| A | B |
|---|
| aa | A Hawaiian term for a lava flow that has a rough, jagged surface. |
| Absolute Time | Geologic time expressed in years before the present. |
| Acid Rain | The acidity in rain due to gases from internal combustion engines and coal and oil-burning power plants. |
| Aftershock | An earthquake that follows and has its epicenter near a larger earthquake. |
| Archipelago | A group of islands; an expanse of water with scattered islands. |
| Asthenosphere | The weak or "soft" zone in the upper mantle just below the the lithosphere, involved in plate movement and isostatic adjustments. It lies 70 to 100 km below the surface and may extend to a depth of 400 km. |
| Atmosphere | The layer of gases (air), that surrounds a planet or moon. |
| Atoll | A roughly circular reef with an occasional small, low, coral sand island surrounding a shallow lagoon. |
| Barrier Reef | A coral reef separated from the mainland by a lagoon. |
| Basin | 1. A low, bowl-shaped area of land surrounded by higher lands. 2. Any large depression in which sediments are deposited. |
| Bedrock | The rock beneath the soil. |
| Bering Land Bridge | The vast tundra plain that was exposed between Asia and North America during the Last Glacial Maximum, about 21,000 years ago; it served as a migration route for people, animals, and plants. Also known as Beringia. |
| Body Wave | Any seismic wave that travels through the body of Earth, rather than along its surface. |
| Boundary | The tectonic region in which two plates meet. |
| Caldera | A large, basin-shaped volcanic depression, more or less circular in form. Typically steep-sided, found at the summit of a shield volcano. |
| Calving | The breaking away of ice from the front of the glacier when it ends in a lake or an ocean. Produces icebergs. |
| Casts | Fossils formed when water containing materials leaks into a mold. The minerals harden to form a copy of the original structure or organism. |
| Cave | A natural open space underground, large enough for a person to enter. Most commonly occur by the dissolution of soluble rocks, generally limestone. |
| Cementation | The process by which a binding, or cementing, agent is precipitated in spaces among individual particles of a deposit. Common cementing agents are calcite, quartz, and dolomite. |
| Chemical Sediment | Sediment formed by chemical precipitation from water. Example: halite precipitated as the result of the evaporation of sea water. |
| Chlorofluorocarbons (CFC's) | Gases that can be dissociated by solar radiation, which releases chlorine, which in turn destroys ozone. |
| Cinder Cone | A conical volcano formed by the accumulation of pyroclastic debris around a vent. |
| Cirque | Steep-walled hollow in a mountain side , shaped like an amphitheater, or bowl, with one side partially cut away. Place of origin of a mountain glacier. |
| Clast | An individual grain or constituent of a rock. |
| Clastic | Refers to rock or sediments made up primarily of broken fragments of pre-existing rocks or minerals. |
| Cleavage | Property possessed by certain rocks of breaking with relative ease along parallel planes or nearly parallel surfaces in their crystal structures where the bonds are weakest. |
| Coal | A sedimentary rock composed of combustible matter derived from the partial decomposition of plant material. |
| Collisional Boundary | Where two plates collide to form mountains. |
| Compaction | Reduction of pore space between individual particles as the result of overlying sediments or of tectonic movements. |
| Compost | To make a mixture of decaying organic materials to use as fertilizer. |
| Compression Fossil | Formed when an organism is flattened (compressed) and a thin film of organic material from its body is left in the rock. |
| Conduction | Heat transport by direct transfer of energy from one particle to another, without moving the particle to a new location. |
| Cone of Depression | A downward distortion or dimple in the water table that forms as a well pumps water faster than it can flow through the aquifer. |
| Continent | A thickened elevated region of Earth's crust that is mainly (but not entirely) above sea level. |
| Continental Crust | The part of the crust that directly underlies the continents and continental shelves. Averages about 35 km in thickness, but may be over 70 km thick under largest mountain ranges. |
| Continental Divide | A major drainage divide separating the drainage to once ocean from another. |
| Convection | Heat transport by moving particles, and the thermal energy that they carry, to a new location. |
| Convergent Boundary | Where one plate slides beneath another plate as the two are pushed together, a subduction zone. |
| Core | The innermost zone of Earth. It consists of two parts, an outer liquid section and an inner solid section, both chiefly iron and nickel with about 10 percent lighter elements. It is surrounded by the mantle. |
| Crater | 1. A steep-walled, usually conical depression at the summit or on the flanks of a volcano, resulting from the explosive ejection of material from a vent. 2. A bowl-shaped depression with a raised, overturned rim produced by the impact of a meteorite other energetic projectile. |
| Creep | The very slowly, generally continuous downslope movement of soil and debris under the influence of gravity. |
| Crevasse | 1. Breach in a natural levee. 2. Deep crevice or open fracture in glacier ice. |
| Crust | The outermost layer of the Earth, varying in thickness from about 10 kilometers (6 miles) below the oceans, to 65 kilometers (about 40 miles) below the continents; represents less than 1 percent of the Earth's volume. |
| Crystal | A geometrical form taken by a mineral, giving external expression to orderly internal atomic arrangement. |
| Decomposition (chemical weathering) | Weathering processes that are the result of chemical reactions. Example: the transformation of orthoclase to kaolinite. |
| Delta | A low, nearly flat accumulation of sediment deposited at the mouth of a river or stream, commonly triangular or fan-shaped. |
| Density | The mass of an object divided by its volume. |
| Deposition | Any accumulation of material, by settling from water or air, chemical precipitation, evaporation from solution, etc. |
| Desertification | A process of land degradation initiated by human activity, particularly in the zones along the margins of deserts. |
| Discharge | In a stream, the volume of water passing through a channel in a given time. |
| Disintegration (mechanical weathering) | The processes of weathering by which physical actions such as frost wedging break down a rock into fragments, involving no chemical change. |
| Divergent Boundary | Where two plates are moving in opposite directions as in a mid-ocean ridge. |
| Drainage Basin | The area from which a stream and its tributaries receive its water. |
| Drift | Glacial deposits laid down directly by glaciers or laid down in lakes, ocean, or streams as result of glacial activity. |
| Dust Bowl | An area subject to dust storms, especially south central United States. |
| Dust Storm | A large volume of dust-sized particles lifted high into the atmosphere. |
| Earth System | A system involving continuous interaction of the solid Earth, the atmosphere, the oceans and living things. |
| Elevation | The height of a place above sea level. |
| El Nino | A time of unusual winds and currents in the Pacific Ocean. El Nino generally causes warmer-than-normal sea surface temperatures and increased rainfall and storm activity. |
| Epicenter | The point on the Earth's surface that is directly above the focus of an earthquake. |
| Equator | An imaginary circle around the earth that represents the halfway mark between the North and South Poles and establishes the boundary between the Northern and Southern Hemispheres. |
| Equinox | The two days of the year on which neither hemisphere is tilted toward or away from the sun. |
| Erosion | The processes (mechanical and chemical) responsible for the wearing away, loosening, and dissolving of materials of the Earth's crust. |
| Escarpment | A steep or vertical cliff, either above or below sea level. |
| Estuary | An area where fresh water comes into contact with seawater, usually in a partly enclosed coastal body of water; a mix of fresh and salt water where the current of a stream meets the tides. |
| Erratic | A stone or boulder, glacially transported from place of origin and left in an area of different bedrock composition. |
| Exotic River | A river that is able to maintain its flow throughout a desert because of water received from outside the desert. |
| Extrusive | Igneous. Antonym of intrusive. Synonym of volcanic. Pertaining to igneous rocks or features formed from lava released on the Earth's surface. |
| Fault | A fracture or zone of fractures along the boundaries of tectonic plates. |
| Fjord | A glaciated valley now flooded by the sea. |
| Fluctuate | To change back and forth uncertainly. |
| Focus | The initial point within the Earth that ruptured in an earthquake, directly below the epicenter. The point within the Earth which is the center of an earthquake, at which strain energy is first released and converted to elastic wave energy. |
| Fold | Bent rock strata. |
| Fold and Thrust Mountains | Mountains, characterized by extensive folding and thrust faulting, that form convergent plate boundaries on continents. |
| Fossil | Evidence in rock of the presence of past life, such as a dinosaur bone, an ancient clam shell, or the footprint of a long-extinct animal as well as history artifacts. |
| Fossil Fuel | A hydrocarbon (coal or petroleum) that can be extracted from the Earth for use as a fuel. |
| Fracture | The way in which a rock or mineral breaks in random patterns rather than cleaving. |
| Frost Wedging | A type of disintegration in which jointed rock is forced apart by the expansion of water as it freezes in fractures. |
| Geologic Column | The arrangement of rock units in the proper chronological order from youngest to oldest. |
| Geologic Time Scale | The chronological sequence of units of Earth time. |
| Geology | The science that deals with the study of the planet Earth--the materials of which it is made, the processes that act to change these materials from one form to another, and the history recorded by these materials; the forces acting to deform the outer layers of the Earth and create ocean basins and continents. |
| Geothermal Energy | Heat extracted from the Earth for use as a power source. |
| Geyser | A type of thermal spring which ejects water intermittently with considerable force. |
| Glaciation | The formation, advance and retreat of glaciers and the results of these activities. |
| Glacier | A mass of ice, formed by the recrystallization of snow, that flows forward, or has flowed at some time in the past. |
| Global Positioning System (GPS) | A system that uses a constellation of 24 satellites, their ground stations, and individual GPS receivers to accurately locate points on Earth. |
| Global Warming | The prediction that climate will warm as a result of the addition to the atmosphere of humanly produced greenhouse gases. |
| Gondwana | The southern portion of the late Paleozoic supercontinent known as Pangea. It means, literally "Land of the Gonds" ( a people of the Indian subcontinent). The supercontinent existed from Cambrian to Jurassic time, mainly composed of South America, Africa, Madagascar, India, Antarctica, and Australia. |
| Gravity | The attractive force between two objects; its magnitude depends on their masses and the distance between them. |
| Greenhouse Effect | The effect of water and carbon dioxide absorbing outgoing infrared radiation, raising a system's temperature. The term is generally used with reference to the Earth's temperature, although it can also be applied to other systems, such as greenhouses and automobiles. |
| Greenhouse Gases | Gases (primarily water and carbon dioxide, but also a variety of sulfur and nitrogen compounds and gaseous hydrocarbons) that trap the Sun's heat in the atmosphere. |
| Groove | A broad, deep, generally straight furrow carved in bed rock by the abrasive action of debris embedded in a moving glacier. Larger and deeper than a glacial striation. |
| Ground Moraine | Till deposited from main body of glacier during ablation. |
| Hardness | The resistance of a mineral to scratching, as measured by the Mohs scale. |
| Hardpan | A general term for a relatively hard layer of soil at or just below the ground surface, cemented by silica, iron oxide, calcium carbonate, or organic matter. |
| Hemisphere | Either the northern or southern half of the Earth as divided by the equator, or the eastern or western half as divided by a meridian. |
| Hot Spot | A region of high heat flow on the Earth;s surface, thought to lie above a mantle plume. |
| Hydrologic Cycle | The pattern of water circulation from the ocean to the atmosphere to the land and back to the ocean. |
| Humus | The generally dark, more or less stable part of the organic matter in a soil, so well decomposed that the original sources cannot be identified. |
| Ice Sheet | A broad, mound-like mass of glacier ice that usually spreads radially outward from a central zone. |
| Ice Shelf | A floating ice sheet extending across from a land-based glacier. |
| Icecap | A small ice sheet. |
| Igneous Rock | A rock that has crystallized from molten state. |
| Inertia | The tendency of a moving object to continue in a straight line or a stationary object to remain in place. |
| Inner Core | The solid innermost part of the core with a diameter of a little over 1,200 km. |
| Intrusive | Plutonic. Antonym of extrusive. Pertaining to igneous rocks or features formed by the emplacement of magma in pre-existing rocks. |
| Island Arc | A curved belt of volcanic islands lying above a subduction zone. |
| Karst | A landscape that develops from the action of ground water in areas of easily soluble rocks. It is usually characterized by caves, underground drainage and sinkholes. |
| Kettle | A depression in the ground formed by the melting of a block of glacier ice buried or partially buried by drift. |
| Lahar | A mudflow composed chiefly of pyroclastic material on the flanks of a volcano. |
| Latitude | Imaginary lines on a map or globe that measure distance in degrees north or south of the equator. Latitude lines extend horizontally, from east to west on a globe. |
| Laurasia | A supercontinent that existed from the Jurassic to Early Tertiary after splitting from Pangea; composed of Laurentia, Baltica, Avalonia, (modern North America, Scandinavia, Greenland, Western and Central Europe); eventually fragmented into Eurasia and North America in the Tertiary with the opening of the North Atlantic Ocean. The northern portion of the late Paleozoic supercontinent called Pangea. |
| Lava | Any molten material that is extrusive or volcanic, or the rock that forms from a molten extrusive. Molten rock that flows at the Earth's surface. |
| Lava Dome | A steep-sided rounded extrusion of highly viscous lava squeezed out from a volcano and forming s dome-shaped or bulbous mass above and around the volcanic vent. The structure generally develops inside a volcanic crater. |
| Levees | Banks of sand and silt along stream bank built by deposition in small increments during successive floods. |
| Liquefaction | The transformation of a soil from a solid to a liquid state as the result of increased pore pressure. |
| Lithification | The process by which an unconsolidated deposit of sediments is converted into solid rock. |
| Lithosphere | The rigid outer shell of the Earth. It includes the crust and uppermost mantle and is on the order of 100 km in thickness, |
| Loess | Deposits of wind-borne dust. |
| Longitude | Imaginary lines on a map or globe that measure distance in degrees east or west of the prime meridian. Longitude lines extend vertically, from pole to pole on a globe. |
| Luster | The reflection of light on a given mineral's surface, classified by intensity and quality. |
| Magma | Molten rock, containing dissolved gases and suspended solid particles. At the Earth's surface, magma is known as lava. |
| Magnetic Polarity | The direction, north (normal) or south (reversed), that a magnetic compass needle points. |
| Magnetic Pole | The point on the Earth's surface where a magnetic needle points vertically downward (north magnetic pole) or vertically upward (south magnetic pole). |
| Magnitude | A measure of the strength of an earthquake based on the amount of movement recorded by a seismograph. |
| Mantle | The portion of the Earth below the crust and reaching to about 2,780 km, where a transition zone of about 100 km thickness separates it from the core. |
| Meander | A sharp bend, loop or turn in a stream's course. When abandoned, it is called a meander scar or an oxbow. |
| Mesosphere | A zone in the Earth between 400 and 670 km. below the surface separating the upper mantle from the lower mantle. |
| Metamorphic Rock | A rock changed from its original form and/or composition by heat, pressure, shearing stress, or chemically active fluids, or some combination of them. |
| Mid-Ocean Ridges | Elongated rises on the ocean floor where basalt periodically erupts, forming new oceanic crust. |
| Mineral | A naturally occurring inorganic solid that has a well-defined chemical composition and in which atoms are arranged in an ordered fashion. |
| Mineral Deposit | Any natural concentration of a valuable material in the Earth's crust, whether that material can be extracted profitably or not. |
| Moraine | A mound or ridge of sediment deposited by a glacier. |
| Natural Resources | Materials that are found in nature that are useful or necessary for people to live. |
| Nuee Ardente | A dense, hot (sometimes incandescent) cloud of volcanic ash and gas produced in a Pelean eruption. |
| Oceanic Crust | The Earth's crust underlying the ocean basins which is formed at mid-oceanic ridges. It is typically 5 to 10 kilometers thick composed of basalt. |
| Oceanic Trench | Deep steep-sided depression in the ocean floor caused by the subduction of oceanic crust beneath either other oceanic crust or continental crust. |
| Open Pit Mining | Surficial mining, in which the valuable rock is exposed by removal of overlying rock or soil. |
| Ore | The naturally occurring material from which a mineral or minerals of economic value can be extracted at a profit. |
| Ore Deposit | A continuous well-defined mass of material of sufficient ore content to make extraction economically feasible. Compare mineral deposit. |
| Orogeny | The process of mountain building. |
| Outcrop | Any place where bedrock is visible on the surface of the Earth. |
| Outer Core | The outermost part of the core. It is liquid, about 1,700 km thick, and separated from the inner, solid core by a transition zone about 565 km thick. |
| Oxbow | An abandoned meander. |
| Ozone | A molecule composed of three atoms of oxygen and mostly found in the stratosphere. Though beneficial in the upper atmosphere, at ground level, ozone is called photochemical smog, and is a respiratory irritant and considered a pollutant. |
| Ozone Depletion | Destruction of the ozone layer caused by the release of CFC's (chlorofluorocarbons) into the atmosphere which react chemically with ozone and break it down into different gases. |
| Ozone Layer | An atmospheric shield providing the Earth with protection from ultra-violet rays which can cause sunburn, skin cancer and the destruction of the delicate plant life which supports the planet's food chain. |
| P-Wave (primary wave, compressional wave) | A seismic body wave that involves particle motion, alternating compression and expansion, in the direction of wave propagation. It is the fastest seismic wave. Compare S-Wave. |
| Pahoehoe | A Hawaiian term for a basaltic lava flow with a smooth, or ropy surface. |
| Pangea | A supercontinent that existed from the end of the Permian to the Jurassic, 300 to 200 million years ago, assembled from large continents like Euramerica, Gondwana, and Siberia, as well as smaller land masses like the Cathaysian and Cimmerian terranes; Greek for "all lands". |
| Particulate Air Pollution | The very small particles of dirt, soot, and other pollutants that are present in the air. |
| Peat | A deposit of partly decayed plant remains in a very wet environment; marsh or swamp deposit of plant remains containing more than 50 percent carbon. |
| Pelean Eruption | A type of volcanic eruption characterized by nuees ardentes and the development of lava domes. |
| Permafrost | Soil conditions prevailing in area whose mean annual temperature is 0 degrees celsius. |
| Petroleum | A general term including both oil and natural gas. |
| pH | A measure of acidity. |
| Plate | A rigid segment of the Earth's lithosphere that moves horizontally and adjoins other plates along zones of the seismic activity. Plates may include portions of both continents and ocean basins. |
| Plate Boundaries | The zones of seismic activity long which plates are in contact. |
| Plate Tectonics | The theory of Plate Tectonics states that the Earth's crust is fragmented into a dozen or more large and small pieces floating on a semi-molten mantle. |
| Plutonic | Applies to igneous rocks formed beneath the surface of the Earth; typically with large crystals due to the slowness of cooling. |
| Pothole | A hole or basin cut into bedrock of a stream by the abrasive action of pebbles and sand swirled by turbulent stream flow. |
| Prime Meridian | The great circle on the Earth's surface passing through The North and South Poles, which is considered 0 degrees longitude. The prime meridian passes through Greenwich, England, and is used as a reference point for measuring longitude east and west. |
| Pyroclastic | Pertaining to clastic material formed by volcanic explosion or aerial expulsion from a volcanic vent. |
| Radiation (Electromagnetic Radiation) | Energy that travels through space in the form of waves without the intervention of matter, as in the transport of heat from the Sun to the Earth. |
| Rain Shadow Deserts | Deserts formed by blocking moisture-bearing winds with mountain barriers. |
| Reef | A large ridge or mound-like structure within a body of water that is built by calcareous organisms such as corals, red algae, and bivalves. |
| Renewable Resources | Living parts of the environment that can renew or replace themselves. |
| Reserves | That portion of the resources for a valuable mineral commodity that can be extracted from the Earth at a profit today. |
| Resources | The reserves of a valuable mineral commodity plus all other mineral deposits that may eventually become available, even those that are presumed to exist but have not yet been discovered and those that are not economically or technologically exploitable at the moment. |
| Rift (graben) | A valley caused by extension of the Earth's crust. Its floor forms as a portion of the crust moves downward along normal faults. |
| Rock | An aggregate of one or more minerals in varying proportions. |
| Rock Cycle | The concept of a sequence of events involving the formation, alteration, destruction and reformation of rocks as a result of geologic processes. |
| Runoff | The precipitation that runs directly off the surface to stream or body of standing water. |
| S-Wave (secondary wave, shear wave) | A seismic body wave that involves particle motion from side to side, perpendicular to the direction of wave propagation. S-waves are slower than P-waves and cannot travel through a liquid. |
| Salinity | The amount of dissolved salt in water. |
| Salinization | A process by which salts accumulate in soil. |
| Scientific Model | A detailed mathematical description of the cause-and-effect relationships between events that can be used to predict or explain other such events. |
| Seafloor Spreading | The process by which ocean floors spread laterally from crests of main ocean ridges. As material moves laterally from the ridge, new material replaces it along the ridge crest by welling upward from the mantle. |
| Sediment | Any solid material that has settled out of a state of suspension in liquid. |
| Sedimentary Rock | Rock formed from the accumulation of sediment, which may consist of fragments and mineral grains of varying sizes from pre-existing rocks, remains or products of animals and plants, the products of chemical action, or mixtures of these. |
| Seismograph | An instrument that detects, magnifies, and records vibrations of the Earth, especially earthquakes. |
| Seismology | The study of earthquakes, and of the structure of the Earth by both natural and artificially generated seismic waves. |
| Seismoscope | An instrument that merely indicates the occurrence of an earthquake. |
| Shield Volcano | A volcano in the shape of a flattened cone, broad and low, built by very fluid flows of basaltic lava. |
| Silicate | One of several rock-forming minerals that contain at least 95% silica (quartz) and usually one or more other common elements. |
| Sinkhole | A natural depression in the surface of the land caused by the collapse of the roof of a cavern or subterranean passage, generally occurring in limestone regions. |
| Smelting | The process of removing metal from ore. |
| Soil | All unconsolidated materials above bedrock. Natural earthy materials on the Earth's surface, in places modified or even made by human activity, containing living matter, and supporting or capable of supporting plants out of doors. |
| Solstice | The two days of the year on which the noon sun is directly overhead at either 23.5 degrees South or 23.5 degrees North. |
| Specific Gravity | Ratio between weight of given volume of material and weight of equal volume of pure water. |
| Spring | Occurs at the intersection of the water table with the ground surface. |
| Stalactite | An icicle-shaped accumulation of dripstone hanging from cave roof. |
| Stalagmite | A post of dripstone growing up from a cave floor. |
| Stratification | The accumulation of mineral in layers or beds. |
| Stratovolcano (composite volcano) | A volcano that is composed of alternating layers of lava and pyroclastic material, along with abundant dikes and sills. Viscous, intermediate lava may flow from a central vent. Example: Mt. Fuji in Japan. |
| Stratum | A layer of sedimentary rock; plural is strata. |
| Striations | Scratches, or small channels, gouged by glacier action. Occur on boulders, pebbles, and bedrock. Striations along bedrock indicate direction of ice movement. |
| Strip Mining | Open pit mining, typically for coal. |
| Subduction | The process of one plate descending beneath another. |
| Subduction Zone | A narrow, elongate region in which one lithospheric plate descends relative to another. |
| Superposition | A statement of relative age in layered rocks: In a series of sedimentary rocks that has not been overturned, the topmost layer is always the youngest and the bottommost layer is always the oldest. |
| Suspended Load | The amount of material a stream carries in suspension. |
| Suspension | A method of sediment transport in which the turbulence of a fluid is able to keep particles supported in the fluid. |
| Tectonic Plates | Enormous, thick sheets of rock that are part of the Earth's upper mantle that move and adjoin each other along zones of seismic activity. Many tectonic plates extend underneath both continents and sea floor. |
| Thrust Fault | A reverse fault on which the dip angle of the fault plane is 15 degrees or less. |
| Till | Glacial drift composed of rock fragments that range from clay to boulder size and randomly arranged without bedding. |
| Transform Boundary | A plate boundary in which plates on opposite sides of the boundary move past each other in opposite directions. The San Andreas fault of California is a good example. |
| Trench | A narrow, steep-walled depression in the ocean floor, much deeper than the adjacent ocean and associated with a subduction zone. |
| Triangulation | The method of locating an epicenter by determining how far it lies from three widely separated seismographs. |
| U-Shaped Valley | A valley carved by glacier erosion and whose cross-valley profile has steep sides and a nearly flat floor, suggestive of a large letter "U". |
| Uniformitarianism | The principle that states the processes operating to change the Earth in the present also operated in the past. |
| Viscosity | The internal resistance to low in a liquid. |
| Volcanic Ash | The dust-sized, sharp-edged, glassy particles resulting from an explosive eruption. |
| Watershed | An area of land that delivers runoff water, sediment, and dissolved substances to surface water bodies, such as rivers or lakes. All watersheds consist of boundaries, a basin and collection areas. |
| Water Table | The surface between the zone of saturation and the zone of aeration. |
| Wave Crest | The top of a wave. |
| Wave Height | The vertical distance between the crest and adjacent trough of a wave. |
| Wave Length | The distance between two successive wave crests or troughs. |
| Wave Trough | The low spot between two successive waves. |
| Weathering | The physical, chemical, and biological processes by which rock at or near the Earth's surface is broken down into smaller pieces. |
| Zone of Aeration | The area immediately below the ground surface within which pore spaces are partially filled with water and partially filled with air. |
| Zone of Leaching | The upper horizons in a soil, through which gravitational moisture travels, removing soluble decomposition products. |
| Zone of Saturation | The zone below the zone of aeration in which all pore spaces are filled with water. |
