Plate Tectonics 22.4

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

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

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

Mid Ocean Ridge

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

Sea Floor Spreading

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

Subduction

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

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

Divergent

Convergent

Transform

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

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

References en.gif en.gif en.gif en.gif mages/convergentBoundary.jpg mages/convergentBoundary.jpg mages/convergentBoundary.jpg mages/convergentBoundary.jpg learning/geolearning/en/mountain_building/plate_tectonics/media /transform1.jpg learning/geolearning/en/mountain_building/plate_tectonics/media /transform1.jpg learning/geolearning/en/mountain_building/plate_tectonics/media /transform1.jpg learning/geolearning/en/mountain_building/plate_tectonics/media /transform1.jpg