University of Colorado GEOLOGY 1010 Class Note Glossary

aa:a blocky or rubbly basaltic lava flow. (Please note that this definition was inverted with pahoehoe in the first version of this glossary).

accretionary wedge: A peice of continental crust that is accreted or attached to a larger mass.

aeolian: wind deposited an in desert sands.

aesthenosphere: literally "weak sphere" the region of the mantle below the lithosphere. This region of the mantle undergoes plastic deformation, but is too weak to have brittle deformation that causes eathquakes.

amorphous: Non-crystalline; lacking a crystal structure; a solid such as glass, opal, wood, coal, that lacks an ordered atomic arrangement.

anion: A negatively charged atom; an atom with more electrons than protons.

anticline: A concave-downward fold, i.e. the limbs are depressed and the center raised.

aquifer: A porous and permeable layer below the water table.

aquitard: An impermeable layer below the water table that retards the flow of water.

arete: A narrow ridge separating two cirque valleys.

artesian: free-flowing; the pressure in an aquifer exceeds the water column of the burial depth, and the water flows onto the surface without pumping.

ash flow: A flow or deposit of (usually) silicic volcanic ash as a result of an explosive eruption.

atmophile: A geochemical class of elements that form vanderWaals bonds and are highly volatile and depleted in the Earth relative to cosmic (solar)abundances.

atomic number: The number of protons in the nucleus of a particular element; the charge on the nucleus.

atomic weight: The average mass number of a particular element; the mass (in grams) of Avagadros number of atoms of an element.

avalanche: an air-fluidized slide of snow, ice, or rock and soil debris. The slide may travel at speeds in excess of 100 mph and become airborne in places.

badland: A deeply gullied terrain in horizontally bedded rock in unvegetated arid or semiarid terrain.

barchan: A crescent-shaped dune with limbs downwind.

basalt: a volcanic igneous rock that is low in silica (40-50%), and high in Fe and Mg. It is produced by partial melting of the mantle, and forms the bulk of the oceanic crust and may also occur in continenetal environments.

basin: A low-lying area of low relief.

baymouth bar: A narrow strip of sand closing a bay off from the ocean.

batholith: A large (>100km2 exposed body of plutonic igneous rock.

bed load: The sediment transported by a stream that is dragged or bounced along the bottom.

bedding: a series of visible layers in a rock that reflect the original surfaces on which sediemnts were deposited.

Benioff zone: A zone in the upper mantle, usually beneath an oceanic trench, where a cool, brittle plate, being subducted back into the mantle, gives rise to deep earthquakes.

bergschrund: A crevasse formed at the head of a cirque valley as the glacier ice pulls away from the ice attached to the mountain.

blowout dune: A crescent-shaped dune with limbs upwind (same as parabolic dune).

blueschist: a high pressure, low temperature metamorphic rock characteristic of subduction zones.

boulder: a large rock greater than 256mm (10") in diameter.

breccia: a sedimentary rock containing abundant angular pebble, cobble, and boulder-sized particles.

butte: A small (<~10ac), conspicuous, isolated hill bounded by cliffs.

cation: A positively charged atom; an atom with fewer electrons than protons.

chalcophile: A geochemical class of elements that form covalent bonds,commonly occur in sulfide minerals, and depleted in the Earth relative to cosmic (solar)abundances.

chondrite: A type of primitive stoney meteorite containing chondrules, quenched droplets of early condensates from the solar nebula.

cinder cone: A small volcanic cone built up around a basaltic vent.

cirque: A bowl-shaped valley at the head of a glacier.

clay: A particle less than 0.004mm (4 micrometers) in diameter. Also a group of layer-silicate minerals characterized by poor crystallinity and fine particle size.

cobble: a rock particle 64 to 256mm in diameter.

conglomerate: a sedimentary rock containing abundant, rounded pebble, cobble, and boulder-sized particles.

convection: the vertical circulation of a fluid in response to uneven heat distribution.

convergent boundary: A plate boundary at which plates approach eachother.

core: The region o fthe Earth's interior below a depth of 2900 km which is composed of liquid (outer) and solid (inner) metallic iron-nickel.

craton: The old, stable, interior portion of a continent.

creep: the imperceptably slow movement of soil downslope under the force of gravity.

crevasse: A deep tensional fracture formed on a glacier.

cross bedding: A sedimentary rock texture characterized by overlapping and cross-cutting bedding, typical of aeolian sands.

crust: the region of the earth from the surface to the Moho. The crust is part of the lithosphere and undergoes brittle deformation that causes earthquakes. The crust is divided into continetal crust which is thick, (30 - 60km) light, silica-rich, and old, and oceanic crust which is thin (<20km) dense, silica-poor, and young.

cuesta: An asymmetric hill or ridge with a gentle slope on one side and a steep outcrop slope on the other.

debrisflow: a water-fluidized flow of rock and soil debris, typically on slopes steeper than 20 degrees and leaving a narrow incised channel with debris levees.

deflation: Removal of fine particles by wind erosion.

desert: A region that receives less than 25cm (10in) of rain per year.

desert pavement: A pebble/cobble strewn surface of a desert that results from deflation.

dike: A small, discordant (injected into massive igneous, metamorphic, or across layers of sedimentary rock) body of intrusive igneous rock.

dip: An angle giving the orientatio n of a planar feature such as bedding or a fault plane; it is the acute angle measured between the planar feature and the horizontal. It is measure perpendicular to the strike direction.

divergent boundary: A plate boundary at which the plates are moving apart as a result of spreading.

dolomite: A rhombohedral carbonate mineral of formula CaMg(CO3)2. A rock composed predominantly of the mineral dolomite.

drainage basin: The total area drained by a stream.

drainage divide: The boundary between two drainage basins.

drumlin: A low, rounded, elongate hill or ridge of compact till left by a glacier.

earthquake: A trembling or shaking of the ground caused by a sudden release of energy stored in the rocks beneath the earth's surface.

eclogite A high pressure, high temperature metamorphic rock composed predominantly of garnet and clinopyroxene and which is compositionally equivalent to basalt.

electron A fundamental subatomic particle having an electric charge of -1 and a rest mass of 9.11 x 10-28 gm.

epicenter: The point on the surface of the earth's surface directly above the focus or release point of an earthquake.

erosion: The physical transport of unconsolidated materials at the earth's surface by wind and water.

esker: A low sinuous ridge of sand and gravel left by a subglacial stream.

evaporite: A sedimentary rock formed by evaporation of sea water. A typical evaporite sequence of minerals is 1)calcite (CaCO3, 2) gypsum CaSO42(H2O), 3) halite (NaCl), and 4) sylvite (KCl).

exotic terrane: A piece of continental crust of exotic or different origin than the main mass.

fault: a fracture in rock on which movement has taken place.

felsic: opposite of mafic; "rich in feldspar"; a term applied to magmas or igneous rocks that are silica-rich as rhyolites or granites.

ferromagnesian: Minerals or rocks that are rich in iron (Fe) and magnesium (Mg), such as olivine and pyroxene.

fjord: A long, narrow, U-shaped, glacier-carved inlet from the ocean.

foliation: A rock texture formed by alignment of sheet-like features or grains.

focus: (Seismology) The actual point or plane of rupture of an earthquake.

fractional crystallization: The process of enriching a magma in silica by early crystallizing mafic minerals that drop to the bottom of the magma chamber.

geyser: a hot spring that undergoes periodic catastrophic boiling (erupting).

glacier: large permanent mass of ice that forms on land and moves downhill under the force of gravity.

gneiss: a high grade metamorphic rock with well developed lineation or foliation, typically granitic in composition.

gradient: The average drop of a stream in ft/mi (USA) or m/km (world).

granite: an intrusive (plutonic) igneous rock of hig silica (SiO2) content typical of continental regions.

granulite: a high grade metamorphic rock with an equant texture (no foliation or lineation).

groundwater: liquid water that lies below the surface in fractures and porespace in rocks.

hogback: A narrow ridge formed by the outcrop near-vertical sedimentary beds.

horn: A high, sharp-pointed, steep sided, pyramidal mountain peak formed by glacial erosion.

hornfels: a high temperature, low pressure metamorphic rock typically with an equant texture (no foliation or lineation).

hydration: a chemical rection by which water or hydrogen is added to a compound or mineral. This usually disrupts the crystalline structure of a mineral.

hydrologic cycle: The movement of water from the ocean by evaporation, over land, precipitation and transport back to the ocean as surface and ground water.

hydrostatic: equal in all directions as pressure under water.

hydrothermal: formed by precipitation from hot aqueous solutions.

ice cap: A mountain glacier that flows outward in several directions.

ice sheet: A large mass of ice covering a significant portion of a continent as in Greenland and Antarctica.

inner core: The innermost portion of the core which is composed of solid iron-nickel metal.

ion: A charged atom; an atom with more or fewer electrons than protons.

isomorph: Two compounds that have the same crystal structure, but diferent compositions. Examples: halite/sylvite, forsterite/fayalite, halite/galena.

isostacy: The principal of gravitational balance or equilibrium.

joint: A fracture in rock on which no movement has taken place.

karst: A type of topography marked by sinkholes, springs, disappearing streams indicating underground drainage in limestone caverns.

landslide: a large flow of rock, soil, and debris, typically slow-moving.

laterite: A soil typical of tropical rain forests characterized by extreme leaching and removal of soluble elements.

lava: A magma that is on the surface (i.e. volcanic).

limestone: a sedimentary rock made up predominantly of calcite.

lineation: A rock texture formed by alignment of rod-like features or grains.

lithification: The solidification of sediments to form sedimentary rocks.

lithophile: A geochemical class of elements that form ionic bonds,commonly occur in oxygen minerals, and are enriched in the Earth's crust relative to cosmic (solar)abundances.

lithosphere: The near-surface region of the crust and uper mantle that undergoes brittle fracture.

loess: An aeolian deposit of angular sand-, silt- and clay-sized particles.

load: The total sediment transported by a stream.

longitudinal dune: A sand dune that forms as a ridge parallel to the wind direction.

lower mantle: The lower and largest portion of the mantle extending from a depth of 670km to 2900km. It composes approximately 50% of the mass of the planet.

mafic: A term applied to igneous rocks that are rich in ferromagnesian minerals or low in silica as basalt or gabbro.

magma: Any molten rock.

mantle: The region of the Earth from the base of te crust (Moho) to the core-mantle boundary at a depth of ~2900km. It is composed of solid silicate rock.

marble: metamorphised limestone, a metamorphic rock composed predominantly of calcite.

mass number: The number of protons plus neutrons in the nucleus of a particular isotope of an element.

mesa: A relatively small flat-topped hill or mountain.

metamorphism: The solid-state transformation of pre-existing rock into texturally or mineralogically distinct new rock as the result of high temperature, high pressure, or both.

metasomatism: Chemical alteration of a rock by the action of hydrothermal fluids.

migmatite: A high grade metamorphic rock that has undergone partial melting, typically with segregations of K-feldspar.

mineral: a naturally occurring homogeneous solid of definite chemical composition and ordered atomic arrangement. It is usually formed by inorganic processes; a natural crystalline phase.

Moho The Mohorivicic discontinuity (seismic reflector) at the base of the crust.

monocline A fold in rock connecting two vertically offset, horizontal sections of sedimenary rocks.

moraine A deposit of till (rock and soil) left by a glacier.

mountain A large mass of rock projecting abouve surrounding terrain.

mudstone A sedimentary rock made up of clay-sized particles, typically massive and not fissile.

neutron A fundamental subatomic particle having an electric charge of 0 and a rest mass of 1.67 x 10-24 gm.

obsidian: A dense, usually black, volcanic glass.

ogive: A compressional wave on the surface of a glacier as near the bottom of an icefall.

orogenic belt: A range of mountians all formed in the same orogeny (event).

orogeny: An episode of mountain building.

outer core: The outer portion of the core of the earth which is composed of liquid (molten) iron-nickel metal.

oxidation: a chemical reaction resulting in the increase in valence state of an element. This usually disrupts the crystalline structure of a mineral. Example oxidation of Fe from +2 (ferrous) to +3 (ferric).

P-wave: A primary, or compression, body seismic wave that travels through the depth of the earth.

pahoehoe: A smooth or "ropey" surfaced basaltic lava flow.(Please note that this definition was inverted with aa in the first version of this glossary).

parabolic dune: A crescent-shaped dune with limbs upwind (same as blowout dune).

partial melting: The process of deriving a melt from a rock to generate a magma that is more silicic in composition than the original rock.

pebble: A rock particle 2 to 64 mm in diameter.

pedalfer: soils of humid regions thatare characterized by highly leached clays due to downward movement of water.

pedocal: soils of arid regions that are characterized by calcite (CaCO3) cementation due to upward movement of water (evaporation).

pegmatite: An extremely coarse-grained (> 2 cm) igneous rock, usually silicic.

permeability: The ability of water (or other fluid) to move through a rock.

pH: A measure of acidity. Actually the negative logarithm (base 10) of the hydrogen ion concentration in an aqueous solution. A pH of 7.0 is neutral, that is distilled water has a hydrogen ion concentration of 1 in 107 or 0.1 ppm. A pH of less than 7 is acidic. A pH of greater than 7 is basic (caustic).

plateau: An elevated area with relatively little internal relief.

playa: A desert lake that is dry for most of the year.

pluton: Any irregularly-shaped body of intrusive igneous rock.

polymorph Two compounds that have the same composition, but different crystal structures are said to be polymorphs. Examples: calcite/aragonite, quartz/coesite, forsterite/wadsleyite, sillimanite/andalusite/kyanite.

porosity The volume percent of open or pore space in a rock.

proton A fundamental subatomic particle having an electric charge of +1 and a rest mass of 1.67 x 10-24 gm.

pumice: A volcanic glass foam.

rain shadow: A region on the downwind side of a mountain range that receives less rain because of the mountains.

refraction: The bending of waves on passing between media of different veolocities.

rhyolite: A silicic or felsic volcanic rock.

ripple marks: wave-like patterns in sedimentary bedding due to movement of water.

rockfall: a fall of rock off of a cliff or very steep outcrop.

S-wave A secondary, or shear, body seismic wave that travels through the depth of the Earth. S-waves can only be transmitted by solids.

saltation The process of bouncing of grains along a surface by flowing air (wind) or water.

sandstone A sedimentary rock made up of sand-sized particles, typically quartz.

saturated zone: The zone below the water table.

schist A foliated metamorphic rock rich in mica.

sedimentary rocks: Rocks formed by solidification (lithification) of sediments formed and transported at the Earth's surface.

seismometer: A device to detect seismic waves consisting of a suspended mass and an electronic or mechanical amplification system.

serac: A large irregular fragment of glacier ice formed as a glacier moves over a steep icefall.

shale A sedimentary rock made up of clay-sized particles, typically fissile (fractures easily on bedding planes).

shards: Ash, fragments of broken volcanic glass that compose tuff.

shield: The protion of a craton that is denuded or free of sedimentary cover. siderophile: A geochemical class of elements that form metallic bonds with iron, and are depleted in the Earth's crust and enriched in the core, relative to cosmic (solar)abundances.

silicic: opposite of mafic; "rich in silica"; a term applied to magmas or igneous rocks that are silica-rich such as rhyolites or granites.

sill: A small, concordant (injected between layers of sedimentary rock) body of intrusive igneous rock.

silt: A rock fragment or particle 0.004 to 0.06 mm in diameter.

slate: A fine-grained metamorphic rock with well developed foliation and cleavage. The rock is the metamorphic equivalent of a shale or mudstone.

soil: an accumulation of weathered rock material together with organic matter at the Earth's surface.

spit: A narrow penninsula of sand extending a beach into an open bay.

slump: the movement of a coherent mass of rock and soil debris a short distance along a curved lower boundary surface under the force of gravity.

strain: deformation of an object in response to an applied force (stress).

stress: a force applied to an object.

strike: An angle giving the orientation of a planar feature such as bedding or a fault plane; it is the compass direction of the line of intersection of the planar feature and the horizontal. It is usually given as "N40E" (forty degrees east of north, or "N60W" etc.

stock: A small (<100km2 exposed body of plutonic igneous rock.

stream: A body of water that is confined to a channel and moves downhill under the force of garvity.

subduction: The process of dragging a tectonic plate back into the depths of the earth.

subduction zone: A zone, usually an oceanic trench, where a plate is being subducted back into the mantle.

syncline: A concave-upward fold in rock, i.e. the limbs are raised and the center depressed.

terrane: A particular region or locale. (Note spelling, not terrain; term refers to a region regardless or topography.)

till: A deposit of unsorted angular fragmentys of rock left by a glacier.

tombolo: A beach deposit of sand connecting the land to a rocky promontory.

traction: Dragging or rolling of particles on a surface.

transform boundary: A plate boundary where the plates slip past eachother as a the San Andreas Fault in California.

transition zone: the region of the mantle at depths between 400 and 670 km where the seismic velocities rise continuously from the upper to the lower mantle regions.

transverse dune: A sand dune that forms as a ridge perpendicular to the wind direction.

tsunami: A seismic sea wave generated by an earthquake or underwater landslide.

tufa: A hot spring deposit of calcite travertine.

tuff: A volcanic rock made up of consolidated ash.

ultramafic: A term applied to rocks that are extremely mafic or olivine-rich such as peridotite.

unit cell: The smallest unit of a crystal that contains all of the physical properties and symmetry of the crystal. The unit cell is repeated by translation symmetry toform the crystal.

unsaturated zone: The zone below the surface and above the water table.

upper mantle: The upper portion of the mantle extending from the Moho to a depth of 400km.

vitrophyre: The dense, black, glassy, basal portion of a welded ash flow that is not devitrified (crystallized).

water table: The natural level of standing water in a well; the level below which the pore space in entirely filled by liquid water.

wave height: Amplitude; the vertical distance between wave crest and trough.

wavelength: The horizontal distance between wave crests.

weathering: The breakdown of rocks at the Earth's surface as a result of chemical reaction or mechanical abrasion.

xenolith: An accidental inclusion in an igneous body of a rock of different origin.


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GEOL 1010 Syllabus

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