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Date Posted: Mon, Nov 10 2003, 23:46:12
Author: no name
Subject: Another C******** fic!

A | B | C | D | E | F | G | H | I | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Z

- A -

Alkali metal: A strongly basic metal like potassium or sodium.

Alluvial fan: A low, cone shaped deposit of terrestrial sediment formed where a stream undergoes an
abrupt reduction of slope.

Alluvium: An unconsolidated terrestrial sediment composed of sorted or unsorted sand, gravel, and
clay that had been deposited by water.

Angle of repose: The steepest slope angle in which a particular sediment will lie without cascading
down.

Angular unconformity: An unconformity in which the bedding planes of the rocks above and below
are not parallel.

Aquifer: A permeable formation that stores and transmits groundwater in sufficient quantity to supply
wells.

Arkose: A variety of sandstone containing abundant feldspar and quartz, frequently in angular, poorly
sorted grains.

Artesian well: A well that penetrates an aquiclude to reach an aquifer containing water under
pressure. Thus water in the well rises above the surrounding water table.

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- B -

Banded iron ore: A sediment consisting of layers of chert alternating with bands of ferric iron oxides
(hematite and limonite) in valuable concentrations.

Basalt: A fine-grained, dark, mafic igneous rock composed largely of plagioclase feldspar and
pyroxene.

Basement: The oldest rocks recognized in a given area, a complex of metamorphic and igneous rocks
that underlies all the sedimentary formations. Usually Precambrian or Paleozoic in age.

Basic rock: Any igneous rock containing mafic minerals rich in iron and magnesium, but containing no
quartz and little sodium rich plagioclase feldspar.

Basin: In tectonics, a circular, syncline-like depression of strata. In sedimentology, the site of
accumulation of a large thickness of sediments.

Batholith: A great irregular mass of coarse-grained igneous rock with an exposed surface of more
than 100 square kilometers, which has either intruded the country rock or been derived from it
through metamorphism.

Bedding: A characteristic of sedimentary rocks in which parallel planar surfaces separating different
grain sizes or compositions indicate successive depositional surfaces that existed at the time of
sedimentation.

Biochemical precipitate: A sediment, especially of limestone or iron, formed from elements extracted
from sea water by living organisms.

Block fault: A structure formed when the crust is divided into blocks of different elevation by a set of
normal faults.

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- C -

Caldera: A large, circular depression in a volcanic terrane, typically originating in collapse, explosion,
or erosion.

Carbonate rock: A rock composed of carbonate minerals, especially limestone and dolomite.

Chemical sediment: One that is formed at or near its place of deposition by chemical precipitation,
usually from sea water.

Chemical weathering: The total set of all chemical reactions that act on rock exposed to water and
atmosphere and so change it minerals to stable forms.

Chert: A sedimetary form of amorphous or extremely fine-grained silic, partially hydrous, found in
concretions and beds.

Cinder cone: A steep, conical hill built up about a volcanic vent and composed of coarse pyroclasts
expelled from the vent by escaping gases.

Cirque: The head of a glacial valley, usually with the form of one half of an inverted cone. The upper
edges have the steepest slopes, approaching vertical, and the base may be flat or hollowed out and
occupied by a small lake or pond.

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

Clay: Any of a number of hydrous aluminosilicate minerals formed by weathering and hydration of
other silicates; also, any mineral fragment smaller than 1/255 mm.

Contact metamorphism: Mineralogical and textural changes and deformation of rock resulting from
the head and pressure of an igneous intrusion in the near vicinity.

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- D -

Declination: At any place on Earth, the angle between the magnetic and rotational poles.

Delta: A body of sediment deposited in an ocean or lake at the mouth of a stream.

Density: The mass per unit volume of a substance, commonly expressed in grams/ cubic centimeter.

Deposition: A general term for the accumualtion of sediments by either physical or chemical
sedimentation.

Detrital sediment: A sediment deposited by a physical process.

Diatomite: A siliceous chert-like sediment formed from the hard parts of diatoms.

Diatreme: A volcanic vent filled with breccia by the explosive escape of gases.

Dip: The angle by which a stratum or other planar feature deviates from the horizontal. The angle is
measured in a plane perpendicular to the strike.

Dome: In structural geology, a round or elliptical upwarp of strata resembling a short anticline.

Drift (glacial): A collective term for all te rock, sand, and clay that is transported and deposited by a
glacier either as till or as outwash.

Drumlin: A smooth, streamlined hill composed of till.

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- E -

Eclogite: An extremely high pressure metamorphic rock containing garnet and pyroxene.

Elevation: The vertical height of one point on the Earth above a given datum plane, usually sea level.

Eon: The largest division of geologic time, embracing several Eras, for example, the Phanerozoic, 600
m.y. ago to present); also any span of one billion years.

Epoch: One subdivision of a geologic period, often chosen to correspond to a stratigraphic series.
Also used fo a division of time corresponding to a paleomagnetic interval.

Era: A time period including several periods, but smaller than an eon. Commonly recognized eras are
Precambrian, Paleozoic, Mesozoic, and Cenozoic.

Erosion: The set of all processes by which soil and rock are loosened and moved downhill or
downwind.

Eskar: A glacial deposit in the form of a continuous, winding ridge, formed from the deposits of a
stream flowing beneath the ice.

Evaporite: A chemical sedimentary rock consisting of minerals precipitated by evaporating waters,
especially sal and gypsum.

Exfoliation: A physical weathering process in which sheets of rock are fractured and detached from
an outcrop.

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- F -

Facies: The set of all characteristics of a sedimetary rock that indicates its particular environment of
deposition and which distinguish it from other facies in the same rock.

Fault: A planar or gently curved fracture in the Earth's crust across which there has been relative
displacement.

Fault plane: The plane that best approximates the fracture surface of a fault.

Felsic: An adjective used to describe a light-colored igneous rock poor in iron and magnesium
content, abundant in feldspars and quartz.

Fluid inclusion: A small body of fluid that is entrapped in a crystal and has the same composition as
the fluid from which the crystal formed.

Flume: A laboratory model of stream flow and sedimentation consisting of a rectangular channel filled
with sediment and running water.

Fold: A planar feature, such as a bedding plane, that has been strongly warped, presumably by
deformation.

Foliation: Any planar set of minerals or banding of mineral concentrations including cleavage, found in
a metamorphic rock.

Formation: The basic unit for the naming of rocks in stratigraphy: a set of rocks that are or once were
horizontally continuous, that share some distinctive feature of lithology, and are large enough to be
mapped.

Fossil: An impression, cast, outline, or track of any animal or plant that is preserved in rock after the
original organic material is transformed or removed.

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- G -

Gabbro: A black, coarse-grained, intrusive igneous rock, composed of calcic feldspars and
pryoxene. The intrusive equivalent of basalt.

Geosyncline: A major downwarp in the Earth's crust, usually more than 1000 kilometers in length, in
which sediments accumulate to thicknesses of many kilometers. The sediments may eventually be
deformed and metamorphosed during a mountain-building episode.

Glacial striations: Scratches left on bedrock and boulders by overriding ice, and showing the direction
of motion.

Glacier: A mass of ice and surficial snow that persists throughout the year and flows downhill under
its own weight. The size range is from 100 meters to 10,000 kilometers.

Gneiss: A coarse-grained regional metamorphic rock that shows compositional banding and parallel
alignment of minerals.

Graben: A downthrown block between two normal faults of parallel strike but converging dips; hence
a tensional feature. See also horst.

Graded bedding: A bed in which the coarsest particles are concentrated at the bottom and grade
gradually upward into fine silt, the whole bed having been deposited by a waning current.

Granite: A coarse-grained, intrusive igneous rock composed of quartz, orthoclase feldspar, sodic
plagioclase feldspar, and micas. Also sometimes a metamorphic product.

Granitization: The formation of metamorphic granite from other rocks by recrystallization with or
without complete melting.

Gravel: The coarsest of alluvial sediments, containing mostly particles larger than 2 mm in size and
including cobbles and boulders.

Gravity anomaly: The value of gravity left after subtracting from a gravity measurement the reference
value based on latitude, and possibly the free-air and Bouguer corrections.

Gravity survey: The measurement of gravity at regularly-spaced grid points with repetitions to control
instrument drift.

Greenschist: A metamorphic schist containing chlorite and epidote (which are green) and formed by
low-temperature, low-pressure metamorphism.

Groundwater: The mass of water in the ground below the phreatic zone, occupying the total pore
space in the rock and moving slowly downhill where permeability allows.

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- H -

Hard water: Water that contains sufiqcient dissolved calcium and magnesium to cause a carbonate
scale to form when the water is boiled or to prevent the sudsing of soap.

Hill: A natural land elevation, usually less than 1000 feet above its surroundings, with a rounded
outline. The distinction between hill and mountain depends on the locality.

Hornfels: A high-temperature, low-pressure metamorphic rock of uniform grain size showing no
folia-tion. Usually formed by contact metamorphism.

Horst: An elongate, elevated block of crust forming a ridge or plateau, typically bounded by parallel,
outward-dipping normal faults.

Humus: The decayed part of the organic matter in a soil.

Hydration: A chemical reaction, usually in weathering, which adds water or OH to a mineral
structure.

Hydrocarbon: An organic chemical compound made up of carbon and hydrogen atoms arranged in
chains or rings.

Hydrology: The science of that part of the hydrologic cycle between rain and return to the sea; the
study of water on and within the land.

Hydrothermal activity: Any process involving high-temperature groundwaters, especially the alteration
and emplacement of minerals and the formation of hot springs and geysers.

Hydrothermal vein: A cluster of minerals precipitated by hydrothermal activity in a rock cavity.

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- I -

Igneous rock: A rock formed by congealing rapidly or slowly from a molten state.

Inclination: The angle between a line in the Earth's magnetic field and the horizontal plane; also a
synonym for dip.

Intrusion: An igneous rock body that has forced its way in a molten state into surrounding country
rock.

Intrusive rock: Igneous rock that is interpreted as a former intrusion from its cross-cutting contacts,
chilled margins, or other field relations.

Iron formation: A sedimentary rock containing much iron, usually more than 15 percent as sulfide,
oxide, hydroxide, or carbonate; a low-grade ore of iron.



- J -

Joint: A large and relatively planar fracture in a rock across which there is no relative displacement of
the two sides.

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- K -

Kimberlite: A peridotite containing garnet and olivine and found in volcanic pipes, through which it
may come from the upper Mantle.

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- L -

Laccolith: A sill-like igneous intrusion that forces apart two strata and forms a round, lens-shaped
body many times wider than it is thick.

Laminar flow: A flow regime in which particle paths are straight or gently curved and parallel.

Lapilli: A fragment of volcanic rock formed when magma is ejected into the air by expanding gases.
The size of the fragments ranges from sand- to cobble-size.

Lateral moraine: A moraine formed along the side of a valley glacier and composed of rock scraped
off or fallen from the valley sides.

Lava: Magma or molten rock that has reached the surface.

Leaching: The removal of elements from a soil by dissolution in water moving downward in the
ground.

Limb (fold): The relatively planar part of a fold or of two adjacent folds (for example, the steeply
dipping part of a stratum between an anticline and syncline).

Limestone: A sedimentary rock composed principally of calcium carbonate (CaCO2), usually as the
mineral calcite.

Lineation: Any linear arrangement of features found in a rock.

Lithology: The systematic description of rocks, in terms of mineral composition and texture.

Lode: An unusually large vein or set of veins containing ore minerals.

Longitudinal profile: A cross section of a stream from its mouth to its head, showing elevation versus
distance to the mouth.

Lopolith: A large laccolith that is bowl-shaped and depressed in the center, possibly by subsidence of
an emptied magma chamber beneath the intrusion.

Luster: The general textural impression of a mineral surface, given by the light reflected from it. Terms
such as metallic, submetallic are standardized but subjective.

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- M -

Mafic mineral: A dark-colored mineral rich in iron and magnesium, especially a pyroxene, amphibole,
or olivine.

Magma: Molten rock material that forms igneous rocks upon cooling. Magma that reaches the
surface is referred to as lava.

Magmatic water: Water that is dissolved in a magma or that is derived from such water.

Magnetic anomaly: The value of the local magnetic field remaining after the subtraction of the dipole
portion of the Earth's field.

Magnetometer: An instrument for measuring either one orthogonal component or the entire intensity
of the Earth's magnetic field at various points.

Mantle: The main bulk of the Earth, between the crust and core, ranging from depths of about 40 to
3480 kilometers. It is composed of dense mafic silicates and divided into concentric layers by phase
changes that are caused by the increase in pressure with depth.

Massive rock: A rock that is little or not at all broken by joints, cracks, foliation, or bedding, tending
to present a homogeneous appearance.

Mass spectrometer: An instrument for separating ions of different mass but equal charge (mainly
isotopes in geology) and measuring their relative quantities.

Mechanical weathering: The set of all physical processes by which an outcrop is broken up into small
particles.

Medial moraine: A long stripe of rock debris carried on or within a glacier resulting from the
convergence of lateral moraines where two glaciers join.

Metamorphism: The changes of mineralogy and texture imposed on a rock by pressure and
temperature in the Earth's interior. Meteoric water: Rainwater, snow, hail, and sleet.

Migmatite: A rock with both igneous and metamorphic characteristics that shows large crystals and
laminar flow structures. Probably formed metamorphically in the presence of water and without
melting.

Mineral: A naturally occurring element or compound with a precise chemical formula and a regular
internal lattice structure. Organic products are usually not included.

Mineralogy: The study of mineral composition, structure, appearance, stability, occurrence, and
associations.

Mohs scale of hardness: An empirical, ascending scale of mineral hardness with talc as 1, gypsum 2,
calcite 3, fluorite 4, apatite 5, orthoclase 6, quartz 7, topaz 8, corundum 9, and diamond 10.

Monocline: The S-shaped fold connecting two horizontal parts of the same stratum at different
elevations. Its central limb is usually not overturned.

Moraine: A glacial deposit of till left at the margin of an ice sheet. See specifically by name, ground
moraine, longitudinal moraine, medial moraine, and terminal moraine.

M.y.: Abbreviation for "million years."

Mylonite: A very fine lithified fault breccia commonly found in major thrust faults and produced by
shearing and rolling during fault movement.

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- N -

Native metal: A natural deposit of a metallic element in pure metallic form, neither oxidized nor
combined with sulfur or other elements.

Normal fault: A dip-slip fault in which the block above the fault has moved downward relative to the
block below.

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- O -

Obsidian: Dark volcanic glass of felsic composition.

Oil shale: A dark-colored shale containing organic material that can be crushed and heated to liberate
gaseous hydrocarbons.

Opaque mineral: A mineral which transmits no light through a thin section under a microscope.
Usually a native metal, sulfide, or metallic oxide mineral.

Ore: A natural deposit in which a valuable metallic element occurs in high enough concentration to
make mining economically feasible.

Ore mineral: The mineral of an ore that contains the useful element.

Orogenic belt: A linear region, often a former geo-syncline, that has been subjected to folding, and
other deformation in a mountain-building episode.

Outcrop: A segment of bedrock exposed to the atmosphere.

Oxidation: A chemical reaction in which electrons are lost from an atom and its charge becomes
more positive.

Oxidized element: An element occurring in the more positively charged of two common ionic forms.

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- P -

Paleontology: The science of fossils, of ancient life-forms, and their evolution.

Pegmatite: An igneous rock with extremely large grains, more than a centimeter in diameter. It may
be of any composition but most frequently is granitic.

Peridotite: A coarse-grained mafic igneous rock composed of olivine with accessory amounts of
pyroxene and amphibole but little or no feldspar.

Potable water: Water that is agreeable to the taste and not dangerous to the health.

Ppm: Abbreviation for "parts per million."

Proven reserves: Deposits of fossil fuels whose location and extent are known, as opposed to
potential but unproved ('*discovered") deposits.

Pumice: A form of volcanic glass, usually of silicic composition, so filled with vesicles that it resembles
a sponge and is very light.

Pyroclastic rock: A rock formed by the accumulation of fragments of volcanic rock scattered by
volcanic explosions.

Pyroclastic texture: The unsorted, angular, and un-rounded texture of the fragments in a pyroclastic
rock.

Pyroxene granulite: A coarse-grained contact metamorphic rock containing pyroxene, formed at high
temperatures and low pressures.

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- Q -

Quartz arenite: A sandstone containing very little except pure quartz grains and cement.

Quartzite: (1) A very hard, clean, white metamorphic rock formed from a quartz arenite sandstone.
(2) A quartz arenite containing so much cement that it resembles ( 1 ).

Quartzose sandstone: (1) A quartz arenite. (2) A clean quartz sandstone, less pure than a quartz
arehire, that may contain a moderate amount of other detrital minerals and/or calcite cement.

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- R -

Recrystallization: The growth of new mineral grains in a rock at the expense of old grains, which
supply the material.

Recumbent fold: An overturned fold with both limbs nearly horizontal.

Regional metamorphism: Metamorphism occurring over a wide area and caused by deep burial and
high internal temperatures of the Earth.

Regolith: Any solid material lying on top of bedrock. Includes soil, alluvium, and rock fragments
weathered from the bedrock.

Regression: A drop in sea level that causes an area of the Earth to be uncovered by sea water,
ending marine deposition.

Relief: The maximum regional difference in elevation.

Remote sensing: The study of Earth surface conditions and materials from airplanes and satellites by
means of photography, spectroscopy, or radar.

Replacement deposit: A deposit of ore minerals by hydrothermal solutions that have first dissolved
the original mineral to form a small cavity.

Rhyolite: The fine-grained volcanic or extrusive equivalent of granite, light brown to gray and
compact. Richter magnitude scale: See Magnitude.

Rift valley: A fault trough formed in a divergence zone or other area of tension.

Right-lateral fault: A strike-slip fault on which the displacement of the far block is to the right when
viewed from either side.

Ring dike: A dike in the form of a segment of a cone or cylinder, having an arcuare outcrop.

Rock flour: A glacial sediment of extremely fine (silt-and clay-size) ground rock formed by abrasion

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