Acidic. A descriptive term applied to those igneous rocks that contain more than 66%. slllca.
Adsorb. To adhere in an extremely thin layer to the surface of a solid body.
Agglomerate. A pyroclastic rock containing a predominance of rounded fragments greater than 32 mm. in diameter.
Aggradation.The process of building up a surface by deposition.
Amphibole. A dark-colored rock-forming group of minerals which includes hornblende, actinolite, , and glaucophane.
Amphibolite . A crystalline rock consisting mainly of amphibole and plagioclase. Quartz is absent or present in small amounts only.
Andesite. A volcanic rock composed of plagioclase and one or more mafic constituents.
Anion. A negatively charged ion, e.g. OH .
Anticline. A fold or arch in rock strata, dipping in opposite directions from an axis.
Aplite. A dike rock consisting almost entirely of light-colored mineral constituents and having a characteristic fine-grained granitic texture.
Aquifer. A part of a geologic formation containing sufficient saturated material to yield significant quantittes of water to wells and springs, e.g. a sand stratum.
Arkosic sandstone. A sandstone in which much feldspar is present. This may range from unassorted products of granular disintegration of medium-grained granite to a partly sorted river-laid or even marine sandstone.
Artesian. Synonymous with confined.
Ash.Volcanic dust and particles less than 4 mm. in diameter.
Bailer Test. A method of estimating the yield of a well by cyclic bailing of the well.
Basalt, A fine-grained, dark-colored sxtrusive igneous rock. A solidified lava.
Basic.. A descriptive term for those igneous rocks that are comparitively low in silica content.
Bivalent. 1. An ion with ~ double electrical charge; 2. Having a valence of two, e.g. Fe, CO3, etc.
Boulder, A rounded rock fragment larger than 256 mm. in diameter.
Breccia. A rock made up of highly angular, coarse fragments.
Capillary Fringe. The zone immediately above the water table in which all or some of the pores are filled with water that is under less than atmospheric pressure and that is continuous with the water below the water table.
Cation. A positively charged ion, e.g. H .
Cation Exchange. Replacement of ions adsorbed, or exposed at the surface of a solid, by ions from a solution. Also called base exchange.
Chart. A compact siliceous rock of sedimentary origin.
Cinder. Volcanic particles in the range from 4 to 32 mm. in diameter.
Claypan. A stratum of stiff, , relatively impervious clay which is not cemented. It becomes plastic when =ixed with water and it differs from hardpan.
Cobble. A rounded rock fragment between 64 and 256 mm. in diameter..
Coliform. A type of bacteria that thrives in the digestive tracts of warm-blooded animals.
Colloid. A substance that is exceedingly fine-grained and when apparently dissolved in water, forms a gelatinous mass.
Confining Bed. A body of relatively impermeable =aterial overlying a more permeable aquifer. Also called an aquitard or aquiclude..
Conglomerate. A cemented rock containing rounded fragments corresponding in size to gravel.
Coquina. Soft porous limestone composed of broken shells.
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Deflocculate. To convert into very fine particles.
Detritus, Fragmental =material, such as sand, silt, and =mud, derived from older rocks by disintegration.
Diabase. A rock of basaltic composition in which lath-shaped feldspar crystals are embedded in a matrix of fine-frained pyroxene
Diatomite. An earthy deposit composed of nearly pure silica and consisting of the shells of microscopic algae called diatoms.
Diorite. An intrusive igneous rock composed of the mineralsfeldspar and hornblende, biotite, or pyroxene.
Distal. Remote from the point of origin.
Drawdown. The vertical distance from the static water level in well to the pumping level.
Eclogite. A granular metamorphic rock composed essentially of garnet and pyroxene..
Electrical Conductivity.. Synonymous with specific conductance.
Embayment. A coastline area that has undergone sufficient subsi- to receive a thick succession of sediments.
Eolian. Of, relating to, formed by, or deposited from the wind.
Extrusive. Said of a rock that has been formed on the ground surface from the solidification of molten lava.
Fault. A fracture, or fracture zone, along which there has been displacement of the two sides relative to one another parallel to the fracture. This displacement may be a few inches or many miles.
Faulted. Affected by movement along a fault.
Feldspar. A group of abundant, light-colored rock-forming minerals. Includes orthoclase, , plagioclase, , and microcline.
Ferrous. Bivalent iron, Fe .
Ferric. Trivalent iron, Fe
Fetid. Having a disagreeable odor caused by decomposition of organic matter.
Fissile.The property of splitting easily along closely spaced parallel planes.
Flocculate. To separate into small lumps.
Floodplain. A strip of relatively smooth land bordering a stream built of sediments carried by the stream.
Friable. Easily crumbled.
Gabbro. A coarse-grained, dark colored igneous rock consisting of feldspar and pyroxene. Olivine may be present; quartz is absent.
Gaining Stream. A stream which receives water from] the ground water body.
Gastropod.. A member of the mollusc family and includes both land and marine snails.
Geohydrology. The science of relating geologic factors to hydeo-phenomena.
Geomorphic Province. A mayor geologic and landform unit. There are 11 geomorphic provinces in California, such as the Coast Ranges, Great Valley, Sierra Nevada provinces, etc.
Geosyncline. A large trough that subsided deeply throughout a long period of time in which a thick succession of stratified marine sediments accumulated.
Glauconite.. A green mineral commonly occurring in sandstones of marine origin.
Glaucophane. A bluish-colored amphibole occurring in metamorphic rocks.
Granitic Rock. A coarse-grained igneous rock including granite granodiorite,, diorite, , granite porphyry, diorite porphyry, and gabbro.A coarse-grained igneous rock consisting of quartz feldspar, biotite, hornblende, and pyroxene..
Graves.. An accumulation of rounded rock fragments larger than 2 mm.
Graywacke. A type of sandstone marked by large grains of quartz and feldspar in a clay matrix. Commonly a gray color and containing small fragments of shale or slate.
Greenstone. An altered basic igneous rock of decided greenish color due to the presence of such minerals as chlorite, hornblende, and epidote.
Ground Water. Subsurface water occurring in the zone of saturation.
Gneissose. Having composite structure similar to gneiss, with alternating bands which differ in mineral composition and texture.
Hardpan. A hard impervious layer, composed chiefly of clay, cemented by relatively insoluble materials, does not become plastic when mixed with water, and limits the downward movement of water and roots. It differs from claypan.
Hydraulic Gradient. The change in static head per unit of distance in a given direction.
Hydrograph. A graph showing the changes in the water level in a well with respect to time.
Hydrologic Cycle. The complete cycle through which water passes, commencing as atmospheric water vapor, passing into liquid (rein) and solid (snow) as precipitation, thence along or into the ground surface, and finally again returning to the form of atmospheric water vapor by means of evaporation and transpiration. Hdrology. The science that relates to the distribution and phenomena of naturally-occurring water.
Hydroxide. A compound containing the hydroxyl ion, OH, and one or more positive ions, e.g. ferrous hydroxide, Fe(OH)2.
Igneous. Rock formed from the solidification of molten magma, either at depth or on the ground surface.
Insoluble. Incapable or very difficult in being dissolved in a liquid.
Intercalated. One body of material interbedded or interlaminated with another.
Interfinger. To grade or pass from one material to another through a series of interlocking or overlapping wedge-shaped layers.
Intrusive.Said of a rock that has solidified from magma below the ground surface
Ion. An electrically charged atom or molecule, e.g. H+, Oh, etc.
. Of, or pertaining to a lagoon.
Lamprophyre. A dark, fine-grained dike rock in which dark minerals, such as biotite,, hornblende, and pyroxene occur both as crystals and in the matrix.
Lava. Fluid rock such as that which issues from a volcano; also the same material solidified by cooling.
Lignite. A brownish-black coal in which the alteration of vegetal material has proceeded farther than in peat but not so far as bituminous coal.
Limestone. A bedded sedimentary rock consisting chiefly of calcium carbonate.
Limonite. Brown hydrous iron oxide (ferrous oxide).
Losing Stream. A stream which contributes recharge to the ground water body.
Mafic.Basic; applies to dark minerals such as hornblende, etc.
Magma. Naturally occurring fluid rock material, generated within the earth and capable of intrusion and extrusion, and from which igneous rocks form by solidification.
Manganous. Bivalent manganese, Mn
Manganic. Trivalent manganese, Mn+++
Mathematical Model. A computer technique which simulates dynamic responses of a ground water basin to changes in recharge and pumping patterns. Used as a tool to predict future water levels.
Metabasalt.. Metamorphosed basalt.
Metagraywacke. A graywacke that has undergone a slight degree of metamorphism.
Metamorphic. Rock which has formed in the solid state in response to pronounced changes of temperature, pressure, and/or chemical environment and which takes place below the ground surface. A metamorphic rock originally was of a different form, i.e. it originally was igneous, sedimentary, etc.
Micromho. The standard unit of specific fic conductance.
Mineral. 1. A naturally-occurring chemical compound which forms rocks. Minerals usually, but not always, have definite crystal structure. 2. A chemical constituent of water, such as sodium, chloride, iron, etc.
Monitoring Well, A well used for the periodic measurement of water levels and/or periodic sampling for water quality analyses.
Mudstone. A clay rock which is not fissile.
Mutual Water Company. A corporation or association formed to deliver water to its members or stockholders at cost and not for profit. It is not obliged to serve water to any but its own members or stockholders, and it is not under the jurisdiction of the Public Utilities Commission.
Nitrate. An ion containing the completely oxidized form of nitrogen, i.e. NO3-. Nitrogen in the nitrate ion has of N5+.
Nitrite. An ion containing the partially oxidized form of nitrogen, i.e. NO2-. Nitrogen in nitrite ion has the form of N+++ .
Nodular. Having the shape of or composed of nodules.
Nodule. A small more or less rounded body generally somewhat harder than the enclosing sediment or rock matrix.
Nonwater-Bearing. Any geologic formation which normally does not yield supplies of ground water to wells in quantities sufficient for most beneficial uses. Nonwater-bearing rocks yield one or both of the following: (l) Meager supplies of water sufficient only for limited domestic use; (2) Unpotable water..
Obsidian. Volcanic glass.
Ooze. A fine-grained marine deposit which contains more than 30%. Of material of organic origin.
Orogeny. The process of forming mountains, particularly by folding and faulting.
Oxidation. 1. The process of combining with oxygen. 2. Increasing the electrical charge of an ion or atom in the positive direction. (See also Reduction.)
Oxide.. 1. The final product of oxidation. 2. A compound of oxygen and one or more positive ions.
Peat. A dark brown to black material produced by the partial de composition of plants,
Pebble. A smooth rounded stone ranging from 2 to 64 mm. in diameter.
Pegmatite. Coarse-grained igneous rocks occurring as dikes the' cut across igneous rocks of finer grain size.
Pelecypod. A mollusc such as the clam
Perched. Said of ground water that is separated from the under- main ground water body by a zone of unsaturated materials. A perched ground water body has its own water table separate from that of the underlying ground water body.
Peridotite.. A general term for essentially non-feldspathic intrusive, igneous rocks consisting of the mineral olivine,, with or without other minerals such as amphibole and pyroxene..
Perlite.A volcanic glass having numerous concentric cracks.
Permeability. The ability of a geologic material to transmit fluids such as water. The degree of permeability depends on the size and shape of the pore space and the extent, size, and shape ape of their interconnections.
Physiography. The study of the physical features (landforms) of the earth. Includes physical geography and physical geology.
Piezometric Surface. Synonymous with potentiometric surface.
Pillow Structure. The peculiar form exhibited by some basic lavas which consist of a sequence of rounded masses that resemble pillows or filled sacks. The rounded masses fit closely upon one another. Pillow structure is generally believed to be the result of a submarine eruption.
Plagioclase.. A series of rock-forming minerals belonging to the feldspar e group.
Porosity. The ratio of the total volume of the pores in a rock or soil to its total volume; expressed as a percent,
Porphyry.. An igneous rock in which larger crystals are set in a finer ground mass which may be crystalline, glassy, or both.
Potentiometric Surface. The Imaginary surface to which water will rise In a well tapping a given aquifer. The potentiometric surface may be above ground; in this case, the well would flow. The water table is the potentiometric surface in an unconfined aquifer en
Precipitate. 1. To separate or become separated from a liquid. 2. The substance in A state separated from A liquid AS A con&emdash; sequence of some chemical or physical change.
Precipitation. Rain, snow, mist, etc.; also the quantity of water
Primary Opening. Openings or voids existing when the rock was formed. In sedimentary rock, primary openings are usually the result of the arrangement and nature of the original sediment.
Pumice. Solidified volcanic froth; it is very light in density and will float on water.
Pumpage. The total amount of water pumped by wells from a ground water body.
Pyroclastic.. A rock consisting of a mixture of solid material of all sizes ejected from a volcanic vent.
Quartz. A basic rock-forming mineral; crystalline silica dioxide.
Quartz Diorite. An intrusive igneous rock similar to diorite with the addition of quartz.
Reduction. 1. The process of removing oxygen. 2. Increasing the electrical charge of an ion or atom in the negative direction. (See also Oxidation.)
Regression. Gradual contraction of a shallow sea resulting in emergence of land as when sea level falls or land rises.
Rhyolite. A fine-grained to porphyitic extrusive igneous rock of the same mineral composition as granite.
Salt. Any of a class of compounds formed when the hydrogen of an acid has been replaced by a metal, as ferrous sulfate (FeSO4) is an iron salt of sulfuric acid (H2504).
Safe Yield. 1. The annual amount of water that can be withdrawn from a ground water basin without producing any undesired result A draft in excess of safe yield is termed overdraft. 2. The rate at which water can be withdrawn from an aquifer without depleting the supply to such an extent that withdrawal at this rate is no longer economically feasible.
Sanitary Seal. The cement grout envelope in the annular space between the well casing and the wall of the hole to ensure that no surface water can enter the well.
Schist. A medium or coarse-grained metamorphic rock in which the rock splits into thin, irregular plates. Mica is the dominant mineral.
Scoria.. Volcanic slag. Volcanic material, usually of basaltic composition,, characterized by dark color, vesicles, and heaviness.
Sedimentary. Said of rocks formed from sediments. Includes such rock types as sandstone, conglomerate. shale. etc.
Of en . A rock which is the alteration product of several types
Serpentize. The conversion of ultrabasic rocks to serpentine.
Shearing. The deformation of rocks by the cumulation of small lateral movements along inumerable parallel planes, resulting from pressure.
Silica Carbonate Rock. An altered form of serpentine; an extremely hard rock which ranges from green to brown and contains quartz and other silica minerals as well as a variety of carbonate
Sill. A relatively thin body of intrusive Igneous rock that has been emplaced parallel to the structure or bedding of the adjacent
Siltstone.. A very fine-grained rock composed predominantly of particles of silt size (l/16 to 1/256 mm. In diameter).
Specific Capacity. The discharge of a water well expressed as rate of yield per unit of drawdown..
Specific Conductance. The measure of the ability of a fluid to conduct an electrical current. Because conductance is the reciprocal of resistivity the unit of conductance is reported as the reciprocal of the ohm, called the "mho"
Specific Yield. As applied to a rock or soil unit, it is the ratio of (1) the volume of water which, after being saturated, it will yield by gravity to (2) its own volume. This ratio is expressed as a percentage.
Spilite. A type of basalt.
Static Head. The height to which a column of water will rise in response to pressure at a given point.
Static Level. The minimum depth to water In a nonpumping well.
Subsidence. The sinking, or lowering, of a part of the earth's crust.
Syncline.. A fold in rocks in which the strata dip inward from both sides toward the Axis.
T
Tectonic. Of, or pertaining to the forces of deformation of the earth's crust.
Transgression. Gradual expansion of A shallow sea resulting in the progressive submergence of land AS when sea level rises or land subsides.
Total Dissolved Solids. The sum of the principal ions in a water quality Analysis. A measure of the total mineralization of water.
Transmissivity. The rate of flow of water through each vertical strip of aquifer one foot wide having A height equal to the thick- of the aquifer And under A unit hydraulic gradient.
Transpiration. The process by which water vapor escapes from a living plant And enters the atmosphere.
Trivalent. An ion with a triple electrical charge, e.g. Fe+++.
Tuff. A rock composed of compacted volcanic fragments smaller than
Tuff Breccia. A volcanic breccia in which the matrix, composed of tuff, Accounts for from 25 to 75 percent of the total volume,
Ultrabasic. Dark-colored igneous rocks which contain no quartz or feldspar.
Ultramafic .
Unconfined, 1. Water in an aquifer that has a water table. 2. An aquifer containing unconfined ground water.
Uncontormity. A surface of erosion that separates younger strata
Unpotable Water. Water that is not fit for human consumption.
Vesicle. A small cavity in a volcanic rock formed by the expansion on of a bubble of gas or steam during solidification of the rock
Water-Bearing. Any geologic formation which normally yields supplies of potable ground water to wells in quantities sufficient for most beneficial uses.
Water Quality. The study and identification of the various constituents in naturally-occurring ground and surface water.
Water Table. 1. The upper surface of A zone of saturation except where that zone is confined by an impermeable stratum. 2. The locus of points in soil water at which the pressure is equal to atmospheric pressure. 3. The level at which water stands in A well that penetrates a ground water body just far enough to hold standing water.
Welded Tuff. A tuff which has been transformed into a very hard dense rock by the action of heat contained in the particles And in the enveloping hot gases.
Zeolite.. A group of minerals characterized by their easy And reversible loss of water of hydration and their significant capacity for ion-exchange.
Zone of Aeration. The zone between the land surface And the deepest water table. It includes the capillary fringe.
Zone of Saturation. That part of the earth's crust below the deepest water table in which all voids are filled with water.
American Geological Institute. "Glossary of Geology and Related Sciences, with Supplement''. 2nd Edition.. 1960.
Hem, J. D. "Study and interpretation of the Chemical Characteristics of Natural Water". U. S. Geological Survey. Water-Supply Paper 1473, 1959.
Lohman, S. W. And others. "Definitions of Selected Ground-Water Terms: Revisions And Conceptual Refinements". U. S. Geological Survey. Water-Supply Paper 1988. 1972.
Poland, J. F. and others. "Glossary of Selected Terms Useful in Studies of the Mechanics of Aquifer Systems and Land Subsidence Due to Fluid Withdrawal". U. S. Geological Survey. Water-Supply Paper 2025, 1972.
Thomasson, N. G. and others. "Geology, Water Resources and Usable Ground-Water Storage Capacity of Part of Solano County, California". U. S. Geological Survey. Water-Supply Paper 1464. 1960.
Todd, D. K. "Ground Water Hydrology". John Wiley 6 Sons. 1960.
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