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The Theory of Plate Tectonics
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Vocabulary
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 * Plates**: parts of the lithosphere that have broken up into sections
 * Scientific theory**: a well tested concept that explains a wide range of observations
 * Plate tectonics**: a theory that states pieces of Earth's lithosphere are in constant slow motion driven by convection currents in the mantle
 * Faults**: breaks in Earth's crust where where rocks have slipped past each other
 * Transform boundary**: a place where two plates slip past each other moving in opposite directions
 * Divergent boundary**: a place where two plates move apart or diverge
 * ---Rift valley**:a deep valley that forms along the divergent boundary
 * Convergent Boundary**: a place where two plates come together or converge

A Theory of Plate Motion

 * J. Tuzo Wilson combined what geologists knew about **Sea-Floor Spreading**, Earth's plates, and the continental drift into a single theory, the theory of plate tectonics
 * The theory of plate tectonics explains the formation, movement, and subduction of Earth's plates

Plate Boundaries

 * There are three kinds of boundaries
 * Transform boundaries
 * Divergent boundaries
 * Convergent boundaries

The Continent's Slow Dance
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 * the plates move very slowly( 1 to 10 centimeters a year)
 * North American and Eurasian plates are floating apart at a rate of 2.5 centimeters a year( as fast as your fingernails grow)