Plate TectonicsPlate Tectonics

Brigitte SteinmetzBrigitte Steinmetz

John Adams Middle SchoolJohn Adams Middle School

DisclaimerDisclaimer

The images, maps and diagrams in this presentation were taken from the public

domain on the world wide web. Permissions were granted where possible. Any privately owned images not available

for this non-commercial, educational project will gladly be removed.

E-mail: steinmetz@smmusd.org

Earth’s InteriorEarth’s Interior

Oceanic CrustA.

B.

C.D.

E.

Outer Core

Inner Core

Lithosphere

Continental Crust

OceanicCrust

AsthenosphereMantle

The MantleThe Mantle• Upper part = hot &

rigid (hard)– part of the

lithosphere.

• Middle part = hotter & soft (asthenosphere)

• Lower part = hottest & solid http://pubs.usgs.gov/publications/text/inside.html - 12/7/2004

The Earth is HOTThe Earth is HOT

• Review Heat Transfer– Radiation =

• Energy transferred through an empty space (i.e. sun energy).

– Conduction = • Energy transferred directly from one object to

another (i.e. burning feet at the beach).

– Convection = • Energy transferred through the movement of a

heated fluid.

Convection inside EarthConvection inside Earth

http://pubs.usgs.gov/publications/text/unanswered.html - 12/7/2004

Convection inside EarthConvection inside Earth

• Convection in the mantle causes the crust’s plates to move!

http://www2.nature.nps.gov/geology/usgsnps/animate/A08.gif - 12/7/2004

Continental DriftContinental Drift

• Alfred Wegener:– Hypothesis:

• About 300 MYA all continents were once joined together forming a SUPER continent!

– He named it PANGEA!

Continental Drift TheoryContinental Drift Theory• Pangaea begins to break apart and

continents move to present day locations

• Occured tens of millions of years ago

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Evidence of DriftEvidence of Drift• Continents fit together like a puzzle

• Land forms similar on different continents (like mountain ranges)

Evidence of Drift ContinuedEvidence of Drift Continued• Fossils found in

unlikely places– For example:

• Reptiles were found in Antarctica.

• Tropical plants found in ice covered places. http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/

images/fossil_correlation_lge.jpg - November 27, 2005.

What about the FUTURE?

Plates on the MovePlates on the Move

• Plates move 1-10cm/year.• Moving apart.• Moving plates

cause:–Earthquakes–Volcanoes

http://pubs.usgs.gov/publications/text/Krafla.html - December 13, 2004.

Plate BoundariesPlate Boundaries

• Place where two plates meet and interact.

• Three Types:–Transform –Divergent –Convergent

http://pubs.usgs.gov/publications/text/ridge.html - December 13, 2004.

Convergent BoundariesConvergent Boundaries

• Occurs when two plates collide (run into each other).

• Two types:

Continental Oceanic

http://pubs.usgs.gov/publications/text/understanding.html - December 13, 2004.

Continental ConvergenceContinental Convergence

• Two plates collide and buckle upwards forming mountains and cause earthquakes!

Oceanic ConvergenceOceanic Convergence• When two plates collide, one goes under

the other called subduction!

• Causes volcanoes.

Divergent Plate BoundariesDivergent Plate Boundaries

• When two plates move apart.

• Occurs at two places:

Mid-Oceanic Ridge Land – Rift Valley

http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0006339.html - December 13, 2004

Sea Floor SpreadingSea Floor Spreading

• Magma comes up forming new rock and pushes old rock to sides.

http://www.uwsp.edu/geo/faculty/ritter/glossary/S_U/sea_flr_spread.html - December 13, 2004.

Which Rock is Older?Which Rock is Older?

• The older rock is closer to the continents.

• New rock is at the mid-oceanic ridge.

http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/science/oceanic_constr.html

- December 13, 2004.

Where are Mid-Ocean Ridges?Where are Mid-Ocean Ridges?

Pacific vs. Atlantic OceansPacific vs. Atlantic Oceans

Atlantic Ocean is getting

bigger – USA and Europe are moving

apart!

Pacific Ocean is getting smaller – continents are

coming together. Oceanic crust is

moving under them.

http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/science/oceanic_constr.html - December 13, 2004.

Transform BoundaryTransform Boundary

• Plates slide past each other in opposite directions.

• Causes a lot of earthquakes.