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Superglossary - Geology Category: Sciences > Geology Date & country: 15/12/2013, USA Words: 757

Aa
A blocky and fragmented form of lava occurring in flows with fissured and angular surfaces.

Acidic Rock
An igneous rock that has a relatively high silica content. Examples are granite and rhyolite. Also s

Acquisition
Obtaining the legal right to test a property for mineral resources and produce any that are discover

Acre-Foot
The volume of water needed to flood one acre of land to a depth of one foot. Equivalent to 43,560 cu

Acreage
An area, measured in acres, that is owned or controlled by one or more owners or lessees.

Algal Mat
A layered communal growth of algae observed in fossils an in present day tidal zones associated with

Alkali
Used in reference to materials that are rich in sodium and/or potassium.

Alkali Metal
A strongly basic metal like potassium or sodium.

Alluvial Fan
A fan-shaped wedge of sediment that typically accumulates on land where a stream emerges from a stee

Alluvium
Unconsolidated terrestrial sediment composed of sorted or unsorted sand, gravel, and clay that has b

Amphibolite
Amphibolite is a non-foliated metamorphic rock that forms through recrystallization under conditions

Andesite
A fine-grained, extrusive igneous rock composed mainly of plagioclase with other minerals such as ho

Angle Of Repose
The maximum angle that a soil, sediment or other loose material can be placed or accumulate and be s

Angstrom
A length of 10 to the minus tenth meter or one hundred millionth of a centimeter.

Angular Unconformity
An erosional surface that separates rock units of differing dips. The rocks below the surface were d

Anthracite
The highest rank of coal. By definition, a coal with a fixed carbon content of over 91% on a dry ash

Aquiclude
A subsurface rock, soil or sediment unit that does not yield useful quanties of water.

Aquifer
A subsurface rock or sediment unit that is porous and permeable. To be an aquifer it must have these

Aquifer (Artesian)
An aquifer that is bounded above and below by impermeable rock or sediment layers. The water in the

Aquifer (Confined)
An aquifer that is bounded above and below by impermeable rock or sediment layers. There may or may

Aquifer (Unconfined)
An aquifer that is not overlain by an impermeable rock unit. The water in this aquifer is under atmo

Arkose
A sandstone that contains at least 25% feldspar. Easily recognized because the feldspar grains are t

Arroyo
A steep-sided and flat-bottomed gulley in an arid region that is occupied by a stream only intermitt

Artesian Well
A well that penetrates an aquiclude to reach an aquifer containing water under pressure. Thus water

Asthenosphere
A portion of the upper mantle that is directly below the lithosphere. A zone of low strength in the

Astrobleme
An ancient circular scar on Earth's surface produced by the impact of a meteorite or comet. Use our

Atmosphere (Unit)
A unit of pressure equal to 101,325 newtons per square meter, or about 14.7 pounds per square inch.

Atoll
A ring-shaped group of coral islands that are surrounded by deep ocean water and that enclose a shal

Backwash
The seaward rush of water down a beach that occurs with a receding wave.

Banded Iron Ore
A rock that consists of alternating layers of chert and iron oxide mineral (usually hematite) with t

Bank Storage
Water that seeps into the ground along the banks of a stream during a time of high flow. This loss o

Bankfull Stage
A height of water in a stream that completely fills the natural channel. If the water rises any high

Bar
An underwater ridge, usually of sand and/or gravel, that forms from the deposition and reworking of

Bar (Stream)
An accumulation of sediment, usually sandy, which forms at the borders or in the channels of streams

Bar-Finger Sand
An elongated lens of sand deposited during the growth of a distributary in a delta. The bar at the d

Barchan
A sand dune that is crescent-shaped in map view. Barchan dunes form in areas of limited sand supply.

Barrier Island
A long, narrow island parallel to the shore, composed of sand and built by wave action.

Basalt
A dark-colored fine-grained extrusive igneous rock composed largely of plagioclase feldspar and pyro

Base Flow
Water that seeps into a stream through a permeable rock or sediment unit that outcrops in the bottom

Base Level
The lower limit of erosion by a stream. Sea level is the ultimate base level. However, lakes can ser

Basement
The oldest rocks recognized in a given area, a complex of metamorphic and igneous rocks that underli

Basic Rock
An igneous rock that has a relatively low silica content. Examples are gabbro and basalt. Also see e

Basin
In tectonics, a circular, syncline-like depression of strata. In sedimentology, the site of accumula

Batholith
A great irregular mass of coarse-grained igneous rock with an exposed surface of more than 100 squar

Bathymetry
The measurement of ocean depths and the preparation of topographic maps of the ocean floor.

Bauxite
The principal ore of aluminum. A mixture of aluminum oxides and hydroxides that forms from intense c

Bed Load
The larger, heavier particles that are being transported by a stream. Instead of being dissolved or

Bed-Load
The sediment that a stream moves along the bottom of its channel by rolling and bouncing.

Bedding
The characteristic structure of sedimentary rocks in which layers of different composition, grain si

Bedding Plane
A distinct surface of contact between two sedimentary rock layers.

Bedrock
Solid rock present beneath any soil, sediment or other surface cover. In some locations it may be ex

Beta-Particle
An electron emitted with high energy and velocity from the nucleus of an atom during radioactive dec

Biochemical Precipitate
A sediment, especially of limestone or iron, formed from elements extracted from seawater by living

Biochemical Rocks
A sedimentary rock that forms from the chemical activities of organisms. Organic (reef and fossilife

Bioturbated
An adjective used in reference to a sediment or sedimentary rock. Bioturbated sediments have been di

Bituminous Coal
A rank of coal that falls between anthracite and semi-bituminous. The most abundant rank of coal. Fr

Block Fault
A structure formed when the crust is divided into blocks of different elevation by a set of normal f

Block Fault Mountain
A linear mountain that is bounded on both sides by normal faults.

Blowout
A shallow, round or trough-shaped depression in sand or dry soil that is formed by wind erosion. The

Bolson
In arid regions, a basin filled with alluvium and intermittent playa lakes and having no outlet.

Bond
The force that holds together two atoms in a compound. It may be derived from the sharing of electro

Breccia
A clastic sedimentary rock that is composed of large (over two millimeter diameter) angular fragment

Butte
A conspicuous hill with steep sides and a flat top. The top is usually a cap-rock of resistant mater

Caldera
A large, bowl-shaped crater associated with a volcanic vent. A caldera can form from a volcanic blas

Carbonate Ion
The anion group CO3 with a charge of minus two.

Carbonate Platform
A submarine or intertidal shelf whose elevation is maintained by active shallow water carbonate depo

Carbonate Rock
A rock made up primarily of carbonate minerals (minerals containing the CO3 anionic structure). Lime

Carbonic Acid
A weak acid (H2CO3) that forms from the reaction of water and carbon dioxide. Most rain water is a v

Carrying Costs
The costs incurred by a lessee to retain exploration and property rights after acquisition but befor

Cataclastic Rock
A breccia of powdered rock formed by crushing and shearing during tectonic movements.

Cation
Any ion with a positive electric charge.

Cement
A solid precipitate of calcium carbonate, silica, iron oxide, clay minerals or other materials that

Cementation
The processes through which chemical precipitates form within the pore spaces of a sediment and help

Central Vent
The largest vent of a volcano, situated at the center of its cone.

Chemical Sediment
One that is formed at or near its place of deposition by chemical precipitation, usually from seawat

Chemical Sedimentary Rock
A rock that forms from the precipitation of mineral material from solution. Examples are chert and r

Chemical Weathering
The breaking down of surface rock material by solution or chemical alteration. Common alteration pro

Chert
A microcrystalline or cryptocrystalline sedimentary rock material composed of SiO2. Occurs as nodule

Christmas Tree
The valves, pipes and fittings installed above ground surface at an oil or gas well site. These cont

Cinder Cone
A steep, conical hill built up about a volcanic vent and composed of coarse pyroclasts expelled from

Cirque
The head of a glacial valley, usually with the form of one half of an inverted cone. The upper edges

Clastic
A sedimentary rock (such as shale, siltstone, sandstone or conglomerate) or sediment (such as mud, s

Clastic Rock
A sedimentary rock formed from mineral particles (clasts) that were mechanically transported.

Clay
A clastic mineral particle of any composition that has a grain size smaller than 1/256 mm. The term

Coal
A brown or black sedimentary rock that forms from accumulated plant debris. A combustible rock that

Coal Gasification
The process of converting solid coal into gas, usually by heating. The gas is then used as a fuel or

Coal Liquefaction
The process of converting solid coal into a liquid fuel such as synthetic crude oil or methanol.

Coastal Plain
An area of low relief along a continental margin that is underlain by thick, gently dipping sediment

Compaction
A compression process that reorients and reshapes the grains of a sediment in response to the weight

Composite Cone
A cone-shaped volcanic mountain composed of alternating layers of cinders and lava flows. Also known

Cone Of Depression
A cone-shaped lowering of the water table around a producing well.

Conglomerate
A clastic sedimentary rock that contains large (greater then two millimeters in diameter) rounded pa

Contact Metamorphism
Mineralogical and textural changes and deformation of rock resulting from the head and pressure of a

Contour Line
A line on a map that traces locations where the value of a variable is constant. For example, contou

Contour Map
A map that shows the change in value of a variable over a geographic area through the use of contour

Crude Oil
A liquid hydrocarbon produced from natural underground reservoirs. It might also include liquid hydr

Cubic Feet Per Second
A unit of measure frequently used to quantify the rate of flow of a stream. It is equal to a volume

Datum
A reference location or elevation which is used as a starting point for subsequent measurements. Sea

Datum Plane
An artificially established, well surveyed horizontal plane against which elevations, depths, tides,

Daughter Element
Also 'daughter product'. An element that occurs in a rock as end product of the radioactive decay of