C.K.K.K.+1.5

toc =**Section 5 The Theory of Plate Tectonics**=

**Vocabulary**
scientific theory- a well- tested concept that explains a wide range of observations. plate tectonics- the geologic theory that states that piece of Earth's lithosphere are in constant, slow motion, driven by convection currents in the mantle. transform boundary- a place where two plates slip past each other, moving in opposite directions. divergent boundary- a place where two plates move apart. convergent boundary- a place where two plates come together. rift valley- when continental plates pull apart at a divergent boundry on land, this forms.

**A Theory of Plate Motion**

 * plates move slowly by the convection currents.
 * as plates move, different things happens.
 * they can collide, pull apart, or grind each other.
 * change also happens to the plates.
 * volcanoes can be formed.
 * mountain ranges can be made.
 * deep- sea trenches also can form.

**Plate Boundries**

 * There are three types of plate boundaries.
 * Transform Boundary
 * they slip past each other moving in opposite directions.
 * Dirvergent Boundary
 * they move apart.
 * rift valley can be formed.
 * Converagant Boundary
 * two plates come together
 * when they converge, a collision occurs
 * oceanic crust and continental crust
 * oceanic crust and oceanic crust
 * continental crust and continental crust
 * when they collide one subducts into a deep- ocean trench

**The Continent's Slow Dance**

 * moving at a slow rate
 * about 1-10 centimeters a year
 * North America, and Eurasia are moving apart
 * at the rate of 2.5 cm.
 * continents were once one great landmass
 * 225 million years ago this great landmass started to break apart