Details Title: Exam 3 Description: Evidence for Plate Tectonics (cond) (4/6) Total Flash Cards: 25 Created: 04/06/2009 19:50:41		New Users: To study from this flashcard set, or to create your own your own study flash cards, REGISTER HERE. Existing Users: CLICK HERE. Additional Geology Flashcards
Cards in this set: Term Divergent Boundaries   Definition -tensional forces -boundaries occur when plates rift, and move apart -creating large expanses oceanic crust (characterized) -volcanism -normal faulting & graben formation -sedimentary deposits Term Crustal lenthening/Extension Definition -crust (basalt) created in this type of boundary -new crust added to trailing edge of each seperating plate Term Transform Faults Definition -spherical earth requires adjustment of rigid crust -offsets in the crust exist Term Convergent Boundaries Definition -compressional forces -leading edges of two plates come in contact w/eachother (CHARACTERIZED) -metamorphism -volcansim -reverse faulted/folded mountains -sedimentary wedges Term Crustal Shortening Definition -oceanic crust is destroyed at this type of boundary Term Ocean : Ocean Definition -resulting in a deep ocean trench (rate of plate movements affects the features) Term Continent: Ocean Definition -resulting in devleopment of a deep sea trench -assoicated w/ volcanic terrains (METAMORPHISM) Term Melange Structures Definition -mixture of broken, jumbled, and thrust-faulted rock -subduction zone (mixed up minerals) Term Ophiolite Suites Definition -fragments of oceanic crust found on continents -washed up on contintents (peridotite>Gabbro>Sheeted Dikes>Pillow Basalts) buttom to top Term Blue Schist Definition -subduction zone (metamorphism->subduction zone) -high P, low T -blue amphiiboles Term Back-arc Basins Definition -basaltic magma rise at newly formed spreading center  -new oceanic crust forms -behind & parallel to subduction zone -sinking subducting plate faster than forward motion of overriding plate which is slower (tensional stress=pulling) Term Transform Plate Boundaries (shear,strike-slip) Definition -shear forces -boundaries occur where one plate moves laterally past another -crust neither created or lost (CHARACTERIZED) -localized metamorphism -strike-slip faulting -minor igneous intrustions   Term Back-arc basins (cont) Definition oceanic or extension of contintenal margin progressed to extreme slate it forms by -behind and parallel to magmatic arc of subduction zone   Term Continent: Continent Definition -resulting by folded -reverse and thrust faulted mountains (some igneous cores, others metamorphosed) -rocks are sutured together (metamamorphism) Term Transform Plate boundaries (shear, strike-slip) Definition -shear forces -boundaries=one plate moves laterally past another -localized metamorphism, strike-slip faulting, minor igneous intrusions (crust neither created or lost) Term Craton Definition -ancient rock makes up core of continent -applied to crust that has attained tectonic & isostatic stability (north america) Term Orogens Definition -elongate regions of crust that have been intensely folded & faulted during continental collision -thicker crust then cratons -eroded roots of ancient mountain ranges formed by collision b/w cratons -differ by history,age,size Term Shield (continental shield) Definition -assemblage of cratons & ancient oregens that has reached isostatic equilbrium (largest) -thin layer of little-deformed sediments (canada) Term Passive Continental Margin Definition -accumulation of sediment -stable interior plate -places where great thickness of sediment accumulates Term plate triple juntion Definition -meeting point formed by three spreading edges -angle b/w any two edges is 120° -spreading continues along two edges -third edge is failed rift Term Accreted Terrain continental margin Definition -former convergent or transform fault margins modified by addition of crust such as (rafted-in, exotic fragments of crust) (ex.island arc) -those pieces crust not subducted are accreted (san andrea fault) Term Continental Convergent Margin Definition edge of continent coincides w/ convergent plate margin in which oceanic litosphere is subducted beneath contintal litosphere Term Continental Volcanic Arc Definition -wet particle melting in mantle activated by water -released by subducted Nazca Plate produced the andesitic magma  Term Continental Collision Margin Definition edges of two continents, each on a different plate, come into collision Term Transform fault continental margin Definition -margin of continent coincides w/ a transform fault boundary of a plate  (san andrea fault)