Plate Tectonics 22 4 Plate Tectonics n Theory

Plate Tectonics n Theory that explains the formation and movement of Earth’s plates

Continental Drift n n n Theory put forth by Alfred Wegener that hypothesized that

Mid Ocean Ridge n n In the 1950’s, sonar was used to map the

Formation of Oceanic Crust n n n In the crack along the mid ocean

Subduction n n When oceanic plates collide with continental plates, the oceanic plate sinks

Theory of Plate Tectonics n n Movement of the plates based on the convection

Plate Boundaries n n n Divergent: plates are pulling apart Convergent: plates are pushing

Mountain Building n n n Mountains form along plate boundaries Convergent: Himalayas, Andes, Swiss

Essential Questions n n n What is theory of plate tectonics? What evidence supports

References n n n http: //www. platetectonics. com/book/images/Midoceanridge. jpg http: //library. thinkquest. org/17457/platetectonics/seafloor. jpg

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Plate Tectonics 22. 4

Plate Tectonics n Theory that explains the formation and movement of Earth’s plates

Continental Drift n n n Theory put forth by Alfred Wegener that hypothesized that continents looked liked they fit together like pieces of a puzzle One large supercontinent was formed called Pangaea “all land” Pangaea’s eventual split is called continental drift, powered by sea floor spreading

Mid Ocean Ridge n n In the 1950’s, sonar was used to map the sea floor Mountains were discovered The mid ocean ridge is the Earth’s longest mountain chain Alongside it, runs a deep valley

Mid Ocean Ridge

Formation of Oceanic Crust n n n In the crack along the mid ocean ridge, magma rises to the surface As it cools, it gets pushed aside by new magma Older crust gets pushed farther and farther apart and the sea floor spreads

Sea Floor Spreading

Subduction n n When oceanic plates collide with continental plates, the oceanic plate sinks below it because it is denser Oceanic plate is destroyed

Subduction

Theory of Plate Tectonics n n Movement of the plates based on the convection of the mantle Heat from the core and radioactive decay are two engines that drive plate movement

Plate Boundaries n n n Divergent: plates are pulling apart Convergent: plates are pushing together Transform: plates are sliding side by side

Divergent

Convergent

Transform

Mountain Building n n n Mountains form along plate boundaries Convergent: Himalayas, Andes, Swiss Alps Divergent: Iceland

Essential Questions n n n What is theory of plate tectonics? What evidence supports plate tectonics? How is rock in the ocean formed? What force powers the movement of the continents? Describe three ways in which the plates move along plate boundaries.

References n n n http: //www. platetectonics. com/book/images/Midoceanridge. jpg http: //library. thinkquest. org/17457/platetectonics/seafloor. jpg http: //www. whoi. edu/annualreport 02/images/scihigh_subduction_ en. gif http: //www. oceansjsu. com/images/exp 5_divergent. GIF http: //www. bgs. ac. uk/discovering. Geology/hazards/earthquakes/i mages/convergent. Boundary. jpg http: //www. cms. fu-berlin. de/geo/fb/elearning/geolearning/en/mountain_building/plate_tectonics/media /transform 1. jpg