Plate Tectonics

Lynn Hahn

Tectonic Plate Theory Theory that explains the

movement of continents across the globe. It explains why some earthquakes occur and volcanoes on land and the ocean floor.

The Tectonic Plates

The Tectonic Plates Tectonic plates

are large pieces of the lithosphere

2 different types of plate: Oceanic and Continental

How the plates move Convergent -

Plates are moving towards each other

Divergent - Plates are moving away from each other

Transverse - Plates are moving past each other

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Convergent Plate Boundaries

3 different types of convergent boundaries Oceanic – Oceanic

Convergence (2 oceanic plates converge

Oceanic – Continental Convergence (1 oceanic plate and 1 continental plate)

Continental – Continental Convergence (2 Continental plates

Convergent – when two objects move towards one another

The two objects are two tectonic plates

Oceanic – Oceanic Boundaries

Oceanic – Oceanic Boundaries

The slower moving plate SUBDUCTS the faster moving plate

Subducted plate – the plate that is forced into the mantle (the slower plate)

Forms trenches and volcanoes.

Hawaii is the result of underwater mountain ranges reaching above water.

Oceanic – Continental Boundaries

Oceanic – Continental Boundaries

Oceanic Plate is denser

Oceanic plate will subduct the continental plate

Forms offshore volcano range and an underwater trench

Ex. Andes Mountains

Continental – Continental Boundaries

Continental – Continental Boundaries Two continental plates

colliding Neither plate subducts

the other One plate will crumble

and break apart Forms mountain

ranges and a higher plateau

Ex. Himalayan Mountains and Tibetan Plateau

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Divergent Plate Boundary

Divergent Plate Boundaries

Moving apart and makes a gap

Magma rises from asthenosphere and creates mountains as magma cools

Ex. Mid Atlantic Ridge Results in new crust

forming at a Rift Valley

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Transform Plate Boundaries

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Transform Plate Boundaries

Form Faults Breaks in the

lithosphere Rocks move past each

other Ex. San Andreas Fault

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Evidence for Plate Tectonics In the middle of the oceans – The N and S are

magnetic Poles Magnets have a certain arrangement that makes them

magnetic. Every 200,000 years the earth’s magnetic poles switch and S becomes North and North become South

The magnetic rocks on earth reflect the direction of magnetic North and magnetic South

Evidence Cont’d As magma comes out of the floor at a divergent

boundary, the material aligns itself the current magnetic poles. After the magma cools, this become permanent.

Once the poles switch, the new magma will have a new arrangement

PROOF!! – We see bands on the sea floor that reflect changes in magnetic N and S. IF the sea floor was not spreading, we wouldn’t

http://scign.jpl.nasa.gov/learn/plate4.htm

Other Evidence Fit of the Continents - Noted the similarity in

the coastlines of North and South America and Europe and Africa. Today the fit is done at the continental shelf and it is nearly a perfect match.

Rock Similarities Rocks of same age match across ocean basins. Termination of mountain chains.

http://geology.csupomona.edu/drjessey/class/Gsc101/Plate.html

References and Pictures US Geological Survey Western Earth

Surface Processes Team and the National Park Service, http://www2.nature.nps.gov/grd/usgsnps/pltec/pltec3.html#convergent.