Plate Tectonics

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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 describing the large-scale motion of the massive plates that make up Earth's rigid outer layer.

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Example: This diagram shows a convergent plate boundary, where two tectonic plates collide, causing one to slide under the other, which can form volcanoes.

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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 Earth's continents have moved across the ocean bed over geologic time relative to each other.

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Example: This map shows the supercontinent Pangaea, where all of Earth's continents were once joined together before they began to move apart.

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Seafloor Spreading Noun

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[see-flor spred-ing]

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Seafloor Spreading

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The process at mid-ocean ridges where new oceanic crust is formed through volcanic activity and then gradually moves away.

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Example: Magma rises from the asthenosphere at a mid-ocean ridge, creating new oceanic crust and pushing older crust away in opposite directions.

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Convection Noun

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[kun-vek-shun]

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Convection

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The heat transfer by movement of a fluid, where hotter, less dense material rises and cooler, denser material sinks.

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Example: Heat from the stove causes warmer, less dense water to rise, while cooler, denser water sinks, creating a circular flow called a convection current.

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Mantle Noun

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[man-tl]

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Mantle

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The vast, mostly solid layer of Earth's interior between the crust and the core, where convection currents occur.

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Example: This diagram shows the Earth's layers, with the mantle being the thickest layer located between the thin outer crust and the hot central core.

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Lithosphere Noun

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[lith-oh-sfeer]

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Lithosphere

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The rigid, outermost shell of a terrestrial-type planet or natural satellite, which is broken into tectonic plates.

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Example: This map shows that the Earth's lithosphere is not one solid shell but is broken into many large, moving pieces called tectonic plates.

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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, irregularly shaped slab of solid rock, composed of both continental and oceanic lithosphere, that moves over the asthenosphere.

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Example: This diagram shows the Earth's rigid lithosphere is broken into tectonic plates that move on the flowing asthenosphere due to underlying convection currents.

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Plate Boundary Noun

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[playt bown-duh-ree]

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Plate Boundary

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The region where two or more tectonic plates in the Earth's crust meet, resulting in significant geological activity.

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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.

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Mid-ocean Ridge Noun

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[mid-oh-shun rij]

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Mid-ocean Ridge

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An underwater mountain range, formed by plate tectonics, where seafloor spreading creates new oceanic crust at a divergent boundary.

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Example: This diagram shows magma rising from the mantle to form a mid-ocean ridge, pushing two tectonic plates apart in a process called seafloor spreading.

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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 relatively thin, dense part of the Earth's crust that underlies the ocean basins, primarily composed of basalt.

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Example: This diagram shows the thinner, denser oceanic crust sinking below the thicker continental crust in a process called subduction, a key part of plate tectonics.