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Plate Tectonics

Science, Grade 8

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Eurasian Plate North American Plate Eurasian Plate Arabian Plate African Plate South American Plate Pacific Plate Indian Plate Australian Plate Antarctic Plate Nazca Plate Cocos Plate Earth’s Crust Earth’s outermost layer is the crust. There are two different types of crust. Basaltic oceanic crust pours out from the mantle and is found under the oceans. It is the denser of the two types of crust, but it is also the thinner of the two. The second type of crust is continental crust. The crust moves over the Earth’s surface in large pieces called tectonic plates. Tectonic plates are constructed in layers with crust on the top and a piece of the solid upper mantle below. Geologists call this combination of crust and upper mantle the lithosphere. Tectonic Plate Boundaries The three types of plate boundaries - convergent , divergent and transform – are found at the edge of the lithospheric plates and are characterized by their distinct motions. A divergent boundary, or spreading center At this boundary, two plates move away from one another. As the two plates move apart, mid-ocean ridges are created as magma from the mantle rises through a crack in the oceanic crust and cools. New oceanic crust is formed on both sides of the creack in the ocean floor. A convergent boundary or subduction zone At this boundary the plates converge or push into one another. The type of convergence that takes place between plates depends on the kind of lithosphere involved. Convergence can occur between an oceanic and a continental plate, or between two oceanic plates, or between two continental plates. A conservative or transform boundary This boundary is called conservative because plate material is neither created nor destroyed at these boundaries, but rather plates slide past each other horizontally. An example of a transform plate boundary is the San Andreas Fault in southern California. Tectonic Plates According to the theory of plate tectonics, scientists believe that the Earth's surface is broken into a number of shifting slabs or plates. These plates are in constant motion traveling a few centimeters per year. The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes and mountain building. Major Tectonic Plates 1. Pacific plate 2. North American plate 3. Cocos plate 4. Nazca plate 5. South American plate 6. African plate 7. Eurasian plate 8. Indian plate 9. Australian plate 10. Antarctic plate volcanoes Continental crust Oceanic crust rift valley magma Lithosphere Convergent boundary Convergent boundary Transform boundary Divergent boundary Divergent boundary Lithosphere trench trench mid-ocean ridge Su bd uc tio n zo ne 1. 2. 3. 4. 5. 6. 7. 7. 8. 9. 10 . Plate Tectonics © Copyright NewPath Learning. All Rights Reserved. 94-4105 www.newpathlearning.com Subduction Zone Tr enc h Volcanic ar c Continental crust

Tr enc h Volcanic ar c volcanoes 1. 2. 3. 4. 5. 6. 7. 7. 8. 9. 10 . Tectonic Plate Boundaries There are three types of plate boundaries. 1. _________________________________ Describe: ____________________________________ ____________________________________ ____________________________________ 2. _________________________________ Describe: ____________________________________ ____________________________________ ____________________________________ Earth’s Crust Earth’s outermost layer is the _________________________. There are two different types of crust. ____________________________ pours out from the mantle and is found under the oceans. It is the denser of the two types of crust, but it is also the thinner of the two. The second type of crust is __________________________. The crust moves over the Earth’s surface in large pieces called ____________________________. Tectonic plates are constructed in layers with crust on the top and a piece of the solid upper mantle below. Geologists call this combination of crust and upper mantle the _____________________________. Tectonic Plates Describe the theory of plate tectonics: _________________________________________ _________________________________________ _________________________________________ _________________________________________ Major Tectonic Plates 1. _____________________ 2. _____________________ 3. _____________________ 4. _____________________ 5. _____________________ 6. _____________________ 7. _____________________ 8. _____________________ 9. _____________________ 10. _____________________ Continental crust Oceanic crust rift valley magma Lithosphere Lithosphere trench trench mid-ocean ridge Su bd uc tio n zo ne 3. _________________________________ Describe: ____________________________________ ____________________________________ ____________________________________ Key Vocabulary Terms • basaltic oceanic crust • conservative • continental crust • continental plate • convergent • divergent • Earth’s crust • lithosphere • oceanic plate • spreading center • subduction zone • tectonic plates • theory of plate tectonics • transform \|xiBAHBDy01792pzY Plate Tectonics © Copyright NewPath Learning. All Rights Reserved. 94-4105 www.newpathlearning.com

Plate Tectonics

Science, Grade 8

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