Date post: | 21-Dec-2015 |
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“If we are to believe Wegener’s Hypothesis,
we must forget everything which has been learned in the last 70 years and start over again.”
–Critic of Continental Drift in
1928
• Earth’s “surface” (lithosphere) is broken into plates
• Plates move on asthenosphere
• “Geology happens” where the plates interact with one another
Basic Plate Tectonics
Three Layers:Based on CompositionLayer Composition
Crust Rock: Felsic & Mafic
Mantle
Rock: Ultramafic
Core Metal: Iron & Nickel
Crustal Properties
CrustCrust DensityComposit
ionThickne
ssAge
continecontinentalntal
~2.8 g/cm3 Felsic
Thick:20-70 km
Old:up to4 Byrs
oceanicoceanic ~3.2 g/cm3 Mafic
Thin:2-10 km
Young:<200 Mys
Five Layers:Based on Physical
PropertiesLayer “State”
Lithosphere
Solid / Rigid
Asthenosphere
Partly Liquid / “Plastic”
Lower Mantle
Solid
Outer Core Liquid
Inner Core Solid
Part #1of Plate Tectonics
DefinitionEarth’s “surface” is broken into rigid plates
Surface = Lithosphere
(includesContinental Lithosphere and
Oceanic Lithosphere)
Part #2of Plate Tectonics
DefinitionPlates move…
…on the “plastic” Asthenosphere
…at about 1-10 cm/yr
Part #3of Plate Tectonics
Definition“Geology happens” where the plates interact with one
anotherHow do they interact?
1. Pull Apart from one another (Diverge)(New rock is formed)
2. Push into one another (Converge)(Rock is destroyed)
3. Slide past one another(Rock is conserved)
Convergent Boundary: Subduction
Results in the formation & growth of Continental Crustand destruction of Oceanic Crust
Melting
Produces More Felsic Magma
1. Earth’s lithosphere is broken into 12-24 rigid plates
2. Plates move about 1-10 cm/yr on the plastic Asthenosphere
3. “Geology happens” where the plates interact with one another along Divergent, Transform, Subduction and Collisional Boundaries
Basic Plate Tectonics - Revised