Continental Drift

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Geologic Time Scale Noun

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[jee-uh-loj-ik tahym skeyl]

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Geologic Time Scale

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A system of chronological dating that relates geological strata to time, used to describe events in Earth's history.

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Example: This chart organizes Earth's 4.5-billion-year history into major time chunks called eras and periods, showing when different life forms appeared in the fossil record.

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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 theory that Earth's continents have moved over geologic time relative to each other, once forming a single supercontinent.

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

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Supercontinent Noun

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[soo-per-kon-tuh-nuhnt]

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Supercontinent

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A large landmass formed by the convergence of multiple continents, such as the ancient landmass known as Pangaea.

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Example: This diagram 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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Pangaea Noun

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[pan-jee-uh]

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Pangaea

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The name of the single supercontinent that existed approximately 250 million years ago before breaking apart into today's continents.

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Example: This diagram shows the ancient supercontinent Pangaea, with modern continents like North America and Africa labeled to illustrate how they once fit together.

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Fossil Noun

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[fos-uhl]

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Fossil

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The preserved remains, impression, or trace of an organism that lived in the geologic past, used as geological evidence.

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Example: This image shows the preserved remains of an ancient organism (a pterosaur) in rock, which is a fossil. Fossils provide key evidence for continental drift.

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Plate Tectonics Noun

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[pleyt tek-ton-iks]

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Plate Tectonics

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The geological theory stating that pieces of Earth's lithosphere are in constant, slow motion, driven by mantle convection currents.

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Example: This diagram shows tectonic plates moving apart under the ocean. Hot magma rises from the mantle to form new crust, pushing the plates and continents.

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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 upper mantle, which is broken into tectonic plates.

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Example: The lithosphere is the Earth's rigid outer layer, made of the crust and the solid upper part of the mantle, which is broken into plates.

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Mantle Noun

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[man-tl]

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Mantle

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The layer of the Earth between the crust and the core, where convection currents occur that drive plate tectonic movement.

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Example: This diagram shows the Mantle as the thick layer between the Earth's crust and core, where the movement that drives continental drift occurs.

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Convection Current Noun

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[kuhn-vek-shuhn kur-uhnt]

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Convection Current

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The movement of a fluid caused by differences in temperature and density that transfers heat within the Earth's mantle.

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Example: Hot, less-dense material from the mantle rises, cools, and sinks, creating circular currents that move the tectonic plates on the Earth's surface.

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Oceanic Crust Noun

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[oh-shee-an-ik kruhst]

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Oceanic Crust

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The younger, denser, and thinner part of Earth's crust found beneath the oceans, primarily composed of basalt rock.

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Example: This diagram shows oceanic crust, which is thinner and denser, sinking (subducting) beneath the thicker continental crust, a process that drives continental drift.