5. Seafloor Spreading

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Students take what they know about earthquake, volcano and mid-ocean ridge distributions (The Big One and Plate Patterns) and put it together with what they know about convection in the Earth’s mantle (Journey Through Earth and Convection in a Pan). They revisit what they know about how earthquakes are created, by the sudden release of energy as plates collide or rub together (but not so much when they split apart). They look for patterns in their world maps, observing that mid-ocean ridges and dense earthquake/volcano zones tend to lie on the opposite side of plates. With this information, they can infer the direction that the plates are moving. Next students build a model illustrating seafloor spreading and discuss the magnetic and seafloor age data that support this model. Finally, students codify the different types of plate boundaries, describing the various features and characteristics of each.

Seafloor Spreading: Animation created by the US Geological Society.Seafloor Spreading: Animation created by the US Geological Society.Objectives
Can find patterns on a map and use that information to infer the direction of plate motion.
Can diagram and explain what causes earthquakes and volcanoes.
Can build and interpret a physical model of seafloor spreading.
Can describe some of the evidence supporting seafloor spreading.
Can describe the characteristics of the 3 major classes of plate boundaries as well as differences between subducting convergent boundaries and continent-continent convergent boundaries.

Seafloor Spreading with Magnetic Reversals: Animation courtesy of the US Geological Society.Seafloor Spreading with Magnetic Reversals: Animation courtesy of the US Geological Society.Mantle
Mid-ocean ridge
Tectonic plate
Oceanic plate
Continental plate
Seafloor spreading
Convergent boundary
Divergent boundary
Transform boundary
Island arc

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5sea_floor_spreading.doc 67.5 KB
sea_floor_model.doc 402.5 KB
sea_floor_model.pdf 697.86 KB