KYTL1.5

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Vocabulary:

 * Scientific theory**-a well-tested concept that explains a wide range of observation
 * Plates**-the lithosphere broken into separate sections
 * Plate tectonics**-a geological theory that states the pieces of Earth's lithosphere are in a constant, slow motion, driven by convection currents in the mantle
 * Faults**-breaks in Earth's crust where rocks have slipped past each other
 * Divergent boundary**-where two plates move apart, or diverge, usually occurs in the mid-ocean ridge
 * Transform boundary**-where two plates slip past each other, moving in opposite directions
 * Rift valley**-a deep valley that forms where two plates move apart
 * Collisions**-when two plates converge, it's called a collision, it may bring together oceanic crust and oceanic crust, oceanic crust and continental crust, or continental crust and continental crust

Outline:
A Theory of Plate Motion Plate Boundaries The Continents Slow Dance
 * the theory of plate tectonics explains the formation, movement, and subduction of Earth's plates
 * pieces of Earth's lithosphere are in slow motion
 * plates move by floating on the top of the asthenosphere
 * plates can do a lot:
 * collide,
 * pull apart
 * grind past each other
 * three boundaries:
 * transform boundaries
 * crust is neither created nor destroyed
 * divergent boundaries
 * when divergent boundaries form on land, two of Earth's plates slide apart
 * convergent boundaries
 * when two plates collide, the density of the plates determines which one comes out on top
 * oceanic crust is more dense than continental crust
 * when two plates carrying continental crust collide, subduction does not take place
 * Plates move at 2.5 centimeters per year (very slow)
 * these plates have been moving for tens of millions years
 * about 260 million years ago, the continents were joined together in the supercontinent that Wegener called Pangaea.
 * about 225 million years ago, the supercontinent broke apart.