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50 Cards in this Set
- Front
- Back
sedimentary structure
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Any feature of sedimentary rock formed during deposition or by later sedimentary processes- for example, layering, ripple marks, or fossils.
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bedding
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Layering that develops as sediments are deposited; also called stratification.
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cross-bedding
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A sedmentary structure in which wind or water deposits small beds at an angle to the main sedimentary layering.
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ripple marks
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Small, parallel ridges and troughs formed in sediment by wind, water currents, or waves, which are often preserved when the seidment is lithified.
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mud cracks
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Irregular polygonal fractures that develop when mud dries, forming patterms that may be preserved when the mud is lithified.
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sedimentary structure
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Any feature of sedimentary rock formed during deposition or by later sedimentary processes- for example, layering, ripple marks, or fossils.
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bedding
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Layering that develops as sediments are deposited; also called stratification.
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cross-bedding
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A sedmentary structure in which wind or water deposits small beds at an angle to the main sedimentary layering.
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ripple marks
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Small, parallel ridges and troughs formed in sediment by wind, water currents, or waves, which are often preserved when the seidment is lithified.
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mud cracks
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Irregular polygonal fractures that develop when mud dries, forming patterms that may be preserved when the mud is lithified.
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fossil
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The imprint, remains, or any other trace of a plant or animal preserved in rock.
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metamorphism
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The process by which rocks and minerals change form in response to changes in temperature, pressure, chemical conditions, and/or deformation.
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metamorphic grade
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The intensity of metamorphism that formed a rock; the maximum temperature and pressure attained during metamorphism.
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folliation
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The layering in micas and other minerals created by metamorphism.
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slaty cleavage
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A metamorphic folliation producing a parallel fracture pattern that cuts across original sedimentary bedding in micas or other metamorphic rocks.
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Mercalli Scale
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(1902) measure of earthquake destruction
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Earthquake hazard
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anything associated with an earthquake that may affect the
normal activities of people. This includes surface faulting, ground shaking, landslides, liquefaction, tectonic deformation, tsunamis, and seiches. |
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Earthquake risk
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probable building damage, and number of people that are
expected to be hurt or killed if a likely earthquake on a particular fault occurs. |
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Primary EQ damage
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a. surface shaking
b. ground rupture c. differential subsidence d. liquefaction |
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Secondary EQ damage
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a. fire
b. landslides and slumps c. Tsunami |
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mass extinction
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A sudden, catastrophic event during whciha significant part of all life-forms on Earth become extinct.
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relative age
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An approach to mesuring geologic time based on the order in which events occured, but not measured in years.
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absolute age
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Time measured in years
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principle of original horizontality
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The principle that most sediment is deposited as nearly horizontal beds, and therefore most sedimentary rocks started out with nearly horizontal layering.
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principle of superposition
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The principle that in any undisturbed layers of sediment or sedimentary rock, the age becomes progressively younger from bottom to top; younger layers always accumulate on top of older layers.
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principle of cross-cutting relationships
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The obvious principle that a rock or feature must first exist beofre anything can happen to it; thus if an intrusion of rock cuts across an existing rock, the dike (intrusion) is younger.
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principle of faunal succession
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The principle that species succeeded one another through time in a definite order, so that sedimentary rocks of the same age contain identical fossils and rocks of different ages contain different fossils; therefore, the relative ages of rocks can be identified from their fossils.
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conformable
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A term describing sedimentary layers that were deposited continuously without detectable interruption.
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unconformity
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An interruption in sediment deposits or a break between eroded igneous and over-lying sedimentary layers, causing a gap in the geological record for that place. Types of unconformities include disconformity, angular unconformity, and nonconformity.
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disconformity
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A type of unconformity in which the sedimentary layers above and below the unconformity are parallel.
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angular unconformity
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An unconformity in which younger sediment or sedimentary rocks rest on the eroded surface of tilted or folded older rocks.
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nonconformity
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A type of unconformity in which layered seidmentary rocks lie on an erosion surface cut into igneous or metamorphic rocks.
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correlation
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The process of establishing the age relationship of rocks or geologic features from different locations on Earth; can be done by comparing characteristics of the layers or the the types of fossils found in those layers. There are two types of correlation: time correlation (age equivalence) and lithologic correlation (continuity of the rock unit).
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index fossil
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A fossil that dates the layers where it si found because it came from an organism that is abundantly preserved in rocks, was widespread geographically, and existed as a species or genus for only a relatively short time.
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key bed
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A thin, widespread, easily recognized sedimentary layer that can be used for correlation because it was deposited rapidly and simultaneously over a wide area.
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isotopes
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Atoms of the same element that have the same number of protons but different numbers of neutrons.
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half-life
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The time it takes for half of the atoms of a radioactive isotope ina sample to decompose.
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radiometric dating
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The process of measuring the abolute age of rocks, minerals, and fossils by measuring the concentrations of radioactive isotopes and their decay products.
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geologic column
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A composite, columnar diagram that shows the sequence of rocks at ta given palce or region, arranged to show their position in the geologic time scale.
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geologic time scale
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A chronological arrangement of geologic time sub-divided into eons, eras, periods, and epochs.
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eon
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The largest unit of geologic time. The most recent eon, the Phanerozoic Econ, is further subdivided into eras.
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era
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A geologic time unit. Eons are divided into eras and eras are divided into periods.
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Precambrian
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A term referring to all of geologic time befor ethe Paleozoic Era, encompassing approximately the first 4 billion years of Earth's history. Also refers to all rocks formed during that time.
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Hadean Eon
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The earliest time in Earth's history, ranging from 4.6 billion years ago to 3.8 billion years ago.
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Archean Eon
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A division of geologic time 3.8 to 2.5 billion years ago. The oldest known rocks formed at the bginning of, or just prior to, this eon.
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Proterozoic Eon
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The portion of geologic time occuring during a period from 2.5 billion to 543 million years ago.
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Phanerozoic Eon
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The most recent 543 million years of geologic time, including the peresnt, represented bby rocks that contain evident and abundant fossil records.
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Paleozoic Era
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548 to 248 million years ago. During this era invertebrates, fishes, amphibians, reptiles, ferns, and cone-bearing trees were dominant.
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Mesozoic Era
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248 to 65 million years ago. Dinosaurs rose to prominence and became extinct during this era.
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Cenozoic Era
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65 million years ago to present
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