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geology exam #1
| Term | Definition |
|---|---|
| geology | the science of Earth, including its composition, structure, origin, life forms, the physical and chemical processes that affect it, and its history |
| Earth history | study of the origin and development of Earth, including its life forms, through time (AKA historical geology) |
| scientific methodology | a general term for a scientific investigation involving an iterative process of empirical observation, hypothesis building, and testing |
| scientific theory | a scientific concept that is tantamount to fact |
| evolutionary theory | the scientific theory that explains processes by which biologic species give rise to other species, principally by way of genetic charges and natural selection |
| plate tectonics theory | the scientific theory that Earth's outer shell is composed of pieces that interact with each other as they "float" on a hot, deformable asthenosphere |
| lithosphere | the outer, relatively rigid layer of Earth, approximately 100 km thick, overlying the asthenosphere; includes the entire upper crust and the upper mantle |
| crust | the outermost layer of Earth, defined by density, composition, and seismic velocity differences from the underlying mantle |
| asthenosphere | the layer within the upper mantle and below the lithosphere where rocks are relatively ductile and easily deformed |
| Earth system | the sum of the physical, chemical, and biological processes operating on and within Earth |
| uniformitarianism | the principle that processes acting on Earth today have also operated in the geologic past |
| principle of superposition | in an undisturbed succession of strata, the oldest strata are at the base of the succession, and the youngest strata are at the top of the succession |
| principle of original horizontality | sedimentary strata were originally deposited nearly horizontally and parallel to Earth's surface |
| principle of original lateral continuity | at the time of deposition, a sedimentary unit extended laterally and continuously in all directions until it thinned out or otherwise reached the limits of its depositional range |
| principle of cross-cutting relationships | a rock unit, sediment body, or fault that cuts another geologic unit is younger than the unit that was cut |
| principle of included fragments | fragments of a rock or sediment body contained within another rock or sediment are from a preexisting rock or sediment than the one in which they are contained |
| principle of biotic succession | body fossils occur in strata in a definite, determinable order |
| rock | a mixture of minerals |
| mineral | a naturally occurring crystalline solid or a synthetic, chemically identical equivalent |
| crystal | a solid composed of atoms and molecules that have a regular internal structure and an external form defined by flat faces |
| biomineralization | secretion of minerals as bones, teeth, shells, external coverings, or other structures by biologic organisms |
| silicate mineral | a mineral that has a silicate tetrahedron as the basic chemical property |
| carbonate mineral | a mineral that contains a carbonate ion |
| rock cycle | a conceptual model that describes the origin, alteration, and destruction of rocks through the action of Earth processes |
| igneous rock | rock formed from the crystallization of magma |
| magma | molten rock, including any suspended crystals and dissolved gases |
| sediment | unconsolidated particles of rock that have been transported by agents of erosion and unconsolidated particles formed as skeletal material through biomineralization |
| sedimentary rock | a rock, usually layered, formed from sediments and from minerals precipitated under aqueous conditions |
| metamorphic rock | rock whose original mineralogy or texture has been transformed through any combination of heat, pressure, chemical environment, and shearing stress |
| intrusive rock | igneous rock, usually coarsely crystalline, that resulted from the cooling and solidification of magma within Earth's crust (AKA plutonic rock) |
| extrusive rock | igneous rock, usually finely crystalline, that resulted from the cooling and solidification of magma erupted onto Earth's surface (AKA volcanic rock) |
| lithification | the processes involved in changing sediments to rock |
| evaporite | a mineral deposited under evaporative conditions |
| bedding | layering in sedimentary rocks (AKA lamination) |
| diagenesis | all the chemical, physical, and biologic changes that sediments undergo between the time of deposition and the time of lithification |
| regional metamorphism | metamorphism that affects large areas of the crust |
| contact metamorphism | localized metamorphism associated with the intrusion or extrusion of an igneous magma; heat and hydrothermal fluids may be involved in the metamorphic activity |
| relative age dating | the technique of establishing a chronology of events arranged in relative sequential order |
| stratigraphy | the study of layered rocks, including their compositions, origins, geometric relationships, and ages |
| numerical age dating | the technique of establishing when events occurred according to how much time has elapsed since their occurrence; geologic time that has elapsed is measured in thousands, millions, or billions of years |
| correlation | matching of strata from one location to another |
| lithostratigraphy | stratigraphic correlation on the basis of rock type |
| formation | the fundamental unit of lithostratigraphy; it has a definable top and bottom and its mappable across geographic space |
| biostratigraphy | zoning of stratigraphic layers and arrangement of those layers according to relative time of deposition, using the ranges of fossils |
| biozone | a stratigraphic interval defined by its fossil content and usually given the name of a characteristic fossil present in that interval (AKA zone) |
| chemostratigraphy | correlation of strata using ratios of chemical isotopes |
| isotropic excursion | a positive or negative shift in the isotopic ratio of an element, as recorded through a succession of stratigraphic layers |
| sequence stratigraphy | correlation of strata on the basis of erosion surfaces that separate packages of sediments or sedimentary rocks called sequences |
| unconformity | a surface of erosion or nondesposition |
| disconformity | an unconformity in which strata below and above the erosion surface are parallel |
| eustatic sea level | global sea level |
| geologic time scale | a chronology of Earth history |
| global boundary stratotype section and point (GSSP) | an internationally ratified point in strata marking the boundary between two time-rock units and their equivalent time units |
| chronostratigraphic unit | a time-rock or time-stratigraphic unit; the tangible representation of a geologic time unit |
| system | the fundamental unit of chronostratigraphy |
| period | the unit of geologic time equivalent to a system |
| parent | in a radioactive decay series; an unstable isotope that decays, or transforms, into a daughter product |
| daughter | an isotope formed from the radioactive decay of a parent isotope |
| facies | a sedimentary unit that has a set of characteristics particular to a local environment |
| grain size | the general dimensions of particles in a sediment or rock |
| sorting | a measure of the range of grain sizes in a sedimentary deposit |
| roundness | the degree to which a sedimentary particle's original edges and corners have been smoothed |
| bioturbation | reworking of sediment by organisms |
| ripple | a sedimentary bed form that has a roughly triangular transverse cross-section and formed by the interaction of a moving air or water current with a mobile sediment |
| cross-bedding | strata inclined at different angles formed by the rippling of sediment |
| graded bedding | a single-event sedimentary bed in which there is a progressive vertical change in grain size |
| mudcracks | irregular, polygonal fractures formed by the drying and shrinkage of mud |
| geopetal structure | a sedimentary feature that shows the younging direction of strata |
| stromatolite | a thinly layered biogenic-sedimentary structure that results from the trapping and binding of fine sediment in layers by photosynthetic cyanobacteria |
| concretion | a rounded body enclosed in sedimentary rock; are normally formed by microbially mediated precipitation of minerals during the decay of an organism |
| paleosol | an ancient soil horizon or profile |
| Walther's law of facies | the concept that in an unbroken sequence, vertically superimposed lithofacies were laterally adjacent to each other at the time of deposition |
| transgression | a rise of sea level; marine facies shift landward |
| continental shelf | the part of the continental margin between the shoreline and the continental slope; characterized by a very low slope |
| regression | a drop of sea level; continental facies shift seaward |
| alluvial fan | a relatively low, sloping mass of sediment, shaped like an open fan, deposited by a stream where it issues from a narrow mountain valley onto a broad plain |
| barrier island | a long, narrow, sandy coastal island above high tide level and parallel to the shoreline |
| delta | a sedimentary wedge that develops near the mouth of a stream or river as sediment is rapidly deposited in relatively quiet water of an ocean or a lake |
| reef | a wave-resistant structure constructed by organisms |
| continental slope | the part of the continental margin between the continental shelf and the continental rise, if there is one; characterized by a relatively steep slope |
| greenhouse gases | atmospheric gases that trap the heat from solar radiation near Earth's surface |
| continental drift | the hypothesis that the continents moved to their present positions after fragmentation of a larger landmass in the geologic past |
| seafloor spreading | the hypothesis that ocean basins expand through the addition of new rock from spreading centers and that older rock is destroyed near the basin margins |
| basin | a relatively depressed area of the Earth's crust that receives sedimentary deposition |
| continental crust | the solid, outer part of the Earth underlying the continents and continental shelves, composed largely of granitic rocks |
| oceanic crust | the solid, outer part of the Earth underlying the ocean basins, consisting largely of basaltic rocks |
| Pangea | the late Paleozoic to early Mesozoic supercontinent comprising most of the world's continental crust |
| Glossopteris flora | an assemblage of plants, dominated by fossil leaves of Glossopteris, occurring in Carboniferous-Permian strata of the Southern Hemisphere |
| triple junction | a junction of three spreading edges of plates |
| graben | an elongate basin formed through downdroppping of a fault block and bounded on both sides by a normal fault |
| aulacogen | a failed continental rift that has filled with sediment |
| guyot | a sunken seamount, or undersea volcano, that has a flat top due to erosion at sea level |
| paleomagnetism | the study of natural remnant magnetism in rocks to determine properties of Earth's magnetic field in the geologic past |
| hot spot | a volcanic center, often in the interior of a plate caused by a plume of magma rising from the mantle |
| divergent plate boundary | a tectonic boundary between two plates that are moving apart |
| passive margin | the trailing edge of a tectonic plate, where active tectonic interaction with another plate is not occurring |
| subduction zone | a long, narrow belt, usually including a deep-sea trench, along which subduction occurs |
| convergent plate boundary | a boundary between two plates that are moving toward each other |
| volcanic arc | an arcuate line of active volcanoes and igneous plutons associated with a convergent plate margin where subduction is occurring |
| transform fault boundary | a boundary between two crustal blocks that is characterized by a transform fault and where crust is neither created nor destroyed |
| tectonostratigraphic terrane | a rock body having an internally consistent geologic makeup and separated from a continental block or another terrane by bounding faults |
| orogenesis | the process of building mountain chains and consequently deforming granitic-type crust |
| ophiolite | an assemblage of ultramafic and mafic igneous rocks and representing ocean crust |
| foreland basin | a linear sedimentary basin that subsides in response to thrust loading of the crust |
| clastic wedge | a wedge-shaped deposit of sediments shed from an active thrust belt and filling a foreland basin |
| Archean Eon | the unit of geologic time beginning with Earth's formation, perhaps 4.567 billion years ago, and ending at the beginning of the Proterozoic Eon, 2.5 billion years ago |
| Proterozoic Eon | the unit of geologic time beginning 2,500 million years ago and ending at the beginning of the Phanerozoic Eon, 542 million years ago |
| craton | the core of the continent--the part of Earth's continental crust that has attained relative stability and received little deformation for at least 1 billion years |
| Canadian Shield | a large area of Precambrian basement rocks that made up the exposed core of North America and shows at the surface mostly across Canada and the northern United States |
| meteorite | a relatively small rock that falls to a planetary surface from interplanetary space |
| asteroid | one of many irregularly shaped planet-like rock bodies, including those orbiting the Sun between Mars and Jupiter |
| magma ocean | the condition of molten magma covering the outer surface of a planet or a moon |
| outgassing | the process of releasing gases, including water vapor, from magma |
Created by:
emilybobal
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