Appendix D
Glossary of Terms1


alluvium

-general term for unconsolidated material (clay, sand, silt, gravel) deposited by streams


bajada

-a broad alluvial slope extending from the base of a mountain range into a basin.,. formed by joining of a series of alluvial fans; occurs in add and semiarid conditions

base level

-theoretical lowest level toward which erosion of the Earth's surface constantly progresses; lowest level to which a river flows - locally could be into another river or lake; ultimately, into the ocean. Sea level is called the ultimate base level.

batholith

-a large mass of hardened molten rock with more than 100 km2 of surface exposure with no known lower limit

berm

-a relatively narrow horizontal man-made shelf, ledge, or bench which breaks the continuity of a slope

breccia

-a coarse-grained rock composed of angular rock fragments held together by mineral cement

brittle deformation

-deformation in which rocks behave rigidly, by cracking and breaking, when a force or stress is applied


caliche

-secondary calcareous material found in layers on or near the surface in arid and semi-add regions, composed of soluble calcium salts with varying amounts of gravel, silt, clay, and sand; a carbonate layer produced by soil-forming (pedogenic) processes

capillary force

-the action by which a fluid, such as water, is drawn up in small interstices as a result of surface tension of other droplets of water

clast

-a grain or fragment of rock, such as silt, sand, pebble or boulder



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Ward Valley: An Examination of Seven Issues in Earth Sciences and Ecology Appendix D Glossary of Terms1 alluvium -general term for unconsolidated material (clay, sand, silt, gravel) deposited by streams bajada -a broad alluvial slope extending from the base of a mountain range into a basin.,. formed by joining of a series of alluvial fans; occurs in add and semiarid conditions base level -theoretical lowest level toward which erosion of the Earth's surface constantly progresses; lowest level to which a river flows - locally could be into another river or lake; ultimately, into the ocean. Sea level is called the ultimate base level. batholith -a large mass of hardened molten rock with more than 100 km2 of surface exposure with no known lower limit berm -a relatively narrow horizontal man-made shelf, ledge, or bench which breaks the continuity of a slope breccia -a coarse-grained rock composed of angular rock fragments held together by mineral cement brittle deformation -deformation in which rocks behave rigidly, by cracking and breaking, when a force or stress is applied caliche -secondary calcareous material found in layers on or near the surface in arid and semi-add regions, composed of soluble calcium salts with varying amounts of gravel, silt, clay, and sand; a carbonate layer produced by soil-forming (pedogenic) processes capillary force -the action by which a fluid, such as water, is drawn up in small interstices as a result of surface tension of other droplets of water clast -a grain or fragment of rock, such as silt, sand, pebble or boulder

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Ward Valley: An Examination of Seven Issues in Earth Sciences and Ecology clastic -pertaining to a rock or sediment composed of fragments of pre-existing rocks compression -a system of forces or stresses which result in the decrease in volume or shortening of the crust cone of depression -a cone-shaped depression in the water table around a well which develops when water is withdrawn from the well conglomerate -a coarse-grained sedimentary rock composed of rock fragments larger than 2 mm in diameter and a fine grained matrix and/or cement of silt, sand, or calcium carbonate; the rock fragments usually are rounded, as pebbles, rather than angular as in a breccia continental crust -the crust which underlies the continents; mainly granite, a light colored, low density rock, high in silica and aluminum, low in iron and magnesium continental margin -edge of the continent which is between the shoreline and the abyssal ocean floor continental shelf -the part of the continental margin between the shoreline and the continental slope; the fiat, gently sloping extension of the continent under the ocean correlative -belonging to the same stratigraphic position or level, generally implies strata of the same age, having formed at the same time in the geologic past crust -the outermost layer of the earth crustal extension -pulling apart of the outermost layer of the Earth's surface as a result of strain crystalline rock -a rock consisting wholly of relatively large mineral grains, refers generally to highly metamorphosed rocks Darcy's Law -a formula for calculating the rate of flow of fluids through a matrix of soil or porous rock on the assumption that flow is laminar and that inertia can be neglected deep sod water flux -deep percolation of water in the unsaturated zone deformation -the process of folding, faulting, shearing, compression, or extension of rocks as a result of earth forces deposition/sedimentation -the process of accumulation of loose rock material into layers or masses on the earth's surface above or below the sea

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Ward Valley: An Examination of Seven Issues in Earth Sciences and Ecology detachment fault -a low-angle fault formed at the base of a horizontal or gently dipping body of rock; can be a thrust fault as a result of compression, or a normal fault as a result of extension. dike -an igneous intrusion which cuts across the layered structure of the surrounding rock; magma that fills a crack in the crust and hardens dilution -reduction in the concentration of a solution by addition of more solvent dip -an angle down from the horizontal that a sloping structural surface, e.g., a bed or a fault plane, makes dispersion -distribution of a substance outward in all directions drainage system -the network of surface streams, including a main stream and all of its tributaries, which drains a particular region drawdown -in a body of water, the difference between the water-surface elevation at a constriction, and what the elevation would be with no constriction ductile deformation -deformation in which rocks behave like a viscous substance erosional exhumation -the uncovering or exposure by erosion of a surface, landscape, or feature that has been buried beneath other rocks evaporite -a non-clastic sedimentary rock composed of minerals produced from a saline solution, mainly the ocean or salt lake, due to evaporation, such as salt (sodium chloride) or gypsum evapotranspiration -loss of water from a land area through transpiration by plants and evaporation from the soil extension -a strain term signifying pulling apart the crust resulting in an increase in length flux -the rate of water movement through the unsaturated zone, regardless of direction fold -a curve or bend of a rock strata or other planar feature resulting from explosive volcanic activity that pulverizes rock as it blasts it out of the volcano ground water -subsurface water located in the saturated zone below the water table

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Ward Valley: An Examination of Seven Issues in Earth Sciences and Ecology hydraulic conductivity -a measure of the unsaturated zone's transmission of water hydraulic gradient -in an aquifer, the rate of change of total head per unit of distance in a given direction infiltration -the movement of water downward into soil or porous rock island arc -a chain of near shore islands rising from deep sea floor, produced by the down-plunge of oceanic crust beneath a continental margin isothermal -maintaining a constant temperature during any process or procedure lateral flow -flow of water across a sloping surface or through a matrix because of gravity lateral subsurface flow -water infiltrating the surface soil and moving laterally in the subsurface following a shallow slope or gradient magma -molten rock, formed deep in the earth's crust, from which igneous rocks solidify magmatism -the development and movement of magma matric potential -is a measure of how tightly water is held by the soil matrix matrix -the fine-grained material enclosing, or filling the interstices between, the larger grains of a sediment or sedimentary rock metamorphism -the chemical, mineralogical, and/or structural change of rocks as a result of change in temperature and/or pressure mountain building -the formation of mountains through the process of thrusting, folding, and faulting of layers of the earth resulting from continental collisions. Deeper layers of the crust also undergo metamorphism during this process. oceanic crust -the crust which underlies the ocean basins; mainly basalt, a dark, dense rock, low in silica and aluminum, high in iron and magnesium osmotic potential -the energy required to remove dissolved salts from soil water paleosol -a buried soil horizon of the geologic past perched water -accumulated water trapped in the unsaturated zone by either some impermeable layer or some structural feature

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Ward Valley: An Examination of Seven Issues in Earth Sciences and Ecology pereolation -the downward movement of water through small openings within a porous material, such as in the unsaturated zone permeability -the property or capacity of a porous rock, sediment or soil for transmitting a fluid; the interconnected pore spaces that allow movement of water from one place to another piston flow -the uniformly distributed downward movements of water in the unsaturated zone playa -a dry, vegetation-free fiat area at the lowest part of an undrained desert basin; a dry lake bed in the desert pluton -an igneous intrusion; a large amorphous mass of magma formed deep within the earth, moved upward, and hardened before reaching the surface potential -refers to energy as function of position or of condition precipitation -the solidification of dissolved particles and settling out of solution by gravity probable maximum precipitation (PMP)2 -the theoretical greatest depth of precipitation for a given duration that is physically possible over a given size storm area at a particular geographical location probable maximum flood (PMF)2 -the most severe flood that is considered reasonably possible at a site as a result of meteorologic and hydrologic conditions preferential flow -movement of water downward through the unsaturated zone, along non-uniformly distributed pathways Proterozoic -the period of time before the Cambrian period, prior to macroscopic life recharge -the process of adding water to the saturated zone regional uplift -large-scale, long-term upward movement of an area of the crust relief -the vertical difference in elevation between hilltops or mountain summits and lowlands or valleys in a particular area. An area of high relief has great vertical variation and an area of low relief has little variation in elevation. root zone -area in the sediment in which living plant roots are found

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Ward Valley: An Examination of Seven Issues in Earth Sciences and Ecology saturation -the point at which the interstices of a material, such as a rock, contain the maximum possible amount of water; all pores are filled with water sill -an igneous intrusion which parallels the planar structure of the surrounding rock; magma that forces its way between layers and then parallels the layered structure when it hardens. soil-water potential -a measure of how tightly water is held by the soil matrix as result of capillary and other forces sorption -the taking up of a fluid or solution by a porous medium standard deviation -a quantification of the error range (±) of values about the average of a number of measurements storage capacity -the ability of a soil to hold water; the amount of water that can be held in the unsaturated zone texture -the general physical appearance or character of a rock; the pattern or interconnection of rock particles tuff -a general term for unconsolidated ash and fine fragments of rocks, resulting from explosive eruptions of volcano. unconfined aquifer -ground water that has a free water table, i.e. water not confined by pressure beneath impermeable rocks unsaturated zone -a subsurface zone including the soil that may contain water under pressure less than that of the atmosphere, including water held by capillary forces; it is the zone above the water table vadose zone -another term for unsaturated zone volcanism -the processes by which magma and its associated gases rise into the crust and are extruded onto the surface as lava flows and into theatmosphere water table -the surface between the saturated zone and the unsaturated zone, the uppermost part of ground water water table divide -a ridge or elevated zone in the water table from which ground water moves away in both directions xeroriparian-refers to species typically found in or along washes in arid environments