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30 Cards in this Set
- Front
- Back
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Angular conformity
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consists of tilted or folded sedimentary rocks that are overlain by younger, more flat lying strata.
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catastrophism
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people who believed that Erth's lanscapes had been developed primarily by great catastrophes.
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comformable
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when we observe layers of rock that have been deposited essentially without interruption.
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correlation
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to develop a geologic time scale
- rocks of similar age in different regions must be matched up. |
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Principle of cross cutting relationships
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when a fault cuts through other rocks, or when magma intrudes and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected.
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disconformity
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little evidence of erosion
rocks are essentially parallel older rocks easier to identify because ancient erosion is cut deeply |
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eon
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represents the greatest expansion of time.
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epoch
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12 periods of time divided into still smaller units.
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fossil
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the remains or traces of prehistoric life
are important inclusions in sediment and sedimentary rock. |
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principle of fossil succession
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fossils succeed one another in a definite order and therefore any time period can be recognized by its fossil.
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geologic time scale
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geologists who divided the whole of geologic history into units of varying magnitude.
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half life
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time required for one half of the nuclei in a sample to decay.
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inclusions
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pieces of one unit rock that are contained within annother
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index fossil
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wide spread geographically are are limited to a short span of geographic time, so their presence provides an important method of matching rocks of the same age.
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nonconformity
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the break of rock seperates older metamorphic or intrusive rocks from younger sedimentary strata.
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numerical date
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specifies the actual number of years than have passed since an event occured.
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Principle of original horizontality
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Layers of sediment are generally deposited in a horizontal position.
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paleontology
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blends geology and biology in an attempt to understand all aspects of the succession of life over the vast expanse of geologic time.
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radioactivity
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nuclei are unstable because the forces binding protons and neutrons together are not strong enough
-nuclei break apart and decay |
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radiocarbon dating
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to date very recent events using carbon 14 (radioactive isotope of carbon).
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relative dating
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placing rocks in their proper sequence of formation
-can't say when a event took place but what event it occured after and preceded another. |
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law of superposition
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undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it.
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unconformity
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long period during which deposition ceased
-erosion removed previously formed rocks -deposition resumed |
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uniformitarianism
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physical,chemical, and biological laws that operate today have also operated in the geologic past.
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archaeon eon
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earth's crust formed; unicellular organisms are earliest forms of life
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cenozoic era
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The latest era of the Phanerozoic Eon, following the Mesozoic Era and continuing to the present time, and marked by the presence of a wide variety of mammals,
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mesozoic era
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characterized by the development of flying reptiles, birds, and flowering plants and by the appearance and extinction of dinosaurs
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paleozoic era
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expanded into 6 geologic periods
-great forests of primitive plants thrived on land forming the great coal beds of Europe and eastern North America. By the end of the era, the first large, sophisticated reptiles and the first modern plants (conifers) had developed. |
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phanerozoic eon
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The Phanerozoic Eon represents geologic time from the end of Precambrian time
-includes all 3 eras |
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proterozoic eon
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which begins with the appearance of abundant macroscopic hard-shelled animals in the fossil record and extends to the present time.
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