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Plate Tectonics
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Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.
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The Crust The outermost layer 5 – 40 km thick
Middle The outermost layer 5 – 40 km thick Made of Oxygen, Silicon, Aluminum
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The Mantle Layer of Earth between the crust and the core
Contains most of the Earth’s mass Has more magnesium and less aluminum and silicon than the crust Is denser than the crust Middle Middle
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The Core Located below the mantle and to the center of the Earth
Believed to be mostly iron Outer core is liquid (currents in this liquid produce Earth’s magnetic properties) Inner core is solid iron (extremely high temperature and pressure keep it in a solid state)
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Tectonic Plates
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Plate Tectonics Greek – “tektonikos” of a builder
Pieces of the lithosphere that move around Each plate has a name Fit together like jigsaw puzzles Float on top of mantle like ice cubes in a bowl of water
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Continental Drift Alfred Wegener 1900’s
2. Continents were once a single land mass that drifted apart. 3. Fossils of the same plants and animals are found on different continents. 4. Called this supercontinent Pangea, Greek for “all Earth”. Million years ago 6. Split again – Laurasia & Gondwana 180 million years ago
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Evidence of Pangea
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Mid-Ocean Ridge The mid-ocean ridge curves like the seam of a baseball along the sea floor, extending into all of Earth's oceans.
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Sea Floor Spreading
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Sea Floor Spreading 1. Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins 2. Magma rises to the surface and solidifies and new crust forms 3. Older crust is pushed farther away from the ridge
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E Sea Floor Spreadingoor
apart along both sides of the mid-ocean ridge as new crust is added.
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Evidence for Sea-Floor Spreading
New material is indeed erupting along the mid-ocean ridge.
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Subduction
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How Plates Move
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Different Types of Boundaries
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1. Divergent Boundary – plates are moving away from each other Arabian and African Plates
Arabian Plate Red Sea African Plate
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Divergent Boundary – Iceland North American Plate and Eurasian Plate
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Divergent Boundary - Oceanic
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Divergent Boundary - Continental
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2. Convergent Boundary – plates are moving toward each other Indian and Eurasian Plates
Indian Plate
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Convergent Boundary – Oceanic & Continental
&
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Convergent Boundary – Oceanic & Oceanic
Note – plates are reversed &
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Convergent Boundaries - Continental
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3. Transform Boundary –plates slide past each other San Andreas Fault, in California
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Review Name the 3 main layers of the Earth What is a tectonic plate?
What was Pangea? What is Sea-Floor spreading? Name the three different types of plate boundaries and one location on Earth for each one
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