Earth’s Skin: Plate Tectonics

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Earths SkinPlate Tectonics
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On the agenda

• What is the theory of plate tectonics? what are
  some important concepts in plate tectonics?
• What is the evidence in support of plate
  tectonics?
• Why do we study plate tectonics?

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Important Concepts in Plate Tectonics
Earths crust is made up of several large

plates that fit together like a jigsaw puzzle.
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Important Concepts in Plate Tectonics
There are three types of plate boundaries
Satellite image of the red sea
1. Divergent (Extensional)
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Seafloor topography (Smith and Sandwell 1997)
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Important Concepts in Plate Tectonics
2. Convergent(Compressional)
Satellite image of Himalayas
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Important Concepts in Plate Tectonics
3. Boundaries along which plates slide past each
other
Photo of an offset stream along the San Andreas
Fault
Source Paul Mann
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Important Concepts in Plate Tectonics
These plate are all moving right now at 2-15
cm/year
We can describe the plate motion with three types
of relative motion.
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Important Concepts in Plate Tectonics
Convection currents are the engine that help to
push plates
around. Radioactivity provides the heat energy.
asthenosphere
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Important Concepts in Plate Tectonics
New crust is generated at spreading centers
(divergent margins).

Old crust is recycled at subduction zones.
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Important Concepts in Plate Tectonics
The latest understanding of the driving mechanism
for plate tectonics favors the notion that
plates are pulled along by gravitational forces
operating on their subducting oceanic slabs.
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Important concepts in Plate Tectonics
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Important concepts in Plate Tectonics

• To summarize
• Earths crust is made up of several large plates
  that fit together like a jigsaw puzzle.
• These plates are all moving right now at 2-15
  cm/year.
• Although convection currents in the mantle are
  engines that help push plates around
  (radioactivity provides the heat energy), the
  latest understanding of the driving mechanism for
  plate tectonics favors the notion that plates
  are pulled along by gravitational forces
  operating on their subducting oceanic slabs.
• New crust is generated at spreading centers. Old
  crust is recycled at subduction zones.
• Pangea is a supercontinent that existed about 200
  million years ago.

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On the agenda

• What is plate tectonics? What are some of the
  important concepts in plate tectonics?
• The evidence in support of plate tectonics
• Why we are going to study plate tectonics

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Evidence for Plate Tectonics
Earthquake Volcano Activity
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Evidence for Plate Tectonics
Changes in Sea Floor Magnetism
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Evidence for Plate Tectonics
ridge
Magnetic stripes along the Reykjanes Ridge.
From Vine 1966
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Evidence for Plate Tectonics
Mantle Hotspots
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Evidence for Plate Tectonics
Sea Floor Spreading
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Age of the ocean floor (Mueller et al., 1996)
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On the agenda

• What is plate tectonics? What are some of the
  important concepts in plate tectonics?
• What is the evidence in support of plate
  tectonics?
• Why do we study plate tectonics?

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Why are we studying plate tectonics?

• Plate tectonics is THE unifying theory in Geology
  

magnetic pole reversals
volcanoes
sea floor spreading
earthquakes
mantle hotspots
continental drift
Distribution of natural resources (hydrocarbons,
and precious metals/minerals/ gems, etc.)
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About our WorkUTIGs PLATES Project What type
of research do we do and how do we do it?

• Refinement of our plate models
• Breaking up the major plates into smaller
  elements as a means of dealing with the
  non-rigidity of plates
• Extension of our plate model ever further into
  the past

GPS Station in Antarctica (left)
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• Data
• Seafloor-spreading data (anomalies/fracture
  zones)
• Free-air gravity data (constrains fracture zones,
  shelf edges, other features)
• Hotspot data/tracks, large igneous provinces
• Paleomagnetic data
• Onshore geologic data
• Tools
• Interactive plate reconstruction software
• Plotting software (both in-house GMT)