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Intermission: Plate Tectonics. National Oceanic and atmospheric Administration/National Geophysical Data Center. Alfred Wegener. Evidence: (1) Continents Fit Together. Evidence: (2) Rocks & Structures Match Up. Evidence: (3) Glacial Features. Evidence: (4) Fossils. Pangea. Animation Link. - PowerPoint PPT Presentation
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National Oceanic and atmospheric Administration/National Geophysical Data Center
AlfredWegener
Evidence:(1)
Continents Fit
Together
Evidence:
(2) Rocks & Structures Match
Up
Evidence: (3) Glacial Features
Evidence: (4) Fossils
Pangea
Animation Link
“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
HarryHess
Evidence:
Seafloor
Seafloor Spreadin
g
Seafloor Age
Seafloor Age
Plate Tectonics
• Earth’s “surface” (lithosphere) is broken into plates
• Plates move on asthenosphere
• “Geology happens” where the plates interact with one another
Basic Plate Tectonics
What do we mean by the Outer
Part of the
Earth?
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
another
Earthquake Distribution
Volcanoes and Plate Tectonics
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)
Divergent Boundary
Results in the formation of Oceanic Crust
Examples:
Transform Boundary
Transform Example
San Andreas Fault
Convergent Boundary: Subduction
Results in the formation & growth of Continental Crustand destruction of Oceanic Crust
Melting
Produces More Felsic Magma
Example:Pacific
Northwest
Example:Andes
Mountains
Convergent Boundary: CollisionResults in the growth of Continental Crust
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
What Drives Plate Tectonics?
Internal Heat
Convection Models
Set the “Wayback Machine” to return to
the Hadean…
Return to Hadean ppt