Glossary Database

Select a Letter to view the associated terms.

 Glossary Term: 


 C horizon  The lowest zone of soil consisting of partly decomposed bedrock underlying the B horizon. It grades downward into fresh, unweathered bedrock.
 Cache  A collection of items kept in one location.
 Caecum  refers to a sack or pouch connected to the intestine of mammals. A caecum is usually found in herbivorous mammals and they house bacteria, which help digest the plant material that the mammal eats.
 Calcar  1. a spur or spurlike process projecting from the leg of a bird. 2. a bony or cartilaginous process on the heel bone of bats, which helps to support the portion of the wing membrane lying between the legs (Morris 1992).
 Calcite  A common rock-forming mineral composed of calcium carbonate (CaCO3).
 Caldera  A large, more or less circular depression or basin associated with a volcanic vent. Its diameter is many times greater than that of the included vents. Calderas are believed to result from subsidence (or collapse) and may or may not be related to explosive eruptions.
 Calving  A process in which large chunks of ice break off from tidewater glaciers (one that terminates in a body of water), to form icebergs.
 Cambium  In vascular plants, a layer of meristematic tissue that gives rise to the xylem, phloem and (in woody plants) bark (Morris 1992).
 Cambrian  The earliest period of the Paleozoic era, from 570 to 500 million years ago. View timeline of geologic events.
 Capacity  The maximum quantity of sediment a given stream, glacier, or wind can carry under a given set of conditions.
 Cape  A piece of land projecting into water
 Capital  City that is the seat of government.
 Capitol  The building where the government meets.
 Carapace  The dorsal component of the shell in turtles, usually composed of both epidermal and bony plates (Peters 1964).
 Carbon 14  A radioactive isotope of carbon. Its half-life is 5730 years. Synonymous with radiocarbon.
 Carbonaceous  Containing carbon.
 Carbonate mineral  A mineral formed by the bonding of carbonate ions (CO32-) with positive ions. Examples: calcite (CaCO3), dolomite [CaMg(CO3)2].
 Carbonate rock  A rock composed mostly of carbonate minerals. Examples: limestone, dolomite.
 Carbonation (carbonized)  A process in which a fossil forms when the volatile components of the soft tissues are driven off, leaving behind a thin film of carbon.
 Carnivorous  Of animals, meat eating (Morris 1992). It refers to mammals that are predominantly meat eaters. A good example is a bobcat and as well as other members of the cat family (Felidae), or members of the weasel family (Mustelidae).
 Carrion  The decaying flesh of a dead body, esp. when regarded as food for scavenging animals (Guralnik 1970)
 Castor  scent from the gland of a beaver
 Catastrophism  The belief that geologic history consists of major catastrophic events involving processes that were far more intense than any we observe now. Contrast with uniformitarianism.
 Cation  A positively charged ion.
 Caudal autotomy  Breakage and loss of the tail in a spontaneous and intrinsic fracturing across an autotomy plane by convulsive contractions of tail muscle initiated by the animal (Peters 1964).
 caudal fin  Tail fin.
 caudal peduncle  The posterior stem of a fish's body from the base of the anal fin to the caudal fin.
 Cave  A naturally formed subterranean open area, chamber, or series of chambers, commonly produced in limestone by solution activity or in basalt flows as lava tubes.
 Cellulose  a polysaccharide that is the major complex carbohydrate in plants, especially their cell walls (Morris 1992).
 Cement  Minerals precipitated from groundwater in the pore spaces of a sedimentary rock and binding the rock's particles together.
 Cementation  The process by which clastic sediment is lithified by precipitation of mineral cement, such as calcite cement, among the grains of the sediment.
 Cenozoic  1. the most recent geologic era, extending from the beginning of the Tertiary period (about 65 million years ago) to the present. 2. referring to the rock formed during that time (Morris 1992).
 Cenozoic Era  The latest of the four eras into which geologic time is subdivided; 65 million years ago to the present. View timeline of geologic events.
 Chalcedony  A general term for fibrous cryptocrystalline quartz. It is common in petrified wood, and fills open spaces in many volcanic rocks. If colorful, it may be called agate.
 Chalk  A variety of limestone composed of shells of microscopic oceanic organisms.
 Chaparral  1.)A type of dry habitat consisting of short shrubs and scrubby oaks.2.) a type of vegetation characterized by low, thickly growing evergreen shrubs or bushes with flat, broad leaves and interlacing branches; the typical natural growth of many areas with a climate of cool moist winters and long dry summers, as in much of the western United States (Morris 1992).
 cheek  Area between the eye and preopercular bone.
 Chemical weathering  Chemical reactions that act on rocks exposed to water and the atmosphere so as to change their unstable mineral components to more stable forms. Oxidation, hydrolysis, carbonation, and direct solution are the most common reactions.
 Chert  A sedimentary rock composed of granular cryptocrystalline silica.
 Chevron  A shape of a mark, much like >, found on some caterpillars and butterflies.
 Chinook  Oncorhynchus tshawytscha This is Alaska's state fish and is one of the most important sport and commercial fish native to the Pacific coast of North America. These fish are also known as king salmon, as well as spring, quinnat, tyee, tule and blackmouth. They are the largest of the Pacific salmon.
 Chironomids  minute, long-legged nonbiting two-winged flies with piercing mouthparts; the aquatic larvae of various species are green, blue, yellow, colorless, or red type called bloodworms (Morris 1992).
 Chlorite  A group of platy, monoclinic, usually greenish minerals. They are widely distributed in low grade metamorphic rocks. Associated with and resemble the micas.
 Chronological  Arrangement of events in the order of occurrence.
 Chrysalis  The smooth outer covering of a butterfly pupa. Often, the term chrysalis is used to refer to the pupa itself.
 Cinder  A fragment of volcanic ejecta from 0.5 to 2.5 cm in diameter.
 Cinder cone  1. A steep, cone-shaped hill composed of volcanic fragments erupted from a vent. The rock fragments, often called cinders or scoria, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and then cooled quickly. 2. Cone-shaped hill formed by accumulation of cinders and other pyroclastic material around a volcanic vent.
 Circadian  refers to a 24 hour period. A circadian cycle would be a 24 hour period and a circadian rhythm would refer to the rhythm of activity of a specific mammal.
 circuli  Fine bony ridges on fish scales which form concentric rings.
 Cirque  An amphitheater-shaped depression at the head of a glacial valley, excavated by ice plucking and frost wedging.
 Clastic  1. Pertaining to fragments (such as mud, sand, and gravel) produced by the mechanical breakdown of rocks. 2. A sedimentary rock composed chiefly of consolidated clastic material.
 Clastic texture  The texture of sedimentary rocks consisting of fragments of minerals, rocks, and organic skeletal remains.
 Clasts  An individual constituent, grain, or fragment of sediment or rock, produced by mechanical or chemical disintegration of a larger rock mass.
 Clay  Sedimentary material composed of fragments with a diameter of less than 1/256 mm. Clay particles are smaller than silt particles.
 Clay minerals  A group of hydrous silicates formed by weathering of minerals such as feldspar, pyroxene, or amphibole. Silicate tetrahedra are arranged in sheets.
 Cleavage  A mineral's tendency to break in a preferred plane in a crystal lattice.
 Climate  The long-term average of precipitation, temperature, and wind direction and orientation.
 Climatology  The study of climates.
 Cloaca  The common chamber into which the intestinal, urinary and reproductive ducts discharge their contents (Peters 1964).
 Clutch  A nest of eggs or a brood of newly hatched birds (Morris 1992)
 Cobble  A rock fragment with a diameter between 6.4 cm (about the size of a tennis ball) and 25.67 cm (about the size of a volleyball). Cobbles are larger than pebbles but smaller than boulders.
 Cocoon  A silken sturcture that encloses the pupa of some butterflies and skippers. Most butterfly pupae are naked, and what you see is eally their skin!
 Columnar jointing  A system of fractures that splits a rock body into long prisms, or columns. It is characteristic of lava flows and shallow intrusive igneous flows.
 Compaction  Tighter packing of sedimentary grains causing weak lithification and a decrease in porosity, usually from the weight of overlying sediment.
 Compass  An instrument with a swinging magnetic needle pointing north for showing direction.
 Competence  The maximum size of particles that a given stream, glacier, or wind can move at a given velocity.
 Composite volcano  A large volcanic cone built by extrusion of ash, lava, and shallow intrusions. Synonymous with stratovolcano.
 compressed  Flattened from side to side.
 Compression  A system of stresses that tends to reduce the volume of, or shorten a substance.
 Concave  Curving inward like the inside of a hollow ball.
 Concentric  Circular or spheroidal.
 Conchoidal fracture  A type of fracture that produces a smooth, curved surface. It is characteristic of quartz and obsidian.
 Concordant  Pertaining to an igneous intrusion that is parallel to the layering of country rock.
 Concretion  A spherical or ellipsoidal nodule formed by accumulation of mineral matter after deposition of sediment.
 Condensation  The change of a gas to either the liquid or solid state.
 Conduction  Transmission of heat energy by the impact of moving atoms. Contrast with convection.
 Cone  A solid with a circle for its base and a curved surface tapering to a point.
 Cone of depression  A conical depression of the water table surrounding a well after heavy pumping.
 Cones  visual receptors of the vertebrate retina that can distinguish different wavelengths of the visual spectrum and is especially sensitive to bright light (Morris 1992).
 Confined aquifer  An aquifer in which the confining geologic formation exists on top of aquifer causing aquifer pressure to be (usually) greater than atmospheric pressure. See also: artesian water.
 Congener  An organism that is a member of the same genus as another animal (Morris 1992).
 Conglomerate  A coarse-grained sedimentary rock composed of rounded fragments of pebbles, cobbles, or boulders.
 Coniferous  of or relating to the conifers (Morris 1992).
 Consolidated  Combined into one unit. Taking loose, soft, or liquid earth materials and making firm such as the cooling of lava or the cementation of a sand.
 Contact  The surface separating two different rock bodies.
 Contact metamorphism  Metamorphism due to heat and fluids from an intruding magma.
 Continent  A large landmass composed mostly of granitic rock. Continents rise abruptly above the deep-ocean floor and include the marginal areas submerged beneath sea level.
 Continental accretion  The growth of continents by incorporation of deformed sediments, arc magmas, and accreted terranes along their margins.
 Continental crust  The type of crust underlying the continents, including the continental shelves. The continental crust is commonly about 35 to 70 km thick. Its density is typically 2.7 g/CM3, and the velocities of primary seismic waves traveling through the crust are less than 6.2 km/sec. Contrast with oceanic crust.
 Continental divide  A drainage divide that separates streams flowing toward opposite sides of a continent.
 Continental drift  The theory that the continents move in relation to one another.
 Continental glacier  A thick ice sheet covering large parts of a continent. Present-day examples are found in Greenland and Antarctica.
 Continental margin  The zone of transition from a continent to the adjacent ocean basin. It generally includes a continental shelf, continental slope, and continental rise.
 Continental rise  The gently sloping surface located at the base of a continental slope. See abyssal plains diagram.
 Continental shelf  The submerged margin of a continental mass extending from the shore to the first prominent break in slope, which usually occurs at a depth of about 120 m. See abyssal plains diagram.
 Continental slope  The slope that extends from a continental shelf down to the ocean deep. In some areas, such as off eastern North America, the continental slope grades into the more gently sloping continental rise.
 Contour interval  The contour interval on a topographic map is the amount of vertical distance between contour lines. For example, a forty-foot contour interval means that each contour line represents a change in elevation of forty feet.
 Contour line  A line drawn on a map representing points with equal value; on a topographic map contour lines represent points of equal elevation.
 Convection  Transmission of heat energy by the rise of buoyant hot material and sinking of cold material.
 Convection cell  The space occupied by a single convection current.
 Convergent  To come together, as in two lithosphere plates moving toward each other until they collide or one submerges.
 Convergent plate boundary  A plate boundary where two lithospheric plates collide head-on. Convergent plate boundaries are sites of considerable geologic activity and are characterized by volcanism, earthquakes, and crustal deformation. See also: subduction zone.
 Convex  Curving outward like the surface of a sphere or ball; the opposite of concave.
 Copernican Period  The period of lunar history during which rayed craters, such as Copernicus, and their associated rim deposits were formed (from 2 billion years ago to the present).
 Coprophagy  the act of eating feces (Morris 1992).
 Copulation  The act of sexual coupling by male and female (Morris 1992).
 Coquina  A limestone composed of an aggregate of shells and shell fragments.
 Coral  A bottom-dwelling marine invertebrate organism of the class Anthozoa.
 Core  he central part of Earth below a depth of 2900 km. The core is thought to be composed mostly of iron, in contrast to the overlying mantle of silicate rock.
 Coriolis effect  The tendency of moving fluids (such as air and water) on Earth's surface to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Caused by Earth's rotation.
 Corridor  a connection between adjacent land areas that allows the passage of fauna form one area to the other (Morris 1992).
 Costal fold  The fold along the leading edge of the forewing of a butterfly. It often contains scent scales used to attract other butterflies.
 Costal grooves  The deep, vertical groove on the side of a salamander's body, indicating the position of a rib (Peters 1964)
 Country rock  1. A general term for rock surrounding an igneous intrusion. 2. The rock enclosing on igneous intrusion or mineral deposit.
 Covalent bond  A chemical bond in which electrons are shared between different atoms so that none of the atoms has a net charge.
 Crater  An abrupt circular depression formed by extrusion of volcanic material, by collapse, or by the impact of a meteorite.
 Craton  The stable continental crust, including the shield and stable platform areas, most of which have not been affected by significant tectonic activity since the close of the Precambrian Era.
 Creep  The imperceptibly slow down-slope movement of material as a result of gravity.
 Cremaster  A structure, much like a hook, on the rear of a chyrsalis, which helps to secure the chrysalis to a leaf, twig, etc.
 Crepuscular  Active or primarily active at the time around dawn or dusk (Morris 1992).
 Cretaceous  The final period of the Mesozoic Era from approximately 135 to 65 million years ago. View timeline of geologic events.
 Crevasse  1. glacial geology A deep crack in the upper surface of a glacier. 2. natural levee A break in a natural levee.
 Cross stratification  Arrangement of beds inclined to the original horizontal surface upon which the sediment accumulated.
 Cross-bedding  Stratification inclined to the original horizontal surface upon which the sediment accumulated. It is produced by deposition on the slope of a dune or sand wave.
 Crosscutting relations  The principle that a rock body is younger than any rock across which it cuts.
 Crown  The top part of the head (Morris 1992).
 Crust  The outermost compositional layer, or shell, of Earth (or any other differentiated planet). The crust consists of low density materials compared to the underlying mantle. Earth's crust is generally defined as the part of the Earth above the Mohorovicic discontinuity. It represents less than 1% of Earth's total volume. See also: continental crust, oceanic crust.
 crustaceans  A group of usually aquatic invertebrates that have jointed appendages.
 Crustal warping  Gentle bending (up-warping or downwarping) of the crust.
 Cryptocrystalline texture  The texture of rocks composed of crystals too small to be identified with an ordinary microscope.
 Crystal  A solid, polyhedral form bounded by naturally formed plane surfaces resulting from growth of a crystal lattice.
 Crystal face  A smooth plane formed by growth of the surface of a crystal.
 Crystal form  The geometric shape of a crystal. Example cubic, prismatic.
 Crystal lattice  A systematic, symmetrical network of atoms within a crystal.
 Crystal structure  The orderly arrangement of atoms in a crystal.
 Crystalline texture  The rock texture resulting from simultaneous growth of crystals.
 Crystallization  process by which matter becomes crystalline from a gaseous, fluid, or dispersed state
 ctenoid scales  Fish scales with teeth on surface making them feel rough to touch.
 Cuesta  An elongate ridge formed on the tilted and eroded edges of gently dipping strata.
 Current  The concentrated flowing of water, air, or other fluid.
 Cusps  one of the protuberances on or near the masticating surface of a tooth (Morris 1992).
 Cycloid scales  1.) fish scales without teeth on surface and smooth to touch. 2.) Scale resembling a circle (Morris 1992).