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

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

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

Transform Plate Boundaries

Transform Plate Boundaries Form Faults Breaks in the lithosphere Rocks move past each other Ex. San Andreas Fault

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.