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Geology terms glossary page 2
Geology terms explained in plain English. 899 words and meanings, most familiar first.
| Word | Meaning |
|---|---|
| cirque noun | A curved depression in a mountainside with steep walls, forming the end of a valley. |
| conglomerate noun | A rock consisting of gravel or pebbles embedded in a matrix. |
| moulin noun | A cylindrical, vertical shaft that extends through a glacier and is carved by meltwater from the glacier’s surface. |
| tripoli noun | A sedimentary rock composed of the shells of diatoms etc., used for polishing. |
| degrade verb | To reduce in altitude or magnitude, as hills and mountains; to wear down. |
| shale noun | A fine-grained sedimentary rock of a thin, laminated, and often friable, structure. |
| incumbent adjective | Resting on something else; in botany, said of anthers when lying on the inner side of the filament, or of cotyledons when the radicle lies against the back of one of them |
| intrusive adjective | Of rocks: forced, while in a plastic or molten state, into the cavities or between the cracks or layers of other rocks. |
| sill noun | A stratum of rock, especially an intrusive layer of igneous rock lying parallel to surrounding strata. |
| repose noun | The period between eruptions of a volcano. |
| tectonic adjective | Of, relating to, or caused by large-scale movements of the Earth's (or a similar planet's) lithosphere |
| brash noun | Broken and angular rock fragments underlying alluvial deposits. |
| mobilization noun | The softening of rock such that geochemical migration can take place. |
| sinkhole noun | A hole formed in soluble rock by the action of water, serving to conduct surface water to an underground passage. |
| optimum noun | Any long period of time marked by a persistently warm climate; a climatic optimum. |
| mica noun | Any of a group of hydrous aluminosilicate minerals characterized by highly perfect cleavage, so that they readily separate into very thin leaves, more or less elastic. |
| transgression noun | A relative rise in sea level resulting in deposition of marine strata over terrestrial strata. |
| pothole noun | A vertical cave system, often found in limestone. |
| shear noun | The response of a rock to deformation usually by compressive stress, resulting in particular textures. |
| abrasive noun | Rock fragments, sand grains, mineral particles, used by water, wind, and ice to abrade a land surface. |
| discordant adjective | Of a differing type of rock cutting across a formation. |
| acidic adjective | Containing a high percentage of silica; opposed to basic. |
| geyser noun | A boiling natural spring which throws forth jets of water, mud, etc., at frequent intervals, driven upwards by the expansive power of steam. |
| distal adjective | Remote from the point of attachment or origin. |
| celestine noun | A mineral with orthorhombic crystals, SrSO4, colourless or white with blue and sometimes red shades. |
| retrograde adjective | Of a metamorphic change: resulting from a decrease in pressure or temperature. |
| moonstone noun | A translucent gemstone, an orthoclase feldspar, that has a pearly lustre. |
| disintegration noun | The wearing away or falling to pieces of rocks or strata, produced by atmospheric action, frost, ice, etc. |
| hiatus noun | A gap in geological strata. |
| basset noun | The edge of a geological stratum at the surface of the ground; the outcrop. |
| cataclysm noun | A sudden and violent change in the earth's crust. |
| millstone noun | A coarse-grained sandstone used for making such stones; millstone grit. |
| obsidian noun | A type of naturally occurring black glass produced by volcanoes. |
| inclusion noun | Any material that is trapped inside a mineral during its formation, as a defect in a precious stone. |
| silt noun | A particle from 3.9 to 62.5 microns in diameter, following the Wentworth scale. |
| dislocation noun | The displacement of parts of rocks or portions of strata from the situation which they originally occupied. |
| serpentine noun | Any of several green/brown minerals consisting of magnesium and iron silicates that have similar layered crystal structure, whose appearance somewhat resembles a snake's skin. |
| ephemeral adjective | Usually dry, but filling with water for brief periods during and after precipitation. |
| abrasion noun | The effect of mechanical erosion of rock, especially a river bed, by rock fragments scratching and scraping it. |
| epoch noun | A geochronologic unit of hundreds of thousands to millions of years; a subdivision of a period, and subdivided into ages (or sometimes subepochs). |
| intruded adjective | Intrusive. |
| laminated adjective | Splitting into thin layers parallel to bedding. |
| duplex noun | A system of multiple thrust faults bounded above and below by a roof thrust and floor thrust. |
| meagre adjective | Dry and harsh to the touch (e.g., as chalk). |
| gowan noun | Decomposed granite. |
| mons noun | A mountain or extinct volcano on a planet or a moon. |
| uplift noun | A tectonic upheaval, especially one that takes place in the process of mountain building. |
| cinders noun | Fragments of lava; scoria |
| hoodoo noun | A tall thin spire of rock that protrudes from the bottom of arid basins and badlands. |
| proximal adjective | Closer to the point of attachment or observation. |
| knocker noun | A large, boulder-shaped outcrop of bedrock in an otherwise low-lying landscape, chiefly associated with a mélange. |
| punky adjective | Of or pertaining to punk (touchwood); rotted or soft. |
| buckling noun | A folding into hills and valleys. |
| cobble noun | A particle from 64 to 256 mm in diameter, following the Wentworth scale. |
| onyx noun | A banded variety of chalcedony, a cryptocrystalline form of quartz. |
| blowhole noun | A top-facing opening to a cavity in the ground very near an ocean's shore, leading to a marine cave from which wave water or bursts of air are expelled. |
| basalt noun | A hard mafic igneous rock of varied mineral content; volcanic in origin, which makes up much of the Earth's oceanic crust. |
| abstraction noun | The merging of two river valleys by the larger of the two deepening and widening so much so, as to assimilate the smaller. |
| meteoric adjective | Originating in the atmosphere. |
| maar noun | A broad volcanic crater, usually filled with water to form a lake. |
| ablation noun | The removal of a glacier by melting and evaporation; the lowering of a land surface by any of several means, as in wind erosion or mass wasting. |
| ablative adjective | Relating to the erosion of a land mass; relating to the melting or evaporation of a glacier. |
| abyssal adjective | Pertaining to or occurring at excessive depths in the earth's crust; plutonic. |
| accretion noun | The gradual increase of land by deposition of water-borne sediment. |
| aeolian adjective | Carried, deposited or eroded by the wind. |
| agglomerate noun | A mass of angular volcanic fragments united by heat; distinguished from conglomerate. |
| agglomeration noun | A mass of large volcanic fragments bonded under heat. |
| alkalic adjective | Containing a relatively high proportion of alkali; alkaline. |
| almandine noun | A type of garnet having a deep red color, inclining to purple, with the chemical formula Fe3Al2(SiO4)3. |
| antecedence noun | A geologic process that explains how and why antecedent rivers can cut through mountain systems instead of going around them. |
| anticlinal adjective | Consisting of, related to, or part of an anticline. |
| apophysis noun | A branch of a dike or vein. |
| arenaceous adjective | Arenitic. |
| asperity noun | A section of a fault line with high friction, such that there is no movement along this part of the fault except during an earthquake. |
| asterism noun | A star-shaped figure exhibited by some crystals by reflected light (as in a star sapphire) or by transmitted light (as in some mica). |
| Word | Meaning |
|---|---|
| aureole noun | A ring around an igneous intrusion. |
| autochthonous adjective | Buried in place, especially of a fossil preserved in its life position without disturbance or disarticulation. |
| aventurine noun | A variety of translucent quartz, spangled throughout with scales of yellow mica. |
| barite noun | A mineral, barium sulphate, with the chemical formula BaSO4. |
| bleb noun | A bubble-like inclusion of one mineral within another. |
| brecciate verb | To turn (something) into breccia. |
| caliche noun | A crude form of sodium nitrate from South America; used as a fertilizer. |
| capping noun | The leached upper part of a body or rock that still contains disseminated sulphide mineral deposit. |
| carbonated adjective | Containing calcium carbonate, often as a result of mineral carbonation. |
| carbonation noun | The replacement of calcium hydroxide with calcium carbonate triggered by a chemical reaction. |
| chatoyant noun | A hard stone, such as the cat's-eye, which presents on a polished surface, and in the interior, an undulating or wavy light. |
| chert noun | Massive, usually dull-colored and opaque, quartzite, hornstone, impure chalcedony, or other flint-like mineral. |
| chondritic adjective | Of or pertaining to a chondrite. |
| clastic adjective | Made from fragments of pre-existing rocks. |
| coda noun | In seismograms, the gradual return to baseline after a seismic event. The length of the coda can be used to estimate event magnitude, and the shape sometimes reveals details of subsurface structures. |
| colloid noun | A particle less than 1 micron in diameter, following the Wentworth scale |
| conchoid noun | A conchoidal fracture in rock. |
| concordant adjective | Intruding parallel to the bedding. |
| connate adjective | Trapped within a rock at the time of its formation (especially of water or petroleum). |
| consequent adjective | Of a stream, having a course determined by the slope it formed on. |
| coulee noun | A lava flow. |
| crag noun | A partially compacted bed of gravel mixed with shells, of the Pliocene to Pleistocene epochs. |
| cumulate noun | An igneous rock formed by the accumulation of crystals from a magma either by settling or floating. |
| cupola noun | An upward-projecting mass of plutonic rock extending from a larger batholith. |
| deflation noun | The removal of soil and other loose material from the ground (or another surface) by wind, leaving it exposed to erosion. |
| denudation noun | The laying bare of rocks by the washing away of the overlying earth, etc.; or the excavation and removal of them by the action of running water. |
| differentiation noun | The process of separation of cooling magma into various rock types. |
| dimorphism noun | A property of certain substances that enables them to exist in two distinct crystalline forms. |
| directivity noun | Anisotropy in the propagation of earthquake waves in the direction of rupture. |
| discontinuity noun | A subterranean interface at which seismic velocities change |
| dolomite noun | An evaporite consisting of a mixed calcium and magnesium carbonate, with the chemical formula CaMg(CO3)2; it also exists as the rock dolostone. |
| dorsum noun | A ridge on a hill, or on the surface of a planet or moon. |
| dripstone noun | Stalactites and stalagmites collectively. |
| druse noun | An inner surface with a crust of tiny crystals. |
| efflorescence noun | An encrustation of soluble salts, deposited on rock or soil by evaporation; often found in arid or geothermal environments. |
| effusive adjective | Extrusive; having solidified after being poured out as molten lava. |
| emarginate adjective | Of a crystal: having edges or corners of the primitive form beveled, crossed by a face. |
| emplacement noun | The inclusion of igneous rock in older rocks, or the development or localization of an ore body in older rocks. The latter is referred to as ore deposition. |
| endogenic adjective | Originating within the earth; endogenous or endogenetic. |
| eon noun | The longest geochronologic unit, being a period of hundreds of millions of years; subdivided into eras. |
| eruptive adjective | Produced by eruption. |
| exfoliate verb | To split into scales, especially to become converted into scales as the result of heat or decomposition. |
| fissile adjective | Easily split along a grain. |
| flinty adjective | Siliceous (including basanite). |
| fluorite noun | A widely occurring mineral (calcium fluoride), of various colours, used as a flux in steelmaking, and in the manufacture of glass, enamels and hydrofluoric acid. |
| foliate adjective | Foliated |
| foliated adjective | Having a structure of thin layers. |
| fragmentary adjective | Composed of the fragments of other rocks. |
| glacially adverb | Through glacial action. |
| granule noun | A particle from 2 to 4 mm in diameter, following the Wentworth scale |
| gravimetric adjective | Of or pertaining to measurement of the local gravitational field. |
| hade noun | A slope; (in mining) the slope of a vein, fault or dike from the vertical; the complement of the dip. |
| halite noun | Native salt; sodium chloride NaCl as a mineral; rock salt. |
| heliotrope noun | A bloodstone (a variety of quartz). |
| hircine noun | A fossil amorphous resin which, when burnt, gives off a pungent, hircinous aroma. |
| igneous adjective | Resulting from, or produced by, great heat. With rocks, it could also mean formed from lava or magma. |
| imbrication noun | A sedimentary deposition in which small, flat stones are tiled in the same direction so that they overlap. |
| immure verb | To trap or capture (an impurity); chiefly in the participial adjective immured and gerund or gerundial noun immuring. |
| impregnation noun | An ore deposit, with indefinite boundaries, consisting of rock impregnated with ore. |
| indite noun | An extremely rare indium-iron sulfide mineral. |
| induration noun | The quality of non-friability; the extent to which a rock does not crumble; rock strength. |
| ingressive adjective | Being a source or channel through which water enters or once entered an area. |
| lamina noun | A fine layer that occurs in sedimentary rocks |
| lamination noun | A small scale sequence of fine layers that occurs in sedimentary rocks. |
| lath noun | Microscopic, needle-like crystals, usually of plagioclase feldspar, in a glassy groundmass |
| lineation noun | A linear feature in rock, often structural |
| lithic adjective | Relating to rock |
| loam noun | A type of soil; an earthy mixture of sand, silt and clay, with organic matter to which its fertility is chiefly due. |
| lunette noun | A type of crescent-shaped dune blown up along a lake basin, especially in dry areas of Australia. |
| lustre noun | The way in which the surface of any particular type of mineral reflects light differently from other minerals, which is helpful in telling minerals apart. |
| magnesia noun | Magnesium oxide |
| malachite noun | A bright green mineral, a basic copper carbonate, Cu2CO3(OH)2; one of the principal ores of copper. |
| melange noun | A large-scale breccia formed in the accretionary wedge over a subductional environment. |
| metamorphic adjective | Pertaining to metamorphism; having been structurally altered as a result of, or resulting from, exposure to intense heat and/or pressure (at the contact zone between colliding plates, for example). |
| metamorphism noun | The process by which rocks are changed into other forms by the application of heat and/or pressure. |
Meanings from Wiktionary (CC BY-SA 4.0). Sources