HISTORICAL GEOLOGY
About this set
Created by:
ekirman on April 27, 2011
Description:
Combined Historical Geology Set
Classes:
spiffy science, Earth and Space Science
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51 terms
Terms | Definitions |
|---|---|
 geologic time scale | a record of the geologic events and life forms in Earth's history |
| eon | the longest division of geological time |
| era | a unit of geologic time that includes two or more periods |
| periods | subdivisions of an era in geologic time |
| epochs | smallest and 4th largest divisions of geologic time |
| Phanerozoic | the period from about 5,400 million years ago until the present, means "visible life" |
| Paleozoic | means "ancient life", spans from 544 million to about 230 million years ago |
| Mesozoic | means "middle life" from 230 million to 63 million years ago |
| Cenozoic | means "recent life" approximately the last 63 million years |
| Precambrian | name for the time in earths early history that accounts for ninety percent of earth's time, but only cellular organisms lived |
| radioactivity | the process by which an unstable nucleus gives off nuclear radiation |
| half-life | the time required for one half of the atoms of a radioisotope to emit radiation an decay products |
| radiometric dating | process used to calculate the absolute age of rock by measuring the ratio of parent isotope to daughter product in a mineral and knowing the half-life of the parent |
| radiocarbon dating | method measuring the decay rate of carbon isotopes in organic matter to provide dates for organic materials like wood or fiber |
| parent element | The unstable or starting radioactive element. |
| daughter element | the unstable or starting radiactive element decays into this product |
| alpha emission | the process in which two protons and two neutrons that are bound together and are emitted from the nucleus during some kinds of radioactive decay |
| beta emission | release of an electron from the nucleus |
| electron capture | the process in which an inner orbital electron is captured by the nucleus of the atom that contains the electron |
| radioactive isotope | an isotope that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy |
| carbon 14 | taken up by living things while they are alive--when an organism dies, it decays to form nitrogen 14.used to date fossils younger than 60,000 years. half life=5370 years. |
| uranium 238 | the radioactive isotope of uranium having an atomic mass of 238 and a half-life of 4.5 billion years |
| carbon 12 | stable isotope used to measure the age of organic material |
| fossil | preserved remains or evidence of an ancient organism |
| trace fossil | a type of fossil that provides evidence of the activities of ancient organisms, includes the footprints, tracks, trails, and burrows made by living things |
| index fossil | a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found |
| petrified remains | fossils that form when some of the original materials that made up the organisms are replaced with minerals |
| cast | a type of body fossil that forms when crystals fill a mold or sediments wash into a mold and harden into rock |
| mold | a fossil formed when an organism buried in sediment dissolves, leaving a hollow area |
| amber | hardened tree sap, often a source of insect fossils |
| unaltered remains | fossil retains the organism's original structure and composition; it remains unchanged such as a complete insect in amber |
| altered remains | fossils changed structurally or chemically; minerals may seep into the pores or cavities of an organism's bones, teeth, and shells |
| gastrolith | fossilized stone from the digestive system of a dinosaur |
| trilobite | organism with a three-lobed exoskeleton that was abundant in Paleozoic oceans and is considered to be an index fossil, PA state fossil |
| law of superposition | in undisturbed rock layers, the oldest rocks are on the bottom and the youngest rocks are on the top |
| uniformitarianism | is the idea that the geologic processes that operate today also operated in the past |
| relative dating | method to determine the order of events and relative age of rocks by examining the position of rocks in a sequence |
| principal of cross-cutting relationships | a feature that cuts a layer of rock is younger than the rock itself |
| unconformity | gap in the rock layer that is due to erosion or periods without any deposition |
| principle of original horizontality | layers of sediment are generally deposited in a horizontal position |
| correlation | establishing the equivalence of rocks of similar age in different areas |
| fault | a crack in the earth's crust resulting from the displacement of one side with respect to the other |
| fold | a bend in layers of rock |
| angular unconformities | an unconformity that exists between horizontal sedimentary rock layers and folded or tilted layers of rock |
| disconformities | formed as an erosion surface between parallel layers of sedimentary rock |
| nonconformities | exists where horizontal sedimentary rock layers lie on top of an eroded surface or older metamorphic rock or igneous rock |
| dike | a slab of volcanic rock formed when magma forces itself across rock layers |
| sill | igneous rock feature formed when magma is squeezed into a horizontal crack between layers of rock and hardens underground |
| anticline | a fold in rock that bends upward into an arch |
| syncline | a fold in rock that bends downward to form a valley |
| James Hutton | known as the Father of Modern Geology, is known for creating the theory of Uniformitarianism |
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