Geology 201

Contact metamorphism: affected by the heat of a magma; heat conducted into country rock from an igneous intrusion/Dynamic metamorphism:occurs as a consequence of shearing alone, with no change in temperature or pressure /Dynamothermal metamorphism: involves heat, pressure, and shearing/Exhumation: process (involving uplift and erosion) that returns deeply buried rocks to the surface hydrothermal fluids/Foliation:Layering formed as a consequence of the alignment of mineral grains, or of compositional banding/Gneiss: metamorphic rock typically composed of alternating dark-and light-colored layers/Hornfels: undergoes metamorphism simply because of a change in temperature, without being subjected to differential stress nonfoliated/Marble: composed of calcite and transformed from a protolith of limestone/Metamorphic aureole:The region around a pluton, stretching tens to hundreds of meters out, in which heat transferred into the country rock and metamorphosed the country rock/Metamorphic facies:A set of metamorphic mineral assemblages indicative of metamorphism under a specific range of pressures and temperatures/Metamorphic foliation:A fabric defined by parallel surfaces or layers that develop in a rock as a result of metamorphism; ex. schistocity and gneissic layering/Metamorphic rock:forms when preexisting rock changes into new rock as a result of an increase in pressure and temperature and/or shearing under elevated temperatures; metamorphism occurs without the rock first becoming a melt or a sediment/Metamorphic zone: between two metamorphic isograds, typically named after an index mineral found within the region/Metamorphism: one kind of rock transforms into a different kind of rock’ forms chlorite/ Metasomatism: process by which a rock’s overall chemical composition changes during metamorphism because of reactions with hot water that bring in or remove elements/Migmatite: gneiss is heated high enough so that it begins to partially melt, creating layers, or lenses, of new igneous rock that mix with layers of the relict gneiss/ Mylonite: formed during dynamic metamorphism and characterized by foliation that lies roughly parallel to the fault (shear zone) involved in the shearing process;  very fine grains formed by the nonbrittle subdivision of larger grains/Phyllite: fine-grained metamorphic rock with a foliation caused by the preferred orientation of very fine-grained mica/Preferred orientation: texture that exists where platy grains lie parallel to one another and/or elongate grains align in the same direction/Protolith: original rock from which a metamorphic rock formed/Quartzite: composed of quartz and transformed from a protolith of quartz sandstone; solid mass of interlocking crystals/Regional metamorphism: Metamorphism of a broad region, usually the result of deep burial during an orogeny/Schist:A medium-to-coarse-grained rock that possesses schistosity/Shield:An older, interior region of a continent /Slate:Fine-grained, low-grade metamorphic rock, formed by the metamorphism of shale/Thermal metamorphism:caused by heat conducted into country rock from an igneous intrusion/Aftershock:series of smaller earthquakes that follow a major earthquake/Body wave:Seismic waves that pass through the interior of the Earth/Compressional wave:Waves in which particles of material move back and forth parallel to the direction in which the wave itself moves/Displacement:The amount of movement/slip across a fault plane/Earthquake: caused by the sudden breaking or frictional sliding of rock; occurs along divergent and convergent/Earthquake early warning: provides an alert within microseconds after the first earthquakes waves, but before damaging vibrations /Epicenter: point on the surface of the Earth directly above the focus of an earthquake/Fault: fracture on which one body of rock slides past another/Fault scarp:A small step on the ground surface where one side of a fault has moved vertically with respect to the other/Fault trace: intersection between a fault and the ground surface/Foreshock: series of smaller earthquakes that precede a major earthquake/Friction:Resistance to sliding on a surface/ Intensity:A measure of the relative size of an earthquake (the severity of ground shaking) at a location, as determined by examining the amount of damage caused/Intraplate earthquake: occurs away from plate boundaries/Modified Mercalli scale: characterization scale based on the amount of damage that the earthquake causes/Moment magnitude scale: scale that defines earthquake size on the basis of calculations involving the amount of slip, length of rupture, depth of rupture, and rock strength/Recurrence interval: average time between successive geologic events/Richter scale:A scale that defines earthquakes on the basis of the amplitude of the largest ground motion recorded on a seismogram/Seismic belt:The relatively narrow strips of crust on Earth under which most earthquakes occur/Seismicity:Earthquake activity/Seismic retrofitting: strengthening of an already existing structure (building, bridge, etc.) so that it can withstand earthquake vibrations/Seismic wave:Waves of energy emitted at the focus of an earthquake/Seismogram:The record of an earthquake produced by a seismograph/Seismometer:An instrument that can record the ground motion from an earthquake/Shear wave:Seismic waves in which particles of material move back and forth perpendicular to the direction in which the wave itself moves/Stick-slip behavior:Stop-start movement along a fault plane caused by friction, which prevents movement until stress builds up sufficiently/Stress:The push, pull, or shear that a material feels when subjected to a force; formally, the force applied per unit area over which the force acts/Surface wave:Seismic waves that travel along the Earth’s surface, R and L waves, stronger than B-wave/Travel-time curve:A graph that plots the time since an earthquake began on the vertical axis, and the distance to the epicenter on the horizontal axis/Tsunami:A large wave along the sea surface triggered by an earthquake or large submarine slump/Wadati-Benioff zone:A sloping band of seismicity defined by intermediate- and deep-focus earthquakes that occur in the downgoing slab of a convergent plate boundary;subduction at convergent plate/Accretionary orogeny:An orogen formed by the attachment of numerous buoyant slivers of crust to an older, larger continental block; Exotic terranes collided with the west edge of the North American Cordillera and those that were not subducted became accreted terranes /Anticline:A fold with an arch-like shape in which the limbs dip away from the hinge/Axial surface: imaginary surface that encompasses the hinges of successive layers of a fold/Basin:A fold or depression shaped like a right-side-up bowl/Brittle deformation:cracking n fracturing of a material subjected to stress/Craton:A long-lived block of durable continental crust commonly found in the stable interior of a continent/Cratonic platform:A long-lived block of durable continental crust commonly found in the stable interior of a continent/Crustal root:Low-density crustal rock that protrudes downward beneath a mountain range/Crustal thickening:The process by which the continental crust increases in thickness, becoming up to 70 km thick (vs. normal thickness of about 35 – 40 km); it can occur during continental collision/Deformation:A change in the shape, position, or orientation of a material, by bending, breaking, or flowing/Delamination:The process by which dense lithospheric mantle separates from the base of a plate and sinks into the mantle/Displacement:The amount of movement or slip across a fault plane/ Dome:Folded or arched layers with the shape of an overturned bowl/Ductile deformation: bending and flowing of a material (without cracking and breaking) subjected to slow stress; changes in overall shape of a rock mass w/out breakage/Epeirogeny:An event of epeirogenic movement; Midwest;formation of broad mid-continent domes and basins/Exhumation:The process (involving uplift and erosion) that returns deeply buried rocks to the surface/Exotic terrane: block of land that collided with a continent along a convergent margin and attached to the continent; the term exotic implies that the land was not originally part of the continent to which it is now attached/Fold:A bend or wrinkle of rock layers or foliation; folds form as a consequence of ductile deformation/Fold-thrust belt:An assemblage of folds and related thrust faults that develop above a detachment fault/Foliation:Layering formed as a consequence of the alignment of mineral grains, or of compositional banding in a metamorphic rock/Hinge:The portion of a fold where curvature is greatest/Isostasy:The condition that exists when the buoyancy force pushing litho sphere up equals the gravitational force pulling litho sphere down/ Isostatic equilibrium: force pushing up on lithosphere equals the gravitational force pulling down on it /Joint:Naturally formed cracks in rocks; Arches Nat. monument/Liquefaction:causes sand volcanos,affects sand layers,clay-rich soils become unstable/Limb (of fold):The side of a fold, showing less curvature than at the hinge /Monocline:A fold in the land surface whose shape resembles that of a carpet draped over a stair step/Normal fault:A fault in which the hanging-wall block moves down the slope of the fault/Orogen:A linear range of mountains/Orogenic collapse:The process in which mountains begin to collapse under their own weight and spread out laterally/Pressure:Force per unit area, or the acting on a material in cases where the push (compressional stretch) is the same in all directions/Reverse fault:A steeply dipping fault on which the hanging-wall block slides up/Shear stress:A stress that moves one part of a material sideways past another part/Shield:An older, interior region of a continent/Strain:The change in shape of an object in response to deformation (i.e., as a result of the application of a stress)/Stress:The push, pull, or shear that a material feels when subjected to a force; formally, the force applied per unit area over which the force acts/Strike:The angle between an imaginary horizontal line (the strike line) on the plane and the direction to true north/Strike-slip fault:A fault in which one block slides horizontally past another (and therefore parallel to the strike line), so there is no relative vertical motion/Syncline:A trough-shaped fold whose limbs dip toward the hinge parallel stripes, showing bilateral symmetry across a midline, with rock getting older as you move outward from the midline;/Tectonic foliation:A planar fabric, such as cleavage, schistocity, or gneissic banding, that develops in rocks; caused by compression or shearing during deformation (e.g., during mountain building)/Tension:A stress that pulls on a material and could lead to stretching/Thrust fault:A gently dipping reverse fault; the hanging-wall block moves up the slope of the fault/Uplift:The processes that cause the surface of the Earth to move vertically from a lower to a higher elevation/Vein:A seam of minerals that forms when dissolved ions carried by water solutions precipitate in cracks/Cambrian explosion:The remarkable diversification of life, indicated by the fossil record, that occurred at the beginning of the Cambrian Period/Closure temperature:The temperature below which isotopes are no longer free to move/Contact:The boundary surface between two rock bodies (as between two stratigraphic formations, between an igneous intrusion and adjacent rock, between two igneous rock bodies, or between rocks juxtaposed by a fault)/Correlation:The process of defining the age relations between the strata at one locality and the strata at another/Cross-cutting relations:If one geologic feature cuts across another, the feature that has been cut is older/Daughter isotope:The decay product of radioactive decay/Eon:The largest subdivision of geologic time/Epoch:An interval of geologic time representing the largest subdivision of a period/Era:An interval of geologic time representing the largest subdivision of the Phanerozoic Eon/Fossil assemblage:A group of fossil species found in a specific sequence of sedimentary rock/Fossil succession:In a stratigraphic sequence, different species of fossil organisms appear in a definite order; once a fossil species disappears in a sequence of strata, it never reappears higher in the sequence/Geochronology: dating geologic events in years/Geologic column: composite stratigraphic chart that represents the entirety of the Earth’s history/Geologic history: sequence of geologic events in a region/ Geologic map:A map showing the distribution of rock units and structures across a region/Geologic time: span of time since the formation of the Earth/Geologic time scale: intervals of geologic time/Half-life:The time it takes for half of a group of a radioactive element’s isotopes to decay/Index fossil:Widespread fossil species which survived only for a relatively short interval of geologic time/Isotope:same atomic number but different atomic weights/Isotopic dating: dating geologic events in years by measuring the ratio of parent radioactive atoms to daughter product atoms/Original horizontality:Layers of sediment, when originally deposited, are fairly horizontal/Parent isotope:A radioactive isotope that undergoes decay/Period:An interval of geologic time representing a subdivision of a geologic era/Precambrian:The interval of geologic time between Earth’s formation about 4.57 Ga and the beginning of the Phanerozoic Eon 542 Ma/Radioactive decay : atom undergoes fission or releases particles, becomes a new element/Stratigraphic column:A cross-section diagram of a sequence of strata summarizing information about the sequence/Stratigraphic formation: layer of a specific sedimentary rock types, deposited during a certain time interval, can be traced over a broad region/Stratigraphic group: adjacent stratigraphic formations in a succession/Superposition:each layer must be younger than the one below/Unconformity:boundary representing an interval of time during which new strata were not deposited and/or were eroded.

Uniformitarianism:Theory states that physical processes we observe operating today operated in the past, pillow lava form only underwater/Recrystallization:occurs because thermal energy causes atoms to vibrate rapidly, break existing chemical bonds, and migrate to new positions on the crystal lattice where they are more stable under the hotter conditions/ Exhalation means, to breathe out/ Diagenesis refers to post-decompositional alteration of sediment/.

Rayleigh seismic waves :cause a snakelike movement of the surface/San Andreas Fault: right-lateral strike-slip fault/ Fault breccias: angular fragments of shattered rock within a linear boundary zone between two more intact masses of rock/ Flexural slip folds: component of folding occurs as slippage along numerous parallel, closely spaced surfaces/ Slickensides and slip lineations: fault trace, polished surface, with parallel, linear grooves/ Dip measures the inclination of a plane, and plunge measures the inclination of a line/ Faulting in a thrust-fault system shortens the crust/Convergent boundary mountains: Himalayas, Alps, and Appalachian/Oldest to youngest:Precambrian, Paleozoic, Mesozoic, Cenozoic/ Age of Mammals, Age of Dinosaurs, and longest: Cenozoic, Mesozoic, Precambrian/ William Smith correlated strata from many locations;geo. Map/Radiometric age dating: collecting, separating, extracting, measuring