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Science Do Now: 12-8 EQ: What are plates and how do they move? LG: Describe the three types of tectonic plate boundaries, the forces that move them, and how movement is measured. HW: 7-3 worksheet due Wed, Test on Thursday study session at 8:15 ** List 3 types of convergent boundaries use arrows to show movement** 1. Take out color pencils/markers 2. Take out Plate Tectonic notes Today ~ Complete PPT: Theory of Plate Tectonics ~ Convection Current Organizer ** List 3 types of convergent plate boundaries use arrows to show movement** What is here? 1. Oceanic-Oceanic 2. Oceanic-Continental What is here? 3. Continental-Continental The Theory of Plate Tectonics Think of a Broken EGG! Plate Boundary Plate Plate Tectonics • The Earth’s lithosphere is divided into plates that move on top of the asthenosphere. Lithosphere Asthenosphere When the water moves beneath the raft, the raft moves with it. When the asthenosphere moves, the lithosphere moves with it… Earth’s Major Plates Here is a look at a different map! Where are most plate boundaries located? What plate do we live on? And another … Types of Plate Boundaries • • When two plates meet, they form a boundary. There are three types of boundaries Convergent Boundaries • Two plates push together Oceanic crust sinks, Continental crust rises!! • • Term to know: SUBDUCTION means the crust is SINKING! Three types of convergent boundaries: 1. Ocean/Ocean = TRENCH 2. Ocean/Continental = TRENCH 3. Continental/Continental = MOUNTAINS Convergent Collision #1 (Oceanic/Oceanic) One of the plates will SINK (subduction!) and form a TRENCH. Magma rises and forms and island arc of volcanoes. Convergent Collision #2 (Oceanic/Continental) • The oceanic plate sinks (subduction!) below the continent and the continental plate slides over the top of the oceanic plate. Forms a TRENCH. Subduction Zone Convergent Collision #3 (Continental/Continental) • Both continental plates collide and rise up forming MOUNTAINS. (Ex. Himilayas) Divergent Boundaries • Two plates pull apart forming a rift valley in Rift Valley the middle. • Sea-floor spreading is created by a divergent boundary. Mid Ocean Ridge Click Here to see Divergent Boundaries in motion!!! When the divergent boundary is on land . There is a HUGE rift valley in east Africa called the Great Rift Valley Transform Boundaries • Plates slide past each other in a side to side motion. (Ex. San Andreas Fault) This fence used to line up!! Before the 1906 Earthquake in California San Andreas Fault WHY do the plates move? …CONVECTION CURRENTS in the mantle…Hot rock (less dense) rises to the surface, cools (more dense), and sinks back to the mantle. HOT MOLTEN ROCK RISES COOL MOLTEN ROCK SINKS Convection Currents Less More More = Dense Less = Dense More matter Less matter Rise Sink Same Volume Same Volume = Less Dense = More Dense Less matter More matter Less Rise More Sink Convection Currents Cools off! = more dense = fall to the bottom Hot! = less dense = rise to the top See Animation: http://education.sdsc.edu/optiputer/flash/co nvection.htm REVIEW BOUNDARIES!