Glossary
Plain-language definitions of the terms that come up in geology — 616 entries, searchable and browsable A–Z.
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About the glossary
The Geoscopy geology glossary: 616 geology terms and definitions in plain language, A to Z, from abyssal plain to zosterophylls. Each entry is a short definition you can read in under a minute. Most come with a picture, and almost all name the source they are based on. Search for a term, browse by letter or open any card for a quick look without leaving the list. The term of the day changes daily.
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Abyssal Plain
Abyssal plains are large, flat, and nearly featureless regions of the deep… more →
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Accretion
In geology, accretion refers to the process by which material is added… more →
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Accretionary Wedge
An accretionary wedge is a large, wedge-shaped mass of sediment and oceanic… more →
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Active Margin
An active margin is a type of continental margin that is tectonically… more →
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Aeolian Dune
Aeolian dunes are hills or ridges of sand formed by the wind… more →
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Aeolian Processes
Aeolian processes involve the erosion, transport, and deposition of sediments by wind… more →
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Aeolianite
Aeolianite is a type of sedimentary rock formed from the lithification of… more →
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Agglomerate
Agglomerate is a coarse, volcanic rock composed of angular fragments of volcanic… more →
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Albedo
Albedo is a measure of the reflectivity of a surface, expressed as… more →
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Aleutian Arc
The Aleutian Arc is a volcanic arc located in the northern Pacific… more →
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Alkaline Igneous Rock
Alkaline igneous rocks are a category of igneous rocks that contain higher… more →
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Allochthonous
The term allochthonous refers to rocks or sediments that have been transported… more →
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Alluvial Fan
An alluvial fan is a triangular or fan-shaped deposit of gravel, sand… more →
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Ammonite
Ammonites are an extinct group of marine mollusk animals that existed from… more →
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Amphitheater Valley
An amphitheater valley is a steep-walled, U-shaped valley that resembles an amphitheater… more →
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Anabranch
An anabranch is a section of a river or stream that diverts… more →
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Anaerobic Environment
An anaerobic environment is one that lacks oxygen, which can significantly affect… more →
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Anomalous Magnetic Field
An anomalous magnetic field refers to deviations in Earth's magnetic field from… more →
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Anthracite
Anthracite is the highest grade of coal, known for its high carbon… more →
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Anthropocene
The Anthropocene is a proposed geological epoch that denotes the current period… more →
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Anticline
An anticline is a type of fold in sedimentary strata that is… more →
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Anticlinorium
An anticlinorium is a large-scale anticline or a series of anticlinal folds… more →
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Antiform
An antiform is a fold that has the shape of an arch… more →
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Aphelion
Aphelion is the point in the orbit of a planet, asteroid, or… more →