GEOL 001 Lecture Notes - Lecture 23: Volcanic Arc, Igneous Differentiation, Continental Margin
20 Dec 2020
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How does magma form: temperature increase: radioactive decay within earth early earth produced during big bang. Frictional heat of tectonic plates transfer of heat (convergent margins) Add flux (h2o, co2): addition of volatiles along plate margins reduced the melting temperature of a solid wet melting: volatiles "disrupt" chemical bonds of other compounds: pressure decrease: Hi-p results in higher t to melt solid (bonds are closer together = stronger) If quickly release hi-p, solid will melt (plate divergent margins) Subduction zones one plate goes under the other (introducing materials into plate), can create mountains/volcanoes. Occur in conjunction with deep oceanic trenches (plate convergence) Descending plate partially melts + release h2o (wet melting) A volcanic arc if on a continental margin. Region around the margin is known as the "ring of fire" Greatest volume of volcanic rock is produced along the oceanic ridge system (plate divergence) Associated with plumes of heat in the mantle (transfer of heat)
