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Florida Geological Survey - Geology Topics

Glossary of Geologic Terms

  • amorphous - having no definite shape or boundaries; a term applied to rocks and minerals that have no definite crystalline structure.


  • Archaic Period - 8,000 BC - 500 BC, the period after which paleoindian people settled into permanent residence in Florida.


  • aquifer - a water-saturated zone of rock below the Earth's surface capable of producing water in useful quantities, as from a well.


  • artifacts - objects made by humans, such as stone tools; studied by geoarcheologists.


  • basalt - a dark-colored, fine-grained, igneous rock formed from molten rock that flowed onto the Earth's surface.


  • basement rocks or basement - refers to very deep, ancient rocks that underlie the continents and oceans.


  • basin - a large area of lower elevation than surrounding areas.


  • brachiopods - marine invertebrate animals in which the soft parts are enclosed by two shells, called valves.


  • bryozoa - tiny marine animals that build colonies with their shells.


  • calcareous - containing or primarily made of the mineral calcite (calcium carbonate, CaCO3).


  • Cenozoic Era - the latest of the four eras into which geologic time, as recorded by the stratified rocks of the Earth's crust, is divided; it extends from the end of the Mesozoic Era to and including the present, or Recent.


  • clastics - consisting of fragments of rocks or organic structures: gravels, sands, silts, and clays.


  • confined aquifer - a zone of subsurface water-bearing rocks that contain water under pressure due to zones above and below it having low permeability, which restrict the flow of water into and out of it. An artesian aquifer is a type of confined aquifer.


  • coquina - soft, porous limestone composed of broken shells, corals, and other organic debris.


  • coral - small, colonial, bottom-dwelling, marine animals that secrete external skeletons of calcium carbonate (calcite). The colonies they create with their skeletons can make enormous reef-complexes, such as the Florida Keys, the Australian Great Barrier Reef, and many coral islands in the Pacific Ocean, and other oceans.


  • crinoid - a marine animal consisting of a cup or "head" containing the vital organs, numerous radiating arms, an elongate, jointed stem, and a root-like attachment to the sea bottom while the body, stem and arms float.


  • dolomite - CaMg(CO3)2, a rock-forming, carbonate mineral, very common in Florida.


  • dolostone - a term for a sedimentary rock composed of fragmental, concretionary, or precipitated dolomite of organic or inorganic origin.


  • echinoid - one of a group of invertebrate marine animals, many of which have spines; popularly called "sand dollars, sea biscuits, or sea urchins."


  • ecosystem - a community of organisms, including humans, interacting with one another and the environment in which they live.


  • environment - all of the external factors that may act on an organism, either plant or animal, or on a natural community. For example: gravity, air, wind, sunlight, moisture, temperature, soil, and other organisms are some of the environmental factors that may affect the life processes of an organism.


  • era - a large division of geological time consisting of two or more geological periods.


  • erosion - the natural processes of weathering, disintegration, dissolving, and removal and transportation of rock and earth material, mainly by water and wind, as well as by ice.


  • exotic terrain - a terrain that has undergone significant motion or travel with respect to the stable continent to which it is accreted. Florida could be considered an exotic terrain with respect to the North American continent, because it is thought to have once been part of northwestern Africa.


  • fault - a break in the Earth's rocks along which there has been displacement of the rocks. Displacement may vary from inches to miles.


  • floodplain - land next to a stream or river that is flooded during high-water flow.


  • foraminifera - small, one-celled, mostly marine animals which secrete shells of calcium carbonate or build them of cemented sand grains. They range in size from microscopic to a few centimeters across. They occur in such quantities that their fossil shells make up almost all of certain limestone rocks in Florida and other places in the world.


  • formation - a rock unit possessing distinctive characteristics, such as mineral content, fossils, or color, that allows it to be distinguished from adjacent rock units.


  • fossil - remains or traces of prehistoric animals or plants. The most common types consist of bones, carbon films, shells, molds, casts, and petrified wood.


  • fuller's earth - a type of clay that is commercially valuable and widely used as cat litter and as a dispersant in insecticides.


  • geology - the study of the planet Earth, the materials of which it is made, processes that affect these materials, the changes that the Earth has undergone in the past and the changes it is currently undergoing.


  • geomorphology - the branch of geology which deals with the form of the Earth, the configuration of its surface, and the changes that take place in land forms over time.


  • glacier - a large body of ice with definite lateral limits, which moves in a downslope direction due to its great mass, as in Alaska.


  • granite - a light-colored, coarse-grained, igneous rock formed from magma that cooled below Earth's surface.


  • groin - a shore-protection structure that projects away from shore, usually made of rocks, wood pilings, or sheet metal.


  • heavy minerals - a suite of accessory minerals of a sedimentary rock or sediments having specific gravities greater than 2.9. The most common heavy minerals found in Florida are: rutile, ilmenite, leucoxene, staurolite, zircon, kyanite, sillimanite, tourmaline, spinel, topaz, corundum, and monazite.


  • karst - a type of terrain characterized by sinkholes, caves, disappearing streams, springs, rolling topography, and underground drainage systems. Such terrain is created by ground-water dissolving limestone.


  • kaolin - a rock composed essentially of clay minerals of the kaolinite group, most commonly kaolinite. High purity deposits of this mineral are valuable for making quality ceramic products.


  • landfill - a method of waste disposal wherein materials are buried. Present environmental protection laws require the burial sites to be constructed with impermeable barriers, such as clay or plastic liners, to prevent hazardous wastes or pollutants from escaping to the surrounding soils or air.


  • lava - molten rock that flows onto the surface from a volcano or fissure.


  • limestone - a bedded sedimentary deposit consisting chiefly of calcium carbonate. Limestone is an important and widely distributed of the carbonate rocks; it is the consolidated equivalent of limy mud, calcareous sand, or shell fragments.


  • lithify - to turn to rock. Several geological processes can operate to consolidate loose sediments into hard rocks. Pressure from thick sequences of overlying sediments can cause lithification; for example, loose sand turned into sandstone. Chemical changes caused by ground water can cement loose sediments into hard rocks; for example, loose sea shells and sand cemented into coquina limestone.


  • magma - molten rock generated within the Earth.


  • magnesium - a metal (Mg), which, when chemically combined with calcium carbonate, Ca(CO3), forms the mineral dolomite, CaMg(CO3)2.


  • marine - refers to sea water, to sediments deposited in sea water, or to animals that live in the sea, as opposed to fresh water.


  • mercury - a heavy, silver-white, metallic element, the only metal that is liquid at room temperature; also called quicksilver. A virulent poison, dangerous to handle and work with.


  • mollusks - invertebrate animals, including a variety of marine, fresh water and terrestrial snails; clams, oysters, mussels, scallops; squids, octopus, pearly nautilus, as well as the many extinct varieties.


  • paleoindians - archeological term referring to native American cultures prior to 8,000 BC; prehistoric inhabitants of Florida.


  • paleontology - the science that deals with the life of past geological ages, based on the study of fossils.


  • peat - a dark brown or black, organic residuum produced by the partial decomposition and disintegration of mosses, trees, and other plants that grow in marshes or other wet places. Peat deposits form when the rate of accumulation of plant matter exceeds the rate of destruction by weathering or organisms. One of the largest peat deposits in the world is in the Everglades.


  • percolation - movement of water through the pores or voids in rock or soil.


  • period - one unit of geological time into which Earth history is divided. A period is a subdivision of an era.


  • permeability - a measure of a porous material's ability to allow fluids or gases to flow through its pores. An important property of rocks that determines how much and how rapidly fluids or gases can move through them; for example, how much water can be pumped from an aquifer (see: porosity).


  • phosphate rock - a sedimentary rock containing calcium phosphate. Florida has some of the most extensive deposits of phosphate rocks in the world. Very important in the manufacturing of fertilizer.


  • plate tectonics - a theory that large "plates" of the Earth's colder, upper crustal rocks are capable of moving slowly (like rafts) on top of deeper, hotter, and more fluid rocks in the mantle. Geologists have identified seven large plates and 11 or more smaller ones on the Earth's surface.


  • Pleistocene Epoch - the earlier of the two epochs comprising the Quaternary period.


  • porosity - a measure of the amount of voids (pores) in a material. An important property of rocks that determines the quantities of fluids or gases they can store; for example, the amount of water an aquifer can store (see: permeability).


  • potable water - water that can be consumed by humans without ill effects. Government agencies have adopted standards of quality that specify limits of chemical constituents in water sources.


  • potentiometric surface - an imaginary surface defined by the level to which water in an aquifer would rise in a well due to the natural pressure in the rocks.


  • precipitate(s) - 1. the process whereby solids are left behind when liquids evaporate; for example, vast deposits of salt were created when ancient seas evaporated. 2. precipitates: the solid materials, themselves. (see: precipitation)


  • precipitation - 1. hydrology: water discharged from the atmosphere in the form of fog, rain, snow, sleet, or hail. 2. chemistry: the process of separating different minerals from a solution by evaporation; for example, salt from sea water.


  • radon - an invisible, odorless, tasteless, radioactive gas that is formed when uranium-238 decays. It can accumulate in buildings, causing potential health hazards.


  • reclamation - the act or process of restoring mined-out lands to a useful state. Also, the industry devoted to the recovery or re-use of waste materials.


  • rift or rifting - refers to the breaking apart of continental plates.


  • saline - salty; sea water or water nearly as salty as sea water.


  • sandstone - a type of sedimentary rock made of sand grains cemented together.


  • scarp - an escarpment, cliff, or steep slope along the margin of a plateau, mesa, or terrace.


  • seismic - pertaining to vibrations in the Earth, such as earthquakes; or to equipment or methods used to create Earth vibrations, such as exploding dynamite in oil exploration.


  • shale - a type of sedimentary rock made of clay particles cemented together and which usually can be made to split into thin slabs (see: slate).


  • shoal - an underwater area covered by shallow water which may endanger boats.


  • siliciclastic - pertaining to clastic, non-carbonate rocks that are almost exclusively silicon-bearing, either as forms of quartz or as clays. Examples of Florida siliclastics are loose quartz sands, silts, or clays.


  • siltstone - a sedimentary rock made of silt-size particles cemented together.


  • sinkhole - a depression in the land surface, usually round or funnel-shaped, that connects with a subterranean passage created by solution of limestone rocks by circulating ground water. Sinkholes may also form by collapse of a cavern roof.


  • slate - a type of metamorphic rock created from shale, and is usually harder than shale.


  • solution feature - a topographic or geomorphic feature of a landscape that was formed as a result of water dissolving rocks, usually limestone or dolostone, such as: sinkholes, caves, disappearing streams, springs, and sinkhole lakes.


  • spreading center - a fissure separating continental plates, created when the plates move apart.


  • stratigraphy - the branch of geology that studies the formation, composition, sequence, and correlation of the layered rock-sequences that make up the Earth's crust.


  • structural geology - the branch of geology concerned with the deformation of rock bodies and with interpreting the natural forces that caused the deformations.


  • subduction - the geologic process whereby one continental plate slides under another and is gradually consumed in the Earth's interior.


  • suture - a line or mark of splitting open or of joining together, such as where parts of two continental masses collide and merge.


  • swale - a shallow depression in the land's surface which may be filled with water. In karst terrain it may indicate an incipient sinkhole forming.


  • tectonic - pertaining to the rock structures and external forms resulting from the deformation of the Earth's crust.


  • test - a hard covering or supporting structure of some invertebrate animals; a shell.


  • transmissivity - a property of an aquifer which defines the rate at which water moves through it.


  • transpiration - part of the life process of plants by which water vapor escapes from leaves and enters the atmosphere.


  • trilobites - ancient arthropods having a hard outer skeleton, and which became extinct over 200 million years ago.


  • unconfined - in reference to aquifers, it describes a condition whereby water-bearing rocks are at atmospheric pressure, i.e., water table conditions.


  • unconformity - a surface of erosion or non-deposition that separates younger strata from older rocks. It represents a missing span of time from the rock record.


  • vertebrate - refers to animals that have a backbone.


  • vug- A cavity, void or large pore in a rock that is commonly lined with mineral precipitates.


  • vuggy-see vug above.

  • water table - in an aquifer, it is the upper surface of the zone of saturation under unconfined conditions; water in the rocks is at atmospheric pressure.

Other glossary resources

Last updated: November 10, 2014

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