I , J , K , L Index Glossary geology Science
I , J , K , L Index Glossary geology Science
Ignimbrite
An igneous rock formed by the lithification of ash flow or pyroclastic flow deposits.
Impermeable Layer
A layer of rock, sediment or soil that does not allow water to pass through. This could be caused by a lack of pore space or pore spaces that are so small that water molecules have difficulty passing through.
Igneous Rock
A rock formed by the crystallization of magma or lava.
- A rock made from molten (melted) or partly molten material that has cooled and solidified
Indentured Labor
Work performed according to a binding contract between two parties. During the early colonial period in
International
With 118 national members, the Union aims to promote development of the earth sciences through the support of broad-based scientific studies relevant to the entire earth-system; to apply the results of these and other studies to preserving Earth's natural environment, using all natural resources wisely and improving the prosperity of nations and the quality of human life; and to strengthen public awareness of geology and advance geological education in the widest sense.
Indigo
A plant that yields a blue vat dye.
Inertia Costs of Location
Costs borne by an activity because it remains located at its original site, even though the distributions of supply and demand have changed.
Insular
Either of an island, or suggestive of the isolated condition of an island.
international date line
A line of longitude generally 180 degrees east and west of the prime meridian. The date is one day earlier to the east of the line.
Intervening
The existence of a closer, less expensive opportunity for obtaining a good or service, or for a migration destination. Such opportunities lessen the attractiveness of more distant places.
A waterway channel, maintained through dredging and sheltered for the most part by a series of linear offshore islands, that extends from
ice cap
An alpine glacier that covers the peak of a mountain
Ice Age
A time of widespread glaciation (see Pleistocene).
-A period during which the Earth is substantially cooler than usual and a significant portion of its land surface is covered by glaciers. Ice ages generally last tens of millions of years
industrial water use
water used for industrial purposes in such industries as steel, chemical, paper, and petroleum refining. Nationally, water for industrial uses comes mainly (80%) from self-supplied sources, such as a local wells or withdrawal points in a river, but some water comes from public-supplied sources, such as the county/city water department.
infiltration
flow of water from the land surface into the subsurface.
injection well
refers to a well constructed for the purpose of injecting treated wastewater directly into the ground. Wastewater is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that don't deliver drinking water, unused aquifers, or below freshwater levels.
irrigation
the controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall.
index fossil
The fossil of an organism known to have existed for a relatively short period of time, used to date the rock in which it is found.
index mineral
See metamorphic index mineral.
inselberg
A steep ridge or hill left when a mountain has eroded and found in an otherwise flat, typically desert plain
intermolecular bonding
The act or process by which two or more groups of atoms or molecules combine due to weak positive or negative charges that develop at various points within each group of atoms due to uneven distribution of their electrons. The side of molecule where electrons are more likely to be found will have a slight negative charge, and the side where they are less likely to be found will have a slight positive charge. Such charged regions attract oppositely charged regions of nearby molecules, forming relatively weak bonds
internal deformation
The rearrangement of the planes within ice crystals, due to pressure from overlying ice and snow, that causes the downward or outward flow of a glacier
intrusive rock
An igneous rock formed by the entrance of magma into preexisting rock
ionic bond
The combination of an atom that has a strong tendency to lose electrons with an atom that has a strong tendency to gain electrons, such that the former transfers one or more electrons to the latter and each achieves chemical stability under the octet rule. The atom that loses electrons acquires a positive electric charge and the atom that gains electrons acquires a negative electric charge, so that - the resulting compound is electrically neutral
ionic bonding
The act or process of forming of an ionic bond
ionic substitution
The replacement of one type of ion in a mineral by another that is similar to the first in size and charge
iron catastrophe
The sequence of events resulting in the separation of the Earth's matter into concentric zones of differing densities. This sequence began when the temperature of the Earth at depths of 400 to 800 kilometers below the surface rose to the melting point of iron. Molten iron then gravitated toward the Earth's center, and its movement raised the Earth's temperature to approximately 20,000 C. This led other substances to start melting. The densest matter then sank toward the Earth's center, while lighter matter rose toward the surface. The iron catastrophe took place between a few hundred million and one billion years after the Earth formed
Inclination
The angle between a line in the Earth's magnetic field and the horizontal plane; also a synonym for dip.
Index of refraction
The ratio of the speed of light in a vacuum to the speed in a material; this ratio determines the amount that light is refracted as it passes into a crystal.
Interfacial angle
The angle between two crystal faces of a crystal, characteristic of a mineral's symmetry.
Intermontane basin
A basin between mountain ranges, often formed over a graben.
Isotope geology
The study of the relative abundances of isotopes in rocks to determine their ages (see geo-chronology) or conditions of formation.
Isotropic substance
One in which the magnitude of a physical property, such as transmission of light is independent of crystallographic direction.
inorganic chemical sediment
Sedimentary rocks - such as limestone, chert, and evaporites - that forms when the dissolved products of chemical weathering precipitate from solution. The ornate columns of travertine in caves is one example of an inorganic chemical sedimentar rock.
isotope dating
The process of using relative proportions of parent to daughter isotopes in radioactive decay to determine the age of a given rock or rock stratum.
leach
To dissolve from a rock. For example, when acidic water passes through fractured rocks, soluble minerals leach, or dissolve, from the rocks.
isotope
One of two or more forms of a single element; the atoms of each isotope have the same number of protons but different numbers of neutrons in their nuclei. Thus, isotopes have the same atomic number but differ in atomic mass
A line on a map connecting points that receive equal precipitation.
Interior Drainage
A system of streams that flow into a land-locked basin and evaporate.
Intermediate Rock
An igneous rock that has an intermediate silica content. Examples are syenite and diorite. Also see entries for 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.
Intrusive
Igneous rocks that crystallize below Earth's surface.
Ion
An atom or group of atoms that have gained or lost one or more electrons and as a result have an electrical charge.
Iron Formation
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.
Isograd
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 other side of the line a lower level of metamorphism.
Isostasy
A condition of gravitational balance (similar to floating) in 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.
Jade
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 carved.
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.
Jurisdiction
The right and power to apply the law; the territorial range of legal authority or control.
Juvenile gas
Gases that come to the surface for the first time from the deep interior.
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.
Joint Set
A group of joints that are parallel or nearly parallel. They are frequently formed at the same time interval from a common process.
Jolly Balance
A spring balance used in the determination of specific gravity.
Juvenile Water
Water that is new to the hydrologic cycle. Brought to Earth's surface through volcanic eruptions.
kilogram
one thousand grams.
kilowatthour
(KWH)-a power demand of 1,000 watts for one hour. Power company utility rates are typically expressed in cents per kilowatt-hour.
Karst
A landscape that is characterized by the features of solution weathering and erosion in the subsurface. These features include caves, sinkholes, disappearing streams and subsurface drainage.
Kudzu
A vine, native to China and Japan but imported into the United States; originally planted for decoration, for forage, or as a ground cover to control erosion. It now grows wild in many parts of the southeastern
Kettle
A depression formed in glacial deposits when a buried block of ice, left behind by a retreating glacier, melts.
A lake that forms in a kettle.
K-feldspar
A potassium feldspar such as orthoclase, microcline, sanidine or adularia. Also referred to as potash feldspar.
Kilobar
A unit of pressure equal to 1000 bars (the mean atmospheric pressure at 100 meters above sea level is one bar).
Kimberlite
A variety of peridotite that is found in volcanic pipes which are thought to be intrusions from the upper mantle. Many 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 by a change in underlying bedrock or bedrock structure.
Kerogen
A solid, waxy, organic substance that forms when pressure and heat from the Earth act on the remains of plants and animals. Kerogen converts to various liquid and gaseous hydrocarbons at a depth of seven or more kilometers and a temperature between 500 and 1,000 C
krast
A topography characterized by caves, sinkholes, disappearing streams, and underground drainage. Karst forms when groundwater dissolves pockets of limestone, dolomite, or gypsum in bedrock
Knob
A small hilltop that is round in shape.
laccolith
A large concordant pluton that is shaped like a dome or a mushroom. Laccoliths tend to form at relatively shallow depths and are typically composed of granite. The country rock above them often erodes away completely
lagoon
A shallow body of water separated from the sea by a reef or barrier island
lava
Magma that comes to the Earth's surface through a volcano or fissure.
leeward
Of, located on, or being the side of a dune, hill, or ridge that is sheltered from the wind. See also windward.
lichen
Plant-like colonies of fungi and algae that grow on the exposed surface of rocks. Lichen grows at a constant rate within a single geographic area
lichenometry
A method of absolute dating that uses the size of lichen colonies on a rock surface to determine the surface's age. Lichenometry is used for rock surfaces less than about 9,000 years old.
Lignite
A low-grade brownish coal of relatively poor heat-generating capacity.
- A soft, brownish coal that develops from peat through bacterial action, is rich in kerogen,and has a carbon content of 70%, which makes it a more efficient heating fuel than peat
limestone
A sedimentary rock composed primarily of calcium carbonate. 10% to 15% of all sedimentary rocks are limestones. Limestone is usually organic, but it may also be inorganic.
liquefaction
The conversion of moderately cohesive, unconsolidated sediment into a fluid, water-saturated mass
lithosphere
A layer of solid, brittle rock comprising the outer 100 kilometers of the Earth, encompassing both the crust and the outer most part of the upper mantle. See also asthenosphere.
lithostatic pressure
The force exerted on a rock buried deep within the Earth by overlying rocks. Because lithostatic pressure is exerted equally from all sides of a rock, it compresses the rock into a smaller, denser form without altering the rock's shape
longitudinal dune
One of a series of long, narrow dunes lying parallel both to each other and to the prevailing wind direction. Longitudinal dunes range from 60 meters to 100 kilometers in length and from 3 to 50 meters in height
longshore current
An ocean current that flows close and almost parallel to the shoreline and is caused by the rush of waves toward the shore.
low-velocity zone
An area within the Earth's upper mantle in which both P waves and S waves travel at markedly slower velocities than in the outermost part of the upper mantle. The low-velocity zone occurs in the range between 100 and 350 kilometers of depth.
luster
1. The reflection of light on a given mineral's surface, classified by intensity and quality. 2. The appearance of a given mineral as characterized by the intensity and quality with which it reflects light
Lahar
A mudflow composed of water and volcanic ash. Lahars can be triggered by the flash melting of the snow cap of a volcanic mountain or from heavy rain. Lahars are very dangerous because they can occur suddenly and travel at great speeds.
Laminar Flow
A state of uniform flow within a fluid in which the moving particles travel along parallel paths (compare with Turbulent Flow).
Landslide
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.
Lapilli
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.
Moraine
A mound, ridge or ground covering of unstratified and unsorted till, deposited by ice action or by melting away of a glacier.
- The rocks and soil carried and deposited by a glacier. An "end moraine," either a ridge or low hill running perpendicular to the direction of ice movement, forms at the end of a glacier when the ice is melting.
Lateral Moraine
An accumulation of till along the sides of a valley glacier that is produced by ice action.
Lava Tube
A tunnel below the surface of a solidified lava flow, formed when the exterior portions of the flow solidify and the molten internal material is drained away.
Leaching
The removal of soluble constituents from a rock or soil by moving ground water or hydrothermal fluids.
- A process of soil nutrient removal through the erosive movement and chemical action of water.
- the process by which soluble materials in the soil, such as salts, nutrients, pesticide chemicals or contaminants, are washed into a lower layer of soil or are dissolved and carried away by water.
Left-Lateral Fault
A fault with horizontal movement. If you are standing on one side of the fault and look across it the block on the opposite side of the fault has moved to the left. (Also see Right-Lateral Fault.)
Levee
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 the channel, sediments quickly drop out of suspension and build a ridge over time.
Limb
One side of a fold. The dipping rock units between the crest of an anticline and the trough of a syncline.
Lacustrine Plain
A nearly level land area that was formed as a lake bed.
latitude
Imaginary lines that cross the surface of the Earth parallel to the Equator, measuring how far north or south of the Equator a place is located. A measure of distance north or south of the equator. One degree of latitude equals approximately 110 kilometers (69 miles).
legend
A key to what the symbols or pictures in a map mean.
Longitude
A measure of distance east and west of a line drawn between the North and South Poles and passing through the Royal Observatory at
- Imaginary lines that cross the surface of the Earth, running from north to south, measuring how far east or west of the prime meridian a place is located.
lentic waters
ponds or lakes (standing water).
livestock water use
water used for livestock watering, feed lots, dairy operations, fish farming, and other on-farm needs.
lotic waters
flowing waters, as in streams and rivers.
Legume
A plant, such as the soybean, that bears nitrogen-fixing bacteria on its roots, and thereby increases soil nitrogen content.
Life Cycle Stage
A period of uneven length in which the relative dependence of an individual on others helps define a complex of basic social relations that remains relatively consistent throughout the period.
Light Industry
Manufacturing activities that use moderate amounts of partially processed materials to produce items of relatively high value per unit weight (see Heavy Industry).
loess
A load of silt that is produced by the erosion of outwash and transported by wind. Much loess found in the Mississippi Valley, China, and
Lineament
A straight topographic feature of regional extent which is thought to represent crustal structure. A fault, line of sinkholes, straight stream stretch or a line of volcanoes can be considered linear features.
Lithification
The processes through which sediments are converted into sedimentary rock, including compaction and cementation.
Lithology
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.
Lithospheric Plate
A large slab of the lithosphere that can be moved by convection current motion within the mantle.
Load
The total amount of sediment being carried by a stream or a glacier. Includes suspended materials, dissolved materials and materials moved along Earth's surface. (Also see bed load, dissolved load, suspended load.)
Lode
A rich accumulation of minerals in solid rock. Frequently in the form of a vein, layer or an area with a large concentration of disseminated particles. (See Placer for contrast.)
Longitudinal Profile
A cross section of a stream or valley beginning at the source and continuing to the mouth. These profiles are drawn to illustrate the gradient of the stream.
Longshore Drift
The movement of sediment along a coastline caused by waves striking the coast at an oblique angle. The waves wash sediment particles up the beach at an oblique angle and the swash back to the sea carries the particles down the gradient of the beach. This produces a zig-zag path of particle movement along the beach.
Lineation
Any linear arrangement of features found in a rock.
Lopolith
A large laccolith that is bowl-shaped and depressed in the center, possibly by subsidence of an emptied magma chamber beneath the intrusion.
Lowland
A relatively flat area in the lower levels of regional elevation.