Tectonic Plates

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Plate Tectonics Noun

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[playt tek-ton-iks]

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Plate Tectonics

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The scientific theory that Earth's surface is broken into large, rigid pieces that move with respect to each other.

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Example: This diagram shows two tectonic plates colliding at a convergent boundary, where one plate slides under the other, melting and forming a volcano.

Front

Pangaea Noun

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[pan-jee-uh]

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Pangaea

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The name of the giant supercontinent that existed millions of years ago, composed of all present-day continents joined together.

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Example: This map shows the supercontinent Pangaea, where all of Earth's continents were joined together as one giant landmass millions of years ago.

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Continental Drift Noun

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[kon-tuh-nen-tl drift]

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Continental Drift

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The hypothesis that continents have moved gradually across Earth's surface over geological time to their current positions.

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Example: This image shows the supercontinent Pangaea, where all of Earth's continents were once joined together before they started to drift apart to their current positions.

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Lithosphere Noun

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[lith-uh-sfeer]

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Lithosphere

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The rigid outer part of the Earth, consisting of the crust and the solid upper portion of the mantle.

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Example: This diagram shows a cross-section of the Earth, identifying the lithosphere as the rigid outer layer composed of the crust and the solid upper mantle.

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Asthenosphere Noun

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[as-then-uh-sfeer]

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Asthenosphere

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The dense, weak layer of the upper mantle below the lithosphere, which is solid but can flow very slowly.

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Example: This diagram shows the Asthenosphere as a hot, plastic layer in the upper mantle, located directly beneath the rigid lithosphere (Earth's crust and upper mantle).

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Tectonic Plate Noun

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[tek-ton-ik playt]

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Tectonic Plate

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A massive, slowly moving piece of Earth's lithosphere that can be composed of continental or oceanic crust.

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Example: This map shows how the Earth's outer shell is broken into large, moving pieces called tectonic plates, identifying the major plates by name.

Front

Continental Crust Noun

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[kon-tuh-nen-tl krust]

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Continental Crust

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The relatively thick, less dense part of the Earth's crust that forms the large landmasses on the planet.

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Example: This diagram shows the thick continental crust, which forms land, overriding the thinner, denser oceanic crust at a tectonic plate boundary.

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Oceanic Crust Noun

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[oh-shee-an-ik krust]

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Oceanic Crust

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The thinner, more dense part of Earth's crust that underlies the ocean basins and is created at mid-ocean ridges.

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Example: Magma from below rises to form new oceanic crust as two tectonic plates pull apart at a divergent boundary under the ocean.

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Mantle Convection Noun

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[man-tl kon-vek-shun]

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Mantle Convection

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The circular flow of rock in the mantle where hot rock rises and cool rock sinks, driving plate movement.

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Example: Hot magma from the mantle rises, pushes tectonic plates apart, and creates new crust, showing how mantle convection moves the Earth's surface.

Front

Plate Boundary Noun

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[playt bown-duh-ree]

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Plate Boundary

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The area where two tectonic plates meet, which is where most earthquakes and volcanoes are known to occur.

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Example: This map shows a transform plate boundary, where the Pacific Plate and North American Plate slide past each other along the San Andreas Fault.