Science absolute dating,mass extinction,geologic time periods Essay

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Paleozoic period
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spanning from roughly 541 to 252.17 million years ago.
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Pangea
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A supercontinent containing all of Earth’s land that existed about 225 million years ago.
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Triassic period
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Part of the Mesozoic Era, the period when dinosaurs first appeared. (248-213 million years ago)
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Jurassic period
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Occurred between 206-144 million years ago. The dinosaurs dominated. The first dinosaur-like bird appeared. Early mammals were developing and diversifying
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Daughter atom
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the atom that is the product atom formed during the radioactive decay in a nuclear reaction
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Decay
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When atoms change during their half life
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Geiger counter
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a device for measuring radioactivity by detecting and counting ionizing particles.
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Half-life
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The time required for one half of the atoms of a radioisotope to emit radiation an decay products
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Isotope
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Atoms of the same element that have different numbers of neutrons
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Neutron
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A subatomic particle that has no charge and that is found in the nucleus of an atom
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Radiation
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Energy that is radiated or transmitted in the form of rays or waves or particles.
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Radioactive
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A spontaneous process in which unstable nuclei lose energy by emitting radiation
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Radiometric dating
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the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products
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Mass extinction
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event during which many species become extinct during a relatively short period of time
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Mesozoic period
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middle life 245-144 million years ago – mammals, dinosaurs, rise of birds, extinction of dinosaurs & flowering plants
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Cenozoic period
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Era of Modern life
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Cretaceous-tertiary mass extinction
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Fifth mass extinction. 65.5 mya. 85% of all species disappear from land and oceans. Extinction of dinosaurs.
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Triassic-Jurassic mass extinction
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During the final 18 million years of the Triassic period, there were two or three phases of extinction whose combined effects created the Triassic-Jurassic mass extinction event. Climate change, flood basalt eruptions and an asteroid impact have all been blamed for this loss of life.
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Permian mass extinction
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Carbon dioxide accumulated in the air and trapped heat which caused a Greenhouse effect; in the water the carbon dioxide became carbonic acid which increased the acidity of the ocean; some organisms were unable to continue to make their shells so a large amount of them went extinct
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Devonian mass extinction
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extinction where ostracoderms and many marine organisms were wiped out. , Second extinction;primarily marine; 75% of marine species. , Mass extinction caused by possible meteor impact. Glacian might be another factor.
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Ordovician-Silurian mass extinction
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The third largest extinction in Earth’s history, the Ordovician-Silurian mass extinction had two peak dying times separated by hundreds of thousands of years. During the Ordovician, most life was in the sea, so it was sea creatures such as trilobites, brachiopods and graptolites that were drastically reduced in number.
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Absolute dating
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A technique used to determine the actual age of a fossil
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Law of superposition
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The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.
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Tertiary period
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65-1.8 my “Age of Mammals 11. Mammals evolved to fill virtually all niches vacated by dinosaurs during what period of geological time
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Quaternary period
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The youngest geologic period; includes the present time.

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