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Definitions (25)

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home page


Introduction Discovery Timescale Terrane "I.D." & Activity Case Study: Wrangellia Geologic TImescale Glossary List References
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alfred wegener


Wegener is credited with the theory of continental drift (1912) from which the discipline of plate tectonics grows. Trained as an astronomer, he was also an explorer of Greenland and the Arctic, and had an interest in meteorology.
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subducting


The sinking of the ocean crust edge as a result of convergence with lesser density. This process often causes earthquakes and can result in chains of volcanoes.
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stratified terranes


These terranes have layers of rock which indicate the order of deposition. These terranes can be a.) fragments of continents, characterized by Precambrian basement rock under shallow-water sediments from the Paleozoic and Mesozoic ages; b.) ocean crust, with typical extruded molten rock under layers of siliceous chert; c.) fragments of volcanic arc [..]
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rifting


A process of spreading and thinning of the crustal plate. This forms a depression in the crust and often results in the separation of the crust into two or more smaller plates.
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potassium-argon techniques


Forms of isotope dating tests used on rocks between 100,000 and 4 billion years old. It relies on the extremely long half-life of radioactive isotopes of potassium which decay into argon.
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paleomagentic signatures


are read from rocks to help determine the latitude of the rock at the time of its formation. The fixed orientation of the rock's magnetized fraction does not change even if the magnetic field of the Earth reverses.
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orogeny


The geological term for mountain building, and it is usually associated with a specific historic event such as the Antler orogeny, or the Taconian orogeny.
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microplate tectonics


A term used to indicate the movement of small fragments of crustal plates; formation, drifting, collision, displacement and accretion.
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metamorphic terranes


These terranes show signs of terrane-wide geologic changes, before or after collision, which has been sufficiently powerful to obscure original rock formation.
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