Plate Tectonics and Earthquakes

Plate Tectonics and EarthquakesPlate Tectonics and EarthquakesObjectives:Objectives:

• Students will learn key terms associated withStudents will learn key terms associated with plate tectonic processes. (Part A)plate tectonic processes. (Part A)• Students will understand the specific plateStudents will understand the specific plate motions associated with divergent, motions associated with divergent, convergent, and transform plate boundaries.convergent, and transform plate boundaries. (Part B)(Part B)• Students will gain a global view of EQ’sStudents will gain a global view of EQ’s (where EQ’s typically occur). (Part C)(where EQ’s typically occur). (Part C)• Students will evaluate and apply conceptsStudents will evaluate and apply concepts from lab parts A, B, and C to answer criticalfrom lab parts A, B, and C to answer critical thinking questions. (Part D)thinking questions. (Part D)

The Plate Tectonic Model

• The plate tectonic model describes surface features, geologic environments, and patterns of EQ’s and volcanism.

• Ridged lithospheric plates (continents + ocean floor) ride along the soft layer (like hot wax) called the asthenosphere• Plates spread apart, collide, and slide past one another. • EQ’s, crustal deformation, and volcanism take place at plate boundaries.

EarthquakePatterns

VolcanismPatterns

lithosphere

Asthenosphere (upper mantle)

Plate BoundariesPlate Boundaries

Divergent Boundary – plates move AWAY from each other

Convergent Boundary – plates move TOWARD each other

Transform Boundary – plates SLIDE past each other

Divergent Boundary:Divergent Boundary:• plate material separatingplate material separating

ocean plate divergence Extensional forcescreate EQ’s

continental divergence

Extension createsfaulting

• Earthquake activity

Ocean-ContOcean-Cont Ocean-OceanOcean-Ocean Cont-ContCont-Cont

Convergent Boundary:Convergent Boundary:• interaction of two plates moving toward one anotherinteraction of two plates moving toward one another making contact– hence, collision or convergencemaking contact– hence, collision or convergence• collisions produce earthquakes, volcanic activity, andcollisions produce earthquakes, volcanic activity, and crustal deformationcrustal deformation

Subduction zone SubductioinSubductioin

zonezoneOregon-Washington

CoastAleutian Island(Alaska area)

Himalayan Mountains

ocean-continentocean-continent

ocean-oceanocean-ocean

cont-contcont-cont

• thinner and more dense platethinner and more dense plate subductssubducts• subducted plates melt (160 km)subducted plates melt (160 km) below the surface, and magmabelow the surface, and magma risesrises• EQ’s occur along the subductionEQ’s occur along the subduction zone, and magma plumes risezone, and magma plumes rise

• typically, the older plate will typically, the older plate will subduct (more dense) beneath subduct (more dense) beneath younger plate materialyounger plate material• melting plate material rises,melting plate material rises, creating volcanic arc systemscreating volcanic arc systems• most EQ’s occur within themost EQ’s occur within the subduction zonesubduction zone

• two plates converge with thetwo plates converge with the same densitysame density• same density prevents same density prevents subductionsubduction• extensive deformationextensive deformation

• Earthquake activity

Transform Boundary:• two plates are sliding past one another

• lack the spectacular features associated with divergent/convergent boundaries• marked by linear valleys (slices through the earth’s crust)• shallow-focused EQ’s occur along the slip area of the sliding plates

SAF

Transform boundaries offsettingspreading ridges

• Typical EQ’s occur along the transform boundary. Earthquakes

Cross-sectional view of the SAFand associated LA faults

•SAF – transform motion•LA faults- vertical motion SAF-transform fault

Los Angeles

What moves or drives the plates?What could Wegener have told the geological society?

Only a Model – Think Only a Model – Think ConvectionConvection

Convection – heat transfer through a liquid or gas that results in circular movement of particles

Hot water rises

Cooler water sinks

RiseRise

FallFall

Earth CrustEarth Crust

mantlemantlemantlemantle

The Earth’s MantleThe Earth’s MantleCan you see the convection?Can you see the convection?

Mantle operates like a “lava lamp,” producingMantle operates like a “lava lamp,” producingswelling and shrinking of magma plumes.swelling and shrinking of magma plumes.

Earth’s Surface

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Latitude and Longitude• Where are you on earth?

Latitude/Longitude• a grid system used to locate features on the earth’s surface

Latitude: • parallel lines that move north

and south• 0o latitude = equator

Longitude:• meridian lines that move east and west • 0o longitude is through Greenwich, England 11

Los Angeles, Ca 350 N-lat, 1210 W-longSpokane, Wa 470 N-lat, 1180 W-longNew York, NY 420 N-lat, 750 W-long 12

Latitude (+)Longitude (-)

Latitude (-)Longitude (-)

EastWest

North

South

Latitude (+)Longitude (+)

Equator

Prime M

eridianLatitude (Latitude (-)Longitude (+)

A

B

C

DE

15 N-lat, -132 W-long15 N-lat, -132 W-long

52 N-lat, 78 E long52 N-lat, 78 E long

-18 S-lat, -162 W-long-18 S-lat, -162 W-long-55 S-lat, -15 W-long-55 S-lat, -15 W-long

-25 S-lat, 136 E long-25 S-lat, 136 E long

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Plate Tectonics Lab:• Part A: Plate tectonic definitions

• use lab text• use textbook resources in classroom

• Part B: Identification of plate boundaries• use lab text, colored pencils• use textbook resources in classroom

• Part C: Plotting EQ location• use provided long/lat handouts• use colored pencils

• Part D: Critical thinking questions• use parts A, B, and C and your synthesizing brain.