79 Cards in this Set
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uniformitarianism
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the concept that the present is the key to the past; that is, geologic processes occurring today also occurred in the geologic past and can be used to explain ancient events and the geologic features they produced.
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unconformity
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a boundary between underlying and overlying rock strata, representing a significant break or gap in the geologic record; represents an interval of non-deposition or erosion, commonly accompanied by uplift.
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relative age
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age of a fossil, organism, rock, geologic feature, or event as defined relative to other geologic features or events.
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numeric dating (absolute dating)
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process of determining ages of rocks by using analytical measurements
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fossils
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any remains, trace, or implant of a plant or animal that has been preserved from some past geologic or prehistoric time
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geologic timescale
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chronologic subdivision of geologic time depicting the sequence of geologic events, including those represented by fossils; ages of boundaries are assigned through numeric dating of key rock units.
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original horizontality
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principle that most sediments and many volcanic units are deposited in layers that originally are more or less horizontal
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principle of superposition
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concept that a sedimentary or volcanic layer is younger than any rock unit on which it is deposited
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clast
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individual grain or fragment of rock, produced by the physical breakdown of a larger rock mass
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inclusion
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fragment of older rock or material that is contained within another rock or material, as in a fragment or preexisting rock in a magma.
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crosscutting relationships
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the principle that a geologic unit or feature is older than a rock or feature that it crosscuts
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contact effects
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evidence of baking, passage of hot fluids, or some other manifestation of the thermal and chemical effects of a magma chamber or a hot volcanic unit, as expressed in changes to adjacent wall rocks.
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tributary
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secondary stream that joins or flows into a larger stream, river, or lake.
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terrace
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relatively level or gently inclined surface, or bench, bounded on one edge by a steeper descending slope.
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rock varnish (desert varnish)
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thin, dark film or coating of iron and manganese oxides, silica, and other materials; formed by prolonged exposure at the surface.
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desert pavement
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natural concentration of pebbles and other rock fragments, mantling a desert surface or low relief
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unconformity
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boundary between underlying and overlying rock strata, representing a significant break or gap in the geologic record; represents an interval of nondeposition or erosion, commonly accompanied by uplift.
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angular unconformity
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ancient erosion surface in which the older, underlying strata dip more steeply or at a different angle than the younger, overlying strata
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disconformity
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ancient erosion surface in which the bedding planes above and below the break are essentially parallel, but recording erosion or some other interruption in the deposition of layers.
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nonconformity
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ancient erosion surface in whic the older rocks below the unconformity are not layered.
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analytical dating methods
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systematic methods, commonly using isotopes, to determine the ages and histories of rocks and minerals in hundreds, thousands, millions, and billions of years.
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numeric dating
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process of determining ages of rocks by using analytical measurements
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atomic weight
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sum of of the weight of the subatomic particles in an average atom of an element, given in atomic mass units.
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isotopes
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one or 2 or more species of the same chemical element but differing from one another by having a different number of neutrons
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radioactive decay
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spontaneous disintegration and emission of particles from an unstable atom
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parent atom (parent isotope)
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an atom before it undergoes radioactive decay
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daughter product (daughter atom)
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element produced by radioactive decay of a parent atom
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half-life
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in a radioactive decay refers to the time it takes for half of the parent atoms to decay into a daughter product
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isotopic dating
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process of dating rock using radioactive decay
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mass spectrometer
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an instrument used to measure the abundance of different atoms and isotopes in a material, such as a rock or mineral to be numerically dated.
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fossil
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any remains, trace, or imprint of a plant or animal that has been preserved from some past geologic or prehistoric time.
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petrified wood
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a piece of fossilized wood that has been replaced by silica and other material, preserving some of the original structure of the wood.
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stromatolite
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a mound or- column- shaped feature of concentrically laminated carbonate materials, generally in ancient sedimentary rocks, interpreted to have been constructed by microscopic algae; also modern, live examples
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trace fossils
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features in rocks made by animals that moved across the surface or burrowed into soft sediment
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burrow
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a commonly tubular opening formed when creatures wiggle or tunnel into mud; can be filled with a different type of sediment to form a trace fossil.
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dendrites
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one or more minerals that has crystallized in a branching manner
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concretions
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a hard, compact accumulation of mineral matter in the pores of sedimentary or volcanic rocks; representing a concentration of constituents of the rock or cementing material.
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veins
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a generally tabular accumulation of minerals that filled a fracture or other discontinuity in a rock; formed by precipitation of material from fluids, especially hydrothermal fluids.
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force
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a push or pull that causes, or tends to cause, change in the motion of a body.
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displacement
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stress moves a rock from one location to another
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rotation
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stress tilts, folds, or spins a rock.
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strain
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rock responds to stress by deforming internally - size or shape changes without layers breaking or rotating.
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brittle
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rock or material that deforms by fracturing and frictional processes.
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ductile
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rock or material that is able to flow as a solid or otherwise deform without fracturing and faulting
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recrystallization
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the formation, essentially in the solid state, of new crystalline grains in a rock.
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stress
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the amount of force divided by the area on which the force is applied.
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rock cleavage
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the tendency of a rock, especially a metamorphic rock, to split along mostly parallel lines
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foliation
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planar arrangement of textural or structural features in metamorphic rocks and certain igneous rocks
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lineation
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a linear structure in a metamorphic rock
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schistosity
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a metamorphic foliation representing the parallel arrangement of mineral grains, especially mica in coarse-grained metamorphic rocks
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shear zone
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a generally tabular zone of rock that is more highly sheared and deformed than rocks outside the zone
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gneissic structure
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a metamorphic foliation defined by a preferred orientation of crystals and generally by alternating lighter and darker colored bands representing varying percentages of different minerals
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contact metamorphism
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metamorphism that principally involves heating of the rocks next to a magma or hot igneous material
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regional metamorphism
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metamorphism affecting an extensive region and related mostly to regional burial, heating, and deformation of rocks.
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subduction
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process along a convergent plate-tectonic boundary in which an oceanic lithospheric plate descends beneath the overriding plate
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recrystallization
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formation, essentially in the solid state, of new crystalline grains in a rock
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shear
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type of differential stress that occurs when stresses on the edge of a mass are applied in opposite directions
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compression
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type of differential stress that occurs when forces push in on a rock
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earthquake
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sudden movement of the earth caused by the abrupt release of energy
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fault
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fracture along which the adjacent rock surfaces are displaced parallel to the fracture
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hypocenter (focus)
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place where an earthquake is generated
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epicenter
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point on the Earth's surface directly above where an earthquake occurs
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hanging wall
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wall rock above an inclined fault
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footwall
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wall rock beneath an inclined fault
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normal fault
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fault in which the hanging wall moves down relative to the footwall
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reverse fault
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fault in which the hanging wall moves up relative to the footwall
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strike-slip fault
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a fault in which the relative movement is essentially horizontal, parallel to the strike of the fault surface
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thrust fault
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a reverse fault that has a gentle dip
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seismic wave
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elastic waves produced by earthquakes or generated artificially
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seismic station
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location of a scientific instrument (seismograph) that measures seismic vibrations
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elastic behavior
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The ability fo a material to strain a small amount and then return to it s original shape when the stress is decreased.
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earthquake cycle
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the gradual accumulation of stress on a fault followed by an abrupt decrease in stress during an earthquake
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recurrence interval
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the time between repeating earthquakes
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strain
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change in shape or volume of a body as a result of stress
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stick-slip behavior
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The sequence of a rock straining before an earthquake, rupturing during an earthquake, and then mostly returning to its original shape after the earthquake.
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seismicity
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Earth movements, either on the surface or at depth, caused by earthquakes.
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continental rift
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A low trough or series of troughs bounded by normal faults, especially where two parts of a continent begin to rift apart.
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accretionary prism
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a prism- or wedge-shaped, structurally complex zone of faults, folds, and mostly metamorphosed rocks that form along the upper parts of a subduction zone; material derived from sediment contributed by adjacent volcanoes or a continent, along with oceanic crust scraped off the down-going …
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megathrust
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a huge thrust fault, representing the boundary between the subducted slab and overriding plate
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GEOL 1040: Exam 3