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AA  look up translate image
A term of Hawaiian origin. Used in reference to a basaltic lava that occurs in flows with a fissured, rough and jagged surface.
ACIDIC ROCK  look up translate image
An igneous rock that has a relatively high silica content. Examples are granite and rhyolite. Also see entries for basic, intermediate and ultrabasic rocks.
ACQUISITION  look up translate image
Obtaining the legal right to test a property for mineral resources and produce any that are discovered. The rights can be obtained by purchasing the entire property (surface and mineral rights), purchasing the mineral rights alone, concession, or leasing the mineral rights.
ACRE-FOOT  look up translate image
The volume of water needed to flood one acre of land to a depth of one foot. Equivalent to 43,560 cubic feet, 1,233 cubic meters or 325,851 gallons. One of the most common units of measure used for reservoir capacity. Also used in mineral resource calculations (an acre-foot of coal is a block of coal one acre in area and one foot thick - it weighs approximately 1,800 tons).
ACREAGE  look up translate image
An area, measured in acres, that is owned or controlled by one or more owners or lessees. Gross Acreage is the entire geographic area under control. Net Acreage is the gross acreage multiplied by the fractional share of any individual owner or lessee.
ALKALI  look up translate image
Used in reference to materials that are rich in sodium and/or potassium.
ALLUVIAL FAN  look up translate image
A fan-shaped wedge of sediment that typically accumulates on land where a stream emerges from a steep canyon onto a flat area. In map view it has the shape of an open fan. Typically forms in arid or semiarid climates.
ALLUVIUM  look up translate image
An unconsolidated accumulation of stream-deposited sediments, including sands, silts, clays or gravels.
AMPHIBOLITE  look up translate image
Amphibolite is a non-foliated metamorphic rock that forms through recrystallization under conditions of high viscosity and directed pressure. It is composed primarily of amphibole and plagioclase, usually with very little quartz. Picture of Amphibolite.
ANDESITE  look up translate image
A fine-grained, extrusive igneous rock composed mainly of plagioclase with other minerals such as hornblende, pyroxene and biotite. Picture of Andesite.
ANGLE OF REPOSE  look up translate image
The maximum angle that a soil, sediment or other loose material can be placed or accumulate and be stable. The angle of repose varies for different types of materials and different moisture conditions.
ANGULAR UNCONFORMITY  look up translate image
An erosional surface that separates rock units of differing dips. The rocks below the surface were deposited, deformed and eroded. The younger rocks above then accumulated upon the erosional surface.
ANTHRACITE  look up translate image
The highest rank of coal. By definition, a coal with a fixed carbon content of over 91% on a dry ash-free basis. Anthracite coals have a bright luster, break with a conchoidal fracture, a semi-metallic luster and are difficult to ignite. Frequently referred to by the layman as "hard coal".
AQUICLUDE  look up translate image
A subsurface rock, soil or sediment unit that does not yield useful quanties of water.
AQUIFER  look up translate image
A subsurface rock or sediment unit that is porous and permeable. To be an aquifer it must have these traits to a high enough degree that it stores and transmits useful quantities of water.
AQUIFER (ARTESIAN)  look up translate image
An aquifer that is bounded above and below by impermeable rock or sediment layers. The water in the aquifer is also under enough pressure that, when the aquifer is tapped by a well, the water rises up the well bore to a level that is above the top of the aquifer. The water may or may not flow onto the land surface.
AQUIFER (CONFINED)  look up translate image
An aquifer that is bounded above and below by impermeable rock or sediment layers. There may or may not be enough pressure in the aquifer to make it an "artesian aquifer".
AQUIFER (UNCONFINED)  look up translate image
An aquifer that is not overlain by an impermeable rock unit. The water in this aquifer is under atmospheric pressure and is recharged by precipitation that falls on the land surface directly above the aquifer.
ARKOSE  look up translate image
A sandstone that contains at least 25% feldspar. Easily recognized because the feldspar grains are typically pink and angular in shape.
ARROYO  look up translate image
A flat-bottom gully with steep sides that is a channel for an intermittent stream.
ASTHENOSPHERE  look up translate image
A portion of the upper mantle that is directly below the lithosphere. A zone of low strength in the upper mantle defines the top of the asthenosphere. This weak zone allows the plates of the lithosphere to slide across the top of the asthenosphere.
ASTROBLEME  look up translate image
An ancient circular scar on Earth's surface produced by the impact of a meteorite or comet. Use our Google maps page to get close up images of these meteor impact structures.
ATOLL  look up translate image
A ring-shaped group of coral islands that are surrounded by deep ocean water and that enclose a shallow lagoon.
B-HORIZON  look up translate image
A layer in the soil, below the A-horizon, where materials leached from above accumulate. Typically enriched in clay and oxides.
BACKWASH  look up translate image
The seaward rush of water down a beach that occurs with a receding wave.
BANDED IRON ORE  look up translate image
A rock that consists of alternating layers of chert and iron oxide mineral (usually hematite) with the iron oxide in high enough concentration to be of economic value.
BANK STORAGE  look up translate image
Water that seeps into the ground along the banks of a stream during a time of high flow. This loss of water into the ground slightly reduces the height that the stream will attain and then slowly seeps into the stream as the high water level subsides - hence the term "bank storage".
BANKFULL STAGE  look up translate image
A height of water in a stream that completely fills the natural channel. If the water rises any higher a flood will occur.
BAR  look up translate image
An underwater ridge, usually of sand and/or gravel, that forms from the deposition and reworking of sediments by currents and/or waves. Bars occur in rivers, river mouths and in offshore waters.
BARCHAN  look up translate image
A sand dune that is crescent-shaped in map view. Barchan dunes form in areas of limited sand supply. They move across the desert floor with their gently sloping convex sides facing upwind and their steeply sloping concave sides facing downwind.
BARRIER ISLAND  look up translate image
A long, narrow island that parallels a shoreline.
BASALT  look up translate image
A dark-colored fine-grained extrusive igneous rock composed largely of plagioclase feldspar and pyroxene. Similar in composition to gabbro. Basalt is thought to be one of the main components of oceanic crust. Picture of Basalt.
BASE FLOW  look up translate image
Water that seeps into a stream through a permeable rock or sediment unit that outcrops in the bottom or banks of the stream.
BASE LEVEL  look up translate image
The lower limit of erosion by a stream. Sea level is the ultimate base level. However, lakes can serve as a temporary base level in upstream areas.
BASEMENT  look up translate image
The igneous and metamorphic rocks that exist below the oldest sedimentary cover. In some areas such as shields the basement rocks may be exposed at the surface.
BASIC ROCK  look up translate image
An igneous rock that has a relatively low silica content. Examples are gabbro and basalt. Also see entries for acidic, intermediate and ultrabasic rocks.
BASIN  look up translate image
In tectonics, a circular, syncline-like depression of strata. In sedimentology, the site of accumulation of a large thickness of sediments.
BATHOLITH  look up translate image
A very large intrusive igneous rock mass that has been exposed by erosion and with an exposed surface area of over 100 square kilometers. A batholith has no known floor.
BATHYMETRY  look up translate image
The measurement of ocean depths and the preparation of topographic maps of the ocean floor.
BAUXITE  look up translate image
The principal ore of aluminum. A mixture of aluminum oxides and hydroxides that forms from intense chemical weathering of a soil in tropical environments.
BED LOAD  look up translate image
The larger, heavier particles that are being transported by a stream. Instead of being dissolved or suspended, these are being rolled or bounced along, spending at least part of their time in contact with the stream bottom. See also: load, suspended load, dissolved load.
BEDDING  look up translate image
The characteristic structure of sedimentary rocks in which layers of different composition, grain size or arrangement are stacked one on top of another in a sequence with oldest at the bottom and youngest at the top.
BEDDING PLANE  look up translate image
A distinct surface of contact between two sedimentary rock layers.
BEDROCK  look up translate image
Solid rock present beneath any soil, sediment or other surface cover. In some locations it may be exposed at Earth's surface.
BETA-PARTICLE  look up translate image
An electron emitted with high energy and velocity from the nucleus of an atom during radioactive decay.
BIOCHEMICAL ROCKS  look up translate image
A sedimentary rock that forms from the chemical activities of organisms. Organic (reef and fossiliferous) limestones and bacterial iron ores are examples.
BIOTURBATED  look up translate image
An adjective used in reference to a sediment or sedimentary rock. Bioturbated sediments have been disturbed by animals (such as burrowing worms or shell fish) or plant roots. These have penetrated the sediment and disturbed any or all original sedimentary laminations and structures. Bioturbated rocks were disturbed in this way while still in the soft sediment phase of their formation.
BITUMINOUS COAL  look up translate image
A rank of coal that falls between anthracite and semi-bituminous. The most abundant rank of coal. Frequently referred to by the layman as "soft coal".
BLOCK FAULT MOUNTAIN  look up translate image
A linear mountain that is bounded on both sides by normal faults.
BLOWOUT  look up translate image
A shallow, round or trough-shaped depression in sand or dry soil that is formed by wind erosion. The material removed by the wind may also be referred to as "blowout".
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Geology terminology
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Created by admin
Created on 2012-07-09 17:51:54
Number of terms 613
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