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• Get out your lab and your Ch. 7 Section 3 Notes and on your small paper answer the following question: • What do you think is the driving force that causes the Earth’s tectonic plates to move? • Today’s Schedule • 1. Ch. 7 Section 3 Notes/Discussion • 2. Review Sea-Floor Spreading Lab What We Know So Far What We Want To Know • What causes the plates to move? • THE answer to this question we believe is: convection currents in the mantle. • animation Convection • Convection- heat transfer by the movement of currents within a fluid • Caused by differences of temp. and density within the fluid Convection Currents in Earth • 1. What is the heat source? • 2. What is flowing? • Heat from the core and the mantle itself causes convection currents in the mantle. • Google Image Result for http://www.windows.ucar.edu/earth/interior/e_thermal_history_animated.gif Convection Currents in the Earth • Animation • As the convection currents move through the mantle, it causes the plates to move in the lithosphere. What do you see here? • Plate Boundaries Plate Boundaries • Divergent Boundary- place where 2 plates move apart or diverge. • Most DB’s are at mid-ocean ridges. • On land DB’s form deep valleys called rift valleys • • Fig. 19.21 - Evolution of a Divergent Plate Boundary animation Convergent Boundary • Place where 2 plates come together, or converge. • Oceanic plate + Continental plate = subduction • Continental plate + Continental plate =mountains • OptIPuter Outreach Subduction at Trenches • Deep-ocean trench- underwater canyon where ocean crust sinks into the mantle. • Subduction- process by which ocean crust sinks beneath a deep-ocean trench and back into the mantle • Subduction Animation - Earthguide Online Classroom Transform Boundary • Place where two plates slip past each other in opposite directions. • Transform Boundaries = Earthquakes • • Observe animations of processes that occur along plate boundaries. animation • land masses have slowly moved over time • Plates move on top of asthenosphere • Two plates slip past each other in opposite directions Matching Game • Convergent boundary • Sea-floor spreading • Plate tectonics • Happens at divergent boundaries, allows magma to rise to the ocean floor • Continental drift • Two plates collide with each other • Divergent boundary • Two plates separate with each other • Transform boundary Transform Plate Boundaries Contest Convergent Divergent Ch. 7 Section 3 The Theory of Plate Tectonics Things you should know: what plates are, directions plates move, and some landforms that plate movement creates. Now, you need to figure out what causes the plates to move. Observe these demonstrations to discover the answer.
