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611 Cards in this Set

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Aa
A type of lava flow that has a jagged, blocky surface.
Ablation
A general term for the loss of ice and snow from a glacier
Abrasion
The grinding and scraping of a rock surface by the friction and impact of rock particles carried by water, wind, or ice.
Abyssal plain
Very level area of the deep-ocean floor, usually lying at the foot of the continental rise
Accretionary Wedge
A large wedge-shaped mass of sediment that accumulates in subduction zones. Here sediment is scraped from the subducting oceanic plate and accreted to the overriding crustal bloc.
Active continental margin
usually narrow and consisting of highly deformed sediments. They occur where oceanic lithoshpere is being subducted benearth the margin of a continent
Active layer
The zone above the permafrost that thaws in summer and refreezes in winter.
Aftershock
A smaller earthquake that follows the main earthquake
Alluvial Fan
a fan-shaped deposit of sediment formed when a stream's slope is abruptly reduced
Alluvium
unconsolidated sediment deposited by a stream
Andesitic
Igneous rocks having a mineral makeup between that of grante and basalt, after the common volcanic rock andesite
Angle of repose
the steepest angel at which loose material remains stationary without sliding downslope
Angular unconformity
An unconformity in which the older strata dip at an angle different from that of the younger beds
Anthracite
a hard, metamorphic form of coal that burns clean and hot.
Anticline
a fold in sedimentary strata that resembles an arch
Aphanitic Texture
a texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished with the unaided eye.
Aquifer
rock or sediment through which groundwater moves easily
Aquitard
an impermeable bed that hinders or prevents groundwater movement
Archean eon
the second eon of Precambrian time. The eon following the Hadean eon and preceding the Proterozoic eon. IT extends between about 3.8 and 2.5 billion years ago.
Arete
A narrow, knifelike ridge separating two adjacent glaciated valleys.
Arkose
A feldspar-righ sandstone
Artesian Well
a well in which the water rises above the level where it was initially encountered.
Astenosphere
A subdivision of the mantle situatied below the lithosphere. This zone of weak material exists below a depth of about 100 kilometers and in some regions extends as deep as 700 kilometers. The rock within this zone is easily deformed
Atmoshpere
The gasous portion of a plante; the planet's enevelope of air. One of the traditional subdivisions of Earth's physical environment
Atoll
A continuous or broken ring or coral reef surrounding a central lagoon
Atom
the smallest particle that exists as an element
Atomic mass unit
A mass unit equal to exactly one-twelfth the mass of a carbon-12 atom
Atomic number
the number of protons in the nucleus of an atom
Atomic Weight
the average of the atomic masses of isotopes in a give element
Aureole
a zone or halo of contact metamorphism found in the host rock surrounding an igneous intrusion
Back swamp
a poorly drained area on a floodplain, resulting when natural levees are present
Bar
common term for sand and gravel deposits in a stream channel
Barchan dune
a solitary sand dune shaped like a crescent with its tips pointed downwind
Barchanoid dunes
dunes forming scalloped rows of sand oriented at right angles to the wind. This form is intermediate between isolated barchans and extensive waves of transverse dunes
Barrier island
a low, elongated ridge of sand that parallels the coast
Basal slip
a mechanism of glacial movement in which the ice mass slides over the surface below
basalt
an aphanitic igneous rock of mafic composition
basaltic
term used to describe igneous rocks that contain abundeant dark (ferromagnesian) minerals and about 50 percent silica
Base level
the level below which a stream cannot erode
Basin
a circular downfolded structure
Batholith
a large mass of igneous rock that formed when magma was emplaced at depth, crystallized, and was subsequently exposed by erosion
Baymouth Bar
a sandbar that completely crosses a bay, sealing it off from the main body of water
Beack drift
the transport of sediment in a zigzag pattern along a becak. It is caused by the uprush of water form obliquely breaking waves
Beach nourishment
large quantities of sand are added to the beach system to offset losses caused by wave erosion. By building beaches seaward, becah quality and storm protection are both improved.
Bedding plane
a nearly flat surface separating two beds of sedimentary rock. Each bedding plane marks the end of one deposit and the beginning of another having different characteristics.
Bed load
sediment rolled along the bottom of a stream by moving water, or particles robed along the ground surface by wind
Belt of soil moisture
a zone in which water is held as a film on the surface of soil particles and may be used by plants or withdrawwn by evaporation. The uppermost subdivision of the zone of aeration.
Biochemical
describing a type of chemical sediment that form swhen material dissolved is water is precipatead by water-dwelling organisms. Shells are common examples
Biogenous sediment
seafloor sediments consisting of material or marine-organic origin
Bituminous coal
the most common form of coal, ofter called soft, black coal
blowout (deflation hollow)
a depression excavated by wind in easily eroded materials
body wave
a seismic wave that travels through Earth's interior
bottomset bed
alayer of fine sediment deposited beyond the advancing edge of a delta and then buried by continuous delta growth
Bowen's reaction series
a concept proposted by N.L. Bowen that illustrates the relationship between magma and the minerals crystallizing from it during the formation of igneous rock
Braided stream
a stream consisting of numerous intertwining channels
breakwater
a structure protecting a nearshore area from breaking wave
Breccia
a sedimentary rock composed of angular fragments that were lithifiedq
Brittle deformation
deformation that in volves the fracturing of rock Associated with rocks near the surface
Burial metamorphism
low-grade metamorphism that occurs in the lowest layers of very thick accumulations of sedimentary strata
Caldera
a large depression typically caused by collapse of the summit area of a volcano following a violent eruption
Caliche
a hard layer, rich in calcium carbonate, that forms beneath the B horizon in soils of arid regions
Calving
wastage of a glacier that occurs when large pieces of ice break off into water
Capacity
the total amount of sediment a stream is able to transport
Capillary fringe
a relatively narrow zone at the base of the zone or aeration. Here water rises from the water table in tiny threadlike openings between grains of soil or sediment.
Cap rock
a necessary part of an oil trap. The cap rock is impermeable and hence keeps upwardly mobile oil and gas from escaping at the surface.
Catastrophism
the concept that Earth was shaped by catastrophic events or a short -term nature
Cavern
a naturally formed underground chamber or serioes of chambers most commonly prodeuced by solution activity in limestone
Cementation
one way in which sedimentary rocks are lithified. As material precipitates from water that percolates through the sediment, open spaces are filled and particles are joined into a solid mass
Cenozoic era
a time span on the geologic time scale beginning about 65 million years ago following the Mesozoic era
Chemical sedimentary rock
sedimentary rock consisting of material that was precipitated from water by either inorganie or organic means
Chemical weathering
the processes by whcih the internal structure of a mineral is altered by the removal and/or addition of elements
Cinder cone
a rather small volcano built primarily of pyroclastics ejected from a single vent
Cirque
an amphitheater-shpaed basin at the head of a glaciated valley produced by frost wedging and plucking
Clastic
a sedimentary rock texture consisting of broken fragments of preexisting rock
Cleavage
the tendency of a mineral to break along planes of weak bonding
Col
a pass between mountain valleys where the headwalls of two cirques intersect
Color
a phenomenon of light by which otherwise identical objects may be differentiated
Column
a feature found in cabes that is formed when a stalactite and stalagmite join
Columnar joints
a pattern of crack sthat forms during cooling of molten rock to generate columns
Compaction
a type of lithification in which the weight of overlying material compresses more deeply buried sediment. It is most important in fine-grained sedimentary rocks such as shale.
Competence
a measure of the largest particle a stream can transport; a factor dependent on velocity
Composite cone
a volcano composed of both lava flows and proclastic material
compound
a substance formed by the chemical combination of tow or more elemetns in definite proportions and usually having properties different from those iof its constituent elements
Concordant
a term used to describe intrusive igneous masses that form parallel to the bedding of the surrounding rock
Conduit
a piplike opening through which magma moves toward earth's surface. It terminates at a surface opening called a vent.
Cone of depression
a cone-shaped depression immediately surrounding a well
Confortable layers
rock layers that were deposited with-out interruption
conglomerate
a sedimentary rock consisting of rounded, gravel-size particles
contact metamorphism
changes in rock cause by the heat of a nearby magma body
Continental drift
a hypothesis, credited largely to Alfred Wegener, that suggested all present continents once existed as a single super continent. Further, beginning about 200 million years ago, the super continent began breaking ionto smaller continents, whcih then drifted to their present positions.
Continental rise
the gently sloping surface at the vase of the continental slope
continental shelf
the gently sloping submerged portion of the continental margin, extending from the shoreline to the continental slope
Continental slope
the steep gradient that leads to the deep ocean floor and marks the seaward edge of the continental shelf
Continental volcanic arc
mountains formed in part byt igneous activity associated with the subduction of oceanic lithoshpere beneath a continent. Examples include the Andes and the Cascades.
Convergent plate boundary
a boundary in which two plates move together, resulting in oceanic lithoshpere being thrust beneath an overriding plate, eventually to be reabsored into the mantle. IT can also involve the collision of two continental plates to create a mountain syystem
core
located beneath the mantle, it is Earth's innermost layer. The core is diveided into an outer core and an inner core.
Correlation
establishing the equialence of rocks of similar age in different areas
Crater
the depression at the summit of a volcano or that which is produced by a meterorite impcat
Creep
the slow downhill moveent of soil and regolith
Crevasse
a deep crack in the brittle surface of a glacier
Cross0bedding
structure inwhich relatively thin layers are inclined at an angle to the main bedding. Formed by currendts of wind or water.
Cross-cutting
a principle of relative dating. A rock or fault is younbger than any rock (or fault) through which it cuts
crust
the very thing, outermost layer of earth
Crystal
an orderly arrangement of atoms
Crystal form
the external appearance of a mineral as determined by its internal arrangement of atoms
Crystallization
the formation and growth of a crystalline solid from a liquid or gas
Curie point
the temperature above which a material loses its magnetization
Cut bank
the area of active erosion on the outside of a meander
Cutoff
a short channel segment created when a river erodes through the narrow neck of land between meanders
Dark Silicate
silicate minerals containing ions of iron and/or magnesium in their structure. They are dark in color and have a higher specific gravity than nonferromagnesian silcates
Daughter product
an isotope resulting from radioactive decay
Debris flow
a relatively rapid type of mass wating that involves a flow of soil and regolith containing a large amount of water. Also called mudflows
Decompression melthing
melting that occurs as rock ascends due to a drop in confining pressure.
Deep-focus earthquake
an earthquake focus at a depth of more than 300 kilometers
Deep-ocean basin
the portion of seafloor that lies between the continental margin and the oceanic ridge system. This region comprises almost 30 percent of Earth's surface.
Deflation
the lifting and removal of loose material by wind
Deformation
general term for the processes of folding, faulthing, shearing, compression, or extension of rocks as the result of various natural forces
Delta
an accumultaion of sediment formed where a stream enters a lake of ocean
Dendritic pattern
a stream system that resembles the pattern of a branching tree
Density
the weight per unit volume of a particular material
Desert
one of the two types of dry climate; the of the dry climates
Desert pavement
a layer of coarse pebbles and gravel created when wind removes the finer material
Detachment fault
a low-angle fault that represents a major boundary between unfaultted rocks below that exhibit brittle deformation via faulting
Detrital sedimentary rocks
rocks that form from the accumulation of materials that originate and are transported as solid particles derived from both mechanicla and chemical weathering
Diagenesis
a collective term for all the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithifaction
Dike
a tabular-shaped intrusive igneous feature that cuts through the surrounding rock
Dip
the angle at which a rock layer is inclined from the horizontal. The direction of dip is at a right angle to the strike
Dip-slip fault
a fault in which the movement is parallel to the dip of the fault
Discharge
the quantity of water in a stream that passes a given point in a given period of time
Disconformity
a type of unconformity in which the beds above and below are parallel
Discontinuity
a sudden change with depth in one or more of the physical properties of the material making up Earth's interior. The boundary between two dissimilar materials in Earth's interior as determined by the behavior of seismic waves.
Discordant
a term used to describe plutons that cut across existing rock structures, such as bedding planes
Disseminated deposit
any economic mineral deposit in which the desired mineral occurs as scattered particles in the rock but in sufficient quantity to make the deposit an ore
Dissolved load
the portion of a stream's load carried in solution
Distributary
a section of a stream that leaves the main flow
Diurnal tide
a tide characterized by a single high and low water height each tidal day
Dissolved load
the portion of a stream's load carried in solution
distributary
a section of a stream that leaves the main flow
diurnal tide
a tide characterized by a single high and low water height each tidal day
Divergent plate boundary
a boundary in which two plates move apart, resulting in upwelling of materiial from mantle to create a new sea floor
Divide
an imaginary line that seperates the drainage of two streams; often found along a ridge
dome
a roughly cicular, upfolded structure
drainage basin
the land area that contributes water to a stream
drawdown
the difference in height between the bottom of a cone of depression and the original height of the water table
drawdown
the difference in height between the bottom of a cone of depression and the original height of the water table
Drumlin
a streamlined asymmetrical hill composed of glacial till. The steep side of the hill faces the direction from which the ice advanced
dry climate
a climate in which the yearly precipitation is less than the potential loss of water by evaporation
Ductile deformation
a type of solid-state flow that produces a change in the size and shape of a rock body without fracturing. Occurs at depths where temperatures and confininf pressures are high
Dune
a hill or ridge of wind-deposited sand
dry climate
a climate in which the yearly precipitation is less than the potential loss of water by evaporation
earthflow
the downslope movement of water-saturated clay-rich sediment. Most characteristic of humid regions.
earthquake
vibration of earth produced by the rapid release of energy
Echo sounder
an instrument used to determine the depth of water by measuring the time interval between emission of a sound signal and the return of its echo from the bottom
Elastic deformation
nonpermanent deformation in which rock returns to its original shape when the stress is released
Elastic deformation
nonpermanent deformation in which rock returns to its original shape when the stress is released
elastic rebound
the sudden release of stored strain in rocks that results in movement along fault
electron
a negatively charged subatomic particle that has negligible mass and is found outside the atom's nucleus
Element
a substance that cannot be decomposed into simpler substances by oridnary chemical or physical means
Emergent Coast
a coast where land formerly below the sea level has been exposed either by crustal uplift or a drop in sea level of both
End moraine
a ridge of till marking a former position of the front of the glacier
Energy-level shell
the region occupied by electrons with a specific energy level
Eon
the largest time unit of the geologic time scale, next in order of magnitude above is...era
Epicenter
the location of Earth's surface that lies directly above the focus of an earthquake
Epoch
a unit of the geological time scale that is a subdivision of a period
Era
a major division on the geologic time scale; eras are divided into shorter units called periods
Erosion
the incorporation and transportation of material by a mobile agent, such as water, wind, or ice
Eruption column
buoyant plumes of host ash-laden gases that can extend thousands of meters into the atmosphere
Esker
sinuous ridge composed largely of sand gravel deposited by a stream flowing in a tunnel beneath a glacier near its terminus
Estuary
a partially enclosed coastal water body that is conneted to the ocean. Salinity here is measurably reduced by the freshwater flows of rivers
Evaporite
a sedimentar rock formed of material deposited from solution by evaporation of water
Evapotranspiration
the combined effect of evaporation and transpiration
Exfoliation Dome
large, dome-shaped structure, usually composed of granite, formed by sheeting
Exotic stream
a permanent stream that traverses a desert and has its source in well-watered ares outside the desert
External process
process such as weathering, mass wating, or erosion that is powered by the Sun and transforms solid rock into sediment
Extrusive
igneous activity that occurs at Earth's surface
Fall
a type of movement common to mass0wasting processes that refers to the free falling of detached individual pieces of any size
Fault
a break in a rock mass along which movement has occured
Fault-block mountain
a mountain formed by the displacement of rock along fault
Fault creep
slow, gradula displacement along a fault that occurs relatively smoothly and with little noticeable seismic activity
Fault scarp
a cliff created by movement along a fault. It represents the exposed surface of the fault prior to modification by weathering and erosion
Felsic
a term derived from feldspar and silica (quartz). It is a term used to describe granitic igneous rocks
Fetch
the distance that the wind has traveled across the open water
Fiord
a steep-sided inlet of the sea formed when a glacial trough was partially submerged
Fissure
a crack in rock along which there is a distinct separation
Fissure eruption
an eruption in which lava is extruded from narrow fractures or cracks in the crust
Flood
the overflow of a stream channgel that occurs when discharge exceeds the channel's capactiy. The most common and destructive geologic hazard
Flood basalts
flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thicknesses of hundreds of meters
Floodplain
the flat, low-lying prtion of a stream valley subject to periodic inundation
Flow
a type of movement common to mass-wasting processes in which water-saturated material moves downslope as a viscous fluid
Fluorescence
the absorption of ultraviolet light, which is reemited as visible light
Fold
a best layer or series of layers that were originally horizontal and subsequently deformed
Foliated
a texture of metamorphic rocks that gives the rock a layered appearance
Foliation
a term for a linear arrangement of textural features often exhibited by metamorphic rocks
foreset bed
an inclined bed deposited along the front of a delta
foreshocks
small earthquakes that often precede a major earthquake
fossil
the remains or traces of organisms preserved from the geologic past
fossil fuel
general term for any hydrocarbon that may be used as a fossil fuel, including coal, oil, natural gas, bitumen from tar sands, and shale oil
Fossil succession
fossil organisms succeed one another in a definite and determinable order, and at any time period can be recognized by its fossil content
Fractional crystalization
the process that seperates magma into components having varieds compositions and melting points
fracture(mineral)
one of the basic physical properties of minerals It relates to the breakge of mineral when there are no planes of weakness in the crystalline structure. Examples include conchoidal, irregular, and splintery
Fracture (rock)
any break or rupture in rock along which no appreciable movement has taken place
Frost wedging
the mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices
Fumarole
a vent in a volcanic area from which fumes or gases escape
Gaining stream
streams that gain water from the inflow of groundwater through the streambed
Geology
the science the examines Earth, its form and composition, and the changes it has undergone and is undergoing
Geothermal Energy
natural steam used fro power generation
Geothermal gradient
the gradual increase in temperature with depth in the crust. The average is 30degrees C per kilometer in the upper crust
Geyser
a fountain of hot water ejected periodically from the ground
Glacial Budget
the balance, or lack of balance, between accumulation at the upper end of a glacier, and loss at the other end
Glacial drift
an all-embracing term for sediments of glacial origin, no matter how, where, or in what shape they were deposited
Glacial Budget
the balance, or lack of balance, between accumulation oat the upper end of a glacier, and loss at the other end
Glacial erratic
an ice-transported boulder that was not derived from the bedrock near its present site
Glacial striations
scratches and grooves on bedrock cuased by glacial abrasion
Glacial trough
a mountain valley that has been widened, deepened, and straightened by a glacier
Glacier
a thick mass of ice originating on land from the compaction and recrystallization of snow. The ice shows evidence of past or present flow.
Glass (volcanic)
natural glass produced when molten lava cools too rapidly to permit crystallization. Volcanic glass is a solid composed of unordered atoms
Glassy texture
a term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals
Gneissic Texture
the texture displayed by the metamorphic rock gneiss in which dark and light silicate minerals have separated, giving the rock a banded appearance
Gondwanaland
the southern portion of Pangaea consisting of South America, Africa, Australia, India, and Antartica
Graben
a valley formed by the downward displacement of a fault-bounded block
Graded bed
a sediment layer characterized by a decrease in sediment size from bottom to top
Graded stream
a stream that has the correct channel characterisitcs to maintain the exact velocity required to transport the material supplied to it
Granitic
igneous rocks composed mainly of light coloered silicates (quartz and feldspar) are said to have this composition
Gradient
the slop of a stream; generally measured in feet per mile
Greenhouse effect
carbon dioxide and warer vapor in a planet's atmosphere absorb and reradiate infrared wavelengths, effectibvely trapping solar energy and raising the temperature
Groin
a short wall built at a right angle to the seashore to trap moving sand
Groundmass
the matrix of smaller crystlas within an igneous rock that has porphyritic texture
Ground moraine
an undulating layer of till deposited as the ice front retreats
Groundwater
water in the zone of saturation
Guyot
a submerged flat-topped seamount
Hadean eon
the first eon on the geologic time scale. The eon ending 3.8 billion years ago that preceded the Archean eon
Half-life
the time required for on half of the atoms of a radiocative substance to decay
Hanging valley
a tributary valley that enters a clacial trought at a considerable height above the floor of the trough
Hardness
a mineral's resistance to scratching and abrasion
head
the vertical distance between the recharcge and discharge points of a water table. Also, the source area or beginning of a valley
Headward erosion
the extension upslope of the head of a valley due to erosion
Historical geology
a major division of gelogy that deals with the origin of Earth and its develpment through time. usually involves the study of fossils and their sequence in rock beds.
Hogback
a naroow, sharp-crested ridge formed by the upturned edge of a steeply dipping bed of resistant rock.
Horn
a pyramid-like peak formed by glacial action in three or more cirques surrounding a mountain summit
Horst
an elongated, uplifted block of crust bounded by faults
Hot spot
a proposed concentration of heat in the mantle capable of introducing magma that in turn extrudes onto Earth's surface. The intraplate volcanism that produced the Hawaiian Islands is one exaple.
Hot spring
a spring in which the water is 6-9 degrees C warmer than the mean annual air temperature of its locality
Humus
Organic matter in soil produced by the decomposition of plants and animals
Hydrogenous sediment
seafloor sediments consisting of minerals that crystallize from seawater. The principal example is manganese nodules
Humus
organic matter in soil produced by the decompoistion of plants and animals
Hydrologic Cycle
the unending circulation of Earth's water supply. The cycle is powered by energy from the Sun and is characterized by continuous exchanges of water among the oceans, the atmosphere, annd the continents
Hydrolisis
A chemical-weathering process in which minerals are altered by chemically reacting with water and acids
Hydrosphere
the water portion of our planet; one of the traditional subdivisions of Earth's physical environment
Hydrosphere
the water portion of our planet; one of the traditional subdivisions of Earth's physical environment
Hydrothermal metamorphism
chemical alterations that occur as hot, ion-rich water ciculates through fractures in rock
Hydrothermal solution
the hot, watery soution that escapes from a mass of magma during the latter stages of crystallization. Such solutions may alter the surrounding country rock and are frequently the source of significant ore deposits
Hypotesis
a tentative explanation that is then tested to determine if it is valid
Ice cap
A mass of glacial ice covering a high upland or plateau and spreading out radially
Ice-contact deposit
an accumulation of stratified drift deposited in contact with a supporting mass of ice
Ice sheet
a very large, thick mass of glacial ice flowing outward in all directions from one or more accumulation centers
Igneous rock
a rock formed by the crystallization of molten magma
Immature Soil
a soil lacking horizons
Impact metamorphism
metamorphism that occurs when meterorites strike Earth's surface
Incised Meander
Meandering channel that flows in a steep, narrow valley. These meanders form either when an area is uplifted or when base level drops
Inclusion
a piece of one rock unit contained within another. Inclusions are used in relative dating. The rock mass adjacent to the one containg the inclusion must have been there first in order to provide the fragment
Index fossil
a fossil that is associated with a particular span of geologic time
Index mineral
a mineral that is a good indicator of the metamorphic environemnt in which it formed. Used to distinguish different zones of regional metamorphism
Inertia
objects at rest tent to remain at rest, and objects in motion tend to stay in motion unless either is acted upon by an outside force
Infiltration
the movement of surface water into rock or soil through crack and pore spaces
Infiltration capacity
the maximum rate at which soil can absorb water
Inner core
the solid, innermost layer of Earth, about 1216 kilometers in radius
Inselberg
an isolated mountain remnant characteristic of the late stage of erosion in a mountainous region
Intensity (earthquake)
a measure of the degree of earthquake shaking at a give locale based on the amount of damage
Interior drainage
a discontinuous patter of intermittent streams that do not flow to the ocean
Intermediate
compositional category for igneous rocks found near the middle of Bowen's reaction series, mainly amphibole and the intermediate plagioclase feldspars
Intermediate focus
an earthquake focus at a depth of between 60-300 kilometers
Internal process
a process such as mountain building or volcanism that derives its energy from Earth's interior and elevates Earth's surface
Intraplate volcanism
igneous activity that occurs within a tectonic plate away from plate boundaries
Intrusive rock
Igneous rock that formed below Earth's surface
Internal process
a process such as mountain building or volcanism that derives its energy from Earth's interior and elevates Earth's surface
Intraplate Volcanism
igenous activity that occurs within a tectonic plate away from plate boundaries
Intrusive rock
igneous rock that formed below Earth's surface
Ion
an atom or molecule that possesses an electrical charge
Ionic bond
a chemical bond between two oppositely charged ions formed by the transfer of valance electrons from one atom to another
Isostasy
the concept that Earth's crust is floating in gravitational balance upon the material of the mantle
Isotopes
varieties of the same element that have different mass numbersl their nuclei contain the same number of protons but different number of neutrons
Joint
a fracture in rock along which there has bgeen no movement
Kame
a steep-sided hill composed of sand and gravel originating when sediment collected in openings in stagnant glacial ice
Kame terrace
a narrow, terracelike mass of stratified drift deposited between a glacier and an adjacent valley wall
Karst
a topography consisting of numerous depressions called sinkholes
Kettle holes
depressions created when blocks of ice become lodged in glacial deposits and subsequently melt
Laccolith
a massive, concordant igneous body intruded between preexisting strata
Lahar
mudflows on the slopes of volcanoes that result when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels
Laminar flow
the movement of water particles in straightline parths that are parallel to the channel. The water particles move downstream without mixing
Lateral moraine
a ridge of till along the sides of a valley glacier composed primarily of debris that fell to the glacier from the valley wall
Laterite
a red, highly leached soil type found in the tropics and rich in oxides of iron and aluminum
Laurasia
the nothern portion of Pangea consisting of North America and Eurasia
Lava
magma that reaches earth's surface
Lava dome
a bulbous mass associated with an old-age volcano, produced when thick lava is slowly squeezed from the vent. Lava domes may act as plugs to deflect subsequent gaseous eruptions
Lava tube
tunnel in hardened lava that acts as a horizontal conduit for lava flowing from a volcanic vent. Lava tubes allow fluid lavas to advance great distances
Law of superpoistion
in any undeformed sequence of sedimentary rocks or surface-deposited igneous materials, each layer is older than the one abovie it and younger than the one below it
Law of superposition
in any undeformed sequence of sedimentary rocks or surface-deposited igneous materials, each layer is olden than the one above it any younger than the one below it
Leaching
the depletion of soluble materials from the upper soil by downward-percolating water
Light silicate
silicate minerals that lack iron and or magnesium. They are generally lighter in color and have lower specific gravities than dark silicates
Lithification
the process, generally by cementation and or compaction, of converting sediments to solid rock
Lithosphere
the rigid outer layer of Earth, including the crust and upper mantle
Loess
deposits of windblown silt, lacking visible layers, generally buff colored, and capable of maintaining a nearly vertical cliff
Longitudinal Profile
a cross section of a stream channel along its descending course from head to the mouth
Longitudinal Dunes
Long ridges of sand oriented paralle to the prevailing windl these dunes form where sand supplies are limited
Longitudinal profile
a cross section of a stream channel along its descending course from the head to the mouth
Longshore current
a nearshore current that flows parallel to the shore
Losing stream
stream sthat lose water to the groundwater system by outflow through the streambed
Luster
the appearance or quality of light reflected from the surface of a mineral
Luster
the appearnace or quality of light reflected fromt he surface of a mineral
Mafic
because basaltic rocks contain a high percentage of ferromagnesian minerals, they are also called mafic (from magnesium and ferrum, the latin name for iron).
Magma
a body of molten rock found at depth, including any dissolved gases and crystals
Magnetometer
a sensitve instrument used to measure the intesity of Earth's magnetic field at various points
Magnitude (earthquake)
the total amount of energy released during an earthquake
Manganese nodules
a type of hydrogenous sediment scattered on the ocean floor, consisting mainly of manganese and iron, and usually containing small amounts of copper, nickel, and cobalt
Mantle
the 2885 kilometer (1789 mile) thick layer of Earth located below the crust
Mantle plume
a mass of hotter-than-normal mantle material that ascends toward the suface, where it may lead to igneous activity. These plumes of solid yet mobile material may originate as deep as the core-mantle boundary.
Mass number
the sum of the number of neutrons and protons in the nucleus of an atom
Mass wasting
the downslope movement of rock, regolith, and soil under the direct influence of gravity
Meander
a looplike bend in the course of a stream
Meander Scar
a floodplain feature created when an oxbow lake becomes filled with sediment
Mechanical weathering
the physical disintegration of rock, resulting in smaller fragments
Medial moraine
a ridge of till formed when laterla moraines from two coalescing valley glaciers join
Melt
the liquid portion of magma excluding the solid crystals
Mesosphere
the part of the mantle that extends from the core-mantle boundary to a depth of 660 kilometers. Also known as the lower mantle.
Mesozoic era
a time span on the geologic time scale between the Paleozoic and Cenozoic eras - from about 248 million to 65 million years ago
Metallic Bond
a chemical bond present in all metals that may be characterized as an extreme type of electron sharing in which the electrons move freely from atom to atom.
Metamorphic Rock
Rock formed by the alteration of preexisting rock deep within Earth (but still in the solid state) by heat, pressure, and/or chemically active fluids
Metamorphism
the changes in mineral composition and texture of a rock subjected to high temperature and pressure within Earth
Migmatite
a rock exhibiting both igneous and metamorphic rock characteristics. Such rocks may form when lightcolored silicate minerals melt and then crystallize, while the dark silicate mineral remains soid
Mineral
a naturally occuring, inorganic crystalline material with a unique chemical struture
Mineral resource
all discovered and undiscovered deposits of a useful mineral that can be extracted now or at some time in the future
Modified Mercalli intensity scale
a 12-point scale developed to evaluate earthquake intensity based on the amount of damage to various structures
Moho
the boundary separating the crust and the mantle, discernible by an increase in seismic velocity
Mohs scale
a series of 10 mineral used as a standard in determining hardness
Moment magnitude
a more precise measure of earthquake magnitude than the Richter scale that is derived from the amount of displacement that occurs along a fault zone
Monocline
a one-limbed flexure in strata. The strata are usuallly flat lying or very gently dipping on both sides of the monocline
Mouth
the point downstream where a river empties into another stream or water body
Mud crack
a feature in some sedimentary rocks that forms when wet mud dries out, shrinks, and cracks
Natural Levee
the elevated landforms composed of alluvium that parallel some streams and act to confine their waters, except during floodstage
Neap tide
the lowest tidal range, occuring near the times of the first and third quarters of the moon
Nebular hypothesis
a nodel for the origin of the solar system that assumes a rotating nebula of dust and gases that contracted to produce the Sun and planets
Neutron
a subatomic particle found in the nucleus of an atom. The neutron is electrically neutral, with a mass approximately equal to that of a proton
Nonclastic
a term for the texdture of sedimentary rocks in which the minerals form a pattern of interlocking crystals
Nonconformity
an unconformity in which older metmorphic or intrusive igneous rocks are overlain by younger sedimentary strata
Nonfoiliated
metamorphic rocks that do not exhibit foliation
nonmetallic mineral resource
mineral resource that is not a fuel or processed for the metals it contains
nonrenewable resource
resource that forms or accumulates over such long time spans that it must be considered as fizxed in totaly quantity
normal fault
a fault in wich the rock abuve the fault plane has moved down relative to the rock below
normal polarity
a magnetic field the same as that which presently exists
nucleus
the small, heavy core of an atom that contains its positive charge and most of its mass
nucleus
the small, heavy core of an atom that conotains all of its positive charge and most of its mass
nuee ardente
incandescent volcanic debris that is buoyed up by hot gases and moves downslope in an avalanche fashion
numerical date
date that specifies that actual number of years that have passed since an event occurred
oceanic ridge
a continuous mountainous ridge of the floor of all the major ocean basins and varying in width from 500 to 5000 kilometers (300-3000miles). The rifts at the crests of these ridges represent divergent plate boundaries
octet rule
atoms combine in order that each may have the electron arrangement of a noble gas; that is the outer energy levell contains eight electrons
oil trap
a geologic structure that allows for significant amounts of oil and gas to accumulate
ore
usually a useful metallic mineral that can be mined at a profit. The term is also applied to certain nonmetallic minerals such as fluorite and sulfur
original horizontality
layers of sediment are generally deposited in a horizontal or nearly horizontal position
Orogenesis
the processes that collectively result in the formation of mountain
Outercore
a layer beneath the mantle about 2270 km (1410 m) thick that has the properties of a liquid
Outgassing
the release of gases dissolved in molten rock
Outlet glacier
a tongue of ice normaly flowing rapidly outward from an ice cap or ice sheet, usually through mountainous terrain to the sea
Outwash plain
a relatively flat, gently sloping plain consisting of materials deposited by meltwater streams in front of the margin of an ice sheet
Oxbow lake
a curved lake produced when a stream cuts off a meander
Oxidation
the removal of one of more electrons from an atom or ion. So named because elements commonly combine with oxygen
Pahoehoe
a lava flow with a smooth-to-ropy surface
Paleomagnetism
the natural remnant magnetism in rock bodies. The permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and thae latitude of the rock at the time it became magnetized
Paleontology
the systematic study of fossils and the history of life on earth
Paleozoic era
a time span of the geologic time scale between the Precambrian and Mesozoic eras-from about 540 million to 248 million years ago
Pangaea
the proposed supercontinent that 200 million years ago began to break apart and form the present landmasses
Parabolic dune
a sand dune similar in shape to a barchan dune expect that its tips point into the wind. These dunes often form along coasts that have strong onshore winds, abundant sand, and vegetation that partly covers the sand
Paradigm
theory that is held with a very high degree of confidence and is comprehesive in scope
Parastic cone
a volcanic cone that forms on the flank of a larger volcano
Parent material
the material upon which a soil develops
Parent rock
the rock from which a metamorphic rock formed
Partial melting
the process by which most igneous rocks melt. Because individual minerals have different melting points, most igneous rocks melth over a temperature range of a few hundred degrees. If the liquid is squeezed out after some melting has occured, a melt with a higher silica content results
Passive continental margin
a margin that consists of a continental shlef, continental slope, and continental rise. The are NOT associated with plate boundaries and therefore experience little volcanism and few earthquake
Pedalfer
soil of humid regions characterized by the accumulation of iron oxides and aluminum-rich clays in the B horizon
Pedocal
soil associated with drier regions and characterized by an accumulation of calcium carbonate in the upper horizons
Pegmatite
a very coarse-grained igneous rock (typically granite) commonly found as dike associated with a large mass of plutonic rock that has smaller crystals. Crystalization in water-rich environment is believed to be responsible for the very large crystals
Pegmatitic Texture
a texture of igneous rocks in which the interlocking crystals are all larger than one centimeter in dimater
Peneplain
in the idealized cycle of landscape evolution in a humid region, an undulating plain near base level associated with old age
Perched water table
a localized zone of saturation above the main water table created by an impermeable layer (aquitard)
Peridotite
an igneous rock of ultramafic compoistion through to be abundant in the upper mantle
Period
a basic unit of the geologic calendar that is a subdivision of an era. Periods may be divided into smaller units called epochs
Permafrost
any permanently frozen subsoil. Usually found in the subartic and artic regions
Permeability
a measure of a material's ability to transmit water
Phaneritic texture
an igneous rock texture in which the crystals are roughly equal in size and large enough so that individual mineral scan be identified with the unaided eye
Phanerozoic Eon
that part of geologic time represented by rocks containing abundant fossil evidence. The eon extending from the end of the Proterozoic eon (about 540 mmillion years ago) to the present)
Phenocryst
conspicuously large crystals in a porphyry that are imbedded in a matrix of finergrained crystals (the ground mass)
Physical Geology
a major division of geology that examines the materials of Earth and seeks to understand the processe and forces acting upon Earth's surface from below
Piedmont Glacier
a glacier that forms when one or more valley glaciers emerge from the confining wallas of mountain valles and spread out to create a broad sheet in the lowlands at the base of the mountains
Pillow lava
basaltic lava that solidifies in an underwater environment and develops a structure that resembles a pile of pillows
Pipe
a vertical conduit through which magmatic materials have passed
Placer
deposit formed when heavy minerals are mechanically concentrated by currents, most commonly streams and waves. Placers are sources of gold, tin, platinum, diamonds, and other valuable minerals
Plastic deformation
permanent deformation that results in a change in size and shape through folding or flowing
Plastic flow
a type of glacial movement that occurs within the glacier, below a depth of approximately 50 meters, in which the ice is not fractured
Plate
one of numerous rigid sections of the lithosphere that moves as a unit over the material of the asthenosphere
Plate tectonics
the theory that proposes Earth's outer shell consists of individual plates, which interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself
Playa
the flat central area of an undrianed desert basin
Playa lake
a temporary lake in a playa
Pleistocene epoch
an epoch of the Quaternary period beginning about 1.6 million years ago and ending about 10,00 years ago. Best known as a time of extensive continental ice sheets
Plucking
the process by which pieces of bedrock are lifted out of place by a glacier
pluton
a structure that results from the emplacement and crystallization fo magma beneath Earth's surface
Pluvial lake
a lake formed during a period of increased rainfuall. For example, this occured in many nonglaciated areas during periods of ice advance elsewhere
Point bar
a crescent-shaped accumulation of sand and gravel deposited on the inside of a meander
Polar wandering hypothesis
as the result of paleomagnetic studies in the 1950s, researchers proposed that either the magnetic poles migrated greatly through time or te continents had gradually shifted their positions
Polymorphs
two or more mineral shaving the smae chemical composition but different crystalline structures. Exemplfied by the diamond and graphite forms of carbon
Porosity
the volume of open spaces in rock or soil
Porphyritic texture
a texture of metamorphic rocks in which particularily large grains (porphyroblasts) are surrounded by a fine-grained matric of other minerals
Porphyritic texture
an igneous rock texture characerized by two distinctly different crystal sizs. The large crystals are called phenocrsysa, and the matirc of smaller crystals is termed the groundmass
porphroblastic texture
a texture of metamorphic rocks in whic hparticularly large grains (porphyroblats) are surrounded by a fine-grained matricx of other minerals)
Porphyry
an igneous rock with a porphyritict texture
Pothole
a depression formed in a steram channel by the abrasive action of the water's sediment load
Precambrian
al geologic time prior to the Paleozoic era
Principle of fossil succession
fossil organisms succed one another in a definite and determinable order, and any time period can be recognized by its fossil content
Principle of original horizontality
ayers of sediment are generally deposited in a horizontal or nearly horizontal position
Proterozoic eon
the eon following the ARchean and preceding the Phanerozoixc eon. It exdtends between 2.5 billion and 540 million years ago
Proton
a positively charged subatomic particle found in the nucleus of an atom
P wave
the fastest earthquake wave; travels by compression and expansion of the medium
Pyroclastic flow
a highly heated mixture, largely of ash and pumic fragments, traveling down the flanks of a volcano or along the surface of the ground
Pyroclastic material
the volcanic rock ejected during an eruption. Pyroclastics include ash, bombs, and blocks
Pyroclastic texture
as igneous rock texture resultig from the consolidation of individual rock fragments that are ejected during a violent eruption
Radial drainage
a system of streams running in all directions away from a central elevated structure, such as a volcano
Radioactivity
the spontaneuos decay of certain unstable atomic nuclei
Radiocarbon (carbon-14)
the radioactive isotope of carbon produced continuously in the atmosphere and used in dating events as far back as 75,000 years
Radiometric dating
the procedure of calculating the absolute ages of rocks and minerals containing certain radioactive isotopes
Rainshadow desert
a dry areea on the lee side of a mountain range. Many middle latitude deserts are of this type
Rapidsq
a part of a stream channel in which the water suddenly beings flowing more swiftly and turbulently because of an abrupt steepening of the gradient
Recessional moraine
an end moraine formed as the ice front stagnated during glacial retreat
Rectangular pattern
a drainage pattern that develops on jointed or fractured bedrock and is characterized by numerous right-angle bends
Refraction
a change in direction of waves as they enter shallow water. The portion of the wave in shallow water is slowed, which causes the wave to bend and align with the underwater contours
Regional metamorphism
metamorphism associated with large-scale mountain building
Regolith
the layer of rock and mineral fragments that nearly everywhere covers Earth's land surface
Relative dating
rocks are placed in their proper sequence or ordeer. Only the chronolofical order of events is determined
Renewable resource
a resource that is virtually inexhausitble or that can be replenished over relatively short time spans
reserve
already identified deposits from which minerals can be extracted profitably
reservoir rock
the porous, permeable portion of an oil trap that yields oil and gas
Renewable resource
a resource that is virtually inexhaustible or that can be replenished over relatively over short time spans
Reserve
already identified deposits from which minerals can be extracted profitably
Reservoir Rock
the porous, permeable portion of an oil trap that yields oil and gas
Residual soil
osoil developed directly from the weathering of the bedrock below
Reverse fault
a fault in which the material above the fault plane moves p in relation to the material below
Reverse polarity
a magnetic field opposite to that which present exists
Richter scale
a scale of earthquake magnitude based on the motion of a seismohraph
Ridge push
a mechanism that may contriuvte to plate motion. It involves the oceanic litosphere sliding down the oceanic ridge under the pull of gravity
Rift
a region of Earth's crust along which divergence (speratation) is taking place
Ripple marks
small waves of sand that develop on the surface of a sediment layer by the action of moving water or air
Roche moutonnee
an asymeetrical know of bedrock formed when glacial abrasion smoothes the gentle slope facing the advancing ice sheets and plucking steepens the opposite side as the ice overrides the knob
Rock
a consolidated mixture of minerals
Rock avalanche
the very rapid downslopemovement of rock and debris. These rapid movements may be aided by a layer of air tapped beneat the debris, and they have been known to reach speeds in excess of 200 kilometers per hour
Rock cleavage
the tendency of rock to split along parallel, closely spaced surfaces. These surfaces are often highly inclined to the bedding planes in the rock
Rock cycle
a model that illustrates the origin of the three basic rock types and the interrelatedness of Earth's materials and processes
Rock flour
ground-up rock produced by the grinding effect of a glacier
Rockslide
the rapid slide of a mass of rock downslope along planes of weaknesss
Runoff
water that flows over the land rather than infiltrating into the ground
Saltation
transportation of sediment through a series of leaps or bounces
salt flat
a white crust on the ground produced when water evaporates and leaves its dissolgved naterials behind
Schistosity
a type of foliatio characteristic of coarser grained metamorphic r ocks. Suc h rocks have a parallel arrangement of platy minerals such as the micas
Scoria
hardened lava that has retained the vesicles produced by esaping gases
Sea arch
an arch formed by a wave erosion when caves on opposite sides of a headland unite
seafloor spreadng
the hypothesis first proposed in 1960s by Harry Hess that suggested that new oceanic crust is produced at the crests of mid-ocean ridges, which are the sites of divergence
Seamount
an isolated volcanic peak that rises atleast 100 meters (330feet) above the deep-ocean floor
Sea stack
an isolated mass of rock standing just offshore, produced by wave erosion of a headland
Seawall
a barrier constructed to prevent waves from reaching the area behind the wall. Its purpose is to dfend property from the force of breaking waves
Secondary enrichment
the concentration of inor amounts of metals that are scattered through unwearthered rocks into economically valuable concentrations by wearering processes
Secondary S wave
a seismic wave that involves oscillation perpendicular to the direction of propagation
Sediment
unconsolidated particles created by the waerering and erosion of rock, by chemical precipitations from solution in water, or from the secreatios of organisms , and transported bt waterm wind, or glaciers
Sedimentary rock
rock formed from the weathered products of preexisteing rocks that have been transported, depoisted, and lithified
Seiche
the rhythmic sloshing of water in lkaes, reservoirs, and toher smaller enclosed basinbs, Some seiches are initiated by earthquake activity
Seismic sea wave
a rapidly moving ocean wave genenreated by earthquake activity an capable of inflicting heavy damage iin coastal regions
Seismogram
the record made by a seismograph
Seismograph
an instrument that records earthquake waves
Seismology
the study of earthquakes and seismic waves
Settling velocity
the speed at which a particle flals through a still fluid. The size, shape, and specific gravity of particles influence settling velocity
Shadow zone
the zone between 105 and 140 degrees distance from an earthquake epicenter that direct waves do not penetrate becaues of refraction by Earth's core
Shallow-focus earthquake
an earthquake focus at a depth of less than 60km
Shear
stress that caues two adjacent parts of a budy to side past one another
Sheet flow
runoff moving in unconfined thin sheets
Shelf break
the point at which a rapid steepening of the gradient occurs, marking the outer edge of the continental shelf and the beginning of the continental slope
Shield
a large, relatively flat expanse of ancient metamorphic rock within the stagble continental interior
Sheid volcano
a broad, gently sloping volcano uilt from fluid basaltic lavas
Silcate
any one of numerous minerals that have the silicon-oxygen tetrahedron as their bvasic structure
Silicon-oxygen tetrahedron
a structure composed of four oxygen atoms surrounding a silicon atom that constitutes the basic building block of silicate mienrals
sill
a tabular igneous body that was intruded parallel to the basic building block of silicate minerals
sinkhole
a depression produced in a region where soluble rock has been removed by groundwater
slab-pull
a mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and "pulls" the trainling lithosphere along
slaty cleavage
the type of foliation characteristics of slates in which there is a parallel arrangement of fine-grained metamorphic minerals
slide
a movement common to mass-wasting processes in whcih the material moving downslope remains fairly coherent and moves along a well-defined surface
slip face
the steep, leeward sufrace of a sand dune that maintans a slope of about 34 degrees
slump
the downward slipping of a mass of rock or unconsolidated material moving as a unit along a curved surface
snowfield
an area where snow persists year-round
snowline
lower limit of perennial snow
soil
a combination of mineral and organic matter, water, and airl that portion of the regolith that supports plant growth
Soil horizon
a layer of soil that has identifiable characteristics produced by chemical weathering and other soilforming processes
Soil profile
a vertical section through a soil showing its succesion of horizons and the underliying parent material
solifluction
slow, downslope flow of water-saturated materials common to permafrost areas
Solum
the O, A, and B horizons in a soil profile. Living roots and other plants and animal life are largely confined to this zone
Solution
the change of matter from the solid or gaseous state into the liquid state by its combination with liquid
Sorting
the degree of similarity in particle size in sediment or sedimentary rock
specific gravity
the ratio of a s substances weight to the weight of an equal volume of water
Speleothem
a collective term for the dripstone features found in caverns
Spheroidal weathering
any weathering process that tends to produce a spherical shape from an initially blocky shpae
Spit
an elongated ridge of sand that projects fronm the land into the mouth of an adjacent bad
Spring
a flow of groundwater that emerges naturally at the ground surface
Spring tide
the highest tidal range;p occurs near the times of the new and full moons
stalactite
the icicle-like structure that hangs from the ceiling of a cavern
stalagmite
the columnlike form that grows upward from the floor of a cavern
star dune
isolate dhill of sand that exhibits a complex form and develops where wind conditions are variable
Steppe
one of the two types of dry climate. A marginal and more humid variant of the desert that separates the desert from bordering humid climate
Stock
a pluton similar to but smaller than a batholith
Strata
parallel layers of sedimentary rock
Stratified drift
sediments deposited by glacial meltwater
Streak
the color of a mineral in powdered form
Stream
a general term to denote the flow of water within any natural channel. Thus, a small creek and a large river are both streams
Stress
the force per unit area acting on any surface within a solid
Striation
the multitude of fine parallel lines found on some cleavage faces of plagioclase feldspars but not present of orthoclase feldspar
Striations - glacial
scratches or grooves in a bedrock surface caused by the grinding action of a glacier and its load of sediment
Strike
the compass direction of the line of intersection created by a dipping bed of fault and a horizontal surface. Strike is always perpendicular to the direction of dip
Strike-slip fault
a fault along which the movement is horizontal
Strike
the compass direction of the liner or intersection created by a dipping bed of fault and a horizontal surface. Strike is ALWAYS perpedicular to the directio of dip
Strike-slip fault
afault along which the movement is horizontal
Stromatolite
structures that are deposited by algae and that consist of layered mounds or colums of calcium carbonate
subduction
the process oft hrusting oceanic lithosphere into the mantle along a convergent zone
subduction zeon
a long, anrrow zone where one lithospheric plate descends beneath another
Submarine canyon
a seaward extension of a valley that was cut on the continental shelf during a time when sea level was lower, or a canyon carved into the outer continental shlef, slop, and riseby turbidity currents
Submergent coast
a coast whose form is largely the result of the partial drowing of a former land surface either due to a rise of sea level or subsidence of the crust, or both
Subsoil
a term applied to the B horizon of a soil profile
law of superposition
in any undeformed sequence of sedimentary rocks, each bed is older than the one abouve and youner thanthe one below it
Surf
a collective term for breakers; also the wave activity in the area between the shoreline and the outer limit of breakers
Surface soil
the upper portion of a soil profile consisting of the O and A horizons
Surface waves
seismic waves that travel along the outer layers of earth
Surge
a period of rapid glacial advance; surges are typically sporadic and short-lived
Suspended load
the fine sediment carried within the body of flowing water orair
Swave
an earthquake wave, slower than a P wave, that travels only in solids
Swells
wind-generated waves that have moved into an area of weaker winds or calm
Syncline
a linear downfold in sedimentary strata; the opposite of anitcline
System
a group of initeracting or interdependent parts that form a complex whole
Tabular
describing a feature such as igeneous pluton having two dimensions that are much longer than the thrid
Talus
an accumulation of rock debris at the base of a cliff
Tarn
a small lake in a cirque
Tectonics
the study of the large--scale processes that collectively deform Earth's crust
Temporary (local) base level
the level of a lake, resistant rock layer, or any other bvase level that stands above sea level
Terminal moraine
the end moraine marking the farthest advance of a glacier
Terrace
a flat, benchlike structure produced by a stream that was left elevated as the stream cut downward
Terrane
a crustal block bounded by faults whose geologic history is distinct from the histories of adjoining crustal blocks
Terrigenous sediment
seafloor sediment derived from terrestiral weathering and erosion
Texture
the size, shape, and distribution of the particles that collectively constitute a rock
Theory
a well-tested and widely accepted view that explain certain observable facts
Theory
a well-tested and widley accpeted view that explains certain observable facts
Thermal metamorphism
same as contact metamorphism
Thrust fault
a low-angle reverse fault
Tide
periodic change in the elecation of the ocean's surface
Till
unsorted sediment deposited directly by a glacier
Tillite
a rock formed when glacial till is lithified
Tombolo
a ridge of sand that connects an island to the mainland or the another island
Topset bed
as essentially horizontal sedimentary layer deposited on top of a delta during floodstage
Transform fault
a major strike-slip fault that cuts through the lithosphere and accommodates motion between two plates
Transform fault boundary
a boundary in which tow plates slide past one another without creating or destroying lithosphere
Transpiration
the release of water vapor to the atmosphere by plants
Transported soil
soils that form on uncosolidated deposits
Trancerse dunes
a series of long ridges orientate at right angles to the prevailing windl these dunes form where vegetation is sparse and sand is very plentiful
Travertine
a form of limestone (CaCO3) that is deposited by hot sprinfs or as a case deposit
Trellis drainage
a system of streams in which nearly parallel tributaries occupy valleys cut in folded strata
Trench
an elongate depression in the seafloor produced y bending of oeanic crust during subduction
Tsumani
the japanese word for a seismic sea wave
Turbidite
turbidity current deposit characeterized by graded bedding
Turbidity Current
a downslope movement of dense, sediment-laden water created when sand and mud on he continental shelf and slope are dislodged and thrown into suspension
Turbulent Flow
the movement of water in an erratic fashion often characterized by swirling, whirlpool-like eddies. Most streamflow is of this type
Ultimate base level
sea level; the lowest level to which stream erosion could lower the land
Ultramafic
composition catergory for igneous roks made up almost entirely or ferromagnesion mineral (olivine and pyroxene)
Unconformity
a surface that represents a break in the rock recordl caused by erosion or nodeposition
Uniformitarianism
the concept that the processes that havec shpaed Earth in the geologic past are essentially the same as those operating today
Valence Electron
the electrons involved in the bonding process; the electrons occupying th ehighest principal energy level of an atom
Valley glacier
a glacier confined to a mountain valley, which in most instances had previously been a stream valley
Valley train
a relatively narrow body of stratified drift deposited on a valley floor by melthwater streams that issue from the terminus of a valley glacier
Vein deposit
a mienral filling a fracture or fault in a host rock. Such deposits have a sheetlike, or tabular form
Ventifact
a cobble or pebble polished and shpaed by the sandblasting effect of wind
Wesicles
spherical or elongated epenings on the outer portion of a lava flow that were created by escaping gas
Vesicular texture
a term applied to aphanitic igenous rocks that contain many small cavities, called vesicles
Viscosity
a measure of a fluid's resistance to flow
Volatiles
gaseous components of magma dissolved in the melt. Volatiles will readily vaporize( forma gas) at surface pressures
Volcanic
pertaining to the activities, structures, or rock types of a volcano
Volcanic island arc
a chain of volcanic islands generally located a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another
Volcanic bond
a streamlined pyroclastic fragment ejected from a volcano while the fragment is still molten
Volcanic neck
an isolated, steep-sided, erosional remnant consisting of lava that once occupied the vent of a volcano
Volcano
a mountain formed from lava and or pyroclastics
Wash
a desert stream course that is typically dry except for brief periods immediately following rainfall
Water gap
a pass through a ridge or mountain in which a stream flows
Water table
the upper level of the saturated zone of ground-water
Wave-cut cliff
a seaward-facing cliff along a steep shoreline formed by wave erosion at its bse and by mass wasting
wave-cut platform
a bench or shelf along a shore at sea level, cut by wave erosion
Wave height
the vertical distance between the trough and crest of a wave
Wave length
the horizontal distance separating successive crests or troughs
Wave of oscillation
a water wave in which the wave form advances as the water particles move in circular orbits
Wave translation
the turbulent advance of water created by breaking waves
Weathering
the disintegration and decomposition of rock at or near the surface of the Earth
Wave of translation
the turbulent advance of water created by breaking waves
Wave period
the time interval between the passage of successie creats at a stationary point
Weathering
the disintegration and decomoposition of rock at or near the surface of the earth
Welded tuff
a pyroclastic deposit composed of particles fused together by the combination of heat still contained in the deposit after it has come to rest and by the weight of overlying material
Well
an opening bored into the zone of saturation
Wind gap
an abandonend water gap,. These gorges typically result from stream piracy
Xenolith
an inclusion of unmelted country rock in an igneous pluton
Xerophyte
a plant highly tolerant of drought
Yazoo tributary
a tributary that flows parallel to the main stream because a natural levee is present
Zone of accumulation
the part of a glacier characterized by snow accumulation and ice formation. The outer limit of this zone is the snowline
Zone of aeration
area above the water table where openings in soil, sediment, and rock are not saturated but are filled mainly with air
Zone of fracture
the upper portion of a glacier consisting of brittle ice
Zone of saturation
zone where all open spaces in sediment and rock are completely filld with water
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