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
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-a cone-shaped depression in the water table around a well which develops when water is withdrawn from the well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
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
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
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
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 washesin arid environments