ... – PowerPoint PPT presentation

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Title: How tectonics works


1
How tectonics works
2
Plates forces
  • Tectonic forces applied at edges and transmitted
    through whole plate
  • Internal forces from gravitational potential
    energy
  • Generally isostatic
  • Tractions on top bottom small (air and
    asthenosphere are weak)

3
Plates properties
  • Approximately rigid
  • Hence deform elastically until brittle yield
    strength
  • Heat flow by diffusion
  • Continental and oceanic lithosphere differ

4
Continental lithosphere properties
  • low density (chemical cause)
  • Heterogeneous
  • May have multiple weak and strong layers
  • May be very old

5
Oceanic lithosphere properties
  • Density increases with cooling
  • Homogeneous
  • Approximate as single elastic sheet
  • Recycled by lithospheric convection

6
Plates feedbacks
thickness
Differentiation by partial melt
temperature
stiffness
age
7
Plates dynamics
8
Ridges and rifts forces
  • Doming and downhill sliding (ridge push)
  • Far-field pull
  • Resistance from plate strength

9
Ridges and rifts properties
  • Normal faults dike injection
  • Formation of new lithosphere
  • High temperature and heat flow
  • Low density
  • Low stiffness
  • Thin lithosphere

10
Ridges and rifts feedbacks
Lithospheric thinning
Faulting
Strength in tension
melting
Induced mantle convection
11
Ridges and rifts dynamics
  • Active vs. passive rifting
  • New lithosphere formed (no mass conservation)
  • Advection of mass away from boundary
  • Change in properties with time (distance/velocity
    )
  • Gravity helps faulting

12
Trenches and collisions forces
  • Slab negative buoyancy (slab pull)
  • Far-field push?
  • Resistance from basal drag
  • Resistance from mantle
  • Resistance to bending

13
Trenches and collisions properties
  • Low T slab
  • High density slab
  • High stiffness slab
  • Brittle failure to great depth
  • Friction at interface
  • Accretionary wedge/lubrication

14
Trenches and collisions
15
Trenches and collisions feedbacks
Lithospheric thickening
Plate shortening (mass loss)
Faulting
Slab foundering
Rayleigh-Taylor instability
16
Trenches and collisions dynamics
  • Active vs. free subduction
  • Lithosphere lost (no mass conservation)
  • Advection of mass toward boundary
  • Differentiation of crust
  • Gravity hinders faulting
  • Induced mantle flows

17
Transforms forces
  • Far-field applied forces
  • Resisted by fault friction
  • Resisted by drag

18
Transforms properties
  • Same material always in fault zone
  • Evolution of fault segments
  • Evolution of fault friction

19
Transforms feedbacks
rotation
friction
strain rate
20
Transforms dynamics
  • Passive pulling
  • Localization
  • Gravity does not contribute
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