ESC 2200C Lecture Notes - Lecture 5: Crystallization, Planetesimal, Flux Melting
30 Sep 2016
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Document Summary
Up from the inferno: magma and igneous rocks. Molten rock (melt) is needed to generate volcanic activity and form igneous rocks. Melts can cool above or below ground. Extrusive igneous rocks cool quickly at the surface. Lava flows- streams or mounds of cooled melt. More intrusive than extrusive igneous rocks: intrudes into pre-existing wall rock. Leftover from earth"s formation: planetesimal accretion, gravitational compression, iron differentiation, moon formation, meteorite bombardment. Radioactive decay: primarily in the crust. Magma only forms in special tectonic settings: partial melting occurs in the lower crust and upper asthenosphere, melting is caused by: Base of the crust: hot enough to melt mantle rock. Rocks are solid in the mantle because high p prevents atoms from breaking free of solid form. Melting will occur when p decreases: rocks are carried to shallower depths. Addition of volatiles- flux melting: volatiles help break chemical bonds. Effectively lower the melting t of a hot rock.
