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 BoundariesWhere 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

PlatePlateEurasianEurasianPlatePlate

•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 Plate

AndesAndesMountainsMountains

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 PlatePhilippine

Philippine

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 Plate EurasianEurasian

PlatePlate

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 PlateNorth American PlatePacific Plate

Pacific 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?