GPE Unit 4

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Denudation: The total efffect of all actions that lower the surface of the continents.
Weathering: The physical and chemical disintegration of rock that is exposed to the weather.
Fault: A fracture or zone of fracture where the rock is forcefully broken with an accompanying displacement, that is, an actual movement of crust on one or both sides of the break. The movement can be horizontal or vertical, or combination of both.
Joints: Cracks that develop in bedrock due to stress, but in which there is no appreciable movement parallel to the walls of joint.
Mechanical weathering: The physical disintegration of rock material without any change in its chemical composition.
Frost wedging: Fragmentation of rock due to expansion of water that freezes in rock openings.
Salt wedging: Rock disintegration caused by the crystallization of salts from evaporating water.
Exfoliation: Weathering process in which curved layers peel off bedrock in sheets. This process commonly occurs in granite and related intrusive rocks.
Chemical weathering: The decomposition of rock by the alteration of rock-forming minerals.
Oxidation: The chemical union of oxygen atoms with atoms from various metallic elements to form new products, which are usually more voluminous, softer, and more easily eroded than the original compounds.
Hydrolysis: A chemical union of water with another substance to produce a new compound that is nearly always softer and weaker than the original.
Carbonation: A process in which carbon dioxide in water reacts with carbonate rocks to produce a very soluble product (calcium bicarbonate), which can readily be removed by runoff or percolation, and which can also be deposited in crystalline form if the water is evaporated.
Mass Wasting: The downslope movement of broken rock material by gravity, sometimes lubricated by the presence of water.
Angle of repose: Steepest angle that can be assumed by loose fragments on a slope without downward slope.
Quick clays: Clay formations that spontaneously change from a relatively solid mass into a near-liquid condition as a result of a sudden disturbance or shock.
Fall: Mass wasting process in which in which pieces of weathered rock fragments fall to the bottom of a cliff or steep slope; also called a rock fall.
Talus: Also known as scree. Pieces of rock, of whatever size, that fall directly downslope.
Talus slope: Also known as the talus apron. The fragments of rocks that accumulate relatively uniformly along the base of the slope.
Talus cones: Sloping, cone-shaped heaps of dislodged talus.
Rock glaciers: An accumulated talus mass that moves slowly but distinctly downslope under its own weight.
Landslide: An abrupt and often catastrophic event in which a large mass of rock and earth slides bodily downslope in only a few seconds or minutes. An instantaneous collapse of slope.
Slump: A slope collapse with a backward rotation.
Earthflow: Mass wasting process in which a portion of a water-saturated slope moves a short distance downhill.
Mudflow: Downslope movement of a thick moisture of soil and water.
Debris flow: Streamlike flow of muddy water heavily laden with sediments of various sizes; a mudflow containing large boulders.
Creep: The slowest and least perceptible form of mass wasting, which consists of a very gradual downhill movement of soil and regolith.
Terracettes: A complicated terracing effect, resembling a network of faint trails, which is produced by a creep, usually on steep grassy slopes.
Solifluction: A special form of soil creep in tundra areas that produces a distinctive surface appearance. During the summer the near surface portion of the ground thaws, but the meltwater cannot percolate deeper because of the permafrost below. The spaces between the soil particles become saturated, and the heavy surface material sags slowly downslope.
Fluvial Processes: Processes involving the work of running water on the surface of the Earth.
Streamflow: Channeled movement of water along a valley bottom.
Valley: That portion of the total terrain in which a drainage system is clearly established.
Interfluve: The higher land or ridge above the valley sides that seperates adjacent valleys.
Stream order: Concept that describes the hierarchy of a drainage network.
Stream load: Solid matter carried by a stream.
Dissolved Load: The minerals, largely salts, that are dissolved in water and carried invisibly in solution.
Suspended Load: The very fine particles of clay and silt that are in suspension and move along with the flow of water without ever touching the stream bed.
Bedload: Sand, gravel, and larger rock fragments moving in a stream by saltration and traction.
Saltation: Process in which small particles are moved along by streamflow or wind in a series of jumps or bounces.
Traction: Process in which coarse particles are rolled or slid along the stream bed.
Competence: The size of the largest particle that can be transported by a stream.
Capacity: The maximum load that a stream can transport under given conditions.
Alluvium: Any stream-deposited sedimentary material.
Discharge: Volume of flow of a stream.
Perennial stream: A permanent stream that contains water the year-round.
Ephemeral streams: A stream that carries water only during the "wet season" or during and immediately after rains.
Intermittent stream: A stream that carries water only part of the time, during and immediately after rains.
Thalweg: A line connecting the deepest points of a stream channel.
Sinuous channels: Gently curving or winding stream channel pattern.
Meandering Channels: Highly twisting or looped stream channel pattern.
Braided Channels: A stream that consists of a multiplicity of interwoven and interconnected shallow channels seperated by low islands of sand, gravel, and other loose debris.
Oxbow Lake: A cutoff meander that initially holds water.
Cavern: Large opening or cave, especially in limestone; often decorated with speleothems.
Speleothem: A feature formed by precipitated deposits of minerals on the wall, floor, or roof of a cave.
Stalactite: A pendant structure hanging downward from a cavern's floor.
Karst: Topography developed as a consequence of subsurface solution.
Stalagmite: A projecting structure growing upward.
Sinkhole (doline): A small, rounded depression that is formed by the dissolution of surface limestone, typically at joint intersections.
Collapse Doline: A sinkhole produced by the collapse of the roof of a subsurface cave.
Uvala: A compound doline or chain of intersecting dolines.
Tower Karst: Tall, steep-sided hills in an area of karst topography.
Pillar: An erosional remnant in the form of a steep-sided spire that has a resistant caprock; normally found in an arid or semiarid environment
Mogote: Also known as haystack hills. A steep-sided hill of residual limestone bedrock formed largely by solution action
Swallow Holes: The distinct opening at the bottom of some sinks through which surface drainage can pour directly into an underground channel.
Hydrothermal activity: The outpouring or ejection of hot water, often accompanied by steam, which usually takes the form of either a hot spring or a geyser.
Hot Spring: Hot water at Earth's surface that has been forced upward through fissures or cracks by the pressures that develop when underground water has come in contact with heated rocks or magma beneath the surface.
Geyser: A specialized form of intermittent hot spring with water issuing only sporadically as a temporary ejection, in which hot water and steam spouted upward for some distance.
Fumarole: A hydrothermal feature consisting of a surface crack that is directly connected with a deep-seated source of heat. The little water that drains into this tube is instantly converted to steam by heat and gases, and a cloud of steam is then expelled from the opening.
Playa: Dry lake bed in a basin of interior drainage.
Salina: Dry lake bed that contains an unusually heavy concentration of salt in the lake-bed sediment.
Claypan: A playa surface that is heavily impregnated with clay.
Playa Lake: Shallow and short-lived lake formed when water flows into a playa.
Differential Erosion: The process whereby different rocks or parts of the same rock erode at different times.
Erg: "Sea of sand." A large area covered with loose sand, generally arranged in some sort of dune formation by the wind.
Reg: A desert surface of coarse material from which all sand and dust have been removed by wind and water erosion. Often referred to as desert pavement or desert armor.
Desert varnish: A dark shiny coating that forms on rock surfaces that are exposed to desert air for a long time.
Inselberg: Also known as an island mountain. Isolated summit rising abruptly from a low-relief surface.
Bornhardt: A rounded or domal inselberg composed of very resistant rock that stands above the surrounding terrain because of differential erosion and weathering.
Pediment: A gently inclined bedrock platform that extends outward from a mountain front, usually in an arid region.
Piedmont: Zone at the foot of the mountains.
Piedmont angle: The pronounced change in the angle of slope at a mountain base, with a steep slope giving way abruptly to a gentle one.
Aeolian processes: Processes related to wind action that are most pronounced, widespread, and effective in dry lands.
Deflation: The shifting of loose particles by wind blowing them into the air or rolling them along the ground.
Blowout: Also known as a deflation hollow. A shallow depression from which an abundance of fine material has been deflated.
Sandplain: An amorphous sheet of coarse sand spread across the landscape with no particular surface shape or significant relief.
Sand dune: A mound, ridge, or low hill of loose windblown sand.
Slip face: Steeper leeward side of a sand dune.
Barchan: A crescent-shaped sand dune with cusps of the crescent pointing downward.
Transverse dunes: A cresecent- shaped dune that has convex sides facing the prevailing direction of wind and which occurs where the supply of sand is great. The crest is perpendicular to the wind vector and aligned in parallel waves across the land.
Seif (Longitudinal dune): Long, narrow desert dunes that usually occur in multiplicity and in parallel arrangement.
Loess: A fine-grained, wind-deposited silt. Loess lacks horizontal stratification, and its most distinctive characteristic is its ability to stand in vertical cliffs.
Alluvial Fan: A fan-shaped deposition feature laid down by a stream issuing from a mountain canyon.
Bajada: A continual alluvial surface that extends across the piedmont zone, slanting from the range toward the basin, in which it is difficult to distinguish among individuals fans.
Mesa: A flat-topped, steep-sided hill with a limited summit area.
Scarp: A steep escarpment; nearly vertical cliff.
Plateau: Flattish erosional platform bounded on at least one side by a prominent escarpment.
Stripped plain: A flattish erosional platform where the scarp edge is absent or relatively inconspicuous.
Sapping: An erosional process in which soil particles are removed from a slope by the seepage or trickling out of underground water.
Butte: An erosional remnant of very small surface area and clifflike sides that rises conspicuously above the surroundings.
Badlands: Intricately rilled and barren terrain of arid and semiarid regions, characterized by a multiplicity of short, steep slopes.
Ice Sheets: A vast blanket of ice that completely inundates the underlying terrain to depths of hundreds of thousands of meters.
Periglacial zone: An area of indefinite size beyond the outermost extent of ice advance that was indirectly influenced by glaciation.
Valley glacier: A long, narrow feature resembling a river of ice, which spills out of its originating basins and flows down-valley.
Piedmont glacier: A valley glacier that extends to the mouth of the valley and spreads out broadly over the flat land beyond.
Alpine glacier: Individual glacier that develops near a mountain crest line and normally moves down-valley for some distance.
Cirque glaciers: A small glacier confined to its cirque and not moving down-valley.
Accumulation: Addition of ice into a glacier by incorporation of snow.
Ablation: Wastage of glacial ice through melting and sublimation.
Neve: Also known as firn. Snow granules that have become packed and begin to coalesce due to compression, achieving a density about half as great as that of water.
Equilibrium line: A theoretical line separating the ablation zone and the accumlation zone of a glacier along which accumulation exactly balances ablation.
Plucking: Action in which rock particles beneath the ice are grasped by the freezing of meltwater in joints and fractures and pried out and dragged along in the general flow of a glacier. Also called glacial quarrying.
Glacial flour: Rock material that has been ground to the texture of very fine different from the local bedrock.
Till: Rock debris that is deposited directly by moving or melting ice with no meltwater flow or redeposition involved.
Glacial erratic: Outsize boulder included in the glacial till, which may be very different from the local bedrock.
Glaciofluvial deposition: The action whereby much of the debris that is carried along by glaciers is eventually or redeposited by glacial meltwater.
Roche moutonnee: A characteristic glacial landform produced when a bedrock
Till plain: An irregularly undulating surface of broad, low rises and shallow depressions produced by the uneven deposition of glacial till.
Moraine: The largest and generally most conspicuous landform feature produced by glacial deposition, which consists of irregular rolling topography that rises somewhat above the level of the surrounding terriain.
Kettle: An irregular depression in a morainal surface created when blocks of stagnant ice eventually melt.
Drumlin: A low, elongated hill formed by ice-sheet deposition.
Stratified Drift: Drift that was sorted as it was carried along by the flowing glacial meltwater.
Outwash plain: Extensive glaciofluvial feature that is a relatively smooth, flattish alluvial apron deposited beyond recessional or terminal moraines by streams issuing from ice.
Valley train: A lengthy deposit of glaciofluvial alluvium confined to a valley bottom beyond the outwash plain.
Eskers: Long, sinuous ridges of stratified glacial drift composed largely of glaciofluvial gravel and formed by the choking of subglacial streams during a time of glacial stagnation.
Kame: A relatively steep-sided mound or conical hill composed of stratified drift found in areas of ice-sheet deposition and associated with meltwater deposition in close association with stagnant ice.
Cirque: A broad amphitheater hollowed out at the head of a glacial valley by ice erosion.
Arete: A narrow, jagged, serrated spine of rock; remainder of a ridge crest after several glacial cirques have been cut back into an interfluve from opposite sides of a divide.
Horn: A steep-sided pyramidal rock pinnacle formed by expansive glacial quarrying of the headwalls where three or more cirques intersect.
Tarn: Small lake in the shallow excavated depression of rock benches of a glacial trough or cirque.
Glacial trough: A valley reshaped by an alpine glacier, usually U-shaped.
Col: A pass or saddle through a ridge produced when two adjacent glacial cirques on opposite sides of a divide are cut back enough to remove part of the arete between them.
Glacial Steps: Series of level or gently sloping bedrock benches alternating with steep drops in the down-valley profile of a glacial trough.
Paternoster Lake: A sequence of small lakes found in the shallow excavated depressions of a glacial trough.
Hanging Valley: A tributary glacial trough, the bottom of which is considerably higher than the bottom of the principal trough that joins it.
Proglacial Lake: A lake formed when ice flows across or against the general slope of the land and the natural drainage is impeded or completely blocked so that meltwater from the ice becomes impounded against the ice front.

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