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http://www.geophysics.rice.edu/plateboundary/
Where are the Earth’s tectonic plates and their boundaries?
What happens at plate boundaries?
How do Earth scientists classify plate boundaries?
Part 1.Part 1. Identify the patterns of your area of expertise – Identify the patterns of your area of expertise –
volcanology, seismology, geography, geochronology volcanology, seismology, geography, geochronology - AT PLATE BOUNDARIES- AT PLATE BOUNDARIES
Describe what you observeDescribe what you observe – do not interpret what – do not interpret what you see, just describe the you see, just describe the patternspatterns
Use descriptive terms:Use descriptive terms: Wide or narrow, straight or Wide or narrow, straight or curved, symmetric or not symmetric, deep or curved, symmetric or not symmetric, deep or shallow, ridge or valley, active or inactiveshallow, ridge or valley, active or inactive
Identify 3-5 boundary typesIdentify 3-5 boundary types; color each on your ; color each on your transparency; define in wordstransparency; define in words
Part 2.Part 2. Bring together areas of expertise Bring together areas of expertise
– volcanology, seismology, – volcanology, seismology, geography, geochronologygeography, geochronology
CorrelateCorrelate your data sets; what your data sets; what collective patterns emerge?collective patterns emerge?
Identify 3-5 boundary typesIdentify 3-5 boundary types; ; color each on a master color each on a master transparency; define in wordstransparency; define in words
10 min10 min
10 min10 min
Part 3.Part 3.
Describe the different types of boundariesDescribe the different types of boundaries
What patterns were related in the different What patterns were related in the different data sets?data sets?
What skills did you What skills did you use in undertaking use in undertaking this activity?this activity?
Historical use … Historical use …
How might you use How might you use it in your it in your classroom? classroom?
What might you What might you modify?modify?
Plate BoundariesPlate Boundaries
Where Stuff HappensWhere Stuff Happens
Plate Tectonics TheoryPlate Tectonics Theory• The upper mechanical layer of Earth (lithosphere) is
divided into rigid plates that move away, toward, and along each other
• Most (!) geologic action occurs at plate boundaries in DISTINCT patterns
CompositionalCrust - 2MantleCore
Physical / MechanicalLithosphere
AsthenosphereMesosphere
CrustCrust(Compositional)(Compositional)
Two types of crust:Two types of crust: ContinentalContinental
• 30% of crust30% of crust• Granites and Diorites - rich in Granites and Diorites - rich in
silicates and feldspars (lighter silicates and feldspars (lighter materials)materials)
• 40 Km thick40 Km thick• Oldest is 3.8 billion years (90% Oldest is 3.8 billion years (90%
solar system age; missing ~700 solar system age; missing ~700 m.y.)m.y.)
• 4.4 billion year old zircons in 4.4 billion year old zircons in Western AustraliaWestern Australia
Oceanic crustOceanic crust• Basalt - Mg, Fe (heavier Basalt - Mg, Fe (heavier
materials - relatively)materials - relatively)• 5-10 Km thick5-10 Km thick• 200 Ma oldest; 100 Ma average200 Ma oldest; 100 Ma average• OphiolitesOphiolites
LithosphereLithosphere PLATES in Plate TectonicsPLATES in Plate Tectonics Upper 200 km Upper 200 km Crust and upper mantleCrust and upper mantle RigidRigid
AsthenosphereAsthenosphere 200 km to ~700 Km200 km to ~700 Km Upper mantleUpper mantle Hi temperatures / high pressure: Hi temperatures / high pressure:
little strength; ductile / plastic - little strength; ductile / plastic - NOT A LIQUID!NOT A LIQUID!
Plates moving on thisPlates moving on this Magma generationMagma generation
MesosphereMesosphere Also hot; strong due to pressure Also hot; strong due to pressure
Lithosphere / Lithosphere / AsthenosphereAsthenosphere
(Mechanical)(Mechanical)
3 Basic Boundary
Interactions
5 to 6 Basic Boundary
Types
1. Divergent Boundaries1. Divergent Boundaries
Mid-Mid-AtlanticAtlanticRidgeRidge
North American
North American
PlatePlateNorth American
North American
PlatePlateEurasianEurasianPlatePlate
EurasianEurasianPlatePlate
•Volcanic activity in fissures, some volcanos•Shallow earthquakes, on plate boundary•Young crust, symmetrical around boundary•Ridge•Rocks?
South American Plate
Nazca Plate
Antarctic Plate
Andes Mountains
2. Convergent Boundaries2. Convergent Boundaries(a) Ocean-continent convergence(a) Ocean-continent convergence
Nazca PlateNazca PlateNazca PlateNazca Plate
AndesAndes
MountainsMountains
SouthSouthAmericanAmericanPlatePlate
SouthSouthAmericanAmericanPlatePlate
Peru-Chile TrenchPeru-Chile Trench
•Volcanos tight, parallel boundary, landward•Shallow to deep earthquakes•Age varies on one side of the boundary; not symmetrical•Trench, mountain chain•Rocks?
Foreshadowing …Foreshadowing …
Many on EarthMany on EarthRelatively small … but mighty … Relatively small … but mighty …
2. Convergent Boundaries2. Convergent Boundaries(b) Ocean-ocean convergence(b) Ocean-ocean convergence
Mariana IslandsMariana Islands
Marianas TrenchMarianas Trench
Pacific PlatePacific PlatePacific PlatePacific PlatePhilippine
Philippine
PlatePlatePhilippinePhilippine
PlatePlate
•Volcanos tightly spaced, parallel boundary, arc•Shallow to deep earthquakes•Age varies on one side of the boundary; not symmetrical•Trench, volcanic island chain•Rocks?
Eurasian Plate
Indian Plate
Himalaya Mountains
Tibetan Plateau
Himalayan Mtns.
Mt. Everest
2. Convergent Boundaries2. Convergent Boundaries(c) Continent-continent convergence(c) Continent-continent convergence
TibetanTibetanPlateauPlateau
Indian-Australian PlateIndian-Australian PlateIndian-Australian PlateIndian-Australian Plate EurasianEurasian
PlatePlateEurasianEurasianPlatePlate
HimalayanHimalayanMountainsMountains
•Volcanos rare, dispersed•Shallow (to medium) dispersed earthquakes•No age data•High mountain chain•Rocks?
3. Transform-Fault Boundaries3. Transform-Fault Boundaries
North American Plate
North American Plate
North American Plate
North American PlatePacific PlatePacific PlatePacific PlatePacific Plate
•Volcanos dispersed, most on one side•Earthquakes complex, shallow (to medium) on both sides•Age data not symmetrical, one side of boundary•Complex topography, wide mountains and basins•Rocks?
Plate TectonicsPlate Tectonics• The upper mechanical layer of Earth (lithosphere) is
divided into rigid plates that move away, toward, and along each other
• Most (!) geologic action occurs at plate boundaries in DISTINCT patterns
What’s Driving What’s Driving Plate Tectonics Plate Tectonics
on Earth?on Earth?
MantleMantle 85% volume of Earth85% volume of Earth
Density - 3.3 - 5.5 g/cmDensity - 3.3 - 5.5 g/cm33
Probably material such as Peridotite Probably material such as Peridotite (lots of heavy olivine - Fe, Mg)(lots of heavy olivine - Fe, Mg)
Solid; high pressure Solid; high pressure slow, slow, creeping, viscous movement - creeping, viscous movement - convectionconvection
Samples from kimberlites, xenoliths Samples from kimberlites, xenoliths in volcanic eruptions, basalt in volcanic eruptions, basalt composition; lab experimentscomposition; lab experiments
CoreCore 15% of Earth’s volume / ~half of 15% of Earth’s volume / ~half of
diameter of Earthdiameter of Earth
Outer coreOuter core MoltenMolten Density of pure iron or nickel/iron; Density of pure iron or nickel/iron;
~2x density of mantle~2x density of mantle Convection … Earth’s magnetic fieldConvection … Earth’s magnetic field
Inner core Inner core Solid (very hot, but higher pressure Solid (very hot, but higher pressure
than outer core)than outer core) Density of nickel/iron (~13 g/cmDensity of nickel/iron (~13 g/cm33)) Conducts heat - coolingConducts heat - cooling ~ Size of Moon (~70% of Moon)~ Size of Moon (~70% of Moon)
Earth’s Magnetic Field Earth’s Magnetic Field
Magnetic dipole … a bar magnet Magnetic dipole … a bar magnet tilted ~11 degreestilted ~11 degrees
Generated by eddies in the Generated by eddies in the conductive liquid of the outer core – conductive liquid of the outer core – currents create magnetic fieldscurrents create magnetic fields
Changes over time – north magnetic Changes over time – north magnetic pole wanders, north and south pole wanders, north and south reversereverse
Rather important to life … really Rather important to life … really important to geologyimportant to geology
What’s Driving What’s Driving Plate Tectonics Plate Tectonics
on Earth?on Earth?
How Did Earth (and other planets) Get Layers?How Did Earth (and other planets) Get Layers?