The Glossary draws its authority from the expertise of the more than geoscientists in many specialties who reviewed definitions and added new terms.
Glossary of Geology Author : Julia A. Score: 5. The Glossary draws its authority from the expertise of more than geoscientists in many specialties who reviewed definitions and added new terms. Contour Map: Coal: A map that shows the change in value of a variable over a geographic area through the use of contour lines.
For A brown or black sedimentary rock that forms from example, a contour map of elevation has lines that trace accumulated plant debris. A combustible rock that points of equal elevation across the map. Coastal Plain: Cubic Feet Per Second: An area of low relief along a continental margin that is A unit of measure frequently used to quantify the rate of underlain by thick, gently dipping sediments.
It is equal to a volume of water one foot high and one foot wide moving a linear distance of one foot in one second. Compaction: A compression process that reorients and reshapes the grains of a sediment in response to the weight of overlying deposits.
Also known as a stratovolcano. Contact Metamorphism: Alteration of a rock, mainly by heat, which occurs adjacent to a dike, sill, magma chamber or other magma body.
D Dendritic Drainage: A stream drainage pattern that resembles the veins of a leaf in map view. Occurs mainly where the rocks below have a uniform resistance to erosion. Datum: A reference location or elevation which is used as a Density Current: starting point for subsequent measurements. Sea level is a datum for elevation measurements. The increased density of the water is a result of a measurements or based upon a physical feature such as temperature difference, increased salinity or suspended the base of a rock unit.
Daughter Element: Deposition: The element produced through the radioactive decay of a The settling from suspension of transported sediments. Also, the precipitation of chemical sediments from mineral rich waters. Debris Avalanche: Desert Pavement: The sudden downslope movement of rock and soil on a steep slope.
A horizontal to subhorizntal fault or shear zone with a very large displacement. The rocks above the fault might have been moved thousands of meters or more relative to the Detrital: rocks below the fault. This often produces a situation where the rocks above the fault have entirely different A word used in reference to sediments or sedimentary structures than the rocks below the fault. The term can also be used in reference to All of the changes which happen to a sediment after the removal by wind of any unconsolidated material.
Diagenesis includes compaction, cementation, leaching and replacement. Delta: A deposit of sediment that forms where a stream enters a Diatom: standing body of water such as a lake or ocean. Many of these secrete a shell or internal parts composed of silica.
Diatoms can occur in very large numbers and can make significant contributions The dissolved material being carried by a stream. Drainage Basin: Differentiated Planet: The geographic area that contributes runoff to a stream. It A planet that has layers composed of elements and can be outlined on a topographic map by tracing the minerals of different densities. Also referred to as a surrounded by a rocky mantle, and covered by a crust of "watershed".
Drainage Divide: Dip: The boundary between two adjacent drainage basins. The angle that a rock unit, fault or other rock structure Drainage divides are ridge crests or less obvious locations makes with a horizontal plane.
Expressed as the angular where slope of the landscape changes direction. Runoff difference between the horizontal plane and the structure.
Discharge: Drawdown: The volume of water in a flowing stream that passes a A lowering of the water table around a producing well. The given location in a unit of time. Frequently expressed in drawdown at any given location will be the vertical change cubic feet per second or cubic meters per second. Drift: Discontinuity: A general term for all sedimentary materials deposited directly from the ice or melt water of a glacier. A surface separating rock layers of differing properties or compositions.
See seismic discontinuity. Drumlins are deposits of compacted till that are sculpted beneath the ice of a flowing glacier. The long axis of a drumlin parallels the flow direction of the ice. Typically found in deserts and inland from a beach. Many dunes are moved by the wind.
In this theory, slowly accumulating elastic strain builds within a rock mass over an extended length of time. This strain is suddenly released through fault movement, producing an earthquake.
Earthflow: Electron: A detached mass of soil that moves downslope over a A subatomic particle with a negative charge and of curved failure surface under the influence of gravity. An negligible mass that orbits the nucleus of an atom.
Rates of movement are typically a few inches per year but faster rates can occur. Elevation: The vertical distance between mean sea level and a point or object on, above or below Earth's surface. Earthquake: A trembling of the earth caused by a sudden release of energy stored in subsurface rock units.
Eolian: A term used in reference to the wind. Eolian materials or structures are deposited by or created by the wind. Ebb Tide: A tidal current that generally moves seaward and occurs during the part of the tide cycle when sea level is falling. Eon: see also: flood tide The major divisions of the geologic time scale. Eons are divided into intervals know as "eras". Two eons of the geologic time scale are the Phanerozoic million years Effluent Stream: ago to present and the Cryptozoic 4, million years ago until million years ago.
A stream that gains water from ground water flow. These streams are typical of humid climates where water tables are high. Effluent streams generally increase in discharge downstream and The point on the Earth's surface directly above the focus of contain water throughout the year.
The opposite is an an earthquake. Epoch: Elastic Limit: A subdivision of geologic time that is longer than an age The maximum stress that can be applied to a body without but shorter than a period. From most recent to oldest they are: its original shape after the stress is removed.
Precambrian, Paleozoic, of rock are removed from an outcrop. Mesozoic, and Cenozoic are the eras of the time scale from oldest to youngest. Expansive Clay Expansive Soil : Erosion: A clay soil that expands when water is added and contracts when it dries out.
This volume change when in contact A general term applied to the wearing away and with buildings, roadways, or underground utilities can movement of earth materials by gravity, wind, water and cause severe damage. Extrusive: Esker: Igneous rocks that crystallize at Earth's surface. A long winding ridge of sorted sands and gravel. Thought to be formed from sediment deposited by a stream flowing within or beneath a glacier.
Eustatic Sea Level Change: A rise or fall in sea level that affects the entire earth. Evaporation: The process of liquid water becoming water vapor. Evaporite: A chemical sediment or sedimentary rock that has formed by precipitation from evaporating waters.
Gypsum, salt, nitrates and borates are examples of evaporite minerals. Evapotranspiration: All methods of water moving from a liquid to water vapor in nature.
Includes both evaporation and transpiration. F Flood: An overflow of water onto lands that are normally above local water levels. Can be caused by stream discharge exceeding the capacity of the stream channel, storm winds Facies: and reduced pressure drawing water from a lake or ocean onto the coastline, dam failure, lake level increase, local drainage problems or other reasons.
The characteristics of a rock mass that reflect its depositional environment. These characteristics enable the rock mass to be distinguished from rocks deposited in adjacent environments.
Flood Basalt: A sequence of parallel to subparallel basalt flows that Fault: were formed during a geologically brief interval of time and which covered an extensive geographic area. Thought to have formed from simultaneous or successive fissure A fracture or fracture zone in rock along which movement eruptions. Faunal Succession: Flood Stage: A principle of relative dating that is based upon the A water height that is reached when the discharge of a observed sequence of organisms in the rock record.
The stream exceeds the capacity of the channel. Flood Tide: Felsic: A tidal current that generally moves landward and occurs during the part of the tide cycle when sea level is rising. See neap tide for contrast.
Also used in reference to the magmas from which these rocks crystallize. Felsic rocks are Flowing Well: generally rich in silicon and aluminum and contain only small amounts of magnesium and iron. Granite and A well that taps an aquifer that is under enough pressure rhyolite are examples of felsic rocks.
See mafic to to force water to the surface. Caused when the aquifer has contrast. The basic rock unit of stratigraphy. Focus: Fossil: A point beneath Earth's surface where the vibrations of an earthquake are thought to have originated.
Also known as Remains, imprints or traces of an ancient organism that a hypocenter. Bones, shells, casts, tracks and excrement can all become fossils. Fold: Fossil fuel: A bend or flexure in a rock unit or series of rock units that has been caused by crustal movements. Coal, oil and natural gas are examples of fossil fuels. These can be structural such A vent that emits hot gases, usually associated with past or as cleavage, textural such as mineral grain flattening or current magmatic activity below.
Their shells can make up a significant portion of the carbonate sediment in some areas. Forset Beds: The distinctly dipping sediment layers deposited on the front of a prograding delta or on the lee side of a sand dune. Geothermal Gradient: The progressive increase of temperature with depth into the Earth. Caused by the heating of ground water within a confined opening in hot rock.
Gage Height: Glacial Rebound: A measured height of water above a reference datum. Frequently used to describe the height of water in a A very gradual uplift of Earth's crust that occurs after the stream, lake, well, canal or other water body. Gaging Station: Glacial Striations: A facility on a stream, lake, canal, reservoir or other water body where instruments are installed to automatically Grooves and scratches on a bedrock surface that were monitor the water.
Measurments such as stage, discharge, produced by the movement of a glacier. The orientation of water temperature and pH are automatically taken and the striations gives evidence to the direction of glacial transmitted to hydrologists via satellite, radio or movement.
Measurements from these stations are useful for a wide variety of flood prediction, water management, recreation and navigation purposes. A study of the time relationships of rock units. Includes methods of both relative and absolute dating. Glacier: Geomorphology: A thick mass of ice that forms on land from an accumulation and recrystallization of snow significant enough to persist through the summer and grow year by The science of Earth's landforms, their description, year.
There are two basic types of glaciers: 1 valley or classification, distribution, origin and significance. The rapid and water vapor in the lower portions of the atmosphere cooling does not provide enough time for crystal growth.
Ground Moraine: Graben: A blanket of till that is deposited during the retreat of a An elongated, downthrown block bounded by two steeply glacier. Produced in an area of crustal extension. Ground Water: Graded Bedding: Water that exists below the water table in the zone of saturation. Ground water moves slowly in the same A rock layer that has a progressive change in particle size direction that the water table slopes.
Most common is a sequence with coarse grains at the bottom and fining upwards, which is typically caused by a declining current velocity within the depositional environment. Ground Water Recharge Area: A location where surface water or precipitation can infiltrate into the ground and replenish the water supply of Granite: an aquifer.
Guyot: Granite is thought to be one of the main components of continental crust. A seamount with a flat top. Gravel: Clastic sedimentary particles of any composition that are over 2 mm in diameter. Gravity Anomaly: A geographic area where the gravitational attraction is significantly higher or significantly lower than normal. Produced in to decay into its daughter material. These different stream levels are a result of the rapid downcutting of the glacier being much faster than the slower downcutting of the tributary stream.
Hot Spring: Hard Water: A natural spring that delivers water to the surface that is of higher temperature than the human body. Water that has a significant amount of dissolved calcium and magnesium ions.
This water performs poorly with most soaps and detergents and leaves a scaly deposit in Humus: containers where it is heated or evaporates. Headwater s : Hydraulic Conductivity: The upper portions of a drainage basin where the tributaries of a stream first begin flow. The ability of a porous material to transmit a fluid. Heat Flow: Hydrocarbon: The movement of heat energy from the core of the Earth towards the surface. Any organic chemical compound gaseous, liquid or solid that is composed of carbon and hydrogen.
The term is frequently used in reference to fossil fuels, specifically Hogback: crude oil and natural gas. A narrow ridge with steeply inclined sides of nearly equal slopes.
Formed by differential erosion of steeply dipping Hydrograph: rock units. Example: A stream discharge hydrograph shows the change in discharge of a stream over time.
A point beneath earth's surface where the vibrations of an earthquake are thought to have originated. Also known as the focus Hydrologic Cycle: The natural cycling of Earth's water between the atmosphere, surface and subsurface through the processes of evaporation, transpiration, percolation, infiltration, runoff and precipitation. Hydrology: The science of Earth's water, its movement, abundance, chemistry and distribution on, above and below Earth's surface.
Hydrolysis: A chemical reaction involving water that results in the breakdown of mineral material. Hydrothermal: Pertaining to hot water, the actions of hot water or the products produced by the actions of hot water. Hydrothermal Deposits: Mineral deposits that are formed by the actions of hot water or gases associated with a magmatic source. Hydrothermal Metamorphism: Alteration of rock by hot waters or gases associated with a magmatic source. Hydrothermal Vein: A deposit of minerals precipitated in a fracture by the actions of hot water or gases associated with a magmatic source.
General Dictionary of Geology An igneous rock that has an intermediate silica content. Examples are syenite and diorite. Also see entries for I acidic, basic and ultrabasic rocks. Intrusion: A igneous rock body that formed from magma that forced its way into, through or between subsurface rock units. Igneous Rock: A rock formed by the crystallization of magma or lava.
Intrusive: Igneous rocks that crystallize below Earth's surface. Ignimbrite: An igneous rock formed by the lithification of ash flow or Ion: pyroclastic flow deposits. An atom or group of atoms that have gained or lost one or more electron and as a result has an electrical charge. Impermeable Layer: A layer of rock, sediment or soil that does not allow water Ionic Bond: to pass through. This could be caused by a lack of pore space or pore spaces that are so small that water A chemical bond formed by the electrostatic attraction molecules have difficulty passing through.
Infiltration: Iron Formation: The movement of surface water into porous soil. A layered deposit of chemical sedimentary rocks containing at least 15 percent by weight iron in the form of sulfide, oxide, hydroxide, or carbonate minerals. Injection Well: A well that is used to force a fluid into the ground. The Isograd: injection could be done for disposal or to place the fluid such as natural gas into a subsurface reservoir.
A line on a map that represents a specific degree of metamorphism. Rocks on one side of the line have been subjected to a greater level of metamorphism and on the Interior Drainage: other side of the line a lower level of metamorphism. A system of streams that flow into a landlocked basin and evaporate. Isostasy: A condition of gravitational balance similar to floating in Intermediate Rock: which a mass of lighter crustal rocks are buoyantly supported from below by denser mantle rocks.
The crustal rocks above subside into the mantle until they have displaced an adequate amount of mantle material to support them. General Dictionary of Geology Isotope: One of several forms of an element. These different forms have the same number of protons but varying numbers of neutrons.
They are frequently formed at the same time interval from a common process. Jolly Balance: Jade: A spring balance used in the determination of specific gravity. A translucent gemstone consisting of either jadeite or nephrite that is typically green in color. Jade is a very durable stone and is used for a variety of jewelry and ornamental objects. Typically cut in the cabochon shape or Juvenile Water: carved. Water that is new to the hydrologic cycle. Brought to Earth's surface through volcanic eruptions.
Jadeite: A high pressure clinopyroxene that is frequently carved and polished as a gemstone. Jasper: A variety of colored chert, typically red or green and often found in association with iron ores. Jasper is frequently used as a gemstone or in the production of ornaments. Jet: A variety of coal that is frequently cut and polished for jewelry or ornaments. Jetty: A human made structure built at right angles to a coastline and extending into the water.
Jetties are built to protect an area of shoreline from the effects of currents, erosion or deposition. Joint: A fracture in rock along which there has been no displacement. General Dictionary of Geology A variety of peridotite that is found in volcanic pipes which are thought to be intrusions from the upper mantle.
Many K diamond deposits are found in kimberlite pipes. Knickpoint: An abrupt change in slope. A point on a stream profile where a change in gradient occurs. This could be caused Karst: by a change in underlying bedrock or bedrock structure.
A landscape that is characterized by the features of solution weathering and erosion in the subsurface. These Knob: features include caves, sinkholes, disappearing streams and subsurface drainage. A small hilltop that is round in shape. Kerogen: Solid organic substances frequently found in shales. The organic component of an oil shale. Kettle: A depression formed in glacial deposits when a buried block of ice, left behind by a retreating glacier, melts.
Kettle Lake: A lake that forms in a kettle. Also referred to as potash feldspar. Kilobar: A unit of pressure equal to bars the mean atmospheric pressure at meters above sea level is one bar. Lava Tube: A tunnel below the surface of a solidified lava flow, formed when the exterior portions of the flow solidify and the Laccolith: molten internal material is drained away.
An igneous intrusion that has been forced between two layered rock units. The top of the intrusion is arched upwards and the bottom of the intrusion is nearly flat. Leaching: The removal of soluble constituents from a rock or soil by moving ground water or hydrothermal fluids. Lahar: A mudflow composed of water and volcanic ash. Lahars are very dangerous because they can occur suddenly and travel at A fault with horizontal movement. If you are standing on great speeds. Laminar Flow: A state of uniform flow within a fluid in which the moving Levee: particles travel along parallel paths compare with Turbulent Flow.
A long continuous ridge built by people along the banks of a stream to contain the water during times of high flow. Natural levees can also be built along the banks of a stream.
When the flood water decelerates upon leaving Landslide: the channel, sediments quickly drop out of suspension and build a ridge over time. A downslope movement of rock and soil over a failure surface and under the influence of gravity. Slumps, earthflows, debris flows and debris slides are examples. Limb: One side of a fold. The dipping rock units between the Lapilli: crest of an anticline and the trough of a syncline. Volcanic rock materials which are formed when magma is ejected by a volcano.
Typically used for material that ranges between 2 and 64 millimeters in diameter. Lateral Moraine: An accumulation of till along the sides of a valley glacier that is produced by ice action.
A fault, line of oriented parallel to the direction of the wind. Longitudinal Profile: Lithification: A cross section of a stream or valley beginning at the source and continuing to the mouth.
These profiles are The processes through which sediments are converted drawn to illustrate the gradient of the stream. Longshore Current: Lithology: A flow of water parallel to a coastline that is caused by waves striking the coast at an oblique angle.
The study and description of rocks, including their mineral composition and texture. Also used in reference to the compositional and textural characteristics of a rock. Longshore Drift: The movement of sediment along a coastline caused by Lithosphere: waves striking the coast at an oblique angle. The waves wash sediment particles up the beach at an oblique angle The rigid outer shell of the earth which includes the crust and the swash back to the sea carries the particles down and a portion of the upper mantle.
Lithospheric Plate: Lowland: A large slab of the lithosphere that can be moved by convection current motion within the mantle. A relatively flat area in the lower levels of regional elevation.
Includes suspended materials, dissolved A zone within the upper mantle where seismic wave materials and materials moved along Earth's surface.
Also velocities are relatively low. This zone is located about 35 see: bed load, dissolved load, suspended load. Lode: Luster: A rich accumulation of minerals in solid rock. Frequently in The manner in which light reflects from a mineral surface. See placer of luster. M Magnetic North: The direction that a compass points.
The location where Earth's magnetic field dips vertically into the Earth. Also used in reference to the the north magnetic pole becomes the south magnetic pole magmas from which these rocks crystallize. Mafic rocks and vice versa. Also known as geomagnetic reversal or are generally rich in iron and magnesium.
Basalt and polarity reversal. Earth's magnetic field has reversed many gabbro are examples of mafic rocks. See felsic to times in the past and the time intervals between these contrast. Magma: Magnetic Stratigraphy: Molten rock material that occurs below Earth's surface.
The correlation of rock units and study of Earth's history using magnetic events and magnetic epochs as a time reference. Magma Chamber: A full or emptied magma reservoir in the shallow portion Magnetometer: of the lithosphere. Author : Klaus K. Glossary of Geology Book Review:. Neuendorf,James P. Jr Mehl,Julia A. Glossary of Geology and Related Sciences. A Dictionary of Geology and Earth Sciences. Glossary geology speller. Glossary geology speller Book Review:. Mehl,Julia A. Dictionary of Geological Terms.
Dictionary of Geological Terms Book Review:. Glossary of Geology and Related Science. Supplement to the Glossary of Geology and Related Science. A Dictionary of Geology.
0コメント