Geology term

On this page you will find short definitions of words used in Geology which non professionals may not know.


 * alluvium - deposits of sand or clay that settled out of running water.
 * aqueous rock - A sedimentary rock laid down by water or laid down in water.


 * bathymetry - the measurement of depth of water in lakes and oceans.
 * breaching event - when a lake of water is formed by a dam of earth, rock or ice, sometimes water rises to the point that a small stream starts to cut a larger exit channel. This allows more water to flow, cutting a larger channel and resulting in a sudden very large flow of water, often draining the whole lake in a short time.
 * breccia - (pron. BREH chee ya, or BREH shee ya) a kind of rock made up of angular pieces of rock held together by a cementing material. . Compare conglomerate.


 * channelized flow -
 * clastics - a kind of rock made mostly of broken fragments of other rocks that were carried somehow some distance from the original rocks. The commonest "clastics" are sandstone and shale.
 * clay - small sized soil particles less than 0.002 mm in diameter. Compare soil
 * cliff-sapping - the process where erosion of softer layers at the base of a cliff causes the collapse of large masses of overlying material.
 * conglomerate - a kind of rock made up of smooth, rounded stones held together by a cementing material. Compare breccia.
 * continental shelf - the edge of a continent that is under ocean water. The continents slope very gradually out to sea until you reach the sudden dropoff called the continental slope.
 * cuesta - an asymmetrical ridge with a long, gentle slope on one side and a steep or cliff-like face on the other.


 * endobiontic - a kind of plant or sea animal which lives in bottom sediments.
 * epeiric sea - a sea on the continental shelf or within a continent, also called an inland sea, or an epicontinental sea.
 * epigenesis - change in the minerals of a rock after it is formed because of external (usually surface) influences.
 * erosion - the process of wearing down and transporting away material of planetary crust by natural agencies such as wind, water, ice, and corrosion.


 * facies - a body of rock with specified characteristics. It can refer to one rock unit or several, and sometimes refers more to the characteristics of the rock unit than to the rock itself.
 * biofacies - rock characteristics that depend on the fossil content (biological origins).
 * ichnofacies - a characteristic assemblage of trace fossils.
 * lithofacies - rock characteristics such as grain size and mineral content, etc.


 * fluvial - having to do with rivers, streams, or creeks.
 * flysch - a sedimentary rock that alternates sandstone and shale in layers, usually with large rocks at the base and gradually finer materials (like sandstone and shale) as you move upwards.
 * fossil - a remnant or trace of an organism from the past, typically embedded and preserved in sedimentary rock. There are three types of fossils: imprints, casts, and mineralization.
 * endichnia - traces of animal activity (e.g. worm burrows) inside the casting medium, not touching the upper surface
 * fossiliferous - containing fossils
 * unfossiliferous - not containing fossils
 * hypichnia - traces of animal activity that touch the lower surface (sole) of the casting medium. They may look like a ridge or groove.


 * geochronology
 * hydrologic basin


 * igneous - rocks that were melted and have now solidified.
 * isochron -


 * lacustrine - having to do with lakes
 * lake -
 * bayou
 * oscillating lake


 * limestone -


 * meander -
 * enclosed meander -
 * incised meander - a sinuous, relatively deep, valley or canyon cut by a river.
 * stream meander -


 * monocline -
 * mudstone - sedimentary rock with particles smaller than 0.0625 mm. Sometimes called siltstone if the particles are on the large size, or claystone if smaller. Shale is a mudstone that splits easily into layers.


 * orogenic


 * sand - large size soil particles, 2 - 0.05 mm in diameter. See soil
 * sandstone - a sedimentary rock composed mainly of grains of sand.
 * silt - medium size soil particles, 0.05 - 0.002 mm in diameter. See soil
 * soil texture - Soil texture is the proportion of sand, silt and clay particles. The particle sizes are determined by diameter; sand being 2 - 0.05 mm, silt 0.05 - 0.002 mm and clay is less than 0.002 mm.
 * strata - the plural of the word "stratum" which generally means the same thing as "layer" or "level". In geology, a stratum is a layer of sedimentary rock that generally has the same sediment throughout and normally has other layers above and below it.
 * stream -
 * braided stream - a stream that forms shallow branching and reuniting channels because the speed or quantity of water cannot carry its load of sediment.
 * intermittent stream -
 * underfit stream - a stream that appears too small to have eroded the valley or canyon through which it presently flows.


 * tectonic
 * turbidity current - a muddy current flowing downhill on the floor of a lake or ocean. Because the suspended sediments make the water in the current heavier, it moves swiftly down and spreads out when it comes to a flat part of the bottom. A Turbidity Current can be started by storm waves, earthquakes, tsunamis, very muddy rivers, and by sediment piling up.
 * distal turbidites - the deposit of sediment farthest from the source of the turbidity current.
 * proximal turbidites - the deposit of sediment nearest the source.


 * Walther's law - a statement, used to infer how sedimentary deposits were laid down. It says that generally, if there is no break in the sedimentary sequence, the deposit must have been formed by environments that were side by side. Creationists and other geologists dispute many applications of the law.

Related References

 * Investigation of Several Alleged Paleosols in the Northern Rocky Mountains. Part II: Additional Data and Analysis by Peter Klevberg, Richard Bandy, Michael Oard. CRSQ 44(2):94-106, Fall, 2007.
 * Kanab Canyoun, Utah and Arizona: Origin Speculations by Emmett Williams, Robert Goette, John Meyer. CRSQ 34(3):162-172, December, 1997.
 * Dougherty Gap:Evidence for a Turbidity Current Paleoenvironment
 * Stone Mountain Georgia: A Creation Geologist's Perspective