Plate TectonicsPlate Tectonics

What is Plate TectonicsWhat is Plate Tectonics

• The Earth’s crust and upper mantle are broken into sections called plates

• These plates move around on top of the asthenosphere like rafts

LithosphereLithosphere

• The crust and part of the upper mantle = lithosphere

–Less dense than the material below it so it “floats”

AsthenosphereAsthenosphere

• The “plastic” layer below the lithosphere

• The plates of the lithosphere float on the asthenosphere

2 Types of Plates2 Types of Plates

• Ocean plates - plates below the oceans

• Continental plates - plates below the continents

Plate BoundariesPlate Boundaries

Divergent BoundariesDivergent Boundaries

• Boundary between two plates that are moving apart or rifting

Examples of Divergent Examples of Divergent BoundariesBoundaries

• Mid-ocean ridges

• rift valleys

Convergent BoundariesConvergent Boundaries

• Boundaries between two plates that are colliding

• There are 3 types…

Type 1Type 1• Ocean plate colliding with a

less dense continental plate• Subduction : occurs where the

more dense plate slides under the less dense plate

Subduction Zones occur here Deep ocean trenches may occur here

Mountains and volcanoes may occur

Andes Mountains, Andes Mountains, South AmericaSouth America

Type 2Type 2

• Ocean plate colliding with another ocean plate

• The more dense plate slides under the less dense plate creating a subduction zone called a TRENCH

Aleutian Islands, AlaskaAleutian Islands, Alaska

Type 3Type 3

• A continental plate colliding with another continental plate–a place where folded and thrust

faulted mountains form.

Transform Fault BoundariesTransform Fault Boundaries

• Boundary between two plates that are sliding past each other

• EARTHQUAKES along faults

San Andreas Fault, CASan Andreas Fault, CA

Questions...Questions...

• What are the three types of boundaries?

• What direction do plates go for each?

• Which boundary has a subduction zone…what occurs at a subduction zone?

Causes of Plate Causes of Plate TectonicsTectonics

Convection CurrentsConvection Currents

• Hot magma in the Earth moves toward the surface, cools, then sinks again.

• Creates convection currents beneath the plates that cause the plates to move.

Questions...Questions...

• What causes plates to move?

• How is a convection current formed?

New sea-floor is produced at what New sea-floor is produced at what type of boundary?type of boundary?

A. convergent

B. divergent

C. transfo

rm

D. I

don’t kn

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A. convergent

B. divergent

C. transform

D. I don’t know

Mt. Everest was produced by this Mt. Everest was produced by this type of plate boundary.type of plate boundary.

A. convergent

B. divergent

C. transfo

rm

D. I

Don’t Kno...

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A. convergent

B. divergent

C. transform

D. I Don’t Know

This type of boundary, found near This type of boundary, found near San Francisco CA, is the result of San Francisco CA, is the result of

shear force.shear force.

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A. convergent

B. divergent

C. transform

D. I Don’t Know