Intermission: Plate Tectonics

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IntermissionPlate Tectonics
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National Oceanic and atmospheric
Administration/National Geophysical Data Center
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AlfredWegener
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Evidence(1) Continents Fit Together
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Evidence(2) Rocks Structures Match Up
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(No Transcript)
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(No Transcript)
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Evidence (3) Glacial Features
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(No Transcript)
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Evidence (4) Fossils
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Pangea
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Animation Link
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If we are to believe Wegeners Hypothesis, we
must forget everything which has been learned in
the last 70 years and start over again. Critic
of Continental Drift in 1928
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HarryHess
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Evidence Seafloor
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Seafloor Spreading
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Seafloor Age
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Seafloor Age
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Plate Tectonics
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Basic Plate Tectonics

• Earths surface (lithosphere) is broken into
  plates
• Plates move on asthenosphere
• Geology happens where the plates interact with
  one another

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What do we mean by the Outer Part of the Earth?
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Three LayersBased on Composition
Layer Composition
Crust Rock Felsic Mafic
Mantle Rock Ultramafic
Core Metal Iron Nickel
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Crustal Properties
Crust Density Composition Thickness Age
continental 2.8 g/cm3 Felsic Thick 20-70 km Oldup to4 Byrs
oceanic 3.2 g/cm3 Mafic Thin2-10 km Young lt200 Mys
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Five LayersBased on Physical Properties
Layer State
Lithosphere Solid / Rigid
Asthenosphere Partly Liquid / Plastic
Lower Mantle Solid
Outer Core Liquid
Inner Core Solid
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(No Transcript)
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Part 1of Plate Tectonics Definition
Earths surface is broken into rigid plates
Surface Lithosphere (includes Continental
Lithosphere and Oceanic Lithosphere)
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Part 2of Plate Tectonics Definition
Plates move
on the plastic Asthenosphere
at about 1-10 cm/yr
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Part 3of Plate Tectonics Definition
Geology happens where the plates interact with
one another
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Earthquake Distribution
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Volcanoes and Plate Tectonics
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Part 3of Plate Tectonics Definition
Geology happens where the plates interact with
one another
How 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)

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Divergent Boundary
Results in the formation of Oceanic Crust
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Examples
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Transform Boundary
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Transform Example
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San Andreas Fault
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Convergent Boundary Subduction
Melting Produces More Felsic Magma
Results in the formation growth of Continental
Crustand destruction of Oceanic Crust
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ExamplePacific Northwest
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ExampleAndes Mountains
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Convergent Boundary Collision
Results in the growth of Continental Crust
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Basic Plate Tectonics - Revised

1. Earths 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

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What Drives Plate Tectonics?
Internal Heat
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Convection Models
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