Earth Science Glossary



abrasion - the physical action of scraping, rubbing, grinding, or wearing away of rock surfaces and sediments due to the movement of solid sediments in an erosional system such as a stream or wind.

absolute age - the actual age, or date, in years when a geological event occurred or a rock was formed.

absolute humidity - the amount (mass) of water vapor in a unit volume of air, such as in grams/cubic meter.

absolute zero - theoretically, the lowest possible temperature; no heat energy can be extracted at this temperature.

absorbed - taken into a material.

aerosol - small solid or liquid particles suspended in a gas; suspended solid or liquid water are the aerosols that compose fog and clouds.

air mass - a large body of air in the troposphere with similar characteristics of pressure, moisture, and temperature.

air pressure - see atmospheric pressure.

air pressure gradient - see pressure gradient.

altitude - (1) the vertical distance (elevation) between a point and sea level or Earth's surface (2) the angle of a celestial object above the horizon; usually expressed in degrees.

anemometer - a weather instrument used to meassure wind speed.

angle of incidence - the angle at which the sun's rays hit Earth's surface; also called angle of insolation.

anticyclone - a high-pressure mass of air within the troposphere in which air moves out from the center; rotating clockwise in the N orthem Hemisphere and counterclockwise in the Southem Hemisphere; also called a high.

aphelion - the point in a planet's orbit when it is farthest from the sun.

apparent diameter - the diameter a celestial object appears to have, depending on its distance from an observer; not the actual diameter.

apparent motion - a motion of an object that is not real but appears to be real, such as the daily motion ofthe stars in the sky caused by the real motion of Earth's rotation.

apparent solar day - a day of varying length deterrmined by the time it takes for the sun to arrive at its highest point in the sky on two consecutive days at the same location, often measured by a sundial; see also mean solar day.

arc - a curved line that is part of a circle; the shape of the path of most celestial objects, such as the sun, in their daily motion paths through Earth's sky.

arid climate - a dry climate where the precipitation is less than the potential evapotranspiraton for a large part ofthe year, producing a deficit of moissture and a drought much ofthe time.

asteroid - a solid, rocky and/or metallic body that independently orbits the sun; large, irregularly shaped, except for the few larger spherical ones; mostly located between the orbits of Mars and Jupiter.

asthenosphere - the plastic, partly solid, partly liqquid layer of Earth's mantle just below the lithoosphere that allows plate movements.

atmosphere - the layers of gases surrounding Earth or other celestial object; Earth's atmosphere is divided into layers according to differences in chemical and physical properties.

atmospheric pressure - the weight of the overlying atmosphere pushing down on a given unit of area; affected by changes in temperature, water vapor, and altitude; also called air pressure or barometric pressure.

atmospheric transparency - how transparent the atmosphere is to insolation; how easily insolation can pass through the air.

atom - the smallest part of matter or an element which can't be separated by most chemical or physical processes.

atomic structure - see crystal structure.

axis (of rotation) - an imaginary line through Earth from the north to the south geographic poles, about which Earth rotates; all rotating celestial bodies have an axis.



banding - the layered arrangement of mineral crysstals in some medium to coarse metamorphic rocks; a special type of foliation caused by layering and separation of minerals.

barometer - an instrument used to measure air pressure.

barometric pressure - see atmospheric pressure barrier island a long narrow island, parallel to the shore, built of sand deposited by ocean waves, ocean currents, and wind; separated from the coast by a lagoon.

beach - the narrow portion of the shore or coastline between the low and high tide lines, usually covvered with loose sediments.

bedrock - an area's mostly unweathered rock beneath vegetation, soil, other loose materials, and human-built structures; also called local rock.

bench mark - a permanent marker, usually metal, at a specific location on Earth's surface, that indiicates an exact elevation or altitude at the time of installation.

Big Bang theory - states that the present universe started as a big explosion 10 to 17 billion years ago and has been expanding ever since.

bioclastic sedimentary rock - any rock made by living organisms or mostly composed of materials from life forms; also called organic sedimentary rock.

blizzard - a storm with winds of 35 miles an hour or greater with considerable falling or blowing snow causing low visibility.

breaking waves - the result of waves dragging on the ocean bottom causing the water in the waves to fall forward as the waves bunch together, rise up, and break against the shore.



calorie - a unit of heat energy defined as the amount of heat needed to raise the temperature of one gram of water one degree Celsius.

calorimeter - an instrument used in studies of heat capillarity the process by which water is drawn into openings due to the attractive force between water molecules and the surrounding Earth materials.

capillary migration - the upward movement of water, against gravity, in part of the soil, loose materials, or bedrock due to capillarity; also called capillary action.

capillary water - the water held in soil, loose materiials, and rocks in the zone of aeration as a result of the process of capillarity.

carbon-14 - a radioactive isotope of carbon with a short half-life (5,700 years); used to date recent (up to 70,000-year old) remains of organic material.

carbon-14 dating - the use of carbon-14 in dating rocks and organic remains of relatively recent origin.

carbon dioxide - a colorless, odorless gas, CO2, an important greenhouse gas present in the atmossphere; given off when a fuel containing carbon is burned.

celestial object - any object in the universe outside of Earth's atmosphere, including moons, comets, planets, stars, and galaxies.

cementation - the process by which solid sediments or clasts are "glued" together by precipitated minnerals, forming a sedimentary rock.

change - the alteration or modification of the charracteristics of a part of the environment.

change of state - see phase change.

channel (stream) - see stream channel shape chemical sedimentary rock a rock composed of interconnected crystals of just one mineral that form by evaporation and/or precipitation of disssolved minerals; include rock salt and rock gyppsum; also called an evaporite.

chemical weathering - the processes by which chemmicals, such as oxygen, acids, and water, break down rocks and other Earth materials, resulting in more stable new minerals (chemicals); example-rusting.

classification - the grouping together of similar observations and inferences to make the study of objects and events in the environment more meanningful or easier to understand.

clastic sedimentary rock - rock that is largely composed of solid sediments, such as the sand in sandstone.

clasts - the solid sediments, fragments, or grains in a clastic sedimentary rock such as the sand grains of sandstone.

clay - (1) a chemical group of minerals (2) very small solid sediments or clasts (less than 0.0004 cm in diameter) that often remain suspended in water for long periods of time.

cleavage - the tendency of a mineral to break along the zones of weakness and form smooth to semi -smooth parallel surfaces.

climate - the overall view of a region's weather conditions over long periods oftime; includes not only averages, but extremes.

cloud - a visible mass of suspended liquid water droplets and/or ice crystals in the atmosphere.

cloud cover - the fraction or percent of the total sky at a location that is covered by clouds; usually expressed in tenths.

cold front - the boundary of an advancing cold air mass and a warmer air mass, where the underlyying cold air pushes forward like a wedge; characcterized by a steep slope, rapid changes in weather, thunderstorms, and sometimes hail and tornadoes.

comet - a low density object composed of materials (ices) that easily vaporize and some other solids; independently orbits the sun or other stars; usually has highly eccentric orbit; partly vaporizes forming a visible tail when near the sun.

compaction - the reduction in volume of sediments in the formation of sedimentary rocks, usually caused by the weight of overlying sediments and water causing a reduction of pore space and liquid water.

compound - a substance made of two or more eleements chemically combined in a specific proporrtion, such as most minerals.

condensation - the change in state or phase from a gas to a liquid, such as when water vapor changes to liquid water droplets as clouds form.

conduction - the transfer of heat energy from atom to atom or molecule to molecule, in any state of matter, when vibrating atoms or molecules collide.

constellation - a group of stars that form a pattern and are used to help people locate celestial objects.

contact metamorphic zone - a type of interface or transition zone between rock types caused by the baking or altering of older bedrock by contact with molten rock (lava or magma); much of the older rock is changed into metamorphic rock.

contact metamorphism - process in which older rocks come in contact with the magma of an intruusion or lava of an extrusion and the heat and minneral fluids of the liquid rock alter the older rock by recrystallization.

continental climate - the climate of inland areas not moderated by a large body of water; characterized by hot summers and cold winters, and thus having a wide annual temperature range.

continental crust - the part of Earth's crust (upper lithosphere) that makes up the continents and larger islands; thicker and lower in density than the oceanic crust, and granitic rather than basaltic in composition.

continental glacier - very large glaciers (like those of Antarctica and Greenland), so thick that they cover all landscape features except the highest mounntains; tend to create a smooth and low landscape by erosion and deposition; see mountain glacier.

continental arctic air mass - (cA) the coldest and driest air masses that only invade the contiguous United States from Arctic regions at the coldest times of the year.

continental polar air mass - (cP) cold and dry air masses that invade the contiguous United States from Canada.

continental tropical air mass - (cT) relatively rare hot dry air masses that form in the southwestern United States or northem Mexico, that may cause very hot and dry weather for the contiguous United States in the summer.

contour interval - the difference in elevation indicatted by two consecutive contour lines (of different value) on contour or topographic maps.

contour line - an isoline on a topographic, or contour, map that connects points of equal elevaation on the surface of any solid celestial body, such as Earth.

contour map - see topographic map.

convection - the transfer of heat energy by circulatory movements in a fluid (usually liquids or gases) that results from differences in density within the fluid.

convection current - a circulatory motion in a fluid due to convection; also called a convection cell.

convergence - (1) the coming together of air currrents at Earth's surface and at the top of the trooposphere (2)the direct collision oflithospheric plates in the plate tectonic theory.

convergent plate boundary - the boundary between two colliding plates; often associated with mountain building, ocean trenches, and volcanic island arcs.

coordinate system - a grid or a system of lines for determining location of a point on a surface, such as latitude and longitude of a point on Earth.

core - the center part of Earth below the mantle thought to be composed of iron and nickel; inner part is a solid and outer part a liquid.

Coriolis effect - the deflection of all moving partiicles of matter (such as winds and surface ocean currents) at Earth's surface to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, which provides evidence for Earth's rotation.

correlation - in geology, the process of showing that rocks or geologic events from different places are the same or similar in age.

crater - see impact crater

crust - the outermost portion of Earth's solid lithoosphere; separated from the uppermost mantle and lower lithosphere by the thin Moho interface.

crystal - (1) the individual mineral grains of many rocks (2) a solid with a definite intemal structure of atoms arranged in a characteristic, regular, repeating pattern.

crystalline - composed of intergrown or interconnnected mineral crystals; having a specific arrangeement of atoms.

crystallization - a type of solidification in which molten rock (magma or lava) cools to form igneous rocks composed of mineral crystals; also see solidification.

crystal shape - the outward 3-D shape or geometric shape of a mineral specimen that reflects the internal atomic structure; also called crystal form.

crystal structure - the pattern or arrangement of atoms that characterizes each mineral; also called atomic structure.

cyclic change - an orderly change in the environnment in which an event repeats itself with referrence to time and space; the opposite of random change.

cyclone - a low-pressure portion of the troposphere that has air moving towards its center; usually rotates counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere; includes hurricanes, tornadoes, and mid-latitude cyclones, also called a low.

cyclonic storm - a large type of low-pressure storm system formed in the mid-latitudes; also called mid-latitude cyclones.



daily motion - the apparent, usually east to west movement of celestial objects in the sky caused by Earth's west to east rotation; objects appear to move in circular or arc-shaped paths.

day - the amount of time it takes a planet or other celestial object to make one rotation.

deforestation - the cutting down of trees and other plants of a forest.

delta - the deposit of sediment at the mouth or end of a river or stream where it flows into a quiet body of water such as a lake or ocean.

density - the concentration of matter in an object; the ratio of the mass of an object to its volumeethe mass per each unit of volume.

deposition - the process by which sediments are released, dropped, or settled from erosional sysstems; includes the precipitation of dissolved minerrals in the formation of chemical sedimentary rocks; also called sedimentation.

desert - a region with an arid climate where the average yearly precipitation is much smaller than potential evapotranspiration.

dew - droplets of liquid water that form on Earth's solid surface by condensation; NOT a type of preecipitation.

dew point - the temperature at which the air becomes saturated with water vapor and the relaative humidity is 100%; at temperatures below the dew point, condensation or sublimation of water vapor occurs.

direct rays - rays of sunlight (insolation) that strike Earth at an angle of 90°; also called vertical rays or perpendicular insolation.

discharge - the amount of water that passes a cerrtain spot in a stream in a specific amount of time, such as liters per minute.

distorted structure - the curving and folding of the foliations (mineral layers) and grains or crystals in metamorphic rocks caused by heat and pressure.

divergence - (1) the spreading out of air from rising or falling currents of air in the troposphere (2) the type of plate movement in which Earth's plates spread or rift apart from each other, according to the plate tectonic theory.

divergent plate boundary - the boundary between two plates that are spreading apart at a mid-ocean ridge or at a continental rift zone.

Doppler effect - the apparent wavelength shifting of electromagnetic energy (such as visible light) caused by the relative motion between the energy source and the observer; also see redshift.

down cutting - the erosional process whereby a stream "digs" deeper into Earth's surface.

down-warped ocean basin - an ocean basin, at the margin of a continent, formed by the bending down of the ocean lithosphere by plate movements.

drizzle - liquid precipitation with drops smaller than raindrops.

drought - a time of abnormal dry weather with a large enough deficit of water to cause crops and local water supplies to fail.

drumlin - a low, long, narrow, streamlined oval mound of unsorted sediment that is formed at the bottom of glaciers, usually continental ones.

dry-bulb thermometer - the thermometer of a sling psychrometer without a wick around its bulb, prooviding normal temperature values.

dune - see sand dune.

duration of insolation - the length of time sunlight is received at a location in a day, or the amount of time between sunrise and sunset.

dynamic equilibrium - a condition of the balancing out of opposing forces or actions, such as evaporaation and condensation or erosion and deposition.


earthquake - a natural, rapid shaking of the lithoosphere caused when rocks are displaced due to the release of energy stored in rocks; most caused by rapid movement along faults, but also associated with other events, such as volcanic eruptions.

earthquake magnitude scale - a numbering system that ranks earthquakes according to the total energy they emit.

Earth's interior - the region extending from the rocky part of Earth's surface to Earth's center.

Earth materials - water, gases, soils, minerals, rocks, mineral resources, and other materials and energy sources that are of value to people.

eccentricity - the degree of ovalness of an ellipse, or how far an ellipse is from being a circle.

eclipse - the complete or partial blocking of light when one celestial body moves into the shadow of another celestial body; see lunar eclipse and solar eclipse.

eclipse of the moon - see lunar eclipse

electromagnetic energy - energy that is radiated (given off) from all objects not at a temperature of absolute zero, in the form of transverse waves from vibrating matter into any part of the uniiverse; examples-visible light, radio waves, infrared radiation, and ultraviolet radiation; often called light or radiant energy.

electromagnetic spectrum - a model, such as a chart, that shows the full range of types of electroomagnetic energy, usually in order of wavelengths.

element - any of the different types of atoms such as oxygen, iron, and mercury; 90 naturally occurrring elements exist on Earth.

elevation - the vertical distance or height above or below sea level.

ellipse - a closed curve around two fixed points, called foci, in which the sum of the distances between any point of the curve and the foci is a constant; example-the shape of all planetary orbits.

EI Nino - a series of weather changes on Earth caused by a change from cold surface ocean water to warm surface ocean water in the eastem Pacific Ocean off western South America; occurs every two to ten years.

emergency preparedness - the steps or plans society, govemment agencies, organizations, and individuuals can do to get ready to· cope with disasters; planning an escape route in case of a hurricane or flooding, or storing food at home for a blizzard.

energy - the ability to do work.

environmental equilibrium - the balance that exists among the natural parts of the environment even though all parts of the environment are constantly changing.

eon - the largest division of geologic time, which is divided into eras.

epicenter - the place on Earth's surface lying directly above the focus, or the origin of an earthquake.

epoch - one of the small divisions of geologic time that are combined into periods.

equator - the parallel on Earth midway between the geographic North and South poles with a latiitude of 00.

equinox - a time when the sun is directly overhead at noon at the equator, and there are 12 hours of daylight and 12 hours of darkness over all of Earth.

era - the second longest division of geologic time; combined into eons and divided into periods.

erosion - the carrying away of sediment by wind, water, ice, and other agents; the process by which sediments are obtained and transported; the wearing away and lowering of Earth's land surface features.

erosional-depositional system - the various agents such as streams, glaciers, wind, ocean currents that pick up, transport, and deposit sediments at or near Earth's (or similar celestial object's) surface.

error - the amount of deviation or incorrectness in a measurement; see also percent error.

escarpment - a steep slope or cliff in layered rocks; often formed from certain rock layers that are resistant to weathering and erosion.

evaporation - the change in state from liquid to a gas, such as liquid water into water vapor; also called vaporization.

evapotranspiration - the combination of the processes of evaporation and transpiration.

evaporite - see chemical sedimentary rock event the name used to describe the occurrence of a change in the environment.

evolution - see organic evolution.

extrusion - a mass of igneous rock formed by the cooling and solidification of molten rock (lava) on Earth's surface; examples-a lava flow and a vollcanic mountain.

extrusive - igneous rock a rock formed by solidificaation of lava at or above Earth's surface; also called volcanic igneous rock.


fault - a crack in. a mass of rock or soil along which there has been displacement, shifting, or moveement of the rock or soil on each side of the crack.

faulted (rock) - rock layers that are offset or dissplaced along a type of crack called a fault.

faulting - rapid movements along faults.

field - any part of the universe that has some measurable value of a given quantity at every point, such as Earth's magnetic or Sun's gravitaational fields.

finger lake - a body of water that forms in a long, narrow U -shaped glacial valley, often partly dammed at one end by a mound of glacial moraine sediment; example-the Finger Lakes of central New York.

flood - condition in which so much water flows into a stream that the water pours over the stream's confining banks onto areas not normally covered with water.

flood plain - a nearly level plain that borders a stream that is subject to flooding unless protected artificially; usually composed of layers of riverrdeposited sediment.

focus (plural foci) - (1) in an ellipse, either of two fixed points located so that the sum of their disstances to any point on the ellipse is constant; example-the sun at one of the two foci of the orbit of each solar system planet (2) the place where an earthquake originates.

fog - a cloud that is on, or just above, Earth's surface.

folded (rock) - the bends in layered rock due to movement in the lithosphere; a type of deformed rock.

foliation - texture of metamorphic rocks caused by the layering of mineral crystals.

fossil - any physical evidence of former life, either direct or indirect.

fossil fuel - the organic fuels found within Earth's crust; includes oil (petroleum), natural gas, and coal.

Foucault pendulum - a freely swinging pendulum whose path appears to change in a predictable way, thus providing evidence for Earth's rotation.

fracture - the way in which a mineral breaks prooducing an uneven breaking surface; types of fraccture-earthy, splintery, and curved (conchoidal).

freezing - the change in state of a liquid to a solid by the removal of heat; also see solidification.

freezing rain - rain that freezes as it hits Earth's surface.

front - the interface, or boundary, between two air masses of different characteristics.

fusion - the change of state from a solid to a liquid; also called melting; also see nuclear fusion.


galaxy - the large groupings of millions or billions of stars and other forms of mass held together by gravitation; our galaxy is called the Milky Way.

geocentric model - an early concept of celestial objects and their motions in which all celestial objects revolved around Earth, which was stationnary and was the center of the universe.

geographic poles - the North and South poles of Earth, with a latitude of 90°; located at opposite ends of Earth's axis of rotation.

geologic time scale - a chronological model of the geologic history of Earth using the divisions of eons, eras, periods, and epochs; see History of New York State in the Earth Science Reference Tables.

glacial groove - a long narrow channel or furrow on bedrock formed by the gouging and sanding actions of rocks and sediments frozen to the bottom of a glacier; show the direction of former glacial movement.

glacial parallel scratches - parallel cuts in bedrock formed by abrasion (gouging and sanding) of rocks and sediments frozen to the bottom of a glacier; show the direction of former glacial movement.

glacier - a large mass of naturally formed ice on land that moves downhill due to gravity; also see continental glacier and mountain glacier.

global warming - a recent trend towards a warmming of Earth's surface and lower atmosphere (troposphere) possibly caused by human pollution.

graded bedding - a layering of sediment or sediimentary rock that shows a gradual change in parrticle size, with the largest particles on the bottom and the smallest ones on top.

gradient - the rate of change from place to place within a field; also called slope.

gravitation - the attractive force that exists between any two objects in the universe; proporrtional to the product of the masses ofthe objects and inversely proportional to the square of the disstance between their centers; also called gravitaational force.

gravity - the force that pulls objects toward the cennter of Earth.

greenhouse gases - gases such as carbon dioxide, water vapor, and methane, present in the atmossphere, which absorb long-wave infrared radiation.

greenhouse effect - the process by which the atmossphere transmits short-wave radiation from insolaation and absorbs long-wave radiation emitted by Earth's surface; warms the atmosphere and reduces heat loss by radiation from Earth's surface.

groundwater - the subsurface water found beneath the water table in the zone of saturation; someetimes used to mean all subsurface water..


hail - a round solid form of precipitation composed of concentric layers of ice and snow; only forms from cumulonimbus (thunderhead) clouds.

half-life - the time required for half of the atoms in a given mass of a radioactive isotope to decay, or change, to a different isotope.

hardness - the resistance a mineral offers to being scratched or dented; usually measured by compariison to the Mohs hardness scale of minerals.

hazard - an object, process, or situation that holds the possibility of injury or death to humans or damage to property.

haze - a condition of the atmosphere in which the aerosol content is so high that distant images are blurred, and a cloudless sky does not appear blue.

heat budget - the result of the balance between the total amount of energy an object receives and the total energy it emits, or loses; measured as the average temperature of an object.

heat energy - energy that is transferred from one body to another as a result of a difference in temmperature or thermal energy of two bodies; also called heat; also see thermal energy.

heliocentric model - the modern concept of celestial objects and their motions, in which a rotating Earth and other planets revolve around the sun.

high - see anticyclone.

high tide - the bulge of ocean water directly under the moon's position and on the opposite side of Earth.

hot spot - major regions of volcanic activity in the interior parts of plates away from plate boundaries; may be the cause of chains of volcanic activity within moving plates, such as the Hawaiian Islands.

humid climate - a moist or wet climate where the precipitation is greater than potential evapotrannspiration on a yearly average.

humidity - the amount of water vapor (gaseous water) in the atmosphere; also see relative humidity and absolute humidity.

hurricane - a large, strong cyclonic storm that forms over tropical ocean waters with sustained winds of 74 miles per hour or greater.

hydrologic cycle - see water cycle.

hydrosphere - the liquid water (mostly the oceans) that rests on much of the Earth's solid or rocky surface; included by some scientists-the subsurrface water, water in the atmosphere, sea ice, glaciers, and water in life forms.


ice ages - times of widespread glaciation outside of polar areas (see the Pleistocene epoch in Geologic History Of New York State At A Glance in the Earth Science Reference Tables).

igneous rock - a rock formed when natural, molten rock-forming material (magma or lava) cools and turns into a solid-above, below, or on Earth's surface.

impact crater - an oval-shaped depression with a raised rim formed by a meteorite, asteroid, or comet colliding with Earth's, or any other solid celestial object's, solid surface.

impact event - the colliding of comets, asteroids, and meteoroids or any other type of celestial body.

inclusion - a body of older rock within an igneous rock formed when pieces of rock surrounding liquid rock fall into the magma or lava, but don't melt before the liquid rock solidifies.

index fossil - a fossil used in correlation and relaative dating of rocks; must have lived for a short time and have been distributed over a large geoographic area.

inertia - the concept that an object at rest will tend to remain at rest and that an object in motion will maintain the direction and speed of that motion unless an opposing force affects it.

inference - an interpretation of an observation; a mental process that proposes causes, conclusions, or explanations for what has been observed.

infiltrate - water entering or sinking into, under the influence of gravity, the upper parts of Earth's lithosphere where the water becomes subsurface water; also called seep.

infrared - a type of long-wave electromagnetic radiation.

inner core - the innermost zone of Earth's core, which is thought to be composed of iron and nickel in a solid state.

inorganic - not organic, thus not part of a life form or made by living or former life forms.

insolation - (INcoming SOLar radiATION)the part of the sun's radiation that is received by Earth; also called solar energy.

instrument - a device invented by people to extend the senses beyond their normal limits, thus enabling them to make observations that would otherwise be impossible or highly inaccurate.

intensity of insolation - the relative strength of the sun's radiation intersecting a specific area of Earth in a specific amount of time, such as calories per square meter per minute.

interface - the boundary between regions with diffferent properties; the usual place for energy exchange.

interpretation - see inference.

intrusion - a mass of igneous rock formed when molten rock (magma) squeezes or melts into pre-existing rocks and crystallizes; examples-sills and dykes.

intrusive igneous rock - a rock that forms by the cooling and solidification of magma beneath Earth's solid surface; examples-granite or gabbro; also called plutonic igneous rock.

island arc - a curved series of volcanoes and vollcanic islands that stretch hundreds of miles; form at subduction zones where plates converge and magma rises to form volcanoes; also called a volcanic island arc.

isobar - an isoline used on weather and climate maps that connects points of equal air pressure.

isoline - a line used on a model of a field, such as a map, which connects points of equal value of a field quantity; examples-isotherms, isobars, and contour lines.

isotherm - an isoline used on weather and climatic maps to connect points of equal air temperature.

isotope - one ofthe varieties of an element, which all have the same atomic number and chemical properties, but differ in their atomic masses and physical properties; examples-carbon isotopes carbon-12 and carbon-14.


jet stream - a concentrated curving band of high speed, easterly moving winds usually at the top of Earth's troposphere.

joint - a crack in rocks along which there has been no relative movement or displacement, such as there is with a fault.

Jovian planets - planets that are far from the sun, largely gaseous, and have relatively large diameeters, many moons, rings, and low densities; Jupiter, Saturn, Uranus, and Neptune.


kettle lake - a lake formed when a large block of ice buried in glacial sediments melts, leaving an oval depression which becomes filled with water; very common in New York State.

kinetic energy - the energy of movement of any object; the greater the speed and mass of an object, the greater the kinetic energy.

knots - nautical miles per hour; unit of wind speed landform individual features of Earth's (or any other solid celestial object's) surface from mounntain ranges to a mud crack in a puddle.


landscape - the features of Earth's surface at the interfaces between the atmosphere or the hydroosphere and the top of the lithosphere; also on all other solid celestial bodies.

landscape region - a portion of Earth's surface with landscape (topographic) characteristics that distinnguish it from other areas;· distinguishing characcteristics-rock structure, elevation, degree of slope, and stream drainage pattern.

latitude - the angular distance north or south of the equator; usually expressed in units of angular measurement such as degTees; minimum latitude 0° at the equator and maximum 90° N or 90° S at the geographic poles.

latitudinal climatic pattern - east-west belts, or zones, of climate types on Earth caused by latitudinal changes in climate factors, such as temperature, precipitation amount, wind, and ocean currents.

lava - (1) liquid rock material at or above Earth's surface (2) the extrusive or volcanic igneous rock that forms from solidification of liquid lava.

leveling forces - forces that operate at or near Earth's surface and break down rocks, transport material from higher to lower elevations, and tend to level off and lower the land; examplesering, erosion, deposition, and subsidence.

light - see electromagnetic energy.

lithosphere - the whole crust and the uppermost portion of the mantle (layer of rock that forms the solid outer shell at the top of Earth's interior).

lithospheric plate - see plate.

local time - time based on the rotation of Earth as reflected in motions of the sun in the sky.

longitude - an angular distance east or west of the prime meridian; usually expressed in degrees; minimum longitude 00 at the prime meridian, which runs through Greenwich, England, and maximum longitude 1800 E or 1800 W.

longshore currents - ocean or lake currents that move parallel and close to shore due to the angled advance of waves from one direction; a major agent of erosion and deposition.

long-wave electromagnetic energy - electromagnetic energy with a wavelength longer than visible light, especially infrared energy.

low - see cyclone.

low tide - the level of low ocean water, occurring at right angles to the positions of high tide.

luminosity (of a star) - measures how bright a star would be in relation to the sun if all stars were the same distance from the observer.

lunar eclipse - the darkening of the moon caused by Earth's shadow.

luster - the way a mineral looks or shines in reflected light.


magma - liquid rock material beneath Earth's solid surface.

magnitude - see earthquake magnitude scale

mantle - the mostly solid part of Earth between the crust and the outer core.

marine climate - a coastal climate moderated by the effects of a large body of water (ocean, sea, or lake); having warmer winters and colder summers than areas of similar latitude not near a large body of water; have a smaller annual temperature range than inland areas.

maritime polar air mass - (mP) cool and humid air masses that invade the contiguous United States from the oceans to the northeast and northwest.

maritime tropical air mass - (mT) a very common warm and humid air mass that invades the conntiguous United States from the oceans to the south, east, and west.

mass - the amount of matter in an object; unlike weight, not affected by location.

mass movement - any variety of erosion and depoosition done directly by gravity; examples-soil creep, earthflows, mudslides, avalanches, slumpping, and landslides; also called gravity erosion.

mean solar day - the 24-hour day established for convenience in time-keeping; derived by averaging the lengths of the apparent solar days in a year.

mean solar time - a type of local time divided into exactly 24 hours for the convenience of timekeeping.

meander - a curve or bend in a stream or river.

measurement - a means of expressing an observation with greater accuracy or precision; provides a numerical value for an aspect of the object or event being observed by comparision with a stanndard; example-measuring the length of this page with a ruler.

mechanical energy - all the energy of an object or system not related to the individual motions of atoms and molecules; the total of the potential and kinetic energy of an object or system.

melting - the change in state or phase from a solid to a liquid.

meridian of longitude - any north-south semicircle of constant longitude on maps and globes connectting the north and south geographic poles: also called a meridian.

metamorphic rock - a rock that forms from changes in previously existing rocks (igneous, sedimentary, or other metamorphic rocks) due to heat, pressure, and/or chemical fluids (not weathering or melting).

metamorphism - the process by which heat, presssure, and/or exposure to chemical fluids can change previously existing rock into metamorphic rock.

meteor - path of light from a meteoroid burning as it passes through Earth's atmosphere; also called a shooting star.

meteorite - a meteoroid that has landed on Earth's surface.

meteoroid - solid particles smaller than asteroids and comets that orbit the sun.

methane - the organic compound CH4, often called swamp gas, that is an important greenhouse gas; major part of the fossil fuel called natural gas.

mid-latitude cyclone - see cyclonic storm mid-ocean ridge a mountain range at the bottom of the ocean, composed mostly of volcanoes and lava flows; forms at zones of diverging plates.

MilkyWayGalaxy - the spiral-shaped galaxy that Earth and our solar system are part of.

mineral - a naturally occurring, crystalline solid having a definite chemical composition and physiical and chemical properties that vary within speciified limits; has a unique crystal (atomic) structure.

mineral crystal - an individual grain of a mineral mineral resources Earth materials that people need, including minerals, rocks, and fossils fuels.

misconception - an idea, notion, or concept believed to be correct, but which is NOT true or correct.

model - any way of representing the properties of an object, event, or system; includes graphs, drawwings, charts, mental pictures, numerical data, or scaled physical objects.

Moho - the interface, or boundary zone, between Earth's crust and mantle; short for Mohorovicic discontinuity.

Mohs hardness scale - a scale used to measure the relative hardness of minerals; ranges from 1 to 10 with talc assigned a hardness of 1 and diamond a hardness of 10.

moisture - a somewhat vague term used to mean the liquid or gaseous water in the atmosphere or in the ground (soil, loose materials, or bedrock).

moisture capacity - a measure of the total amount of water vapor the air can hold at a particular temmperature; the maximum absolute humidity of a parcel of air at a particular temperature.

monsoons - cyclic and extreme weather changes caused by the shifting wind and pressure belts; especially strong in southeast Asia where summer brings wet weather from the ocean and winter brings dry weather from the continental interior.

moon - (1) the one natural satellite of Earth (2) a body that orbits a planet or an asteroid as those objects orbit the sun.

moraine - a mound, ridge, or sheet of unsorted, unlayered sediment deposited directly from an edge or bottom of a glacier; types-lateral, medial, and ground.

mountain - usually an area of high elevation, compared to the surrounding area or sea level, that usually has regions of steep gradient and many changes in slope; internally, mountains are characterized by distorted rock structures.

mountain glacier - a long narrow glacier confined to valleys in mountains; results in sharp angular landscape features; see continental glacier.


natural hazard - a non-hum an-related object, process, or situation that has the possibility of causing loss of life, personal injury, or loss of property; includes volcanic eruptions, earthquakes, landslides, floods, storms, and asteroid impacts; also called a natural disaster.

natural resources - the materials and energy sources found in the environment that humans use in their daily lives.

North Pole - the location on Earth's surface at the north end of the axis of rotation with a 90° N latitude; also called the geographic north pole.

North Star - see Polaris.

nuclear decay - see radioactive decay nuclear fusion the combining of the nuclei of smaller elements to form the nuclei of larger elements with some mass being converted into energy; example-the sun produces energy in this way.


observation - the perception of some aspect of the environment by one or more human senses, with or without the aid of instruments.

occluded front - the boundary of opposing wedges of cold air masses formed when a cold front overrtakes a warm front, lifting the warm air mass off Earth's surface, forming mid-latitude cyclones (lows).

ocean - the continuous salty water body that covers 70% of Earth's surface or anyone of its major parts such as the Atlantic Ocean; the major part of the hydrosphere.

ocean currents - see surface ocean currents.

oceanic crust - the portion of Earth's crust that is usually below the oceans and not associated with continental areas; thinner and higher in density than continental crust and basaltic rather than granitic in composition.

ocean trench - the long, steep, and narrow depresssion produced by the bending down of subducting plates, which warps the crust.

orbit - the path of an object revolving around another object, such as the path of Earth around the sun.

orbital speed - the speed of an orbiting body along its orbit at any given time similar to orbital velocity.

ore - a rock or mineral deposit that can supply a mineral resource that is worthwhile to mine or drill.

organic - an Earth material that is composed of and/or was formed by life forms.

organic evolution (theory of) - the theory stating that life forms change through time; new species of organisms arise by gradual transitional changes from existing species.

organic sedimentary rocks - see bioclastic sedimentary rocks.

original horizontality - a concept that states that sedimentary rocks and some extrusive igneous rocks, such as lava flows, form in horizontal layers parallel to Earth's surface

orogeny - (1) the process of mountain building (2) a portion of geologic time when there is much uplift and mountain building such as the Grenville Orogeny in Geologic History Of New York State in the Earth Science Reference Tables; caused by plate convergence or collision

outcrop - location at Earth's surface where bedrock is exposed without a cover of soil or other materials.

outer core - the zone of Earth between the mantle and the inner core; thought to be a liquid because earthquake S-waves do not go through it; believed to be composed of iron and nickel

outgassing - the seeping out of gases from Earth's interior through cracks and volcanic eruptions to Earth's surface.

outwash plain - the landform feature composed of sorted and layered sediments deposited in front of a glacier by running water from the melting ice; . example-southem Long Island.

oxidation - a process where oxygen is added to other elements in chemical weathering; such as in the rusting of the black mineral magnetite to the red mineral hematite.

ozone - a three-atom molecule of oxygen (commpared to the more common two-atom molecule of oxygen) that is a pollutant in the troposphere, but is important in the stratosphere where it absorbs much of the ultraviolet insolation from the sun.


parallels of latitude - east-west circles on maps or globes that are equidistant from the equator at all points; and thus maintain the same value of latitude; also called parallels.

passive margin basin - a broad and long depression of the crust at the border of a continent that is not the site of a plate boundary; usually the site of much deposition of sediments.

pauses (of atmosphere) - the interfaces, or bounddaries, of the layers of Earth's atmosphere.

percent deviation, or percent error - the numerical amount, expressed as a percent, by which a meassurement differs from a given standard or accepted value.

perihelion - the point in a planet's orbit when it is closest to the sun; occurs for Earth about January 3, when Earth is about 147,000,000 kilometers from the sun.

period - (1) the amount of time it takes a planet to make one orbit, or revolution, around the sun; called a year for that planet (2) in geology, a part ofthe geologic time scale smaller than an era but larger than an epoch.

permeability - the degree to which a porous material (such as rock or soil) will allow fluids, such as water and oil, to pass through it; commmonly measured in centimeters per hour.

permeability rate - the speed at which a certain amount of fluid, such as water or oil, can pass through a porous material; the speed at which water moves from above to below Earth's surface, becoming subsurface water-a special permeaability rate called infiltration rate; commonly measured in liters per minute.

perpendicular insolation - see direct rays.

phase (1) - one ofthe three main forms of matter-liquid, solid, or gas; also called state of matter (2) the varying portion of the lighted part of the moon, Venus, or Mercury visible from Earth.

phase change - the change of a substance from one phase or state to another, such as liquid water to gaseous water.

physical weathering - the mechanical or physical breakdown of rock and other Earth materials at or near Earth's surface into smaller pieces (sediiments) without a change in the mineral or chemiical composition; example-frost action splitting rock.

plain - a landscape of low elevation and generally level surface with little change in slope; usually characterized by horizontal rock structure.

planet - largest of non-star celestial objects that revolve around a star; Earth and eight other plannets revolve around our sun.

planetary wind belts - east-west zones on Earth where the wind blows from one direction much of the time; also see prevailing winds; exampleethe prevailing southwest winds that blow over the contiguous United States.

plate - section of the lithosphere that moves around Earth's solid surface; also called a lithospheric plate or tectonic plate.

plateau - a landscape of relatively high elevation composed of undistorted horizontal rock structure and often a more level slope or gradient than that of most mountains.

plate tectonic theory - states that Earth's lithoosphere is divided into sections called plates that can move up and down or sideways on the plastic part of the upper mantle-diverging, converging, and sliding past each other, which results in many of Earth's major physical features and events, including continent and mountain formation, vollcanoes, and earthquakes.

plutonic igneous rocks - see intrusive igneous rocks.

polar front - an ever-changing boundary between the colder air masses toward the poles and the warmer air masses toward the middle latitudes; storm systems (cyclones) of the mid-latitudes are formed at the polar front.

Polaris - the star that is presently almost directly over the geographic North Pole of Earth; also called the North Star.

pollutants - substances or forms of energy that polllute the environment; they include solids, liquids, gases, life forms, and forms of energy such as heat, visible light, and sound.

pollution - the occurrence in the environment of a substance or form of energy in concentrations large enough to have an adverse effect on people, their property, or plant or animal life.

porosity - percentage of open space (pores and cracks) in a material compared to its total volume.

potential energy - the energy possessed by an object as a result of its position or location, chemical connditions, or phase (state) of matter.

potential evapotranspiration - the amount of water that would be lost from a portion of Earth's surrface through evaporation and transpiration over a given time IF the water were available.

precipitation - (1) falling liquid or solid water from clouds toward Earth's surface; (2) a type of sediiment deposition in which dissolved minerals come out of solution to form solids, as in the formation of chemical sedimentary rocks such as rock salt.

precipitation - gauge any instrument used to measure the amount of atmospheric precipitation, such as a rain gauge.

prediction - a type of inference about the conditions and behavior of the environment in the future.

present is the key to the past - concept that the physical, chemical, biological, and geological events today are similar to those in the past; thus we can interpret the past by understanding the present.

present weather - the conditions or state of the atmosphere for a short period of time at a location determined by comparison with a standard list produced by the United States Weather Service; partial abbreviated list is found on the sample staation model in Weather Map Information in the Earth Science Reference Tables.

pressure gradient - the amount of difference in air pressure over a specific distance; the greater the pressure gradient, the greater the speed of the wind; also called air pressure gradient.