Glossary of terms
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A-B | C-D | E-F | G-H | I-K | L-N | O-Q | R-T | U-Z | [Sources]

ice age: any of the times when large protions of the earth were covered with glaciers, as in the late Precambrian, in the early Cambrian, and in the Permian. – Ice Age: the most recent such time, during the Pleistocene, when much of the Northern Hemisphere was covered with glaciers. [AHDOS]

icecap: a permanent covering of ice over large areas of land in the polar regions. [AHDOS]

ice cave: a cave having an accumulation of ice throughout the year. The ice forms when the temperatures drops, freezing any water that seeps into the cave. [AHDOS]

ice foot: a belt or wall of ice extending along the coast in arctic regions. [AHDOS]

iceland spar: a transparent, coarsely crystalline variety of calcite, used extensively for optical purposes. [AHDOS]

igneous: produced by solidification from a molten state. Granite is an igneous rock. [AHDOS]

Illinoian: of or having to do with the third glaciation of the Pleistocene in North America, beginning about 230,000 years ago, and lasting about 55,000 years. [AHDOS]

illite: any of a group of hydrous aluminum silicates resembling mica, found in clay. [AHDOS]

illuvial: having to do with or produced by illuviation. [AHDOS]

illuviation: the additon of underlying levels of soil of salts, colloids, and small mineral particles moving downward by chemical or mechanical processes, most common in humid regions. [AHDOS]

ilmenite: a metallic, black mineral consisitng of iron, titanium and oxygen. [AHDOS]

impact crater: a crater produced by the impact of a meteor. [AHDOS]

impactite: a glassy kind of rock formed by partial fusion as a result of the impact of a meteorite on the surface of the earth. [AHDOS]

inclination: an inclined surface, slope, slant; the amoutn of slope or deviation from the horizontal position; tha acute angle between the earth's magnetic field and the horizontal. [AHDOS]

index fossil: the fossil remains of an organism that lived in a particular geologic age, used to identify or date the rock or strata in which it is found. [AHDOS]

indurate: to harden by heat, pressure or cementation. [AHDOS]

influent: losng water by infiltration from the channel to the groundwater table below. [AHDOS]

influx: the point where a river or stream flows into another river, a lake, or the sea. [AHDOS]

inlier: an area or formation of older rocks completely surrounded by a more recent formation. [AHDOS]

interfluve: a region lying between two adjacent rivers or river valleys. [AHDOS]

interglacial: of or occurring in the period between two glacial epochs. [AHDOS]

interlobate: situated between two lobes of a glacier. [AHDOS]

interstadial: of, belonging to, or designating a period within a glacial epoch when the climate becomes temporarily warmer. [AHDOS]

interstratify: to lie as strata between other strata; to deposit between other strata; arrange in alternate strata. [AHDOS]

intratelluric: located or formed far beneath the earth's surface; denoting the period in the formation of eruptive rock just before its appearance on the earth's surface. [AHDOS]

intrazonal: within a zone or region. [AHDOS]

intrusion: the forcing of molten rock into fissures or between strata; the body of molten rockforced in and solidified in place. [AHDOS]

intrusive: forced into fissures or between strata while molten. [AHDOS]

ironstone: any clay, chert or other type of rock that contains iron; iron ore. [AHDOS]

island arc: an arched chain of oceanic islands lying off the coast of a continent. The Aleutian Islands and the islands of the West Indies are island arcs. [AHDOS]

isoclinal: of, having to do with, or indicating equal magnetic inclinationl inclining or dipping in the same direction; denoting or having to do with a line on a map drawn through points on the earth's surface at which the magnetic dip is the same; (of strata) of or like an isocline. [AHDOS]

isopach: a line drawn on a map or chart joining points of equal thickness in a particular stratum or group of strata. [AHDOS]

itacolumite: a granular quartize that is very flexible when found in thin slabs. [AHDOS]

jade: a hard, compact, lustrous gemstone consisting of either jadeite or nephrite. Most jade is green, but some is whitish. [AHDOS]

jadeite: a pyroxene mineral consisting of silicate of sodium and aluminum, occurring in the form of light green monoclinic crystals. It is the tougher and more highly prized variety of jade.

jarosite: a hydrous sulfate of iron and potassium, occurring in yellowish or brownish rhombohedral crystals. [AHDOS]

jasper: an opaque, cryptocrystalline quartz, usually red, yellow or brown. [AHDOS]

jaspilite: a siliceous metamorphic rock consisting or intrbanded layers of red jasper and hematite. [AHDOS]

jet: a hard, compact black substance, a form of lignite, that becomes glossy when polished. [AHDOS]

joint: a fracture in a mass of rocks, usually occurring in sets of parallel planes dividing the mass into blocks. [AHDOS]

Jurrasic: the middle period of the Mesozoic era, after the Triassic and before the Cretaceous, when dinosaurs dominated the earth and birds first appeared; rocks formed in this period. [AHDOS]

juvenile: having never existed on the surface of the earth or in the atmosphere; coming fresh from the earth's interior. [AHDOS]

kamacite: an alloy of iron and a small amount of nickel, found in some meteorites. [AHDOS]

kame: a hill or ridge of poorly sorted gravel or sand impounded in a glacier and deposited by melting of the ice. [AHDOS]

Kansan: of or having to do with the second period of glaciation in North America, beginning about 470,000 years ago, and lasting for 156,000 years. [AHDOS]

kaolin: a fine white clay consisting of kaolinite, used especially in making ceramics. [AHDOS]

kaolinite: a crystalline, hydrous silicate of aluminum, the chief constituent of kaolin and some other clays. Kaolinite is polymorphous with dickite and nacrite. [AHDOS]

karst: a limestone plateau or region characterized by underground drainage, sinholes, rolling surfaces, and caverns. [AHDOS]

kernite: a colorless or white mineral, an important ore of boron compounds. [AHDOS]

kerogen: the solid bituminous substance fouond in oil shale, which yields oil when the shale is calcined. [AHDOS]

kettle or kettle hole: a depression in the surface of a ground moraine, caused by the melting of a block of subsurface ice after the moraine had formed. [AHDOS]

kimberlite: a mantle-derived peridotic rock found in South Africa, Zaire, Siberia, and some other areas, usually partly altered to serpintine. [AHDOS]

kolm: a carbonaceous material occurring in a certain shale found in Sweden and Norway. It is rich in uranium and radium. [AHDOS]

kyanite: a silicate of aluminum, usually occurring in blue, blade-shaped crystals. it is trimorphous with andalusite and sillimanite. [AHDOS]